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Biology of Amphibians - | é g o >" oe ~e hs A . i «wy f ; a J ar ree ce id > ¥ ba ey William E. Duellman and Linda Trueb Illustrated by Linda Trueb | NOT TO BE FOR TAKEN AWAY REFERENCE ONLY Biology of Amphibians Digitized by the Internet Archive in 2022 with funding from Kahle/Austin Foundation httos://archive.org/details/biologyofamphibi0000duel Biology of Amphibians William E. Duellman Linda Trueb Mhustrated by Linda Trueb T COLLEGE, HAMPSHIRE ae The Johns Hopkins University Press Baltimore and Lonel Contents Copunght 1986 by Witiam E. Dueliman and Linds Truet Preface © 1994 The Johns Hopkins University Press EGP Pee ee ee All nights reserved Printed in the United States cf America on acid-free paper First published in 1986 by the McGraw-Flill Publishing Company dobns Hopkins Paperbacks edition, 194 05 M403 02 01 00 99 98 97 95 65432 The Johna Hopkins University Press 2715 North Charies Street Baltimore. Mardand 21218-4319 The Johns Hopkins Press Lid.. London BIOGRAPHICAL NOTE ix Library af Congress Cataloging-in-Publication Data will be found at the enc of the book FOREWORD BY CHARLES M. BOGERT xi A, cotalog record for ihis book is available from the British Library PREFACE xY PREFACE TO FIRST EDITION xix Chapter 1 INTRODUCTION TO THE AMPHIBIA 1 The World of Amphibians 1 Historical Resumé 2 Prospects for the Future 7 Part 1 LIFE HISTORY Chapter2 REPRODUCTIVE STRATEGIES 13 Reproductive Cycles 13 Reproductive Mode 21 Quantitative Aspects 23 Parental Care 38 Evolution of Reproductive Strategies 47 Chapter3 COURTSHIP AND MATING 51 Location of Breeding Site 41 Secondary Sexual Characters 52 Courtship Behavior 60) Fertilization and Oviposition fl Sexual Selection 80 Evolution of Mating Systems 85 Contents Contents Chapter 4 VOCALIZATION Chapter 12 COMMUNITY ECOLOGY AND SPECIES DIVERSITY Anuran Communication System Community Structure Mechanisms of Sound Production and Reception Species Diversity Kinds of Vocalizations and Their Functions Evolution of Amphibian Communities Abiotic Factors Affecting Vocalizatian Interspecific Significance of Vocalization Part 3 MORPHOLOGY Phylogenetic Implications of Vocalization Chapter 13° MUSCULOSKELETAL SYSTEM Chapter 5 EGGS AND DEVELOPMENT Skull and Hyobranchium Spermatozoa and Fertilization Axial System Egy Structure Appendicular System Eoo Development Integration of Functional Units Hatching and Birth Development and Amphibian Diversity Chapter 14 INTEGUMENTARY, SENSORY, AND VISCERAL SYSTEMS Integument Chapter 6 LARVAE Sensory Receptor Systems Morphology of Larvae Nervous System Adaptive Types of Larvae Circulatory and Respiratory Systems Physiology and Ecology Urogenital System Social Behavior Digestive System Evolutionary Significance of Larvae Endocrine Glands Evolutionary Considerations Chapter 7 METAMORPHOSIS Endocrine Control Part 4 EVOLUTION Other Biochemical Changes Morphological Changes Chapter 15 ORIGIN AND EARLY EVOLUTION Neoteny Nature of a Tetrapod Ecological and Evolutionary Significance of Metamorphosis Primitive Tetrapods Tetrapod Affinities: Lungfishes or Lobe-Fins? Diversity anc Evolution of Early Tetrapods Part 2 ECOLOGY Status of the Lissamphibia Chapter 8 RELATIONSHIPS WITH THE ENVIRONMENT Chapter 16 CYTOGENETIC, MOLECULAR, AND GENOMIC EVOLUTION Water Economy Cytogenetics Temperature Molecular Evolution Gas Exchange Genomic Evolution Energy Metabolism and Energy Budgets Ecological Synthesis Chapter 17 PHYLOGENY Caudata Chapter 9 FOOD AND FEEDING Gymnophiona Prey Selection Anura Location of Prey Capture of Prey Chapter 18 BIOGEOGRAPHY Evolution of Prey-Capturing Mechanisms and Strategies Biogeographic Principles Historical Setting Chapter 10 ENEMIES AND DEFENSE Lissarmphibia Diseases Caudata Parasites Gymnophiona Predators Anura Antipredator Mechanisms Evolution of Defense Mechanisms Chapter 19 CLASSIFICATION Chapter 11 POPULATION BIOLOGY Characteristics of Individuals LITERATURE CITED Movements and Territoriality Demography INDEX Factors Requlating Populations vii Dedication Biographical Note To our graduate students— past, present, and future William E. Duellman has been associated since 1959 with the Univ ersity of Kansas, where he is now curator of the Division of Herpetology in the Museum of Natural History, and Professor in the Department of Systematics and Ecology, He teaches graduate courses in biogeography, reptile biology, and amphibian biology (with Linda Trueb). He maintains an active graduate program in