<6 | “ay 10 (68 3 O BR35 . ren paARY Ry ; WwW YORK ROTANICAL | / A RDEN SOME RN CALIFORNIA: ACADEMY. OF SCIENCES BULLETIN Volume 84 Number 1 BCAS-A84(1) 1-56 (1985) APRIL 1985 a 5a] Southern California Academy of Sciences | Founded 6 November 1891, incorporated 17 May 1907 © Southern California Academy of Sciences, 1985 — OFFICERS Peter L. Haaker, President — | ; Robert G. Zahary, Vice-President ~ Camm C. Swift, Secretary — Takashi Hoshizaki, Treasurer Jon E. Keeley, Technical Editor Gretchen Sibley, Managing Editor are BOARD OF DIRECTORS 1983-1985 1984-1986 1985-1987 Takashi Hoshizaki Charles P. Galt Jules M. Crane Edward J. Kormondy Peter L. Haaker . Michael H. Horn Steven N. Murray | Harlan Lewis - Susanne Lawrenz-Miller Camm C. Swift June Lindstedt-Siva John D. Soule | Robert G. Zahary Martin L. Morton Gloria J. Takahashi Membership is open to scholars in the fields of natural and social sciences, and to any person interested in the advancement of science. Dues for membership, changes of address, and requests for missing numbers lost in shipment should be addressed to: Southern California Academy of Sciences, the Natural History Museum of Los Angeles County, Exposition Park, Los Angeles, California 90007. Annual Members..... ere ee. Me err re $( 52005 Student Members. ....0.. 425 Un ere ae ae bt 8, Gk it seats ae 10.00 Ras (05 (307) Cah 0 0 otc ee a ee 3 oe See ee 300.00 — Fellows: Elected by the Board of Directors for meritorious services. The Bulletin is published three times each year by the Academy. Manuscripts for publication should a be sent to the appropriate editor as explained in “Instructions for Authors” on the inside back cover _ of each number. All other communications should be addressed to the Southern California Academy _ of Sciences in care of the Natural History Museum of Los Angeles County, Exposition Park, Los Angeles, California 90007. Ss Date of this issue 17 April 1985 ‘ke -, Bull. Southern California Acad. Sci. 84(1), 1985, pp. 1-22 © Southern California Academy of Sciences, 1985 Population Dynamics and Ecology of Beach Wrack Macroinvertebrates of the Central California Coast Derrick R. Lavoie Abstract.—Population dynamics and ecology of beach wrack macroinverte- brates of the central California coast by Derrick R. Lavoie, Bull. Southern Cal- ifornia Acad. Sci., 84(1):1-22, 1985. The successional cycle of macroinverte- brates colonizing high intertidal beach wrack islands, decaying clumps of stranded kelp, were examined on a central California high energy beach. Samples from wrack algae and the underlying sand were taken at periodic intervals following island deposition. Mean density and number of different species fluctuated in regular and complementary patterns. Multivariate analysis distinguished early, mid, and late colonizing species. Dipterans and amphipods were initial colonizers succeeded largely by Coleoptera. Temporal changes in faunal populations are attributed to physical and biological factors degrading the wrack and reducing its potential as a resource. Beach wrack is a major nutrient source and substrate shelter for a majority of indigenous beach fauna. The sandy marine beach supports a large variety of macroinvertebrates pri- marily associated with decaying organic debris or beach wrack (Yaninek 1980). Marine macrophytes, deposited on the beach in discrete clumps or islands, are the major wrack source. Wrack islands provide beach fauna with nutrients, shelter, and a hospitable environment for reproduction and growth. Amphipods account for the greatest biomass, dipterans are most abundant, and coleopterans most diverse (Yaninek 1980). Additional constituents include pseudoscorpions, iso- pods, centipedes, spiders, mites, collembolans (Moore and Legner 1974a), and a microfauna of protozoa and bacteria (Eltringham 1971). High beach wrack is a limiting resource due to rapid algal decay, consumption, and environmental dis- turbances responsible for its degradation (Yaninek and Pitelka 1979). Ultimately, periodic wrack deposition is essential for the maintenance, and perhaps the very existence, of an indigenous shore community. Previous studies of the ecology of beach wrack have largely concentrated on the natural history of individual macroinvertebrate taxa. Bowers (1964) and Hayes (1974) studied amphipods and isopods, respectively, Egglishaw (1960), Dobson (1974), and Poinar (1977) seaweed flies, and Moore and Legner (1976) beetles. Others have examined the general ecology of beach wrack (Backlund 1945; Dahl 1952; Eltringham 1971; Pearse et al. 1942; Steele and Baird 1968), and species distributions (Craig 1970; Fawcett 1969). Few considered wrack faunal succession (Griffiths and Stenton-Dozey 1981; Moore and Legner 1974b; Yaninek 1980). This paper describes successional changes in the numbers and densities of macroinvertebrate species from selected high beach wrack islands. Beach wrack community structure and its relative importance to the shore ecosystem is dis- cussed. 2 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES CENTRAL CALIFORNIA Fig. 1. Map of the central California coastal region showing the location of the study site at Hazard Canyon Beach, San Luis Obispo county. Methods The Study Area One kilometer of shoreline at Hazard Canyon Beach, San Luis Obispo county (123°50'N by 35°08'W) was selected as the study site (Fig. 1). Being an open coast high energy beach, Hazard Canyon Beach receives full wave exposure. The beach, composed of fine-grained quartz sand (median particle diameter 400 um), follows a sharp acclivity from low to mid tidal level (beach slope ratio %) becoming a gently sloping berm for approximately 20 m into the high tide zone (slope 4;). It is backed by steep sand cliffs supporting a dune floral community of such species BEACH WRACK MACROINVERTEBRATES 3 as Artemisia pycnocephala, Franseria chamissonis, Lathyrus littoralis, Lupinus arboreus, and Abronia maritima (Munz and Keck 1968). Sampling Temporal changes of high intertidal beach wrack faunal populations were ex- amined for an 80 day period from 21 June to 10 Sept. 1981. Five wrack island cohorts, each consisting of five wrack islands of similar size, algal composition, tidal height, and proximity (within 5 m of each other) were sampled at 2-4 day intervals following initial deposition on the high beach, and thereafter, at about weekly intervals throughout each island’s life. New cohorts were selected from kelp deposited during the high-high spring tides. For each sampling period a sand and wrack sample were taken from one of seven randomly chosen positions of each cohort island. Since each island was roughly rectangular, island volume was calculated from measurements of island length, width, and height obtained using a meter cord. A sand sample consisted of an ’% by ’ m area of surface layer sand cored to a depth of 15 cm beneath a wrack island. A wrack sample constituted approximately '’ by ’ m area of semi-compacted seaweed cored directly above a sand sample. On the beach, the “‘bucket flotation technique” was used to separate organisms from each sample. Sand or wrack algae were lowered into a bucket of sea water causing adult, pupal, and larval macroinvertebrates to float to the surface. They were then dip-netted and preserved directly in 70% ethanol. In the laboratory, organisms were separated into species groups, counted, assigned numbers for easier reference, and usually identified to species using standard keys (Borror et al. 1981; Doyen 1976; Evans 1980; Moore and Legner 1976). Unidentified species were submitted to taxonomic specialists (Doyen, per. comm.; Schlinger, per. comm.). Due to the tendency for adult Diptera to fly away, and amphipods to sink in the collection bucket, early colonization of wrack by these forms was quantified with “‘sticky traps.” Traps were circular plastic plates (0.1 m in diameter) smeared with “‘tangle-foot” (Tangle-foot Company, Grand Rapids, Michigan). Three iden- tical wrack islands (initial volume = 0.5 mm), newly deposited in the high inter- tidal, where inundation was not a factor, were sampled beginning at 0600 at 12, 24, 36, 48, 72, 96, 120, and 148 hour intervals. The numbers of each species were recorded at respective intervals and new traps replaced. Each island was sampled with six replicate traps: two placed on the island near its center (“‘on wrack’’), and four evenly spaced adjacent to its perimeter on the sand (“on sand’’). Data Analysis Species counts were subjected to analysis of variance (ANOVA) and [-tests (prob. Ho: x sand = X wrack) to determine any significant differences between and within sampling positions of each cohort. To describe variations of species between cohorts, similarity correlations were calculated for all possible binary combinations using Dice’s Similarity Coefficient (Pielou 1977): A U B = # of species common to both cohorts A = # of species found in cohort A B = # of species found in cohort B 2(A U B) De (A + B) Unity indicates perfect correlation. 4 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 0.6 COHORT 1 COHORT 2 COHORT 3 COHORT 4 >@®#smOood COHORT 5 o oS o e nN MEAN WRACK VOL, (m’‘) = = 1 5 10 15 20 25 30 TIME (days) Fig. 2. Mean change in wrack volume throughout the sampling period for cohort’s one through five. Reciprocal averaging (RAVG) was used to provide a clearer representation (i.e., separation) of the successional stages by which shore macroinvertebrates colonize beach wrack. RAVG is a multivariate ordination technique utilizing presence- absence data to describe a community in terms of an environmental gradient. It iterates species scores (present = 1; absent = 0) and site scores (survey site | to n) to obtain the distribution of species conforming to a site gradient (Pimentel 1979). In this study the site scores become sampling periods thereby making the site gradient the successional trend through time. Species occurring more than once in all islands of a cohort for a given sampling period were considered as “‘residents.”” Only these species were used in the data analyses. Results Hazard Canyon Beach received an ample supply of deposited wrack algae, mainly Macrocystis pyrifera, Nereocystis luetkeana, and Egregia menziesii, during the sampling period. Wrack islands were typically deposited in localized groups of 10 to 15 islands (approximately 1—2 m in diameter) along relatively narrow sections of coastline (less than 50 m). Zostera marina strand occurred intermit- tently around and on unselected wrack islands. The texture and pigment conditions of the selected high beach wrack island kelp cohorts followed a typical decay sequence. Upon deposition they were dark brown, moist, and flexible, then gradually became wrinkled, less flexible and often BEACH WRACK MACROINVERTEBRATES 5 Table 1. Taxanomically categorized species list of macroinvertebrates collected from selected beach wrack cohorts during the study period. Unspecified species are adult forms. Reference numbers used for initial identification and computer analyses are shown. Asterisks indicate resident species. Taxa Reference number ARACHNIDA Acarina (mites) Bdellidae Neomolgus sp. T-21* Unidentified sp. T-89 Araneae (Spiders) Spirembolus mundus Chamberlin T-25 Pseudoscorpionida (pseudoscorpions) Garypidae Garypus californicus Banks T-41* CHILOPODA Geophilomorpha (centipedes) Schendylidae Nyctunguis heathii Chamberlin T-23* CRUSTACEA Amphipoda (beach hoppers) Talitridae Orchestoidea benedicti Shoemaker T-33* Orchestoidea californiana Brandt T-32* Isopoda (pill bugs) Oniscidae Alloniscus perconvexus Dana T-63 Tylos sp. T-84 Unidentified sp. T-60 INSECTA Coleoptera (beetles) Anabeidae Unidentified sp. T-80 Anthicidae Amblyderus obesus Casey T-95 Carabidae Anisodactylus californicus (larvae) Dejong T-58 Trechus ovipennis Mutschulsky T-19 Curculionidae Curculio sp. T-42 Emphyastes fucicola Mannerheim T-22 Histeridae Bacckmenniolus gandens LeConte T-39* Euspilotus scissus LeConte T-37* Hypocaccus bigemminus LeConte T-36* Neopachylopus sp. T-48 Unidentified larvae T-55 Hydrophilidae Cercyon luniger Mannerheim T-6* SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 1. Continued. Taxa Reference number Unidentified larvae T-46 Limnebiidae Octhebius rectua LeConte T-8 Melyridae Endeodes basilis LeConte T-66 Endeodes basilis (larvae) T-91 Mordellidae Mordella marginata Melsheimer T-52 Nitidulidae Carpophilus sp. T-93 Rhizophagidae Phyconomus marinus LeConte T-11* Salpingidae : Aegialites sp. T-20 Staphylinidae Aleochara sulcicolis Mannerheim T-3* Aleochara sp. T-17 Bledius monstratus Casey T-1* Cafius canescens Maklin T-2* Cafius luteipennis Horn T-16* Hadrotes crassus Mannerheim T-81 Omalium algarum Casey T-96 Pontomalota sp. T-14 Proteinus sp. T-18 Tarphiota geniculata Maklin T-4* Tarphiota pallidipes Casey T-5* Thinopinus pictus LeConte T-10 Thinusa maritima Casey T-15 Unidentified larvae T-65* Unidentified pupae T-92 Tenebrionidae Eleodes sp. (larvae) T-28 Phaleria rotundata LeConte T-73* Phaleria rotundata (larvae) T-29 Diptera (flies) Anthomyiidae Fucellia costallis Stein T-40* Fucellia costallis (larvae) T-45* Fucellia costallis (pupae) T-50 Coelopidae Coelopa vanduzeei Cresson T-30* Coelopa vanduzeei (larvae) T-64* Milichiidae Neophyllomyza sp. T-61 Sphaeroceridae Copromyza atra Meigen T-43* Copromyza atra (larvae) T-47* Copromyza atra (pupae) T-49* Unidentified eggs (T-30, T-40, T-43) T-62* BEACH WRACK MACROINVERTEBRATES 7 Table 1. Continued. Taxa Reference number Hymenoptera (bees and wasps) Ceratinidae Ceratina sp. T-77 Chrysomelidae Unidentified sp. T-24 Pteromalidae Unidentified sp. T-79 Vespidae Unidentified sp. T-12 Orthoptera (grass-hoppers, etc.) Gryllidae Unidentified sp. T-82 Gryllacrididae Stenopelmatinae Unidentified sp. T-75 Mantidae Stagmomantis sp. T-76 NEMOTADA (pin worms) Unidentified sp. T-44* - bleached lighter by the sun. Island volume (biomass) declined initially (one to five days) at a relatively rapid rate, then slowed to a low and steady loss through late succession (30 + days, Fig. 2). Although the interiors of each island retained the greatest amount of moisture, they eventually dried out completely to be blown away by wind, washed back out to sea, or further buried by sand. Faunal Composition Fifty-three species of macroinvertebrates comprising five classes, 12 orders, and 32 families were collected from selected wrack islands of the high intertidal (Table 1). The tidal heights of the cohorts and their collection dates are given in Table 2. The Coleoptera were most diverse, represented by 14 families, with over half of the species in the family Staphylinidae. Twenty-seven species of adult, larval, egg, or pupal stages were distinguished as residents. In all cases, except for dipteran pupae, unidentified taxa represent only a single species. Furthermore, in the cases involving only one adult and one unidentified larva (e.g., T-6, T-46) I strongly suspect the larvae to be the same species as the adults. Faunal Succession The succession of wrack invertebrates followed a characteristic pattern as re- vealed by RAVG multivariate analysis of combined sand and wrack presence- absence data. Species plots for each cohort separated resident species into three main areas which I have designated early (E), mid (M), and late (L) successional