I in Colorado, New h DISTRIBUTION OF ERIGERON PUMILUS AND E. CONCINNUS (ASTERACEAE: ASTEREAE) IN COLORADO, NEW MEXICO, AND ARIZONA GuyL. Nesom 2925 Hartwood Drive Fort Worth, TX 76109 www.guynesom.com ABSTRACT The geographic ranges of Erigeron pumilus var. pumilus and E. concinnus are essentially parapatric in Colorado, northwestern New Mexico, and adjacent Arizona. The two taxa flower at the same time and occur in similar habitats, but putative morphological intermediates are rare. Their close, non-overlapping distribution is analogous to that of E. pumilus var, intermedins and E. concinnus in Nevada. pumilus, E. concinnus, Astereae, Colorado. New Mexico, A sharp morphological and geographical demarcation in Nevada between Erigeron concinnus (Hook. & Am.) Torr. & Gray and E. pumilus Nutt. var. intermedins Cronq. was regarded as evidence that the taxa are reproductively isolated, the former thus appropriately treated at specific rank (as E. , rather than E. pumilus var. concinnoides Cronq.; Nesom 1983). Erigeron concinnus along its eastern border approaches the range of typical E. pumilus, and Cronquist noted (1947, p. 183) tliat these two ''behave almost if not quite as distinct species, where their ranges meet." Harrington (1954, 570) also was aware of their distinction, noting that typical E. pumilus in Colorado w r as "all east of the Continental Divide," while E. concinnus was known from records "scattered in the western one-fourth [of the state]." The current study examines examines in detail the distributions and potential interaction between these two taxa, paralleling the earlier study (Nesom 1983) of E. concinnus andii. pumilus var. intermedins. The three taxa under consideration are distinguished by contrasts in the following key (modified from Nesom 2006). 1. Disc corollas hirsute-strigose with sharp-pointed hairs; outer pappus of scales 0.2-0.5 mm long, inner of (7-)10-14(-15) bristles Erigeron concinnus 1. Disc corollas glabrous or slightly puberulent with glandular-viscid, blunt-tipped hairs: outer pappus of setae or subulate scales, 0.1-0,3 mm, inner of 12-27 bristles Erigeron pumilus 2. Outer pappus of coarse bristles or setiform scales, inner of 12-20 bristles; ra)'s usually pink, sometimes white; indurate portion of disc corollas glabrous or slightly puberulent, relatively dull Erigeron pumilus var. intermedius 2. Outer pappus of inconspicuous, well-developed setae, inner of 15-27 bristles; rays white; indurate portion of disc corollas glabrous, shiny Erigeron pumilus var. pumilus Figure 1 shows the total geographical distributions of Erigeron concinnus and the varieties of E. pumilus, as currently understood. Nesom: Erigeron pumilus and £. concinnus 2 Figure 1. Generalized distributions of Erigeron concinnus (CON), E. pumilus var. pumilus (PUM), and E. pumilus var. intermedius (INT). Modified from Figure 1 in Nesom (1983), with var. pumilus now shown extending south into New Mexico and Arizona and further north in Wyoming. The present study is primarily based on specimens examined from BRIT-SMU, NY, TEX- LL, and UNM (herbarium visits) and NMC and SJC (loans). The online specimen database from herbarium COLO has been used to complete Colorado distributions; recorded annotations by W.A. Weber usually indicate the nature of the outer pappus ("outer pappus of scales" = E. concinnus, or "outer pappus of bristles" = E. pumilus). Vouchers for New Mexico and Arizona are cited; those for Utah and Colorado are from BRIT, NY, SJC, TEX, and Cronquist (1947). Results and discussion. The geographic relationship of Erigeron concinnus with E. pumilus var. pumilus is analogous to its relationship with E. pumilus var. intermedius. Erigerons concinnus and var. pumilus are essentially parapatric in Colorado, New Mexico, and Arizona (Fig. 2), as are E. concinnus and var. intermedius in Nevada. In northwestern New Mexico, where the two taxa occur in closest proximity, intermediates are uncommon to rare (see below), suggesting that some degree of reproductive isolation exists. The same pattern of parapatry continues northward through Wyoming (see Rocky Mountain Herbarium 1998, with some modifications in identifications, fide Ron Hartman). In documentation of the closely associated ranges in new Mexico, specimens studied from that state are cited here (Appendix 1). Because the occurrence of typical Erigeron pumilus in Arizona has been uncertainly known, records for it also are cited here (Appendix 2). Nesom: Erigeron pumilus and E. concinnus The close parapatry of Erigeron concinnus with the two expressions of E. pumilus is remarkable. In San Juan and Rio Arriba counties, New Mexico, where E. concinnus and var. pumilus closely approach each other, the San Juan River roughly marks a boundary between them but they flower concurrently and grow in similar habitats and an ecological factor that might be responsible is not apparent. Competitive exclusion seems unlikely. Figure 2. Geographic distribution of Erigeron pumilus var. pumilus and E. concinnus in Colorado, New Mexico, and Arizona. The slashed E. concinnus symbols in Gunnison Co., Colorado, are plants with very narrow scales. The out-of-range collection of E. concinnus from along the Rio Grande River in Sandoval Co., New Mexico (Heller 3632), possibly was a waif. A chromosome number of In = 18 has been reported for Erigeron concinnus, In = 18 and In = 36 for var. intermedins. Apparently no report exists for var. pumilus. In any case, it would not be surprising to find more than one ploidy level in each of the three, given the high frequency with which polyploidy occurs in the genus, and a cytological study might provide useful biological insights. Even if different ploidal races were parapatrically aligned, however, it seemingly would not account for the sharp boundaries. ACKNOWLEDGEMENTS I am grateful to SJNM and NMC for loans of specimens and to BRIT, NY, TEX, and UNM for hospitality during study there. Ken Heil provided precise information on New Mexico localities. LITERATURE CITED Cronquist, A 1947. A revision of the North American species of Erigeron, north of Mexico. Brittonia 6:121-302. Cronquist, A 1994. Intermountain Flora. Vol. 5, Asterales. New York Botanical Garden, Bronx. Nesom, G.L. 1983, Taxonomy of Erigeron concinnus (Asteraceae) and its separation from E. pumilus. Sida 10:159-166. Nesom, G.L. 2006. Erigeron (Asteraceae: Astereae). Pp. 256-348 in Flora of North America Editorial Committee (eds.) Flora of North America North of Mexico, Vol. 20. Oxford Univ. Press, New York and Oxford. Rocky Mountain Herbarium. 1998. Atlas of the Vascular Flora of Wyoming. Univ. of Wyoming, Laramie. Appendix 1. Erigeron concinnus and E. pumilus var. pumilus in New Mexico. Erigeron concinnus. Rio Arriba Co . : BLM near Gobernador, along gas line N of the El Cedro Compression Station, ca. 1 mi NW of the Gobernador Camp, sagebrush with scattered juniper, 18 May 1993, Heil & Melton 7484 (S.TC); Delasso Loos Road, 9.3 mi E of NM 539, large old pinyon- juniper woodland, Russian olive, rabbitbrush, and willow, gray clay soil, 1 Jun 1997, Reeves 9308 (SJC); mouth of Cottonwood Canyon, Lower Bancos Canyon, pinyon-juniper, clay to sandy soil, 1950 m, 28 May 1987, Wilken 14739 (NMC). San doval Co. : 19 mi W of Santa Fe, along banks of the Rio Grande River, 5450 ft, 31 May 1897, Heller 3632 (MO, NY). San Juan Co.: Aztec, 28 Apr 1899, Baker 664 (MO, NY. RM US, fide Cronquist 1947); B-Square Ranch. Head Canyon ca. mi S of outlet, talus, 5340 ft, 25 May 1999. Heil 13011 (SJC); Bloomfield, N of town on "B" Hill, 9 May 1982, Howcl 16[2032] (SJC); The Badlands, W of Farmington, ca. 1 mi W of the La Plata River, 23 May 1984, Porter 84-214 (SJC); Bloomfield [area], N side of Kutz Canyon, 3 May 1985, Porter 1018 (SJC); Co. Rd. 3590, 1.8 mi N of NM 574, jet 5 mi NW of Aztec, badland ridges, open pinyon- juniper woodlands, 6260 ft, 17 Jun 1997, Reeves 9403 (SJC); Pump Mesa, access from NM 511, gas well 236, pinyon-juniper woodland, sandy clay soil, 17 May 2000, Reeves 10090 (SJC); Farmington, 19 Jun 1911, Standley 7096 "(US, fide Cronquist 1947). Erigeron pumilus var. pumilus. McKinley Co: ca. 6 mi W of Torreon and ca. 2.5 mi E of Ojo Encino, desert