herpetology, and he and his students use the extensive herpetological collections in the museum for diverse research. His studies on the systematics, ecology, and reproductive biology of amphibians have involved extensive field work in the United States, Mexico Central and South America, as well as Australia and Africa. Born in Dayton, Ohio he studied zoology at the University of Michigan, where he received a doctor's degree in 1956. He taught at Wayne State University before joining the University of Kansas. Dr. Duellman’s writings include more than 200 contributions to national and international journals, symposia, and museum publications. Major works are Alvtid Frogs of Middle America (Monogr. Mus. Nat. Hist. Univ. Kansas, 2 vols., 1970} Biographical Nate Liste der Rezenten Amphibien und Reptilen: Hylidae. Centrolenidae, Pseudidae (Das Tierreich, vol 95, 1977); and The Biology of an Equatorial Herpetofauna in Amazonian Ecuador (Misc. Publ, Mus. Nat, Hist. Kansas, vol. 65, 1978), He edited The South American Herpetofauna: Its Origin, Evolution and Dispersal (Monogr. Mus. Nat. Hist. Univ. Kansas, vol. 7, 1979). Linda Trueb teaches at the University of Kansas. Her courses include scientific illustration, evolutionary morphology, and (with William E. Duellman) amphibian biology. She also maintains an active graduate program in the Department of Foreword Systematics and Ecology and in the Museum of Natural History, where she and her students are investigating diverse aspects of vertebrate morphology. She has by Charles M. Bogert carried out extensive field work in Central and South America and also has worked in Affica and Australia. In 1979 she was a visiting lecturer at the University of Audnedlearigdrea, duoAtuset ralwioa.r Oartighien allUyn ivferosmt y Poofm oCnaa,l orCa,l iforBmaiar,e lyL,i ndaw ithT rueemb phdiad hoenr SRE 5 PRE RR ST vertebrate zoology. At the University of Kansas she undertook research on cranial ostealogy of anurans for the Ph.D, which she received in 1968. She has continued investigations on amphibian morphology and systematics, especially of tropical groups of anurans, and has expanded her research to include functional morphology and the role of heterechrony in anuran osteology. Aside from her research, she is @ practicing scientific illustrator. The author of about 36 major, refereed papers, Dr. Trueb has published in both domestic and foreign symposium volumes and in a variety of national and international serials, including Miscellaneous Publications and Occasional Papers of the University of Kansas, Contributions to Science of the Los Angeles County Museum of Natural History, Copeia, Herpetologica, Jounal of Monphology, Joumal of Zoology (London), and South African Journal of Science. Perhaps the earliest amphibians made their debut in an area with a more rigorous climate, but their initial diversification could well have occurred in tropical environments. Climatic conditions similar to those of today in the rainforests and cloud forests of the tropics presumably prevailed during the Pennsylvanian Period when amphibians were already numerous. For well over 250 million years amphibians have been exploiting habitats in moist tropical environments, where the bulk of them remain. Either most living amphibians are restricted to such environments or they belong to groups of species that have representatives with ranges extending into the tropics. In fact, the Gymnophiona, the smallest of the three orders and the one to which the only extant limbless amphibians are assigned, are known solely from moist tropical environments. These superficially wormlke amphibians, known as caecilians, include species that retain fishlike scales hidden in the skin. Fossil caecilians, unknown until recenthy, shed little light on their ancestry, perhaps the oldest of any amphibians extant Salamanders, the tailed amphibians qrouped in the order Caudata, though represented in the American tropics, have the distinction of being more diversified in the United States than ebewhere, Relatively thorough investigations still in progress in this country have already revealed 115 species, almost one-third of the total now recognized. Salamanders continue to be discovered in Mexico, which may prove to support as many species as the United States. However. only 43 species are known from Europe, a thoroughly explored continent. The third order, the Anura, the most widely represented of any group of amphibians now living, contains