periods (Fig. 3). Site plots (i.e., sampling periods) reflect this species pattern 8 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 2. Sampling periods and intertidal beach deposition height above MLLW for all cohorts. ; Tidal Sampling dates nein 1 2 3 4 5 6 7 ft. Cohort 1 6/23 6/25 7/2 7/9 7/15 7/22 7/28 7.0 Cohort 2 7/23 7/25 8/2 8/10 8/18 8/25 8/31 6.8 Cohort 3 8/19 8/21 8/25 8/31 9/6 9/14 9/22 7.3 Cohort 4 9/5 9/7 9/11 9/17 9/25 10/3 10/7 6.5 Cohort 5 9/16 9/18 9/26 10/3 10/10 10/15 10/22 6.4 showing good distinction between successional periods (Fig. 4). In general, early colonizers were adult diptera (Coelopa vanduzeei, T-30; Fucellia costallis, T-40; Copromyza atra, T-43) and amphipods (Orchestoidea californiana, T-32; Or- chestoidea benedicti, T-33) as indicated by RAVG species plots and sticky trap data (Figs. 5 and 6). Diptera eggs (T-62) of at least two distinguishable sizes (approximately 2 mm and 4 mm) were also laid during this period. After raising some of these eggs to larvae, I found the small eggs to be Copromyza atra, and the large eggs to be either Coelopa vanduzeei or Fucellia costallis. The pattern of early colonization determined by sticky traps was similar in both ““on sand” and “‘on wrack’’ samples, but greater numbers of individuals were captured on the wrack samples and two more species were found on the sand samples. No significant differences were evident between the replicates of each sampling position (ANOVA: P-values > 0.05%). Wind was negligible during the sticky trap sampling period. Early successional species declined after about a week to be replaced by a large variety of mid successional forms (Fig. 3), dominated by staphylinid beetles (e.g., Cafius canescens, T-2; Aleochara gulcicolis, T-3; Tarphiota geniculata, T-4) and fly larvae (Coelopa vanduzeei, T-64; Copromyza atra, T-47, Fucellia costallis, T-45). Mites (Neomolgus sp., T-21), pseudoscorpions (Garypus californicus, T-41), and several other beetle families (Rhizophagidae, T-11; Histeridae, T-36 and T-37; Hydrophilidae, T-6) also established this stage. Later successional species were commonly adult terrestrial tenebrionids (T-35) and histerids (T-36 and T-39). In addition, Diptera pupae (T-49 and T-50) were regularly present during late succes- sion, and in some cases Fucellia costallis larvae, T-45 (see cohort one and five, Fig. 4). Diversity and Density Total mean densities for combined species (grand totals), not including adult Diptera or Amphipoda, varied widely between cohorts with cohort three exhib- iting a markedly higher density (Table 3). Greater population totals were evident in sand samples for cohort one and two, but in wrack samples for the other cohorts. None of the ¢-tests comparing sampling positions within cohorts were significant (0.1 > P-value > 0.05%, Table 3). Moreover, one-way ANOVAs revealed no significant differences (P-values > 0.05%) among either sand or wrack replicate island samples for each cohort (Table 4). Fluctuations of resident species were similar for sand or wrack samples of all BEACH WRACK MACROINVERTEBRATES 9 COHORT 1 COHORT 2 COHORT 3 Fig. 3. Reciprocal averaging (RAVG) species plots of combined sand and wrack sampling position presence-absence data for resident species throughout the sampling period of each cohort. Numbers correspond to species classifed as early (E), mid (M), or late (L) successional. Abcissa = first axis; ordinate = second axis. 10 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES COHORT 1 COHORT 2 COHORT 3 COHORT 4 7 COHORT 5 20 40 60 80 Fig. 4. Reciprocal averaging (RAVG) site plots of combined sand and wrack sampling position presence-absence data for resident species throughout the sampling period of each cohort. Numbers correspond to sampling periods. Abcissa = first axis; ordinate = second axis. cohorts (Fig. 7). Numbers of wrack species always increased relatively rapidly for the first few days following algae deposition (early succession), peaked for a few days during mid succession (two to three weeks), then gradually decreased through BEACH WRACK MACROINVERTEBRATES 11 vecseeeeee T 30 C. vanduzeei —-—--T40F. costallis T43 C,atra > Se (—) w i=) 100 MEAN Z¢ OF INDIVID./ 100 cm? ON WRACK Ly) o 15 i : / \ 10 ioe: Bet \ 12 24 36 48 72 96 120 148 TIME (HRS) Fig. 5. Mean number of adult dipterans (T-30, T-40, T-43) caught with sticky trap “on sand” samples for 148 hours following wrack island deposition (three islands, four replicates, N = 12). late succession (four to five weeks). Numbers of sand species increased more slowly than wrack species during early succession, stabilized at a higher relative maximum during later mid succession, then decreased rather quickly thereafter. At late succession, sand species were always greater than wrack species. Dice’s Similarity Coefficient disclosed a high correlation between all binary cohorts, with cohort one and two having identical resident species (Table 5). Mean density changes of all resident species combined (minus adult Diptera and Amphipoda) were also similar for either sand or wrack samples of all cohorts (Fig. 8). Wrack densities commonly increased rapidly to attain maximum values 12 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 50 400 srsesererteere T 30 C. vanduzeei —— — 132 O,californiana = — T 33 O. benedicti --——- 740 F. costallis 300 —— T43 C.,atra MEAN. OF INDIVID./100 cm2 ON SAND TIME (HRS) Fig. 6. Mean number of amphipods (T-32, T-33) and adult dipterans (T-30, T-40, T-43) caught with sticky trap “‘on wrack” samples for 148 hours following wrack island deposition (three islands, two replicates, N = 6). during early—mid succession, then gradually decreased to lower values by late succession. Sand densities increased more gradually during early succession, peaked by mid-late succession, then decreased relatively quickly. Discussion Open sandy beaches support an abundant, stable, and diverse meiofauna (McIntyre 1968; McLachlan 1977a), but generally sustain a relatively impover- ished macrofauna (Eltringham 1971; McLachlan 1977b). However, following de- BEACH WRACK MACROINVERTEBRATES 13 Table 3. Mean number of resident species per %, m? collected from sand (S) and wrack (W) sampling positions for each cohort overall sampling periods. Reference numbers and common names of each taxon identify species which are adult species unless specified as larval (L), pupal (P), or egg (E) forms. Sand, wrack, and grand totals are computed for each cohort, and f-tests compare sampling positions within each cohort. Amphipods and adult Diptera are not included due to inappropriate sampling technique. NS = number of resident species per cohort, n = number of sampling periods. Cohorts 1 3 4 5 NS = 15 NS = 15 NS = 20 NS = 21 NS = 14 Common name Ref. fui Sata pe eee Pane ter ee be al aby ig Sate of taxon num. S W S WwW S W S W S W Beetle T-1 15 5 15 8 6 3 85 36 9 2 Beetle T-2 25 16 20 13 6 5 11 4 39 25 Beetle T-3 25 35 34 144 95 171 100 114 75 71 Beetle T-4 62 18 68 28 66 24 60 52 12 4 Beetle T-6 133 220 52 121 20 75 111 379 93 197 Beetle T-11 375 140 272 159 740 #280 55 35 18 14 Beetle T-16 0 0 0 0 0 0 3 15 0 0) Mite T-21 0 0 0 0 13 DD) 12 28 16 30 Centipede T-23 0 0 0) 0 8 3 18 10 0 0 Beetle T-36 22) 7 28 5 9 3 12 6 0 0) Beetle T-37 0 0 0 0 8 8 DD 8 0 0) Beetle T-39 185 25 192 32 182 83 115 9 0 0 Pseudosc. T-41 0 0 0 0 42 31 11 11 0 0 Nematode T-44 0 0 0) 0 0 0 10 29 0 0) Fly (L) T-45 125 230 32 243 430 1450 151 310 155 345 Beetle (L) T-46 0 0 0 0) 32 25 48 28 197 88 Fly (L) T-47 322 151 380 145 110 355 77 23 +369 144 Fly (P) T-49 620 180 750 219 £510 202 513 252 #4410 140 Fly (P) T-50 32 8 133 18 28 10 92 33 16 4 Fly (E) T-62 230 570 210 = # «4518 80 145 210 680 205 £495 Fly (L) T-64 13 27 25 109 26 102 110 426 108 329 Beetle (L) T-65 10 15 8 24 0 0 0 0 0 0 Beetle T-73 0 0 0 0 10 39 0 0 0 0 Total 2194 1647 2219 1786 2421 3036 1826 2488 1722 1888 Grand total 3841 4005 5457 4314 3610 t-value 0.055 0.068 0.073 0.051 0.085 position of kelp wrack on the high shore, this study has shown that populations of macroinvertebrates increase markedly in abundance and diversity. Wrack fau- nal succession exhibited three distinguishable stages in all five sampled cohorts implying a regular and predictable sequence. Early successional species were flies and amphipods, replaced by a wide variety of mid successional forms (coleop- terans, pseudoscorpions, isopods, mites, etc.), eventually succeeded by more ter- restrial late successional Coleoptera. The high beach wrack successional cycle is curtailed by physical and biological factors which eventually limit the wrack resource. Physical Factors The amount of algae deposited on the beach increases with seasonal storms or high swell activity (Neushul 1967; ZoBell 1971). The kelps, having large surface 14 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 4. One-way analyses of variance comparing mean number of resident species from sand or wrack sampling positions between all sampling periods for each cohort (N = 5). P-value > 0.05% in all cases. ANOVA Source of variation df SS MS F Cohort 1 wrack 4 2374.658 593.644 1.324 Error 70 31,387.097 448.389 Total 74 33,761.755 Cohort 2 wrack 4 1619.396 404.849 0.767 Error 70 36,948.415 527.835 Total 74 38,567.811 Cohort 3 wrack 4 4614.347 1153.587 1.465 Error 95 74,805.964 787.431 Total 99 79,420.310 Cohort 4 wrack 4 3140.792 785.198 1.337 Error 100 61,664.768 587.283 Total 104 64,805.560 Cohort 5 wrack 4 1153.713 288.428 0.731 Error 65 25,646.828 394.566 Total 69 26,800.540 Cohort | sand 4 2773.787 693.447 1.783 Error 70 27,224.491 388.921 Total 74 29,998.277 Cohort 2 sand 4 1530.120 382.830 0.892 Error 70 30,019.171 428.845 Total 74 31,549.291 Cohort 3 sand 4 7524.334 1881.108 2.234 Error 95 79,993.420 842.036 Total 99 87,517.753 Cohort 4 sand 4 1836.354 459.885 0.666 Error 100 72,378.821 689.322 Total 104 74,215.175 Cohort 5 sand 4 2208.913 552.228 1.334 Error 65 26,907.673 413.964 Total 69 29,116.586 areas and a tendency to float on or near the water’s surface, are likely to uproot and drift. Depending on local currents and the wind, kelp rafts may be stranded on a sandy shore. By combining knowledge of such physical parameters with the location of offshore kelp beds a general prediction of the seasonal quantity of wrack deposited on any given beach should be possible. Prima facie, long beaches with wide berms provide greater surface area and potentially receive the most wrack. Persistence of wrack on the shore depends on intertidal island position and the rate of algal degradation. Three subzones based on the reach of the tides and the lag time following deposition can be recognized (slightly modified from Moore and Legner 1974a): BEACH WRACK MACROINVERTEBRATES 15 20 COHORT 1 20-] COHORT 2 15 15 10 S 10 5 5 Ww Ww 1 5 10 15 20 25 30 35 1 5 10 15 20 25 30 35 wn @ re) ® 20-44 conorT 3 20-7 COHORT 4 a. NM 15 15 = S c 10 10 ® S TW 5 5 w wn o a 41 5 10 415 20 25 30 35 1 5 10 15 20 25 30 35 eS ce) e 20-7 COHORT 5 fe) 15 10 TIME (days) Fig. 7. Numbers of resident species from sand (S) and wrack (W) sampling positions throughout the sampling period for each cohort. 1). Area of fresh seaweed (left for one to three days, 4 ft tide level). 2). Area of decaying seaweed, wetted by occasional high tides (left for 4-15 days, 6 ft tide level). 3). Area of dry seaweed, wetted only by the highest tides of the month (left for 15+ days, 7 ft tide level). Table 5. Dice’s similarity correlation coefficients for all binary combinations between all cohorts. Unity indicates perfect correlation and identical species diversities. Cohort 1 Cohort 2 Cohort 3 Cohort 4 Cohort 5 Cohort 1 1.00 1.00 0.76 0.77 0.80 Cohort 2 1.00 0.76 0.77 0.80 Cohort 3 1.00 0.85 0.82 Cohort 4 1.00 0.83 Cohort 5 1.00 16 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES ee ee C2 = ee C3 ae =e 3 ete = We Wie ae ae ae C4 a i es ea Se ake Sak ae = ee C 5 = ee I tae. a= : 22 ee eee = i 1000/1 a2 ----W TIME (days) Fig. 8. Mean densities of combined resident species per 4, m? from sand (S) and wrack (W) sampling positions throughout the sampling period for each cohort. The pattern of succession described by this study for high beach wrack (subzone three) may be quite different for lower intertidal wrack since each subzone supports characteristic macroinvertebrates (Moore and Legner 1974b). Tidal submergence of wrack may prolong island life by adding moisture and perhaps replenishing nutrients (e.g., bacteria, surf plankton) needed for faunal growth and reproduction. However, it may push back the successional cycle by driving out several vulnerable wrack residents. Parenthetically, an island may be washed back out to sea, re- positioned on the beach, or further buried by sand following inundation. It is plausible that the original island deposition site is quite stable. Yaninek and Pitelka (1979) found some wrack islands remained in their originally deposited positions for up to 140 days, and Lavoie (1982) determined the location of reinundated islands to be relatively unaffected by rising tides. Undoubtedly, wave action and wind intersperses sand between the stipes of the kelps to establish an effective anchor for the entire island. Sun and wind dry out the wrack, reduce its suitability as a resource, and thereby stunt the successional cycle. The desiccation sequence, which followed moisture loss from the outside toward the wrack’s interior, could largely account for in- creasing densities and diversities of sand positions towards later succession (Figs. 7 and 8). I suspect moisture is an essential requirement for a majority of the wrack constituents. The fact that the larger volume cohorts supported a progressively greater variety BEACH WRACK MACROINVERTEBRATES 17 and quantity of macroinvertebrates (correlation coefficient r = 0.871; P-value < 0.05%: see Table 3 and Fig. 2) suggest a species-area relationship (Conner and McCoy 1979; MacArthur and Wilson 1967; Preston 1960). Larger islands re- quiring a longer time to desiccate and decay offer greater stability, added habitat, and more potential food. Additionally, larger islands should more effectively reach higher interior decay temperatures and reduce developmental times of egg and pupal stages (Poinar 1977). However, time of development may be based more on the frequency of inundation as determined by the tidal height of islands up the shore. Kompfner (1974) postulated high beach wrack larvae and pupae have longer developmental periods than species of lower beach wrack. It follows, the maturation time of given beach residents required to achieve successful repro- duction must be less than the life of the chosen ““home”’ island. For some species (particularly larval stages) maturation probably must occur before the detrimental effects of the rising tides (Yaninek 1980). Biological Factors Species interactions, patchiness, variable feeding, dispersal, reproductive rates, and even inhibitory effects may affect the successional cycle of high beach wrack organisms. Initial consumption of kelp by amphipods (Griffiths and Stenton- Dozey 1981) and subsequent feeding by dipteran larvae may severely deplete wrack biomass. Perhaps, initial colonizers establish physiological conditions re- quired by mid successional species which, in turn, modify the