LIBRARY OF THE UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN 590.5 FI V.39 cop. 3 NATURAL HISrOKY. SURVEY » Jt i| FIELDIANA • ZOOLOGY Published by CHICAGO NATURAL HISTORY MUSEUM Volume 39 October 29, 1958 No. 23 A NOTE ON THE PHILIPPINE FROGS RELATED TO RANA MACRODON Robert F. Inger CuBATOR, Division of Reptiles and Amphibians In my review of the Philippine amphibians (Inger, 1954), several large aquatic forms of Rana were treated as subspecies of macrodon of Borneo, Sumatra, and the Malay Peninsula. Since that publica- tion appeared, Chicago Natural History Museum has received much additional material from the Philippine Islands and from Borneo. Study of these specimens suggests revision of my previous opinion. That the Philippine forms, acanthi, magna, macrocephala, and visay- anus, differ from macrodon of Borneo and the Malay Peninsula in the possession of vocal sacs has long been known (Boulenger, 1920; Inger, 1954) . That difference, taken by itself, did not seem sufficient reason for separating macrodon from the Philippine frogs at the specific level. The other differences between macrodon and certain of the Philippine populations were not significant to this problem because the charac- ters involved (for example, size, rugosity of skin, ventral coloration) varied from population to population. However, a character of macrodon not noted before re-enforces the difference in vocal sacs. Mature ova of all the Philippine frogs related to macrodon, including the distinct species woodworthi Taylor, have a densely pigmented hemisphere and thus resemble the great majority of their congeners. But the ova of macrodon have no dark hemisphere and are uniformly yellow. A new Bomean member of this group (to be described in a separate publication), a species living with macrodon along forest streams in eastern North Borneo and re- sembling macrodon in lacking a vocal sac, also has pigmented ova. Rana macrodon is thus the only form in this species groups without pigmented ova. 1 The Rana doriae-macrognathus series is excluded from consideration here as it is clearly distinct from macrodon and its Philippine relatives. Library of Congress Catalog Card Number: 58-59721 No. 860 263 J),| ^J^yfffjgf Q^ fHE NATURAE NOV 18 1958 Vkl r, 4„r.„ HISTORY SURVEY W^ 19^3 uBRARilNlVERSITY OF ILLINOIS 254 FIELDIANA: ZOOLOGY, VOLUME 39 In view of this additional distinction, it seems best to separate the Philippine frogs from macrodon at the specific level. Earlier, I considered the relationship of modesta Boulenger to these Philippine frogs to be no closer than that of modesta to micro- disca (Inger, 1954) , Two seemingly trivial characters (among others) differentiate modesta and the macrodon-magna group. A dark, in- verted V appears on the back in about half the individuals of modesta but not in the macrodon-magna group, which often has a dark W, especially in juveniles. Another pattern element, a pair of broad, yellowish, dorsolateral bands, occurs in about one-fourth or one-fifth (three out of fourteen seen) of modesta but never in the others. Con- ceivably each of these distinctions could be accounted for by single gene differences so that they might not represent significant diver- gence. However, the issue here is a decision as to which relationship is closer, that of modesta to microdisca or that of modesta to the macrodon-magna group, and the significant point is that the two trivial characters of modesta crop up in microdisca and not in magna and its allies. If phylogenetic affinity is a measure of the similarity in genetic composition, the more closely two species are related the more likely they are to hold genes in common and, as a corollary, to show simi- larities in trivial characters. Therefore, in the absence of evidence to the contrary, these two minor characters indicate that the rela- tionship of modesta to microdisca, which is sympatric with the macro- don-magna group over much of their ranges, is closer than the rela- tionship of either to macrodon or magna. Consequently, the separation of magna and modesta at the specific level should be retained. Since magna Stejneger is the oldest-named of the Philippine frogs concerned, its name is applied here to the polytypic species that in- cludes the following forms: Rana magna magna Stejneger — Mindanao, Basilan. Rana magna acanihi Taylor — Busuanga, Culion, Palawan, Balabac. Rana magna macrocephala Inger — Luzon, Polillo. Rana mxigna visayanus Inger — Panay, Bohol, Negros, Leyte, Siqui- jor, Dinagat. Since zoogeographic discussions are based on taxonomic conclu- sions, the effect of this modification of taxonomy should be considered. Rana macrodon alone of the Philippine species was placed in a cate- gory of non-endemic species distributed from Sundaland to Papua (Inger, 1954). Now, of course, Rana magna must be placed in the 4M! ^U rHf^VidiJ 1HI cm^iw lO VT' '^{ X INGER: FROGS RELATED TO RANA MACRODON 255 category of endemic species of western affinity. No other changes in my previous zoogeographic conclusions are necessary, because the relationships of the Philippine populations to one another and to species besides macrodon remain the same. REFERENCES BOULENGER, G. A. L 1920. A monograph of the South Asia, Papuan, Melanesian, and Australian P frogs of the genus Rana. Rec. Ind. Mus., 20: 1-226. Inger, R. F. 1954. Systematics and zoogeography of Philippine Amphibia. Fieldiana: Zool., 33: 183-531, figs. 28-98. I