the tailless species known as frogs and toads. These include neary 87 percent of all amphibian species extant. During their long history Foreword Foreword they have probably exploited all but the most inhospitable environments between species problems, and devised experiments that paved the way to significant im- the poles and the Equator. Scarcely 3 percent of the species are represented in provements in the systematists concept of the species, Taking their cues from the United States. Some of these are largely tropical, with distributions that extend Dobzhansky, systematists were soon discussing “closed systems" and carrying out northward to the southern tip of Texas. field investigations to ascertain which “isolation mechanisms” discouraged or prevented interbreeding when related species were sympatric. Although only one popular account of amphibians, The Frog Book (1906). was available until around 1940, a wealth of authoritative handbooks dealing with the The more enlightened systematists realized that their predecessors had depended frogs and salamanders in the United States began to appear. These may well have far too heavily on the examination of preserved specimens. Even though taxon- stimulated the interests of budding herpetologists, and the field expanded. A list omists had refined their techniques of measuring, recording, and evaluating of herpetologists, most of whom were still active when it was published in 1974, morphological characters, the better systematists realized that such information indicated about 800 in the United States, 36 in Canada, but only 1 in Mexico could be interpreted far more effectively if correlated with the results of ecological (where there were at least 3). Not all of these were devoting their efforts to research, and ethological investigations in the field. Ways were devised to supplement field but a fair percentage had published at least one report. studies with breeding experiments canied out under controlled laboratory conditions, perhaps more easily with some frogs than with highly specialized amphibians, Until 1936 only one journal published in the United States provided an outlet Anatomical studies remained important, of course, and systematists continued ta for scientific contributions from herpetolagists, and this journal was shared with rely heavily on the maintenance of extensive collections of well-documented spec- ichthyologists. For the last 25 years, however, three journals have been available imens. These are required not only to deal with the problems of variations but to in the United States and a few in other countries. There are, of course, journals document distributions. Only the most conservative taxonomists regarded collec- of animal behavior, ecology, and other disciplines that also publish the results of tions with the philosophy of the stamp collector, who acquired only one of each investigations dealing with amphibians. Hundreds of such reports appear annually, kind. The acquisition of extensive broadly representative collections by large mu- in addition to books restricted to specialized investigations such as the results of a seums became the sine qua non of “the new systematics." It became important 1976 symposium that dealt only with the reproductive biology of amphibians. to students of evolution to find out whether populations of closely related animals lived side by side or occupied separate ranges or habitats. Ernst Mayr undoubtedly We need only turn back to an earlier summary to discover how much more we clarified the thinking of systematists and other students of evolution when he coined know about amphibians today than half a century ago. G, Kingsley Noble in his the terms allopatric and sympatric. authoritative Biology of the Amphibia (1931) suggested that the frogs, toads, and salamanders now living included only some 1900 species. The caecilians were so Merely pointing out that the class Amphibia proves to be represented by at least poorly known that the only fiqure Noble mentioned represents about a third of twice the number of species that an authority recognized in 1931 may seem off- the species now recognized. Noble's estimate, therefore. would have approximated hand to be of limited significance, Even if systematists continued to recognize fewer than 2000 species. When William E. Duellman and Linda Trueb completed additional species of caecilians, frogs, and salamanders at current rates, which is their survey of the literature summarized