substrate for later forms. Egglishaw (1960) noticed feeding larvae greatly enhanced wrack decom- position and Rowell (1969) found certain sandy beach organisms have food re- quirements dependent upon bacterial synthesis. Connell and Slatyer (1977) crit- icize such a “‘facilitation model” and favor an “inhibition model” whereby early colonists preempt space and resist invading competitors until they die and release the resource to their successors. Although data for other systems are largely con- sonant with the “inhibition model’’ (Lubchenco and Menge 1978; Souza 1979), it seems an alternative “‘tolerance model” better describes wrack succession. This latter hypothesis accounts for a predictable sequence resulting from differing ad- aptations of early, mid, or late successional species (Stearns 1982). For example, adult flies and amphipods, which require highly moist environments for feeding on mucous and laying eggs, decline after a week or so as the wrack dries out and more tolerant mid successional forms invade the wrack, which then are replaced by even more desiccation resistant or terrestrially adapted species. Thus, the physical degradation of wrack by environmental factors alone may determine the physiological tolerances that select for given constituents. Patchinesss may result from beach species congregating at localized wrack co- horts, randomly distributed along the shore. Perhaps this explains the much higher abundance of Coelopa vanduzeei (T-30) and the coincident decrease in density for Fucellia costallis (T-40) on the second day (24—48 hours) of sticky trap sam- pling (Fig. 6). Patchiness may also arise from diurnal, nocturnal, and tidal bio- rhythms, quite common on the shore (Craig 1970; Evans 1976; Moore 1975). A diurnal rhythm seems evident for all three dipteran species during the first 48 hours of sticky trap sampling (Figs. 5 and 6), possibly due to decreased night- time temperatures. Organisms (e.g., flies and amphipods) most capable of long range dispersal 18 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES should colonize newly deposited wrack islands first. Although both visual and chemical cues may be utilized to locate any new islands the sticky trap data in this study did not detect a chemotaxic response. Had there been a predominating wind and chemical dispersal the leeward replicate samples should have captured more individuals. The much higher densities obtained with the “ton wrack”’ sam- ples suggests macroinvertebrate orientation was visual. Predators, scavengers, saprovores, herbivores, and detritivores constitute sev- eral dynamic trophic levels of the beach wrack community (Lavoie 1985). Un- doubtedly, both intra and interspecific interactions involving predation, compe- tition, and parasitism, influence the beach wrack community structure. A large number of predatory forms (Staphylinidae, Histeridae, Carabidae, and Hydro- philidae larvae) suggests the attainment of maximum diversity during mid succes- sion can, in part, be explained by the “‘predation hypothesis’’ (Lubchenco 1978). Predators, by preventing competitive exclusion and high prey abundances, select for greater variety of species (Paine 1966). Orth and others (1977) contend that adult Staphylinidae have a substantial impact on the density of seaweed flies and posit the use of certain species for biological control of noxious beach Diptera. Additionally, the ecological impact of parasitic forms has not been adequately investigated, but may prove to be considerable. Backlund (1945) observed high population levels of parasititc Hymenoptera on Diptera pupae and adult stages, and Yaninek (1980) cited heavy infestations of phoretic mites on adults of Coelopa vanduzeei (T-30). Larval monopolies, reported by Egglishaw (1960), Dobson (1974), and Yaninek (1980), may occur as early colonizers rapidly reproduce. The greater mean density of cohort three (Table 3), attributable to high numbers of Copromyza atra larva (T-47), seems to infer such a monopoly. However, since this effect did not reduce the number of different species or disrupt the characteristic pattern of succession, I suspect competitive exclusion is not an important selective pressure in this community. Although it is possible larger wrack island volumes would allow for effective monopolization. Egglishaw (1960) postulates that larval populations may reduce species diversity through the release of inhibitory substances. Zostera marina, which is sometimes deposited concurrently with kelp, was determined by Harrison and Chan (1980) to inhibit the growth of decaying bacteria. Its presence could significantly alter brown kelp wrack succession and may explain the considerably higher macroin- vertebrate densities reported in brown compared to green algae wrack (Dobson 1976, Yaninek 1980). Ecological Implications Throughout this investigation wrack was usually present within the study site, and often, in large quantities. The question arises: what would happen to the beach fauna, many of which are endemic, during a long absence of wrack depo- sition? Obviously, species capable of flight may disperse to nearby beaches. How- ever, their movement may be impeded by rocky coastline or even the type of beach sand (e.g., coarse to fine). Lavoie (1981) found two species of Bledius (Staphylinidae) to be divided in range by fifteen miles of rugged coarse-grained beach of the Diablo Canyon region along the central California coast. It is also BEACH WRACK MACROINVERTEBRATES 19 possible that some forms burrow down into the sand and remain in a dormant or quiescent state until surface wrack is provided (Moore and Legner 1974a). Kompfner (1974) found larvae to survive for several weeks by burrowing into the sand. This strategy should select for longevity rather than quick reproductions. Theoretically, as decimated wrack becomes buried in the higher shore regions it establishes a below-sand detrital based community. Here macroinvertebrates might seek refuge, albeit at relatively low levels, during paucity of new wrack. At this stage further decomposition and consumption by infaunal species probably ensues. Eventually the degraded organic wrack debris is washed back into the marine system where it may supply an important and direct nutrient source to detritus feeding organisms (Griffiths and Stenton-Dozey 1981) and even surf phytoplank- ton blooms (McLachlan and Lewin 1981). McLachlan (1981) contends surf phy- toplankton to be a major food source of intertidal macrofauna filter feeders. In perspective, the presence of kelp wrack on the shore may have far reaching im- plications to the well being of the sandy beach and adjacent marine ecosystems. Ostensibly, beach organisms must be hardy to survive in the harsh and limiting environment of the shore. But, how adaptable are they to environmental catas- trophy? For instance, in the unfortunate event of a major oil spill or toxic pollutant discharge would beach species be endangered? It is probable that beach fauna are severely impacted by oil, which often accumulates on the shore (Mann and Clark 1978). Acting like sponges, wrack islands could retain heavy fractions of oil and become unsuitable for life support and colonization. An absence of Thalassotre- chus barbara (Carabidae) along several beaches following the 1969 Santa Barbara oil spill supports this contention (Evans 1970). Evans (1970) found the hydrofuge properties of wrack insects’ oleophilic cuticles, which allow them to resist wetting, are ineffective against oil. Logically, the predictability and susceptability of in- digenous wrack fauna make them good subjects for monitoring pollution. Conclusion This paper has shown the beach wrack community structure at Hazard Canyon Beach can be defined by three distinct stages of macroinvertebrate succession. The pattern is predictable for both types and numbers of species expected to be encountered in sand or wrack sampling positions during a given successional phase, but only quantitatively within the same cohort (1.e., islands deposited at the same time, same tidal height, and in close proximity). A “‘climax”’ stage is not achieved, and never will be, in high beach wrack because of physical or biological parameters which, after four or five weeks, result in deterioration of the ephemeral wrack resource. Thus, wrack faunal succession is not typical of that occurring in most marine or terrestrial systems, as the ratio of primary production to biomass decreases with progressing wrack decay. Beach wrack is undoubtedly an essential resource to the sandy beach fauna, virtually providing islands of plenty in a sea of sand. To thoroughly understand how the variable physical and biological factors influence beach wrack community structure and faunal succession will require more indepth investigations. Future beach wrack studies should focus on the role the macro and microfauna play in wrack decomposition and succession both on the high beach and in the lower intertidal. Behavioral studies in the laboratory and the field combined with ex- 20 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES tensive physical data are essential. Perhaps with such information the ecological impact of parasitic forms and environmental pollutants as well as the interrelated effects of each species in the dynamic beach ecosystem could be determined. Acknowledgments I appreciate the help of T. Doyen and E. Schlinger (UC Berkeley) in species identifications. I thank F. Clogston, D. Frey, L. Parker, and T. Richards (California Polytechnic State University) for helpful comments on various stages of research and earlier drafts of this paper. I am grateful to M. D. Robertson for generous assistance in data collections. I am also grateful to S. Yaninek (UC Berkeley) and C. Gardner (Florida State University) for several pertinent suggestions. I partic- ularly thank P. Stiling (Florida State University), who generously gave perceptive criticism and beneficial advice on the final draft. Lastly, D. Strong (Florida State University) provided a cheery perusal. Literature Cited Backlund, H. O. 1945. Wrack fauna of Sweden and Finland: ecology and chronology. Opusc. Ento- mol. Suppl., 5:1-238. Borror, D. J., D. M. Delong, and C. A. Triplehorn. 1981. An introduction to the study of insects, 5th ed. Saunders College Pub. Co., xii + 852 pp. Bowers, D. E. 1964. Natural history of two beach hoppers of the genus Orchestoidea (Crustacea: Amphipoda) with reference to their complemental distribution. Ecology, 45:677-696. Connell, J. H., and R. O. Slayter. 1977. Mechanisms of succession in natural communities and their role in community stability and organization. Am. Nat., 111:1119-1144. Conner, E. F., and E. D. McCoy. 1979. The statistics and biology of the species-area relationship. Am. Nat., 113:791-833. Craig, P. C. 1970. The behavior and distribution of the intertidal sand beetle, Thinopinus pictus (Coleoptera: Staphylinidae). Ecology, 51:1012-1017. Dahl, E. 1952. Some aspects of the ecology and zonation of the fauna of sandy beaches. Oikos, 4:1-27. Dobson, T. 1974. Studies on the biology of the kelp fly Coelopa in Great Britain. J. Nat. Hist., 8:155-177. 1976. Seaweed flies (Diptera: Coelopidae, etc.). Pp. 477-464 in Marine insects. (L. Cheng, ed.), North-Holland Pub. Co., xii + 581 pp. Doyen, J. T. 1976. Marine beetles (Coleoptera excluding Staphylinidae). Pp. 497-520 in Marine insects. (L. Cheng, ed.), North-Holland Pub. Co., xii + 581 pp. Egglishaw, H. 1960. The life history of Fucellia maritima (Haliday) (Diptera, Muscidae). Ent., 93: 225-231. Eltringham, S. K. 1971. Life in sand and mud. Crane, Russak and Co., vi + 218 pp. Evans, W. G. 1970. Thalassotrechus barbara (Horn) and the Santa Barbara oil spill (Coleoptera: Carabidae). Pan-Pac. Ent., 46:233-237. 1976. Circadian and circatidal locomotory rhythms in the intertidal beetle Thalassotrechus barbara (Horn): Carabidae. J. Exp. Mar. Biol., 22:79-90. —. 1980. Insecta, Chilopoda, and Arachnida: insects and allies. Pp. 641-658 in Intertidal invertebrates of California. (R. H. Morris, D. P. Abbott, and E. C. Haderlie, eds.), Stanford Univ. Press, xi + 690 pp. Fawcett, J.J. 1969. Zonation and temporal distribution of three species of beach-dwelling amphipods of the genus Orchestoidea (Talitridae). Unpublished M.S. Thesis, Univ. of California, Santa Barbara, vil + 73 pp. Griffiths, C. L., and J. Stenton-Dozey. 1981. The fauna and rate of degradation of stranded kelp. Est., Cstl. Shelf Sci., 12:645-653. Harrison, P. G., and A. T. Chan. 1980. Inhibition of the growth of micro-algae and bacteria by extracts of eelgrass (Zostera marina) leaves. Mar. Biol., 61:21-26. Hayes, W. B. 1974. Sand-beach energetics: importance of the isopod Tylos punctatus. Ecology, 55: 838-847. BEACH WRACK MACROINVERTEBRATES 21 Kompfner, H. 1974. Larvae and pupae of some wrack dipterans on a California beach (Diptera: Coleopidae, Anthomyiidae, Sphaeroceridae). Pan-Pac. Ent., 50:44—52. Lavoie, D. R. 1981. Ecology and identification of the marine beetles inhabiting beach wrack of the central California coast. Pac. Gas & Elec. Co., Dept. Eng. Res., Ann. Rep. 411, 52 pp. . 1982. Population dynamics and ecology of beach wrack invertebrates of the central California coast, with notes on natural history. Unpublished M.S. Thesis, Calif. Polytechnic State Univ., San Luis Obispo, xii + 96 pp. . 1985. Beach wrack. Outdoor Calif. In press. Lubchenco, J. 1978. Plant species diversity in a marine intertidal community: importance of her- bivore food preference and algal competitive abilities. Am. Nat., 112:23-29. , and B. A. Menge. 1978. Community development and persistence in a low rocky intertidal zone. Ecol. Monogr., 53:67-91. MacArthur, R., and E. O. Wilson. 1967. The theory of island biogeography. Princeton Univ. Press, 203 pp. Mann, K.H., and R. B. Clark. 1978. Long-term effects of oil spills on marine intertidal communities. J. Fish. Res. Bd. Can., 35:791-795. McIntyre, A. D. 1968. The meiofauna and macrofauna of some tropical beaches. J. Zool. Lond., 156:377-392. McLachlan, A. 1977a. Studies on the psammolittoral meiofauna of Algoa Bay II. The distribution, composition and biomass of the meiofauna and macrofauna. Zool. Afr., 12:33-60. . 1977b. Composition, distribution, abundance and biomass of the macrofauna and meiofauna of four sandy beaches. Zool. Afr., 12(2):279-306. 1981. Exposed sandy beaches as semi-closed ecosystems. Mar. Env. Res., 4:59-63. , and J. Lewin. 1981. Observations on surf phytoplankton blooms along the coasts of south Africa. Bot. Mar., 24:553-557. ; Moore, I. 1975. Nocturnal Staphylinidae of the southern California sea beaches. Ent. News, 86: 91-93. , and E. F. Legner. 1974a. Seashore entomology, a neglected fruitful field for the study of biosystematics. Insect World Digest, 4:20-24. 1974b. Succession of the coleopterous fauna in wrack. Wasmann J. Biol., 31:289-290. 1976. Intertidal rove beetles (Coleoptera: Staphylinidae). Pp. 521-553 in Marine insects. (L. Cheng, ed.), North-Holland Pub. Co., xii + 581 pp. Munz, A. P., and D. D. Keck. 1968. A California flora. Univ. of Calif. Press, Berkeley, 1681 pp. Neushul, M. 1967. Studies on subtidal marine vegetation in western Washington. Ecology, 48: 83-94. Orth, R. E., I. Moore, and T. W. Fisher. 