The Systematics of the Frogs of the Hyla Rubra Group in Middle America

Part 1

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UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY

Volume 18, No. 6, pp. 505-545, 7 figs., 4 pls.

December 2, 1969

The Systematics of the Frogs of the Hyla rubra Group in Middle America

JUAN R. LEÓN

University of Kansas Lawrence 1969

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: Frank B. Cross, Philip S. Humphrey, Robert M. Mengel.

Volume 18, No. 6, pp. 505-545, 7 figs., 4 pls. Published December 2, 1969

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY ROBERT R. (BOB) SANDERS, STATE PRINTER TOPEKA, KANSAS 1969

The Systematics of the Frogs of the Hyla rubra Group in Middle America

JUAN R. LEÓN

CONTENTS

PAGE

INTRODUCTION 508 Acknowledgments 508 Materials and Methods 509

THE HYLA RUBRA GROUP 509 Key to Species and Subspecies 510 Key to Known Tadpoles 511

ACCOUNTS OF SPECIES AND SUBSPECIES 511 Hyla boulengeri (Cope) 511 Hyla foliamorta Fouquette 520 Hyla rubra Laurenti 524 Hyla elaeochroa Cope 525 Hyla staufferi Cope 532 Hyla staufferi staufferi Cope 537 Hyla staufferi altae Dunn 540

EVOLUTIONARY HISTORY 540

LITERATURE CITED 543

INTRODUCTION

The tree frogs of the Hyla rubra group are abundant and form a conspicuous element of the Neotropical frog fauna. Representatives of the group occur from lowland México to Argentina; the greatest diversity is reached in the lowlands of southeastern Brazil (Cochran, 1955). The group apparently originated in South America; the endemic Central American species evolved from stocks that invaded Middle America after the closure of the Colombian Portal in the late Pliocene.

Dunn (1933) partially defined the rubra group as it occurs in Central America. Cope (1865, 1876, 1887), Brocchi (1881), Boulenger (1882), Günther (1901), Noble (1918), Kellogg (1932), Dunn and Emlen (1932), Stuart (1935), and Gaige (1936) dealt with the Middle American species now considered to make up the rubra group. More recently, Taylor (1952, 1958), Fouquette (1958), Starrett (1960), and Duellman (1960, 1963, 1966a) studied aspects of the taxonomy and biology of the species of this group. The five species of the rubra group in Central America have received ten different names. One species, Hyla staufferi, has received five names (two subspecies are recognized herein). Hyla boulengeri was named in the genus Scytopis, but the type species of Scytopis is a member of the genus Phrynohyas Fitzinger, 1843 (Duellman, 1956.)

Little has been published concerning the ecology, life history, osteology, and mating calls of the Middle American species of this group. The purpose of the present report is to describe the species occurring in Middle America and to comment on their distributions, ecology, cranial osteology, and mating calls, and in so doing provide evidence for the evolutionary history of the species inhabiting Middle America.

Acknowledgments

For permission to examine specimens in their care, I am grateful to Drs. Richard G. Zweifel, American Museum of Natural History (AMNH); Robert F. Inger, Field Museum of Natural History (FMNH); Ernest E. Williams, Museum of Comparative Zoology (MCZ); Hobart M. Smith, University of Illinois Museum of Natural History (UIMNH); Charles F. Walker, University of Michigan Museum of Zoology (UMMZ); Jay M. Savage, University of Southern California (USC); James A. Peters, United States National Museum (USNM); Richard J. Baldauf, Texas Cooperative Wildlife Collection (TCWC); and W. Frank Blair, Texas Natural History Collection (TNHC). KU refers to specimens in the Museum of Natural History, University of Kansas. For the loan of tape-recordings of mating calls I thank Drs. W. Frank Blair, University of Texas, and Richard G. Zweifel, American Museum of Natural History.

Part 2

I am indebted to the Ford Foundation-Universidad de Oriente (Venezuela) Science Project for a scholarship which enabled me to study for two years at The University of Kansas, foster institution of the project. I have benefited by being able to work in the Museum of Natural History at The University of Kansas and I am grateful to Dr. E. Raymond Hall, Director, for providing space and equipment.

I gratefully acknowledge the assistance and advice of Dr. William E. Duellman, who suggested and directed this work, made available specimens under his care and gave much of his time in reading the manuscript and suggesting improvements. I am grateful to Dr. Frank B. Cross who critically read the manuscript and made many editorial suggestions. I am indebted to Linda Trueb for assistance with the osteological aspects of this study; she helped to clarify many confusing points. I am grateful to Charles W. Myers for making available his field notes on these frogs in Panamá, to Arthur C. Echternacht for reading part of the manuscript, and to John D. Lynch for many suggestions and helpful criticisms. The illustrations were executed by David M. Dennis.