in the present book, their estimate of the most improbable, they would require another century to double the representation total was nearly double that of Noble. In other words, systematists studying the of amphibians. The new systematics, however, is not restricted to morphological amphibians have been adding names to the roster of valid species at an average descriptions. Students of evolution, perhaps more than other specialists, have con- rate of 37 species per year, tributed to the synthesis of the many fields now recognized. We have witnessed the interdigitation of anatomy, physiology, ecology, ethology, endocrinology, and Not all of the species added have necessarily been discovered or even recognized paleontology, to mention only a few disciplines, There is, therefore, a sound basis for the first time. A large percentage of them have nevertheless been diagnosed, for the assumption that advances in our knowledge of the biology of the amphib- described, and validky named since 1931. A good many others, however, had ians in its widest sense closely parallel those that have broadened our understand- been erroneously assigned to subspecific status or even synonymized by students ing of the composition of the class Amphibia. who had underevaluated the exient of the differentiation. In some instances, species represented by populations incapable of interbreeding had been viewed as Paradoxically, the proliferation of humans that led to the exploitation of rain- belonging to one species. For example, tree frogs occupying similar habitats on forests may already be contributing to the decline of the amphibians. We are opposite sides of the southwestern deserts in the United States and superficially informed that the rainforests of the world are being destroyed at rates averaging similar morphologically were regarded as being conspecific for over half a century. approximately 30 acres for every minute of every day. Once comprising 2.4 billion Not until portable tape recorders became available in the 1950s had anyone at- acres of prime amphibian habitat, the rainforests are being converted irretrievably tempted to subject the tree frogs’ mating calls to scientific analysis using audio- into useless wasteland. The frogs, salamanders, and caecilians finely adjusted to spectrograms. These spectrograms revealed such profound differences that no one this environment are being destroyed, and species may be extinguished. has since doubted that two distantly related species are represented, Inevitably field studies disclosed significant differences in the species’ modes of reproduction. Herpetologists must struggle with the abundance of information, old and new. Some find time to examine the more impressive “‘classics’’—multivolumed, some- Satisfactory solutions to innumerable taxonomic problems awaited the introduc- times lavishly illustrated accounts that began to appear even before Linnacus’s tion of new ideas, new concepts, new methods, and new or better equipment. day—but usually can only sample, Herpetologists feel inundated by the flood of Intensive field investigations revealed differentiation in behavioral traits as well as information rolling off the presses. As early as 1950 no one could even pretend adaptive specializations that discouraged or prevented interbreeding between am- to read everything published that pertained to amphibians and reptiles, even if all phibians that earlier workers had regarded as being morphologically indistinct. such publications were accessible. At least the old card index to the literature that Truly satisiactory solutions to some problems of relationships awaited the use of passed through the herpetologist's hands—a laborious system with title cards typed electrophoresis or detailed knowledge of mechanisms of inheritance. Geneticists, by the secretary and organized according to subject—can be superseded by mod- particularly Theodosius Dobzhansky and his students, turned their attention to em retrieval systems. xii xiii Foreword Regardless of how capable, well informed, or experienced, a herpetologist is unlikely to assume the responsibility of preparing a Biology of Amphibians without the support and encouragement of a sympathetic institution. Fortunately William E. Duellman and Linda Trueb are among the very few, either here or abroad, who have the requisite qualifications, including the ambition and efficiency, to summarize virtually all Jeamed thus far about the caecilians. salamanders, and