1977. Year-round survey of Staphylinidae of a sandy beach in southern California. Wasmann J. Biol., 35:169-195. Paine, R. T. 1966. Food web complexity and species diversity. Am. Nat., 100:65-76. Pearse, A. S., H. J. Humm, and G. W. Wharton. 1942. Ecology of sand beaches at Beaufort, N.C. Ecol. Monogr., 12:135-190. Pielou, E.C. 1977. Mathematical ecology. John Wiley and Sons, x + 384 pp. Pimentel, R. A. 1979. Morphometrics, the multivariate analysis of data. Kendall/Hunt Pub. Co., x + 276 pp. Poinar, G.O. 1977. Observations of the kelp fly, Coelopa vanduzeei (Cresson) in southern California (Coelopidae: Diptera). Pan-Pac. Entomol., 53:81-86. Preston, F. W. 1960. Time and space and the variation of species. Ecology, 41:611-627. Rowell, M. J. 1969. Studies on the laboratory culture, anatomy, and nutritional requirements of Coelopa frigida. Unpublished Ph.D. Dissertation, Univ. of Durham, 156 pp. Sousa, W. P. 1979. Experimental investigations of disturbance and ecological succession in a rocky intertidal algal community. Ecol. Monogr., 49:227-254. Stearns, S.C. 1982..The emergence of evolutionary and community ecology as experimental sciences. Persp. Biol. and Med., 25(4):621-648. Steele, J. H., and I. E. Baird. 1968. Production ecology of a sandy beach. Limnol. Oceanogr., 13: 14-25. Yaninek, J. S. 1980. Beach wrack: phenology of an important limiting resource and utilization of macroinvertebrates of sandy beaches. Unpublished M.S. Thesis, Univ. of Calif. Press, Berkeley, 159 pp. 22 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES , and F. A. Pitelka. 1979. The role of algal wrack in sand beach community dynamics. Univ. of Calif. Sea Grant College Prog. Ann. Rep. 67, 7 pp. ZoBell, C. E. 1971. Drift seaweeds on San Diego county beaches. Pp. 269-314 in The biology of giant kelp beds (Macrocystis) in California. (W. J. North, ed.), Beihefte Zur Nova Hedwegia, 32:269-314. Accepted for publication 30 January, 1984. Department of Science Education, The Florida State University, Tallahassee, Florida 32306. Bull. Southern California Acad. Sci. 84(1), 1985, pp. 23-37 © Southern California Academy of Sciences, 1985 The Occurrence and Distribution of Terrestrial Isopods (Oniscoidea) on Santa Cruz Island with Preliminary Data for the Other California Islands Ronald L. Garthwaite, F. G. Hochberg, and C. Sassaman Abstract.—The occurrence and distribution of terrestrial isopods (Oniscoidea) on Santa Cruz Island with preliminary data for the other California islands by R. Garthwaite, F. G. Hochberg, and C. Sassaman. Bull. Southern California Acad. Sci., 84(1):23-37, 1985. During September and October of 1982 sixty locations on Santa Cruz Island, California, were examined for the presence of terrestrial isopods. Isopods were found at 58 of these locations. Thirteen terrestrial isopod species were found—seven littoral species and six non-littoral species. Eight of these species are Pacific coast endemics, three others are European introductions, and two are of uncertain origin. Terrestrial isopods on the island were found to be nearly as diverse as those on the adjacent mainland both with respect to the total number of species and the average number of species per collection site. The local distributions of littoral species on the island reflect the distributions of their preferred microhabitats. Microhabitat may also affect the distribution of non- littoral species, although there may be a significant historical component to their current distributions. Preliminary collection data are given for the other southern California islands. While the terrestrial isopod (Oniscoidea) fauna of North America is depauperate when compared to many other areas of the world, it nevertheless forms a rather large and diverse assemblage. Although many aspects of terrestrial isopod tax- onomy are still in turmoil, there are approximately 100 species north of Mexico, about one third being endemic (Van Name 1936). Many of the remaining species, indeed almost all of the widely distributed and commonly encountered ones, have been introduced into North America from the Old World (particularly Europe) by man (Van Name 1936). Although terrestrial isopods are common and widely distributed throughout much of North America, precise distributional data are, more often than not, sparse and dated. This lack of records is certainly true of California. Even though the California fauna includes approximately 27 terrestrial isopod species, no com- prehensive distributional studies have been reported. Those reports that do exist (Menzies 1950; Miller 1938, 1975; Richardson 1905; Van Name 1936; and others) are patchy and California oniscoids often have more extensive ranges than the literature indicates. Over the past several years we have been collecting isopods throughout North America and particularly in California. This paper reports the findings of a series of collections of terrestrial isopods made on Santa Cruz Island, California. The biota of Santa Cruz Island has been the subject of extensive investigations (Philbrick 1967; Power 1980; for a review see Woodhouse 1981). Some of these investigations have been concerned with intertidal or littoral species and at least 24 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES SCORPION HARBOR FRYS HARBOR PELICAN BAY ROCK | Y/ SLIDE PRISONERS CHRIST! _-—/ @ 25 COVE Fig. 1. Location of the 60 Santa Cruz Island sites examined in this study (see methods for criteria used in choosing collection sites). Closed circles represent sites where isopods were found. Open circles represent sites where apparently suitable habitat was examined but no isopods were found. Also indicated are locations from which oniscoids have been previously reported (see text), and the locations of the seven sites from which the Santa Barbara Museum of Natural History specimens were collected (squares). three (Hewatt 1946; McGill 1978; Straughan and Hadley 1980) have reported the occurrence of oniscoids. There have been, however, no comprehensive reports on the terrestrial isopods of this island. We examined a total of 60 sites on the island for terrestrial isopods during September and October of 1982. Sites were chosen by seeking out areas of suitable isopod habitat (i.e. more or less permanently damp places). If isopods were found in these habitats, representative samples were collected by hand (from a total area usually less than 2 sq m), returned to the laboratory alive, and identified using the following references: Hatch 1947; Menzies 1950; Miller 1975; Mulaik and Mulaik 1942; Richardson 1905; Schultz 1970; and Van Name 1936, 1940. Dis- tribution records were supplemented by an additional seven collections (made in late March and early April of 1983) from the invertebrate collection at the Santa Barbara Museum of Natural History (see Fig. 1). The eastern end of the island and much of the northern coast were not examined by us because they are not easily accessible. Some of the other areas of the island (particularly the south- western interior, Fig. 1) were surveyed for suitable habitats but contained none. Representative specimens are archived in the Department of Invertebrate Zoology at the Santa Barbara Museum of Natural History. Results Terrestrial isopods were quite common and widespread on Santa Cruz Island; we found isopods in all but two of the sites examined. Figure | shows the location of the 58 collection sites (closed circles) plus the two sites (open circles) where apparently suitable habitat was examined but no isopods were found. Also shown in Figure 1 are the locations of sites from which terrestrial isopods have been previously reported (see below). Our collection sites can be divided into four categories with respect to habitat: 1) littoral sites (sites 1-21), 2) sites along permanent streams (sites 22—43), 3) sites near cattle troughs (sites 44-54), and 4) damp areas not associated with standing SMUGGLERS . SANTA CRUZ ISLAND ONISCOIDS 25 water (sites 55-58). Thirteen species of isopods were collected on the island— seven littoral species: Ligia occidentalis Dana 1853, Armadilloniscus holmesi Arcangeli 1933, Armadilloniscus lindahli (Richardson 1905), Littorophiloscia richardsonae (Holmes and Gay 1909), Alloniscus perconvexus Dana 1856, Allon- iscus mirabilis (Stuxberg 1875) (=Alloniscus cornutus Budde-Lund 1885; Schultz, pers. comm.), and Tylos punctatus Holmes and Gay 1909; and six non-littoral species: Porcellio laevis Latreille 1804, Porcellio dilatatus Brandt and Ratzeburg 1833, Porcellio scaber Latreille 1804, Porcellionides sp., Armadillidium vulgare (Latreille 1804), and Venezillo microphthalmus (Arcangeli 1932). Eight of the species collected are Pacific coast endemics (all of the littoral species plus V. microphthalmus), three are almost certainly European introductions (P. /aevis, P. dilatatus, and A. vulgare), and two are of uncertain origin (P. scaber and Porcel- lionides sp.). Table 1 summarizes the occurrences of the thirteen species. A brief discussion of each species follows. Pacific Coast Endemic Species Tylos punctatus Holmes and Gay 1909 Tylos punctatus has a more southerly distribution on the mainland. It is common in Baja California, Mexico (Brusca 1980; Hamner, Smith, and Mulford 1968, 1969; Hayes 1977) and can be found sporadically in the San Diego area. North of San Diego it is much rarer and is seldom found north of Newport Bay (Garthwaite, unpublished data; Hayes 1977). Tylos punctatus is restricted entirely to sandy beaches where it burrows just above the most recent high tide line. On Santa Cruz Island this isopod is found on the west and southwest coasts (Table 1) where most of the extensive sandy beaches are located. A few individuals were collected at West End (site 3), Johnsons Lee (site 8), and the beach at Laguna Harbor (site 12). This isopod is exceedingly common, however, on Christi Beach (site 4) where it reaches densities similar to those found in Baja California. Tylos punctatus was also reported from Christi Beach (Fig. 1) by Hewatt (1946) and from Black Point (Fig. 1) by Straughan and Hadley (1980). Ligia occidentalis Dana 1853 Ligia occidentalis is quite common on the mainland from San Francisco to the Gulf of California, Mexico (Garthwaite, unpublished data; Mulaik 1960; Van Name 1936), and was also common and widespread on Santa Cruz Island (Table 1), usually occurring on the more rocky beaches. Hewatt (1946) reported this species from Scorpion Harbor, Smugglers Cove, and the Prisoners-Pelican rock slide (Fig. 1). McGill (1978) collected L. occidentalis at Prisoners Harbor and Frys Harbor (Fig. 1). Armadilloniscus holmesi Arcangeli 1933 This isopod is common on the southern California mainland and can be found from Washington to Magdalena Bay, Baja California, Mexico (Hatch 1947; Men- zies 1950; Mulaik 1960; Schultz 1971). On the island it was found only at Christi Beach (site 5) and Chinese Harbor (site 19), however it did occur in considerable numbers at the latter site. SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 26 ‘ds sapiuoyjaos0d €S AIGDIS 01]J2IAOd UISLIO UTeLII0U.) O€ St OC 16 $6 Z Sc JADE INA WANIPI]IPOULAP SNIDID]IP 01JaI40g OL SL 08 6 S$ 86 OOT SL € v SIAID] O1]J2I40g suononpojur uesdoing SNUDYIYdOAIIU O[/1ZaUAA I v6 £9 96 66 SIJIQDAIUA SNISIUO]] PE S€ 66 OI L6 OOT8 OOT OOT Gus v6 OOT SnxaAUuorsad SNISIUO]]¥ OO! £€ 9¢ us IDUOSPADYI1A D1IISOJ1YdOs0]}}1T v 1Yopul] SNISIUO]jIpoUAp 96 Sc ISQUAJOY SNISIUO]IPDULAP OO” “i OOT OOT I 001 SZ I S1]DJUAP1II0 VISIT t c6 86 9 snjojound sojd I, SOIWIAPUS JSBOD IYIDeg GC 8G0LG IC SCV CaCG CC, LC 20C Ol SEL OL SI wire cl- Cl UROL 6 8) “2 92S PF SS CI dS UOTDIT[OD “| angi UI dBUI UO SUOTILIO] 0} JOJO SIOQUINU d1Ig (\S—C¢ SITS) 19}eM BUIPULIS YIM Poye1OOsse jOU soyIs dwep pue “(pC-pp Sols) sYsnoI 9[11e9 IeoU SolIs ‘(€p-ZZ SO}IS) SOUS WINS ‘(| Z—] SOUS) SUIS [V10II1] WO “eIUIOJITED “Ppueys] ZNID eJULS UO SpOdoOst [eLI}Sa119} JO SUOTIOIT[OO JO (JUddIOd UT) UONIsOdwOd satsadg *] BQeL 27 SANTA CRUZ ISLAND ONISCOIDS Se 5 ee SO ee a a ee ee Bs a ie ee oe ee ee OoT OOT 9 8 € ‘ds sapiuo1jaa40g c OS 9 66 9€ (4 LS AIQDIS O1[2ILOg UIZIIO UTeLIZ0U.) 98 Sct OF ce IT 91 *8 88 It OS v6 I II OOTLE 06 Ef dUDSINA LUNIPY]IPOULAp 9 ce I Ol cs CI SNIDID/IP O1][9I40d OOT9 sc 09 OOT 8C OOTOOT86 68 8 C 6S OS 86 OOT II OOT I 8S 6 OT OOTOOT SIAQD] O1]]9IAOT suonlonpodur uvesdoing Z SNUDYIYAOAIIMA O[J1Z2UAA 98 SIJIQDAIUL SNISTUOTP snxaauodsad SnIsUo]] Pp QDUOSPADYIIA DIDSO[1YdO1OINT YopUul SnISUOo]]IpoULAy ISAULJOY SNISIUO[JIPDUAP S1]DIJUAP19I0 V181T snjojound soja I SOIWIIPUS 1SBOD IYIOeg re ee ee ee ee ee ee, 8¢ LS 9S SS HS ES TS IS OS 6h 8h Lb OF Sh bh Eh Th IP Ob GE BE LE SE SE. bE EE ZE IE OF dUIS UOTIOI]JOD S00 Sasaao0a5=—aaaoOoOoO@OQ@oooOEOEOEaunaIyIiIiuhaEaEaEoeoooo————aSeeeee ‘ponunuoy *] 21981 28 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Armadilloniscus lindahli (Richardson 1905) On the mainland, 4. lindahli extends from Cedros Island, Baja California, Mexico, to the San Francisco area (Menzies 1950; Schultz 1971). On Santa Cruz Island only a few individuals were found at Chinese Harbor (site 19, Table 1). Littorophiloscia richardsonae (Holmes and Gay 1909) Littorophiloscia richardsonae is common and widespread on the mainland oc- curring at least from Cedros Island, Baja California, Mexico, to Washington (Garthwaite, unpublished data; Hatch 1947; Mulaik 1960; Van Name 1936). It was found in moderate abundance at several island localities (Table 1): Christi Beach (site 5), Willows Anchorage (site 13), Valley Anchorage (site 14), and Chinese Harbor (site 21). Although L. richardsonae usually has a gray-brown color, among the isopods collected at Willows Anchorage was a white individual which appeared to entirely lack pigmentation in both the eyes and body. Alloniscus perconvexus Dana 1856 Alloniscus perconvexus is common and widely distributed along the mainland. It occurs at least from southern California to Washington (Garthwaite, unpub- lished data; Hatch 1947; Van Name 1936) but is much more common north of Point Conception than to the south (Garthwaite, unpublished data). Alloniscus perconvexus was widespread and common on Santa Cruz Island, and was collected at many of the littoral sites examined (Table 1). Like 7. punctatus this species is restricted to sandy beaches and is thus found primarily on the west and southwest coasts of the island. This species also was reported from Scorpion Harbor and Christi Beach (Fig. 1) by Hewatt (1946), and specimens collected on Santa Cruz Island in 1939 are contained in the collections of the Los Angeles County Museum of Natural History (labeled Channel Islands biological survey). Both island and mainland populations of A. perconvexus are highly variable in color and usually closely match the color of the sand in which they live (Garthwaite, unpublished data). On the island, however, a few orange individuals were found (at Johnsons Lee, site 7; and the beach at Laguna Harbor, site 12) which closely approximated the color of the partially dried kelp fronds under which the isopods were burrowed. Alloniscus mirabilis (Stuxberg 1875) Alloniscus mirabilis has previously been collected at Laguna Beach (Stafford 1913) and San Diego Bay (USNM catalog #46093). On the mainland we have collected this species at Newport Bay (Orange Co.), Pebble Beach (San Mateo Co.), and Point Piedras Blancas (San Luis Obispo Co.). On the island it was collected at several littoral sites and one stream site close to the beach (Table 1). Venezillo microphthalmus (Arcangeli 1932) The range of V. microphthalmus is more northern on the mainland and it is not commonly encountered. It has previously been collected at two localities in Tulare County (Woodlake and Hammond; Mulaik and Mulaik 1942); Jackson, near Sacramento (Mulaik and Mulaik 1942); and Saratoga, near San Jose (Van Name 1936). On Santa Cruz Island two individuals were collected along the stream that drains into Willows Anchorage (site 42, Table 1), and several individuals SANTA CRUZ ISLAND ONISCOIDS 29 were encountered in Santa Barbara Museum specimens collected just west of Prisoners Harbor (Fig. 1). European Introductions Porcellio laevis Latreille 1804, Porcellio dilatatus Brandt and Ratzeburg 1833, and Armadillidium vulgare (Latreille 1804) These three species are thought to have been introduced into North America by the actions of man (Van Name 1936). All three are common throughout California (Garthwaite, unpublished data; Miller 1938, 1975) and all three are also common on Santa Cruz Island (Table 1). Porcellio laevis and A. vulgare, in fact, are by far the most common non-littoral species on the island and together inhabit nearly all areas of suitable habitat examined (Table 1, Fig. 2). Porcellio dilatatus has a more restricted range on the island being found primarily in the east-central portion (Table 1, Fig. 2). Specimens of P. dilatatus collected on Santa Cruz Island in 1939 are contained in the collections of the Los Angeles County Museum of Natural History (labeled Channel Islands biological survey). Mainland populations of P. /aevis often contain individuals which, instead of being the usual brownish-gray color with black eyes, are white with black eyes (Garthwaite, un- published data). This color morph was also present on the island (site 33). Also present on the island (site 45) was a color morph of P. dilatatus which was visually indistinguishable from the tan morph described by Sassaman and Garthwaite (1980). This morph is rare but widespread in California (Sassaman and Garthwaite 1980). Finally, a white individual of A. vulgare was found at site 32 (base of La Cascada) which lacked eye and body pigmentation. Populations of A. vulgare typically show a great deal of color variation but individuals are usually some combination of gray, brown, and/or yellow. Uncertain Origin Porcellio scaber Latreille 1804 While this species is native to Europe and is thought by many to have been introduced to North America from Europe, there may also be a subspecies which is native to the Pacific Coast of North America (Arcangeli 1932; Hatch 1947; Miller 1938, 1975). Porcellio scaber is common all along the coast of California but has a more patchy distribution in inland areas of southern California (Garth- waite, unpublished data). It is moderately abundant on Santa Cruz Island, although it appears to be restricted primarily to the east-central portion of the island and Prisoners Harbor (Table 1, Fig. 2). Although P. scaber is usually dark gray in color, an orange individual with orange eyes was found at Prisoners Harbor (site 38). This color morph is similar in many respects to the tan morph of P. dilatatus (Sassaman, unpublished data) and, like the tan morph, is rare but widespread on the mainland (Sassaman and Garthwaite, unpublished data). Porcellionides sp. The Porcellionides on Santa Cruz Island is morphologically similar to P. prui- nosus (Brandt). It has been assumed that P. pruinosus was introduced to North America by man and has subsequently spread across much of the continent (Van Name 1936). In the course of investigations on this species throughout North 30 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Porcellionides sp. Porcellio dilatatus Porcellio scaber Armadillidium vulgare Porcellio laevis Fig. 2. The distributions of synanthropic species of terrestrial isopods on Santa Cruz Island. Closed circles represent collections made during this survey, open circles represent museum collections. SANTA CRUZ ISLAND ONISCOIDS 31 America, however, we have found that “P. pruinosus” is not a homogeneous species (Garthwaite and Sassaman, in prep.). At least two forms exist which are genetically, reproductively, and geographically isolated from each other. The is- land specimens are similar to the southwestern individuals on the mainland. It is not clear at this point which of these species has been introduced from Europe and thus which of these species is truly P. pruinosus. At any rate, Porcellionides sp. is widespread and common throughout mainland California (Garthwaite, un- published data) and is fairly abundant on Santa Cruz Island as well (Table 1). On the island it appears to be restricted, for the most part, to cattle trough sites on the eastern portion of the island (Fig. 2). Discussion Perhaps the two most interesting aspects of the Oniscoidea of Santa Cruz Island are: 1) that when compared to the adjacent mainland the oniscoid fauna is not terribly depauperate, and 2) that they are so ubiquitous. Table 2 contrasts the isopod species found on Santa Cruz Island with those found on the southern California mainland.* Santa Cruz Island possesses 13 species of terrestrial isopods and the southern Californian mainland 17. This diversity on the island is interesting in light of the fact that island faunas of terrestrial organisms are almost invariably depauperate when compared to main- land faunas. The California islands are not, in general, an exception (Power 1980). It is not surprising that the oniscoids do not follow this trend. The terrestrial isopods of southern California can, for the most part, be divided into two cate- gories: 1) littoral species (all of the endemic species listed in Table 2 except Ligidium lapetum Mulaik 1942, Ligidium latum Jackson 1923, Protrichoniscus heroldi Arcangeli 1932, and Venezillo microphthalmus) and 2) synanthropic species (the species listed under “‘European introductions” and “uncertain origin” in Table 2). Littoral species of oniscoids, because they live along the shore, are often washed by waves during high tides and storms and many are undoubtedly washed out to sea either individually. or clinging to debris (Hayes 1977; Menzies 1952). Many (if not all) littoral oniscoids can survive for long periods of time in sea water (Brusca 1966; Hayes 1977; Parry 1953; Wilson 1970). These factors make littoral oniscoids excellent candidates for colonizers of off-shore islands. Synanthropic species ought also to be good colonizers in areas of extensive human activity. Santa Cruz Island has a long history of human occupation (Glas- sow 1980), and has, in past years and to a more limited extent today, been host to extensive ranching operations (Brumbaugh 1980). Conspicuous by its presence on Santa Cruz Island is Venezillo microphthalmus, which has previously been reported only from central and northern California. Conspicuous by its absence from the island is Mauritaniscus littorinus (Miller 1936), which is a common and widespread littoral species on the adjacent main- land (Schultz, Garthwaite, and Sassaman 1982) and has also been found on San Miguel Island (see below). It is not surprising that neither Ligidium lapetum, L. * Not included in the table is a species of Venezillo (probably V. arizonicus (Mulaik 1942)) which is common in the deserts of southern California (Garthwaite, unpublished data) but which, due to its burrowing habits, would not have been collected using our methods even if it occurred on Santa Cruz Island. SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 32 Gx? ¢ I I ‘ds sapiuo1jaa10g ¢ S OI ‘I ¢ €l 4IQDIS 01]]AIO UISLIO UTeLID0U/) 6 ¢ (0) a ¢ el AADS]NA UANIPI]/IPDULAY s S Ol ‘IT ‘I ¢ €I SNIDIDIIP OYjaxd0g S16 ¢ Il 8°S ¢ ¢ Ol ‘I IT ‘¢ SAG Cl SIABD] O1]JAIA0d €l snoiupp sniujoyiYydojdv suoljonpoljul uesdoing ¢ ¢ S OI ‘I SNUJDYIYAOAIIUA O]]1ZIUAA ¢ €l SNULAO}]1] SNISIUDIJLUNDY II ‘6 ‘Z ¢ I ¢ €l SIJIGDAIU SnosIUuo]]P IT L LISORES ¢ Il ‘vl ¢ ¢ el SNXAAUOIAAd SNISIUO]]P ¢ 6 ‘7 ¢ I ¢ €l IDUOSPADYIIA DIISOJIYAOAOINT I tl YDpUul] SNISiuUo]/ipouay I €l ISAUJOY SNISUO]/IPDULAP ¢ ¢ SUD]ADIDUOAOD SNISIUO[JIPDUAP ZI IpJOAIY SNISMUOYIUIOA I UND] UNIpIs1T I unjadv] WNi1pis1T 9 Eats 9 ¢ 9 ‘PT 9° cl SI]DIUAP1II0 VISIT Il L iE L‘vil €l snjpjound soja I SOIWIIPUD 1SBOD IYIIeg dUSWIIIJ -BUTTR}eD SP[OYSIN, eleqieg edeoeuy edeoeuy edeoruy VAIN @) eBSOY jonsiy =: pueyurew ues eyueg ues eJUeS yseq SIPPIN = ISO ejues ejues ues BIWIOFI[eD purys] uzoyINnosg “S9OUIIIJOI IOJ 1X9} 99s (E] ‘ADAING yOOSUT BIUIOFITED Jo AjisdaAtuy) (Z] “AJOWSTH [eANIeNY JO wuNasnyy AyuNOD sajasuy soy ([] ‘AJOISTIE] [eIMeN JO wnasnyy esequeg elURS (OI ‘OP6] DWN UA (6 ‘6€61 Puc puke soUUINS (g ‘O86 A21PEH F uBYsNENs (/ ‘8261 IFOOW (9 (Pastas) 1861 BI9QYOOH (¢ “OPGT NEMO (p ‘L961 SPIT Puk UDAID (¢ “OP6T [19494909 (Z ‘1oded siyi ({ “(S[telap 1OJ 1x91 99S) {sNIIUOZIUD O[]IZIUaAA SI POPNOUI JON ‘spueISI puke PULUTeEU eIUIOJTTeD UJOYINOS dy] JO spodost [eLNsaLIa] “7 JQeL SANTA CRUZ ISLAND ONISCOIDS 33 latum, Protrichoniscus heroldi, nor Haplophthalmus danicus Budde-Lund 1877 were found on Santa Cruz Island since all four species are apparently quite rare in southern California, and the Ligidium spp. and P. heroldi are neither synan- thropic nor littoral. We have found L. /apetum and L. latum only at Refugio Creek (west of Santa Barbara) in southern California and H. danicus only at Marina del Rey (Schultz et al. 1982) and Riverside. In southern California P. heroldi has been collected only at Deep Canyon (3.5 miles south of Palm Desert) (University of California Insect Survey specimen #323027) and nine miles east of Joshua Tree (Insect Survey #297405). Several synanthropic species have distributions on Santa Cruz Island which may suggest a rather recent introduction via human activity. Three of these species (Porcellio dilatatus, P. scaber, and Porcellionides sp.) are restricted to the east- central portion of the island (Fig. 2). The distributions of these species correspond well with the major areas of human activity on the island. Most traffic to Santa Cruz Island is through Prisoners Harbor to the Stanton Ranch, the University of California Field Station, or the naval installation, all of which are in this east- central area. Porcellio laevis and Armadillidium vulgare are two synanthropic species which have much wider distributions on the island (Fig. 2). The difference in distribution between P. dilatatus, P. scaber, and Porcellionides sp. on the one hand, and P. laevis and A. vulgare on the other, may indicate that the latter species have been on the island much longer and have had more time to disperse, and/or that they are more capable of dispersal than the former species. Miller (1938) found that A. vulgare and P. laevis were more capable of withstanding stresses of high tem- peratures and desiccation than P. dilatatus, P. scaber, and Porcellionides sp. This greater tolerance would presumably make them more capable of dispersal. The fact that oniscoids collected on Santa Cruz Island in 1939 (Los Angeles County Museum of Natural History) contain only P. dilatatus and A. perconvexus would argue against a historical cause for the differences in distributions among these species. : Alternately, the differences in the distributions of these isopods on Santa Cruz Island may be caused by their different habitat requirements. Miller (1938) noted that each of these species occupied a characteristic habitat and related this habitat choice to differences in the physiologies of the isopods. Thus, the east-central portion of Santa Cruz Island may have physical, climatic, and/or biotic aspects which differ from the rest of the island; and P. dilatatus, P. scaber, and Porcel- lionides sp. may not be able to extend their range due to lack of suitable habitat. On Santa Cruz Island terrestrial isopods as a whole occupy nearly all areas of suitable habitat, being found at 58 of the 60 sites that we investigated. While we present no quantitative data, it is our experience that this is in sharp contrast to the situation on the mainland where large areas of apparently suitable habitat are not occupied (Garthwaite, unpublished data). For littoral species this difference may be due, in part, to human disturbance of mainland sites. For both littoral and non-littoral species it may also be an example of the phenomenon of density compensation and/or niche expansion (MacArthur, Diamond, and Karr 1972). Since island faunas are generally depauperate, those species that do exist there are able to increase in density or occupy niches in addition to those they would 34 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 20 SITES . 10 NUMBER NUMBER OF SPECIES PER SITE Fig.3. The frequency distribution of species diversity among: A) 58 Santa Cruz Island sites (mean = 1.98), and B) 29 southern California mainland sites (mean = 2.07). Broken line = littoral sites, solid line = littoral and non-littoral sites. occupy on the mainland because of the absence of competitors and/or predators. Thus oniscoids in general may be more common and widespread on Santa Cruz Island because competitors and predators are absent. A wide variety of animals apparently prey on oniscoids including birds (Schmidt & Olsen 1964), shrews, spiders, centipedes, frogs, carabid beetles (Sutton 1970, 1972), and opossums. Even though almost all mainland species of oniscoids occur on the island, some of these species have restricted ranges on the island as discussed above (Fig. 2). Thus isopods in some areas of Santa Cruz Island may be undergoing density compensation and niche expansion because competing species of oniscoids which have recently been introduced to the island have not yet dispersed to these areas. Density compensation and/or niche expansion have been found in several other organisms on the California islands including foxes (Laughrin 1980), birds (Dia- mond and Jones 1980), land snails (Hochberg, unpublished data), and plants (Philbrick 1980). Traskorchestia traskiana (Stimpson 1857), an amphipod which is very similar in ecology to many terrestrial isopods, also has been found to be more widespread on Santa Cruz Island than on the mainland (Busath 1980). It is interesting to note that while oniscoid diversity on the island and mainland is rather high, the diversity at any one site is rather low. Figure 3 shows the frequency distribution of species diversities among the island sites along with data from comparable mainland sites. The mode of the island distribution is 2 species/ site. Thus, while a total of 13 species of oniscoids was found on Santa Cruz Island, SANTA CRUZ ISLAND ONISCOIDS 35 most sites contained only a small number of these species (usually about 2). Mainland sites are similar to island sites in both the mode of species found per site and in the distribution of sites around this mode (Fig. 3). The low number of species per site is easy to understand in light of Miller’s work (1938), our own observations, and the observations of others (Edney 1968; Schultz 1972), which suggest that different species of oniscoids have significantly different microhabitat requirements. The