Materials and Methods

For the purposes of the present study I examined 1383 preserved specimens, 50 skeletons, and 9 lots of tadpoles. External characteristics used in the analysis of variation are those currently employed in the study of anuran systematics. Twelve measurements and six proportions were taken in the manner described by Duellman (1956). Only the most important references are given in the synonymies, except those of the two subspecies of Hyla staufferi, which are more nearly complete. The taxonomic history of each frog is discussed under Remarks in each account. The cranial osteology was studied by using skeletons and cleared and stained specimens of all species. Developmental stages of tadpoles were determined from Gosner's (1960) table. Personal field work in Central America in the summer of 1966 provided an opportunity to make observations on the ecology, calling sites, and color in life; these data were supplemented by field notes from, and discussions with, Dr. William E. Duellman and Charles W. Myers.

The mating calls of the frogs were recorded in the field on Magnemite and Uher Tape Recorders by Dr. Duellman in the course of his work on the hylid frogs of Middle America--supported by grants from the National Science Foundation (G-9827 and GB-1441). These recordings, plus those borrowed from other institutions, provided 50 tapes for analysis of the mating calls. The calls were analyzed on a Vibralyzer (Kay Electric Company).

THE HYLA RUBRA GROUP

Definition.--The species forming the group are small to moderate-sized tree frogs (maximum snout-vent length of males of various species 20-49 mm.), distinguished from other groups in the genus Hyla as follows: Brown, grayish brown, or yellowish tan above; thighs plain, marbled with dark brown, or having vertical bands; vocal sac single, median, subgular; snout flat, protruding, rounded or pointed; webbing between fingers reduced or absent; web between first and second toes reduced to fringe on second toe, rest of toes about half webbed; tarsal fold reduced or absent; shanks robust; inner metatarsal tubercle larger than outer; prevomerine teeth on transverse ridges between small to large sized choanae; skull generally longer than wide; nasals large (length more than 40 per cent total length of skull) and having pointed maxillary processes; maxillary bearing small ventromedial palatine process; quadratojugal slender, always joined to maxillary by bony suture; auditory region of proötic slender and short; delicate spatulate columella ventral to crista parotica, broad basally, compressed anterolaterally, slightly rounded distally; anterior arm of squamosal extending about half distance to maxillary; sphenethmoid wider than long; frontoparietal fontanelle present or absent; prevomerine, premaxillary, and maxillary teeth present; prevomer with two lateral processes forming incomplete bony margin to internal nares; tadpoles having pointed xiphicercal tail, snout short, rounded; 2/3 tooth rows; dorsal fin deeper than ventral fin; sinistral spiracle; short dextral anal tube not reaching edge of ventral fin; mating calls consisting of single long note or series of short notes.

Composition.--This group contains about 24 currently recognized species, most of which occur in Brazil. Only five species--boulengeri, elaeochroa, foliamorta, rubra, and staufferi with two subspecies--occur in Central America. Hyla boulengeri and rubra are widespread in South America, and foliamorta occurs in Colombia, whereas the other species are known only from Middle America.

Distribution.--The species of the Hyla rubra group range from the lowlands of northern Argentina and Bolivia to southern Tamaulipas and Guerrero, México.

Comments.--In Central America two subgroups of species can be recognized. Hyla boulengeri and H. foliamorta are distinctive in the large size of adults (snout-vent lengths 41-49 mm.); both have prominent bars on the thighs, a well-defined interorbital triangular mark, blotches or spots dorsally, and large choanae. Hyla elaeochroa, H. rubra, and H. staufferi are smaller (snout-vent lengths 29-40 mm.); they have the thighs weakly barred or vermiculate anteriorly and posteriorly or unmarked, an ill-defined interorbital triangular mark, linear markings dorsally, and small choanae.

Key to Species and Subspecies

1. Larger frogs (males to 49 mm. snout-vent length); thighs strongly barred; supratympanic fold black; dorsum blotched or spotted 2

Smaller frogs (males to 40 mm. snout-vent length); thighs weakly barred or plain; supratympanic fold pale brown; dorsum usually having linear pattern 3

2. Dorsum tuberculate; snout subacuminate; vocal sac flecked with brown; tarsal fold rudimentary; web absent between fingers; black spots absent in scapular region H. boulengeri

Dorsum smooth; snout pointed; vocal sac dark gray; tarsal fold absent; trace of web between fingers; two or more elongate dark spots in scapular region H. foliamorta

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