shrub community, silty-clay, ca. 5700 ft, 6 May 1995. Clifford 95-117 (SJC); Navajo Nation, 4.5 mi E of Cosote Canyon community [Brimhall P.O.], scattered juniper, big sagebrush, rabbitbrush, 6630 ft, 17 May 2000, Clifford 00-249 (SJC); Navajo Indian Reservation, just W of Ojo Encino School in sagebrush flats, sandy-clay soil, 6800 ft, 30 Jun 1988, Heil 4486 (SJC); Navajo Nation, 1.5 mi down Wildberry Canyon [ca. 5 miles ESE of Coyote Canyon Store], savannah with pinyon, juniper, ephedra, Yucca, sandy, 7066 ft, 17 May 2000, Heil et al. 14579B (SJC); N of Continental Divide community, pinyon-juniper, red sand with gypsum, 7500 ft, 12 Jun 1991, Hevron 1258 (TEX); NW of Ojo Encino near the Continental divide, sagebrush flat, 2127 m, 24 May 2000, O'Kane & Heil 4635 (SJC). Rio Arriba Co : ca. 0.5 mi N of jet Forest Service Roads 314 and 315, Carson National Forest, .Tiearilia District [ca. 13 miles S of US 64 and ca. 1 mile E of the Jicarilla Apache Reservation, ca. 25 miles SSE of Navajo City], ponderosa pine, juniper-oak, 9 Jun 1995, Clifford 115 (SJC); Navajo Canyon, 4.5 mi SW of Canjilon, sagebrush-Pinus edulis, 7400 ft, 14 Aug 1963, Goodrow 694 (UNM); Largo Canyon Road near mouth of Rincon Largo, slopes above the wash and in wash, clay soils on slopes above and sandy alkaline soils in wash, 1936 m, 5 .Tun 2000, Heil & O'Kane 14731 (SJC); Jicarilla Apache Reservation, Largo Canyon, Adobe Knobs area, 1 mi E of NM 537, ca. 6 mi S of 6th Std. Parallel North, pinyon-juniper community, clay, 18 May 1995, Holmes 93 (SJC). Sandoval Co .: Jicarilla Apache Reservation, road across from rest area at jet 537 and 44, first dirt road to left, ca. 1 mi, 6 Jun 1995, Holmes 296 (SJC); Mule Dam area, desert scrub community, 6 Jun 1995. Holmes 313 (SJC); exactly 20 NW of Cuba along NM Hwy 44. . ca. 1/2 mi E of NM 537 (Lindrith/Duke road), 1/4 mi S of hwy, S side of mesa, on S slope over badlands, Artemisia tridentata, in sand, 4 Jun 1984, Spellenberg 77'92 (NY, TEX); NM Hwy 44, 20 NW of Cuba, ca. 1/2 mi S of hwy on W side of mesa, between badland ridges and extending weakly into loamy, alkaline soil, among sagebrush, 7000 ft, 29 May 1986, Spellenberg 8490 (NY, TEX). San Juan Co .: Dufer's Point, 10 mi NE of Huerfano Ml, sagebrush commumrj. with Hilaria jamesii, Bouteloua gracilis, Artemisia tridentata. loamy clay soil, 1981 m, 26 Apr 1987, Anderson 4114 (NMCR); 1.0 mi W of Chuska Peak, ponderosa pine-oak-juniper, gravelly soil, 4 Jun 2001, Atv.'ood & Clifford 27599 (SJC); Navajo Reservation, 6.5 mi SW of Nageezi area, shallow sloping topography above Kimbeto Wash, scattered pinyon-juniper, eolian deposited sand sheet, ca. 6900 ft, 25 May 2000. Clifford 00-354 (SJC); Navajo Nation, Tertiary lerraee 1.5 mi SW of San Juan River-Hogback Monocline crossing, galleta and Indian rice-grass community, silly to sandy soil, 5 170 ft, 1 1 Jul 2000, Clifford 00-738 (SJC); Cutter Dam, 4 Jun 1995, Holmes 285 (SJC); San Juan College [Farmington], Fred Edwards Nature Trail, pinyon-juniper woodland, alluvium, 5700 ft, 4 May 1988, Jenkins cfe Smith 45 (SJC): Navajo Indian Reservation, NIIP, S13 T27N, R16W [ca. 28 miles WNW of Farmington], desert shrub, 1 Jul 1988, Mietty 3114 (SJC); BLM Angel Peak area S of Bloomfield, sagebrush community, sandy soil, 6185 ft, 19 May 1992, Sawyer 45 (SJC). Taos Co .: 18 mi S of Ranches de Taos on Hwy 68 at historical marker, 8 Jun 1979, Holm 16 (BRIT); 5.9 mi W of Penasco on Hwy 75, 8 Jun 1979, Pierce 12 (BRIT); N of Arroyo Aguaje de la Petaca, among sagebrush along power line, 3 1 May 1 978, Spellenberg 4986 (NMC, NY). Appendix 2. Erigeron pumilus var. pumilus in Arizona. Erigeron pumilus var. pumilus. Arizona. Apache Co .: Navajo Reservation, W Chuska Mtns., ca. 2.25 mi E of Wheatfields Lake and 1.5 mi NE of White Cone Peak [New Mexico], ponderosa pine with big sage, silty clay to silt, 7850 ft, 4 Jun 2001, Clifford & Atwood 01-596 (SJC); Defiance Plateau, 7 Jun 1937, Peebles & Smith 13446 (LL, US fide Cronquist 1947); Canyon de Chelly National Monument, west shore of Tsaile L,ake on gravelly, sandy soil, 23 May 2001, Rink 421 (SJC).