difference in habitat between littoral and non-littoral species is obvious, but even within the littoral species there is a wide variety of microhabitats. Ligia occidentalis is found on or under rocks on the more rocky beaches. Tylos punctatus and Alloniscus perconvexus are found only on sandy beaches where they burrow into the sand at approximately the high tide line. Armadilloniscus holmesi and A. lindahli usually occur on rocks under freshly beached kelp. Littorophiloscia richardsonae inhabits similar rocky shores but is found higher up under drier kelp and other debris. Finally, Alloniscus mirabilis is usually found under rocks well above the high tide line. Non-littoral oniscoids may similarly subdivide the habitat on physiological grounds (Miller 1938). Less extensive collections have been made by one of us (FGH; see Hochberg 1981) on the other southern California islands. These data (with minor modifi- cations), along with records obtained from the collections of the Los Angeles Museum of Natural History, the Santa Barbara Museum of Natural History, and previous reports from the literature, are summarized in Table 2. While the faunal list for other islands is preliminary, since it does not represent the same degree of collecting effort that the Santa Cruz Island data do, it nevertheless demonstrates several important points. First, terrestrial isopods are, in general, widespread and common on the islands. Second, two species in addition to the 13 found on Santa Cruz Island occur on other islands: Mauritaniscus littorinus, the only southern California littoral species not found on Santa Cruz Island, was collected on an adjacent island (San Miguel); and Armadilloniscus coronacapitalis Menzies 1950, a species previously reported only from Tomales Bay (north of San Francisco), was collected on San Miguel and Anacapa Islands. Third, Venezillo microphthal- mus, which was previously reported only from central California, appears to be rather widespread on the islands, occurring on Anacapa and Santa Barbara Islands in addition to Santa Cruz Island. Acknowledgments We thank Richard Chacon, Scott Miller, and Ronald Yoshiyama for help in making collections. Isopods collected by the Santa Barbara Museum of Natural History were sorted and identified by Sharon Seyman and by M. Thun and Ernest Iverson, the latter through the courtesy of Dr. Richard Brusca (USC). The fol- lowing individuals were of great assistance in providing transportation and access to facilities on the various islands (for FGH): Dr. Carey Stanton (Santa Cruz Island Company), Dr. Lyndal Laughrin (UCSB-Santa Cruz Island Reserve), Doug Probst (Santa Catalina Island Conservancy), Al Vail (Vail & Vickers Ranch, Santa Rosa Island), Jan Larson (U.S. Navy, San Clemente Island), William Ehorn and staff (NPS, Channel Islands National Park). We would also like to thank Floria Parker for assisting in the preparation of the manuscript, and Saul Frommer for loan of the University of California Insect Survey specimens. 36 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Literature Cited Arcangeli, A. 1932. Isopodi terrestri raccolti dal Prof. Silvestri nel Nord-America. Boll. Lab. Zool. Gen. Agr., Portici, 26:121-141. Brumbaugh, R. W. 1980. Recent geomorphic and vegetal dynamics on Santa Cruz Island, California, pp. 139-158 in D. M. Power, ed., op. cit. (below). Brusca, G. J. 1966. Studies on the salinity and humidity tolerances of five species of isopods in a transition from marine to terrestrial life. Bull. So. Cal. Acad. Sci., 65:146-154. Brusca, R.C. 1980. Common intertidal invertebrates of the Gulf of California. Univ. of Ariz. Press, 513 pp. Busath, A. L. 1980. Genetic differentiation of the semi-terrestrial amphipod Orchestia traskiana in an expanded habitat on Santa Cruz Island, pp. 395-401 in D. M. Power, ed., op. cit. (below). Cockerell, T. D. A. 1940. The insects of California. Proc. 6th Pacific Sci. Cong., 4:283-295. Diamond, J. M., and H. L. Jones. 1980. Breeding land birds of the Channel Islands, pp. 597-612 in D. M. Power, ed., op. cit. (below). Edney, E. B. 1968. Transition from water to land in isopod crustaceans. Am. Zool., 8:309-326. Given, R. R., and D. C. Lees. 1967. Santa Catalina Island biological survey, survey report No. 1. Alan Hancock Foundation, University of Southern California. 126 pp. Glassow, M. A. 1980. Recent developments in the archaeology of the Channel Islands, pp. 79-99 in D. M. Power, ed., op. cit. (below). Hamner, W. M., M. Smith, and E. D. Mulford. 1968. Orientation of the sand-beach isopod Tylos punctatus. Anim. Behav., 16:405—409. : , and 1969. The behavior and life history of a sand-beach isopod, Tylos punctatus. Ecology, 50:442-453. Hatch, M. H. 1947. The Chelifera and Isopoda of Washington and adjacent regions. Univ. Wash. Publ. Biol., 10:155-274. Hayes, W. B. 1977. Factors affecting the distribution of Ty/os punctatus (Isopoda, Oniscoidea) on beaches in southern California and northern Mexico. Pac. Sci., 31:165-186. Hewatt, W. G. 1946. Marine ecological studies on Santa Cruz Island, California. Ecol. Monogrs., 16:186-208. Hochberg, F.G. 1981. Invertebrate fauna. 1. Arthropods: crustaceans and tardigrades, pp. I:48—52, II:197—202 in C. D. Woodhouse, ed., op. cit. (below). Laughrin, L. 1980. Populations and status of the island fox, pp. 745-749 in D. M. Power, ed., op. cit. (below). MacArthur, R. H., J. M. Diamond, and J. R. Karr. 1972. Density compensation in island faunas. Ecology, 53:330-342. McGill, T. J. 1978. Genetic divergence of mainland and insular populations of Ligia occidentalis (Oniscoidea—Isopoda). Ph.D. Thesis, University of California, Santa Barbara. Menzies, R. J. 1950. Notes on the California isopods of the genus Armadilloniscus, with the de- scription of Armadilloniscus coronacapitalis n. sp. Proc. Cal. Acad. Sci., 26:467-481. 1952. The occurrence of a terrestrial isopod in plankton. Ecology, 33:303. Miller, M. A. 1938. Comparative ecological studies of the terrestrial isopod crustacea of the San Francisco Bay region. Univ. Calif. Pub. Zool., 43:113-142. —. 1975. Phylum Arthropoda: Crustacea, Tanaidacea and Isopoda. Pp. 277-312 in Light’s manual: intertidal invertebrates of the central California coast. (R. J. Smith and J. T. Carlton, eds.), University of California Press, Berkeley, xvii + 716 pp. Mulaik, S. B. 1960. Contribucion al conocimiento de los isopodos terrestres de Mexico (Isopoda, Oniscoidea). Rev. Soc. Mex. Hist. Nat., 21:79-292. , and D. Mulaik. 1942. New species and records of American terrestrial isopods. Bull. Univ. Utah, 32:1-23. Parry, G. 1953. Osmotic and ionic regulation in the isopod crustacean Ligia oceanica. J. Exp. Biol., 30:567-574. Philbrick, R. N., ed. 1967. Proceedings of the symposium of the biology of the California islands. Santa Barbara Botanic Gardens, Santa Barbara, 363 pp. 1980. Distribution and evolution of endemic plants on the California islands, pp. 173-187 in D. M. Power, ed., op. cit. (below). SANTA CRUZ ISLAND ONISCOIDS 37 Power, D. M.,ed. 1980. The California islands: proceedings of a multidisciplinary symposium. Santa Barbara Museum of Natural History, Santa Barbara, vii + 787 pp. Richardson, H. 1905. A monograph of the isopods of North America. Bull. U.S. Nat. Mus., 54:i- liii, 1-727. Sassaman, C., and R. L. Garthwaite. 1980. Genetics of a pigment polymorphism in the isopod Porcellio dilatatus. J. Hered., 71:158-160. Schmidt, G. D., and O. W. Olsen. 1964. Life cycle and development of Prosthorhynchus formosus (Van Cleave 1918) Travassos, 1926, an acanthocephalan parasite of birds. J. Parasit., 50:721- 730. Schultz, G. A. 1970. A review of the species of the genus 7y/os Latreille from the New World (Isopoda, Oniscoidea). Crustaceana, 19:297-305. . 1971. A review of species of the family Scyphacidae in the New World (Crustacea, Isopoda, Oniscoidea). Proc. Biol. Soc. Wash., 84:477—488. . 1972. Ecology and systematics of terrestrial isopod crustaceans from Bermuda (Oniscoidea). Crustaceana, Supp. 3:79-99. ——,, R. L. Garthwaite, and C. Sassaman. 1982. A new family placement for Mauritaniscus littorinus (Miller) N. Comb. from the west coast of North America with ecological notes (Crus- tacea: Isopoda: Oniscoidea: Bathytropidae). Wasmann J. Biol., 40:77-89. Stafford, B. E. 1913. Studies in Laguna Beach Isopoda. J. Ent. & Zool., 5:161-172. Straughan, D., and D. Hadley. 1980. Ecology of southern California island sandy beaches, pp. 369- 393 in D. M. Power, ed., op. cit. (above). Sumner, E. I., and R. M. Bond. 1939. An investigation of Santa Barbara, Anacapa and San Miguel Islands. Unpubl. Ms., 73 pp. Sutton, S. L. 1970. Predation on woodlice; an investigation using the precipitin test. Ent. Exp. & Appl., 13:279-285. 1972. Woodlice. Ginn & Company, London, 144 pp. Van Name, W. G. 1936. The American land and fresh-water isopod Crustacea. Bull. Amer. Mus. Nat. Hist.,.71:1-535. 1940. A supplement to the American land and fresh-water isopod Crustacea. Bull. Amer. Mus. Nat. Hist., 77:109-142. Wilson, W. J. 1970. Osmoregulatory capabilities in isopods: Ligia occidentalis and Ligia pallasii. Biol. Bull., 138:96-108. Woodhouse, C. D., ed. 1981. Literature review of the resources of Santa Cruz and Santa Rosa Islands and the marine waters of Channel Islands National Park, California. Vol. 1:1-151, vol. 2:1- 106. Final Technical Report, National Park Service, San Francisco. Accepted for publication 11 February 1984. R. Garthwaite, Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543; C. Sassaman, Department of Biology, Uni- versity of California, Riverside, California 92521; F. G. Hochberg, Department of Invertebrate Zoology, Santa Barbara Museum of Natural History, 2559 Puesta Del Sol Road, Santa Barbara, California 93105. Bull. Southern California Acad. Sci. 84(1), 1985, pp. 38-40 © Southern California Academy of Sciences, 1985 A New Species of Pseudeurythoe (Polychaeta: Amphinomidae) from Central California Jerry D. Kudenov and James A. Blake Abstract.—A new species of Pseudeurythoe (Polychaeta: Amphinomidae) from central California by Jerry D. Kudenov and James A. Blake. Bull. Southern California Acad. Sci., 84(1):38—40, 1985. A new intertidal amphinomid poly- chaete of the genus Pseudeurythoe is described from the Elkhorn Slough in central California. The species is compared to related congeners. The genus Pseudeurythoe Fauvel (Polychaeta: Amphinomidae) is represented by 13 described species (Fauchald 1972; Kudenov 1975), four of which occur in the eastern Pacific. During the course of a benthic survey of the Elkhorn Slough, one of us (JAB) discovered a single specimen of an as yet undescribed species of Pseudeurythoe. That species is described here and compared with related con- geners. The holotype is deposited in the National Museum of Natural History, Smithsonian Institution (USNM). Pseudeurythoe Fauvel Pseudeurythoe reducta, n. sp. Figure | Material examined.—CALIFORNIA: Moss Landing, Elkhorn Slough, June, 1976, Sta. 51A, 100 m north of thermal outfall, high intertidal zone, in fine sand. J. A. Blake collector—(Holotype, USNM 97288). Description. — Holotype complete but fragmented, measuring 50 mm long and 6 mm wide for 96 setigers. Body elongate, widest anteriorly, tapering posteriorly, nearly rectangular in cross section; color in alcohol pink due to prior staining by Rose Bengal. Prostomium pear-shaped, longer than wide (Fig. 1a); anterior lobe with smooth anterior margin, a pair of posteriorly located digitiform antennae and two ven- trolateral cirriform palps; posterior lobe one-half as long as anterior lobe, bearing two pairs of well developed eyes, a small posteriorly located digitiform median antenna, and a short, pad-shaped caruncle on setiger 1, obscured by segmental folds of setigers 1-3. Parapodia biramous throughout, with those of setiger 1 greatly reduced, incon- spicuous (Fig. la). Typical parapodia with widely separated rami (Fig. 1b). No- topodia reduced to papillar lobes; neuropodia well developed, projecting beyond body wall (Fig. 1b). Dorsal and ventral cirri cirriform throughout, tapering, point- ed, with those of setigers 1-4 appearing about equally developed (right ventral cirrus of setiger 2 missing from holotype) (Fig. la); ceratophores smooth. Branchiae from setiger 2 continuing to the end of the body; branchiae arising as tufts resembling dendritic processes on posterior notopodial surfaces (Figs. la—b). A NEW SPECIES OF PSEUDEURYTHOE FROM CALIFORNIA 39 ‘ N ; ; ZS Ag oY / O c-l Fig. 1. a-l. Holotype, USNM 97288, Pseudeurythoe reducta. a, anterior segments, frontal view; b, median parapodium, anterior view; c, thick, smooth notosetal spine; d, harpoon notoseta, lateral view; e, forked notoseta, lateral view; f, serrated capillary seta showing detail of spur, lateral view; g, notoaciculum, lateral view; h, thin-shafted, forked neuroseta, lateral view; i-j, thick-shafted, forked neuroseta, lateral view; k, serrated capillary neuroseta showing detail of basal spur, lateral view; 1, neuroaciculum, lateral view. Scales: a—b = 0.2 mm; c-l = um. Notosetae of six kinds; 1) thick, smooth spines (Fig. 1c); 2) harpoon setae (Fig. 1d); 3) forked spines with denticulate cutting margins (Fig. le); 4) long, slender smooth capillaries; 5) long, slender, basally spurred capillaries with denticulate cutting margins (Fig. 1f); and 6) long, distally inflated acicula numbering four per notopodium (Fig. 1g). Neurosetae of four kinds: 1) forked spines having thin shafts and long, distally serrated cutting margins (Fig. 1h); 2) forked spines having thick shafts and smooth cutting surfaces (Figs. 1i-j); 3) slender, conspicuously spurred capillaries having denticulate cutting margins (Fig. 1k); and 4) stout, distally inflated acicula, numbering three per neuropodium (Fig. 11). Pygidium dorsal with a midventral terminal papilla. 40 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Remarks.—Pseudeurythoe reducta belongs to a small eastern Pacific species group in which the branchiae extend the full length of the body instead of being limited to anterior segments as is typical for the genus. Related species include P. oculata (Treadwell) and P. tripunctata Kudenov. P. reducta differs from both of these species in that branchiae are first present from setiger 2 instead of 3. As a group, all three species occur intertidally and are related ecologically and zoo- geographically as well as morphologically. P. reducta is the most northern species, occurring in sand-mud sediments of central California. P. tripunctata and P. oculata occur either in mangroves or sandy sediments of western Mexico and Central America (Treadwell 1941; Kudenov 1975; Fauchald 1977). Very little is known concerning the habits and mode of life of Pseudeurythoe species. Despite an older census (MacGinitie 1935) and numerous recent studies by the Moss Landing Marine Laboratories only a single complete specimen of P. reducta has turned up in the Elkhorn Slough, now a National Marine Sanctuary. It is possible that the habits of P. reducta are cryptic. A species tentatively iden- tified as P. ambigua Monro has been reported from box core samples in the lower Chesapeake Bay (Karl, Diaz, Boesch, and Kravitz 1980). This species has been shown to be most abundant in anoxic sediments below 10 cm and is greatly undersampled by grabs. It is possible that P. reducta occupies a similar deep habitat in sediments of California estuaries. Etymology.—The epithet, reducta, refers to the remarkable reduction of setiger 1. It is regarded as a noun in apposition. Distribution. —Elkhorn Slough, California. Acknowledgments We are grateful to Nancy Maciolek Blake for reading and commenting on this paper. Rod Bertelsen supplied ecological information on the Chesapeake Bay species. The specimen on which this report is based was collected as part of a 316A demonstration survey of the Elkhorn Slough for Pacific Gas & Electric Company. Literature Cited Fauchald, K. 1972. Benthic polychaetous annelids from deep water off western Mexico and adjacent areas in the eastern Pacific. Allan Hancock Monographs Mar. Biol., 7:1-573. . 1977. Polychaetes from intertidal areas in Panama, with a review of previous shallow-water records. Smithsonian Contribs. Zool., 222:1-81. Karl, N., R. Diaz, D. F. Boesch, and M. Kravitz. 1980. Biogenic structure of Lower Chesapeake Sediments. EPA/Grant R805982-01-0, Final Report, pp. 1-103. Kudenov, J. D. 1975. Errant polychaetes from the Gulf of California, Mexico. Jour. Nat. Hist., 9:65-91. MacGinitie, G. E. 1935. Ecological aspects of a California marine estuary. Amer. Midl. Nat., 16: 629-765. Treadwell, A. L. 1941. Eastern Pacific expeditions of the New York Zoological Society, XXIII: Polychaetous annelids from the west coast of Mexico and Central America. Zoologica, 26(1): 17-24. Accepted for publication 9 March 1984. Department of Biological Sciences, University of Alaska, Anchorage, 3221 Provi- dence Drive, Anchorage, Alaska 99508 (JDK). Batelle New England Marine Re- search Laboratory, P.O. Drawer “AH”, Duxbury, Massachusetts 02332 (JAB). Bull. Southern California Acad. Sci. 84(1), 1985, pp. 41-45 © Southern California Academy of Sciences, 1985 Optimal Foraging in Barn Owls? Rodent Frequencies in Diet and Fauna Orlando A. Schwartz! and Vernon C. Bleich? Abstract. — Optimal foraging in Barn Owls? Rodent frequencies in diet and fauna by Orlando A. Schwartz and Vernon C. Bleich. Bull. Southern California Acad. Sci., 84(1):41-—45, 1985. We determined the frequencies of prey in the diet of Barn Owls by identifying mammal crania contained in pellets, and we determined the frequencies of prey items in the fauna by live and snap trapping. Data from two sites in Southern California showed approximately equal portions of prey in the diet and in the fauna. Such agreement may be expected when the predator per- ceives a low quality habitat, or it might be due to efficient predation methods that eliminate some of the constraints that face foraging predators. The theory of optimal foraging, summarized by Pyke et al. (1977) and Krebs (1978), was developed as a predictive ecological and evolutionary algorithm. Models of this theory attempt to predict an animal’s food choices including op- timal particle size in the diet, the choice of which patch to feed in, when to switch patches, and the pattern of speed and movement within and between patches. Such optimal choices by an animal are contingent on and perhaps constrained by a species’ ability to perceptually gather and neurologically process and store in- formation regarding its past foraging activities and the future potential location of prey items. Ants were shown to make efficient choices of foraging patches and particle size (Taylor 1977; Davidson 1977), and backswimmers were shown to be able to assess prey density and thus decide what proportion ofa prey to consume (Sih 1980). Therefore, animals as perceptually and neurologically simple as insects make near optimal diet choices. The perceptual and predatory abilities of owls are well known. As first reported in the classic work by Dice (1945), owls were successful in obtaining prey in extremely low light and in darkness using only sound to locate prey. The prey of Owls is perhaps as well known as that of any other animal group. They ingest prey items whole and then regurgitate undigestible and largely intact skeletal remains which are readily identifiable. There have been few studies attempting to assess owl prey choice relative to prey density and dispersion (Jaksic and Yanez 1979) or prey size (Marti and Hogue 1979). In this paper we report the frequency of food items in the diet of Barn Owls (Tyto alba) and the corresponding frequencies of food items in this species’ habitat at two Southern California study sites. With these data we have suggested qual- itatively that a forager with evolutionarily advanced perceptual capacities may have much greater latitude in foraging than predicted by present theory. Materials and Methods One study site was the U.S. Naval Weapons Station, Fallbrook Annex, located in northern San Diego County, California. We observed Barn Owls inhabiting 42 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES and nesting in abandoned, wooden water towers on the Annex. A sample of pellets containing 1541 skulls was collected in these towers in May 1974. Bleich (1973) reported abundances of small mammals from over 4000 trap-nights at the Annex, and his data are used here for comparisons with owl pellet data. In this area patches of different vegetation and mammals occur in close proximity to one another, and the location of patches depends on soil type, slope, moisture avail- ability, and solar exposure on hillsides. North facing slopes are characterized by Chaparral communities (2.0 km? total area on the Annex); south facing slopes are characterized by Coastal Sage Scrub communities (10.5 km’); and Grassland (19.8 km’), Southern Oak Woodland (0.5 km’), and Streamside Woodland (0.5 km?) are found where conditions are suitable. On the Annex the following species were found at their highest densities and were considered typical species in the following communities (Bleich 1973) (though most were caught in other communities at much reduced densities): Chaparral: Neotoma fuscipes and Reithrodontomys megalotis; Coastal Sage Scrub: Dipodo- mys agilis and Neotoma lepida; Grassland: Dipodomys stephensi; Southern Oak Woodland: Peromyscus boylii; Streamside Woodland: Peromyscus californicus, Peromyscus eremicus, and Microtus californicus. The Annex is nearly surrounded by urban areas and avocado orchards, so the owls were presumed to forage mostly on the Annex land. Our second study site was in the Carrizo Plains, an area of grazed, Central Valley Grassland, 19 km north of Reyes Station, San Luis Obispo County, Cal- ifornia. We collected pellets containing 997 skulls during March 1974 and January 1975. The pellets were found inside abandoned water tanks, and Barn Owls were seen in the tanks on both collecting trips. We conducted 1077 trap-nights of trapping during late October 1971, January 1973, and March 1974, approximately 1.0 km from the site of the owl roosts. Vegetation was nearly uniform throughout the Carrizo Plains and consisted of low grasses and forbs, and sparse stands of Mormon tea (Ephedra sp.) and saltbush (Atriplex sp.). The upper cranial portion of all skulls was identified to genus and, where possible, to species. Average weights of mammalian species used in data analyses were obtained from the literature (Hawbecker 1945; Fitch 1947; Schwartz and Bleich 1975), and from specimens in the collections of California State University, Long Beach, and the Museum of Natural History, University of Kansas. Results Species and numbers of skulls from the Fallbrook pellets were as follows: Botta’s pocket gopher, Thomomys bottae (549); California vole, Microtus californicus (303); agile kangaroo rat, Dipodomys agilis (199); woodrat, Neotoma spp. (150); Stephens’ kangaroo rat, Dipodomys stephensi (137); pocket mouse, Perognathus spp. (102); deer mouse, Peromyscus spp. (89); birds (6); western harvest mouse, Reithrodontomys megalotis (4); desert shrew, Notiosorex crawfordi (1); and desert cottontail, Sy/vilagus audubonii (1). Species and numbers of skulls from the Car- rizo Plains pellets were as follows: San Joaquin pocket mouse, Perognathus in- ornatus (299); Heermann’s kangaroo rat, Dipodomys heermanni (254); Fresno kangaroo rat, Dipodomys nitratoides (209); giant kangaroo rat, Dipodomys ingens (96); Peromyscus and grasshopper mouse, Onychomys spp. (75); Neotoma sp. OPTIMAL FORAGING IN BARN OWLS 43 Table 1. Frequencies of numbers and biomass of species common to the fauna of the two study areas in California and diet of Barn Owls inhabiting the areas. Propor- Propor- Propor- Propor- tion of tion of tion of tion of Weight numbers numbers biomass biomass Species g in diet in fauna Difference in diet in fauna Difference Fallbrook Weapons Annex M. californicus 50 30.8 0.4 +30.4 22.6 0.4 +22.2 D. agilis 40 20.2 13.9 +6.3 13.5 13.9 —0.4 Neotoma spp. 150 15.2 16.2 —1.0 38.0 44.2 —6.2 D. stephensi 60 13.9 18.2 —4.3 13.9 19.8 —5.9 Perognathus spp. 25 10.4 27.2 —16.8 4.3 12.4 —8.1 Peromyscus spp. 30 9.0 23.8 —14.8 4.5 13.0 —8.5 R. megalotis 25 0.4 0.3 +0.1 0.2 0.3 —0.1 Carrizo Plains D. heermanni 50 33.0 48.6 —15.6 37.0 45.7 —8.7 D. nitratoides 35 40.1 30.4 +9.7 21.3 20.0 +1.3 D. ingens 130 15.1 12.4 +2.7 36.3 30.3 +6.0 Peromyscus and Onychomys sp. 25 11.8 8.6 +3.2 5.4 4.0 +1.4 (30); Thomomys bottae (20); birds (10); Reithrodontomys megalotis (3); and bat (1). Several prey items did not appear in our trap samples. The pocket gopher, 7. bottae;, desert shrew, N. crawfordi; desert cottontail, S. audubonii; and birds and bats are seldom if ever caught in the Sherman collapsible and snap traps we used. We caught no Perognathus inornatus or Neotoma in our Carrizo Plains trapping perhaps indicating that there were owl foraging areas we did not sample. The little pocket mouse, Perognathus longimembris, is almost identical to P. inornatus (Hall and Kelson 1959) and P. longimembris was shown to hibernate for up to 5 months during the cold season of the year (French 1976; Kenagy 1973). We trapped in the Carrizo Plains only during the months of October, January, and March, and if P. inornatus also hibernates, that could explain its absence from our sampling. Trapping data and pellet data were compared in proportions of numbers and biomass for species contained in both trap and pellet collections from each area (Table 1). To attempt to better estimate prey density and biomass proportions of species in the fauna of the Fallbrook Annex, numbers of each species trapped were weighted by multiplying the proportions of species in trapping samples by the total area of the different vegetational communities occupied by that species. We considered the Carrizo Plains to be a homogeneous habitat, so proportions of species in the trapping data were considered to be equivalent to proportions of species in the fauna. Proportions of biomass in the fauna and diet were com- puted by multiplying the proportion of that species in the sample by the average weight of that species. We declined to calculate a goodness of fit statistic between diet and fauna. It would show a significant difference, but only because of data from M. californicus and D. heermanni. Here we emphasize the remarkable degree of similarity in diet and fauna and consider a statistical analysis inappropriate. 44, SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Discussion With two exceptions, one at each study site, the results show approximately equal proportions of numbers and biomass in the diet of owls and in the fauna. The exceptions are in the 50 g weight class, D. heermanni and M. californicus, which were underrepresented in the diet of the Carrizo Plains owls and overre- presented in the diet of the Fallbrook owls, respectively. The difference between diet and fauna relative to D. heermanni may be explained by an unusual suscep- tibility to trapping, ability to avoid owl predation, or deficiencies in our sampling methods. The difference in diet and fauna in M. californicus may be explained as follows. Bleich (1973) trapped this species only in meadows associated with streamside woodlands, but it is widely reported to occur in California Grassland communities (Lidicker 1978). Our trapping could have occurred during a low density phase of this cyclic rodent. According to optimal foraging theory owls should switch to a high intensity search in high density patches (Krebs 1978) should such an abundance of this meadow dwelling vole occur. Given that the 50 g weight class (relative to the fauna) was overrepresented in the owl’s diet in one area and underrepresented in the other, obviously these biases are not due to particle size/weight. Rather these data suggest there is no optimal particle size through a broad range of rodent size classes. For approximately equal proportions of species to occur in diet and fauna, owls must effectively utilize all patches where patchy habitat occurs and they must attempt and regularly succeed in capturing all species encountered. Agreement in proportions of items in diet and fauna may occur when the predator perceives relatively low quality foraging opportunities (Krebs 1978). We suggest in this owl that it may also be due to superior perceptual and predatory ability not requiring “complex strategies” to successfully meet nutritional requirements. Our data and analyses were crude and our conclusion is only one possible explanation of these data. We had no opportunity to follow prey population dynamics that would change patch quality and perhaps owl foraging patterns. Similarly, we had no data to suggest optimal owl foraging strategies that could be superimposed on these data or have changed with changes in the communities thus allowing optimal habitat utilization while still achieving close similarity in frequencies of items in diet and fauna. Future research on owl foraging dynamics could provide interesting extensions of optimal foraging theory. Acknowledgments We thank Peter Lowther and Keith Waddington for critically reading and mak- ing suggestions on drafts of this manuscript and Ronald Quinn for information regarding Southern California rodent population dynamics. Literature Cited Bleich, V. C. 1973. Ecology of rodents at the United States Naval Weapons Station Seal Beach, Fallbrook Annex, San Diego County, California. M.A. Thesis. Calif. State Univ., Long Beach, 102 pp. Davidson, D. W. 1977. Foraging ecology and community organization in desert seed eating ants. Ecology, 58:725-737. Dice, L.R. 1945. Minimum intensity of illumination under which owls can find dead prey by sight. Amer. Nat., 79:385-416. OPTIMAL FORAGING IN BARN OWLS 45 Fitch, H. S. 1947. Predation by owls in the Sierran Foothills of California. Condor, 49:137-139. French, A.R. 1976. Selection of high temperatures for hibernation by the pocket mouse, Perognathus longimembris: Ecological advantages and energetic consequencies. Ecology, 57:185-191. Hall, E. R., and K. R. Kelson. 1959. The mammals of North America. The Ronald Press, New York. Hawbecker, A. C. 1945. Food habits of the Barn Owl. Condor, 47:161—166. Jaksic, F. M., and J. L. Yanez. 1979. The diet of the Barn Owl in central Chile and its relation to the availability of prey. Auk, 96:619-621. Kenagy, G. J. 1973. Daily and seasonal patterns of activity and energetics in a heteromyid rodent community. Ecology, 54:1201-1219. Krebs, J. R. 1978. Optimal foraging: decision rules for predators. Pp. 23-63 in Behavioral ecology an evolutionary approach. (J. R. Krebs and N. B. Davies, eds.), Blackwell Sci. Publ., Oxford. Lidicker, W. Z. 1978. Regulation of numbers in small mammal populations, historical reflections and a synthesis. Pp. 122-141 in Populations of small mammals under natural conditions. (D. P. Snyder, ed.), Spec. Publ. Ser. Pymatuning Laboratory Ecol., 5:1-237. Marti, C. D., and J. G. Hogue. 1979. Selection of prey size in Screech Owls. Auk, 96:319—-327. Pyke, G. H., R. Pulliam, and E. L. Charnov. 1977. Optimal foraging: a selective review of theory and tests. Quart. Rev. Biol., 52:137-154. Schwartz, O. A., and V. C. Bleich. 1975. Comparative growth in two species of woodrats, Neotoma lepida intermedia and Neotoma albigula venusta. J. Mamm., 56:653-666. Sih, A. 1980. Optimal foraging: partial consumption of prey. Amer. Natur., 116:281-290. Taylor, F. 1977. Foraging behavior of ants: experiments with two species of Myrmecine ants. Behav. Ecol. and Sociobiol., 2:147-167. Accepted for publication 6 February 1984. \Department of Biology, University of Northern Iowa, Cedar Falls, Iowa 50614, 2California Department of Fish and Game, P.O. Box 1741, Hemet, California 92343. Bull. Southern California Acad. Sci. 84(1), 1985, pp. 46-47 © Southern California Academy of Sciences, 1985 Research Notes Record of the Pacific Burrfish from Southern California On 27 December 1982, the junior author received a telephone call from the Long Beach Marine Safety Division regarding an unusual fish. The specimen, 198.5 mm SL, 235.0 mm TL, and 456 g (after preservation), was found in relatively fresh condition washed ashore in Long Beach Harbor on Cherry Avenue Beach. It was identified by us as Chilomycterus affinis Giinther, the Pacific burrfish. In Giinther’s (1870) original description of C. affinis, the taxon was based upon a *‘Stuffed [specimen], 15 inches long’; type-locality was unknown. In 1891, Ei- genmann described Chilomycterus californiensis based on a single specimen from San Pedro, California. ““On account of the unreasonable price asked for it I [Ei- genmann] did not obtain it ....’ However, two years later Eigenmann (1893) redescribed C. californiensis and stated: “‘During the summer of 1891 a fisherman captured a specimen of a Chilomycterus near San Pedro, Cal. He preserved it in alcohol and offered it for sale. The price asked was so unreasonably high that I merely took some notes of it. Since then it has been procured by the National Museum, and I am able to redescribe it. This is apparently the first notice of a Chilomycterus on the Pacific coast of North America.”’ An illustration of the specimen (Plate LX XXI.) is included in Eigenmann’s second paper. The type is No. 43860 in the U.S. National Museum. Chilomycterus californiensis has since been treated as a junior synonym of C. affinis. Both Snodgrass and Heller (1905) and Jordan and Evermann (1905), in their respective studies on Pacific fishes, considered these two nominal species as synonymous. We are aware of but three bonafide records of C. affinis from Californian waters. Following Eigenmann’s 1891 record of Chilomycterus from California, a second burrfish was not noted until June 1959, from Newport Beach (Radovich 1961). This specimen, 223 mm SL, is housed in the ichthyological collection, University of California, Los Angeles, W59-219 (Donald G. Buth, Univ. Calif. Los Angeles, pers. commun.). Regarding the Pacific burrfish, Fitch and Lavenberg (1975) state, “no more than three or four individuals have been seen or captured in our waters.” Data on these additional specimens are sketchy at best, no dates or localities are available (Robert J. Lavenberg, Natural History Museum of Los Angeles County, pers. commun.). The first two Californian captures (1891 and 1959) were made during periods of unusually warm marine water. Late 1982 marked the beginning of a period of higher than normal ocean temperatures in the eastern Pacific and has been associated with the El Nino phenomenon. Temperature anomalies at the sea surface in one degree squares off southern California for October through December 1982 were up to 2.2°C above the long term mean (Douglas R. McLain, National Marine Fisheries Service, pers. commun.). It is significant that all three documented captures of C. affinis from southern California were taken during periods of warm water. Biogeographically, C. affinis has a broad and somewhat unusual distribution— tropical and subtropical eastern Pacific including Galapagos Islands, the Hawaiian RESEARCH NOTES 47 Islands, and Japan; nowhere is C. affinis common. The systematics of the genus Chilomycterus are in need of review. The Long Beach specimen is deposited at the Natural History Museum of Los Angeles County, LACM 43449-1. Acknowledgments We would like to thank the Long Beach Safety Division, particularly lifeguard Kelly Coultrup for bringing the Pacific burrfish to our attention. The curators at the following institutions checked their respective collections for material of C. affinis: California Academy of Sciences, Natural History Museum of Los Angeles County, Scripps Institution of Oceanography, and University of California at Los Angeles. Douglas R. McLain provided temperature anomaly charts of the eastern Pacific Ocean. Literature Cited Eigenmann, C. H. 1891. A new diodont. American Naturalist, 25:1133. . 1893. On the occurrence of the spiny boxfish (genus Chilomycterus) on the coast of California. Proc. U.S. Nat. Mus., 15(917):485; Pl. LXXXI. Fitch, J. E., and R. J. Lavenberg. 1975. Tidepool and nearshore fishes of California. Univ. California Press, Berkeley. 156 pp. Giinther, A. 1870. Catalogue of the fishes in the British Museum. Vol. 8th. London. 549 pp. Jordan, D. S., and B. W. Evermann. 1905. The aquatic resources of the Hawaiian Islands. Part I.— The shore fishes. Bull. U.S. Fish Comm. for 1903., 23:574 pp.; 73 col. pls., 65 black-and- white pls. Radovich, J. 1961. Relationships of some marine organisms of the northeast Pacific to water tem- peratures particularly during 1957 through 1959. Calif. Dept. Fish and Game, Fish Bull. No. 112, 62 pp. Snodgrass, R. E., and E. Heller. 1905. Papers from the Hopkins-Stanford Galapagos Expedition, 1898-1899. XVII. Shore fishes of the Revillagigedo, Clipperton, Cocos and Galapagos Islands. Proc. Wash. Acad. Sci., 6:333-427. Accepted for publication 9 August 1983. Robert N. Lea, California Department of Fish and Game, Marine Resources Branch, Monterey, California 93940; Research Associate in Ichthyology, Natural History Museum of Los Angeles County and Marija Vojkovich, California De- partment of Fish and Game, Marine Resources Branch, Long Beach, California 90813. Bull. Southern California Acad. Sci. 84(1), 1985, pp. 48-50 © Southern California Academy of Sciences, 1985 Electrophoretic Comparison of Two Southern California Chipmunks (Tamas obscurus and Tamias merriam1) The chipmunk Tamias obscurus davisi (Callahan) was given species status by Callahan (1977) based on bacular morphology. Except by the ossa genitalia, Tami- as obscurus is not readily distinguished from 7. merriami merriami J. A. Allen, which led to our interest in the systematics of these species. Sympatric in the San Bernardino Mountain range north of the San Gorgonio pass and in the San Jacinto Mountains of southern California, Tamias merriami extends north to the Sierra Nevada (see Hall 1981) whereas 7. obscurus is found south as far in Baja California as San Pablo (Callahan 1977). Esterases have been used in genetic studies of mice (Selander, Smith, Yang, Johnson, and Gentry 1971) and their value in assessing squirrel taxonomy was suggested by Seaman and Nash (1977). Esterases also have been used in the construction of taxonomic keys (Seaman 1975). Because they are easily acquired in the field by sampling peripheral blood, we chose to use these enzymes in evaluating the systematic relationships of Tamias obscurus and T. merriami. Horizontal starch gel electrophoresis was performed using the blood hemolysate of a total of 24 individuals of Tamias from southern California and Washington. 1. Tamias obscurus (5 males, 5 females) Riverside County, 4 km on Black Mountain Road from highway 243, in the San Jacinto Mountains of Cali- fornia. 2. Tamias obscurus (2 males, 2 females) San Bernardino County, 5 km north of Onyx Pass on Highway 38, in the San Bernardino Mountains of California. 3. Tamias merriami (4 males, 3 females) Riverside County, 2 km on Black Mountain Road from Highway 243, in the San Jacinto Mountains of Cal- ifornia. 4. Tamias speciosus (1 male, 1 female) San Bernardino County, 4 km east of Heart Bar State Park Campground, in the San Bernardino Mountains of California. 5. Tamias amoenus (1 female) from Kittitas County, 2 km north of Cliffdell, Washington. The chipmunks were live trapped and taken to the laboratory where blood was acquired by toe-clipping, this way the same individual could be assayed again for verification of results. The specimens were eventually deposited in the Loma Linda University Museum of Natural History and genital bones preserved for species identification. The preparation of the hemolysate, the electrophoretic procedure, and the stain- ing technique were similar to Selander et al. (1971), with the exception that blood was collected in capillaries and frozen immediately to produce lysis before ap- plying the samples to the gel. The samples were run at not more than 200 volts and about 35 ma for 6 hours. After electrophoresis the starch-gels were sectioned into four horizontal slices and stained separately as in Selander et al. (1971). The hemolysate of Tamias obscurus and T. merriami was analyzed for 11 RESEARCH NOTES 49 ES-8 ES-9 Tm To Ta Ts Ts Tm To Ts Ta Fig. 1. Drawing of an actual gel used to compare the four species of chipmunks in this study. The samples are applied in replicate. Tm = Tamias merriami, To = Tamias obscurus, Ta = Tamias amoenus, Ts = Tamias speciosus, ES = Esterase. different enzymes: malate dehydrogenase, glutamate oxalate transaminase, ester- ase, phosphoglucoisomerase, acid phosphatase, glutamic acid dehydrogenase, phosphoglucomutase, fructose-6-phosphate dehydrogenase. Of the above all were either monomorphic or unscorable. Catalase, shikimic acid dehydrogenase and peroxidase were not present in the hemolysate of these species. Esterase was chosen for further study because it was found to be polymorphic in ground squirrels (unpublished data). The esterases present in chipmunks consist of 7 bands (see Fig. 1), which correspond to those of mice (Petras and Biddle 1967). Of these seven bands, no consistent differences were found between Tamias obscurus and T. merriami. There was no sexual dimorphism detected in esterase, and populations in the San Jacinto Mountains were indistinguishable from those in the San Bernardino Mountains. Since interspecific esterase polymorphism for 7amias obscurus and T. merriami was absent, two individuals of 7. speciosus were used for comparison on the same gels. Tamias speciosus differs from T. merriami and T. obscurus by the presence of a fast band, ES-1. One individual of Tamias amoenus was also used for com- parison and differed from 7. merriami and T. obscurus in the relative mobility of ES-3, and from 7. speciosus by the absence of ES-1. The electrophoretic description of Tamias obscurus and T. merriami was rather puzzling when compared with the consistent polymorphism of squirrel and chip- 50 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES munk plasma proteins reported by Seaman and Nash (1977). They observed differences between the species they studied. The potential for polymorphism and the likelihood of unique proteins being present is suggested by the differences between the other two species of chipmunks in our study. A difficulty with the systematics of chipmunks is the major emphasis which has been placed on bacular morphology. The baculum has been implicated in reproductive isolation by a “lock and key” mechanism (Patterson and Thaeler 1982) however. The genetic basis for bacular morphology has not been explained. This is a preliminary study and further systematic work should be done to determine the nature of genetic variability in chipmunk species. Acknowledgments We thank Jean Colton for the drawing and Jim Gibson for collecting the chip- munk from Washington. Literature Cited Callahan, J. R. 1977. Diagnosis of Eutamias obscurus (Rodentia:Sciuridae). J. Mammal., 58:188- 201. Hall, E.R. 1981. The mammals of North America. John Wiley and Sons, New York. Patterson, B. D., and C. S. Thaeler, Jr. 1982. The mammalian baculum: Hypotheses on the nature of bacular variability. J. Mammal., 63:1-15. Petras, M. L., and F. G. Biddle. 1967. Serum esterases in the house mouse, Mus musculus. Can. J. Genet. Cytol., 9:704—710. Seaman, R. N. 1975. A re-evaluation of Nearctic Sciurid phylogeny based upon biochemical, im- munological and numerical taxonomic analyses. Ph.D. dissertation, Colorado State University, Fort Collins, 207 pp. , and D. J. Nash. 1977. An electrophoretic description of five species of squirrel. Comp. Biochem. Physiol., 58:309-311. Selander, R. K., M. H. Smith, S. Y. Yang, W. E. Johnson, and J. B. Gentry. 1971. IV. Biochemical polymorphism and systematics in the genus Peromyscus. I. Variation in the old-field mouse (Peromyscus polionotus). Stud. Gen. VI. Univ. Tex. Publ., 7103:49-90. Accepted for publication 15 February 1984. Daniel J. Blankenship and Gary L. Bradley, Department of Biology, Loma Linda University, Loma Linda, California 92354. Bull. Southern California Acad. Sci. 84(1), 1985, pp. 51-52 © Southern California Academy of Sciences, 1985 Notes on Spawning in the Dolphin Fish, Coryphaena hippurus (Coryphaenidae) from Peru The dolphin fish, Coryphaena hippurus, is found worldwide in warmer seas (Miller and Lea 1976). Little information is available on its reproductive biology. Beardsley (1967) analyzed seasonal gonadal changes in C. hippurus in the Florida current. Other papers (Schuck 1951; Erdman 1956; Williams and Newell 1957; Gibbs and Collette 1959) reported observations of spawning. Schweigger (1964) concluded that this species spawns in Peru during March. Here we present a histological analysis of the gonads of 43 female C. hippurus from northern Peru. Fish were collected 4 June 1983 from Huarmay, Ancash Department, Peru (lat. 10°04’S, long. 78°10'W) by commercial fishermen. Landings of C. hippurus by Peruvian fishermen are not common. Their presence in 1983 was due to the “El Nino” phenomenon during which time warm oceanic waters were found along the Peruvian coast. Our sample therefore, was probably from a tropical population that followed a warm water mass southward. During normal years, the population presumably would be located further north. Fish were shipped on ice to Trujillo, La libertad Department, Peru where we weighed them to the nearest kg using a spring balance, weighed gonads to the nearest g using a torsion balance and fixed gonads in 10% formalin 5 June 1983. Tissue was embedded in paraffin. Ovarian histological sections were cut at 8 wm and stained with Harris’ hematoxylin fol- lowed by eosin counterstain. Gonosomatic indices (GSI = ovary weight/fish weight