frogs. At least, nearly everything confidently regarded as pertinent has been included, This account is not a compendium or an encyclopedia, Nearly every chapter could be expanded to fill an entire volume. What students as well as practicing herpetologists, biology professors, and even enlightened laypersons are likely to prefer is a reasonably complete but concise account of a fairly large, widely dis- Preface tributed group of animals. This is what Linda Trueb and William Buellman, after years of work in the field, in the library, and in the laboratory and classroom, have managed to produce. The University of Kansas, which has long and faithfully supported herpetological research, along with study collections, also deserves credit, Duellman and Trueb, a whether working independently or as a team, in recent decades have been among the most efficient and productive herpetologists in the United States. Anyone who makes full use of this book is unlikely to question this appraisal. CHARLES M. Booert Santa Fe, New Mexico March 1985 Nearly a decade has passed since the publication of Biology of Amphibians by the McGraw-Hill Book Company. The decision by that publishenrot to reprint the book left the biological community in a dilemma, because Biology of Amphibians had become the standard reference in the field and has also been useads a tein xcoturs es at many universities. The copyrighwtas transferred to us by McGraw-Hill, who also provided the original production films of the text: Shortly thereafter, we arranged with the Johns Hopkins University Press to reprint Biology of Amphibians in this solt-cover edition; with the exception of the cover, this preface, and Figure 13-16, which is reproduced correctly herein, this book is identical to the original edition We are sympathetic with the reader who had hoped for a revision of the original text. Indeed, an update and revision would be a timely and significant contribution, but we cannot undertake such an onerous task at this time. Moreover, had the origi nal films not been used to produce this volume, the price of the book would have increased tremendously. In what we hope will be an acceptable compromise, we provide herein references to major works that substantially supplement or modify information presented in the original edition of Biology of Amphibians. The follow- ing comments are organized sequentially according to the chapters in the book. The historical résumé (Chapter 1) is not particularly outdated. However, readers who wish more information about amphibian biologists who are now deceased should consult the detailed, illustrated biographies of 152 herpetologists by K. Ad- ler, 1989, “Herpetologists of the past,” in K. Adler (ed.), Contributions to the His- tory of Herpetology, Contributions to Herpetology, No. 5, Oxford, Ohio: Society for the Study of Amphibians and Reptiles. Preface Preface During the past decade much has been written about reproductive strategies in Several important publications that deal with community ecology and species amphibians (Chapter 2). One of the most important papers is that of R. A. diversity (Chapter 12) have appeared recently. Foremost with respect to herpeto- Nussbaum, (1985, The evolution of parental care in salamanders, Misc. Publ, Mus, faunal communities in neotropical rain forests are five chapters dealing with four Zool, Univ. Michigan, 169-1—50). Nussbaum argued that the sex that chooses the long-term study areas and a comparative summary in A. H. Gentry (ed.), 1990, oviposition site will be the care-giving sex, and that the sequestering of spev- Four Neotropical Rainforests, New Haven: Yale University Press. Species diversity matophores from courtship sites by females of some species determines that the of neotropical frogs was summarized by WE. Duellman, 1988, Patterns of species females of these species will be the care-giving sex. diversity in anuran amphibians in the American tropics, Ann. Missouri Bot. Gard, 75:79-104. Diversity of anurans in Africa and South America was analyzed by We originally devoted 21 pages to the subject of vocalization (Chapter 4). This W. E. Duellman, 1993, “Amphibians in Africa and South America: evolutionary materiahlas been expanded greatly with respect to the structure, function, and evo- history and ecological comparisons” in P. Goldblatt (ed.), Biological Relationships lutionof the auditory system by 28 authorsi n a book of 705 pages: B. Fritesch, M. J, Between Africa and South America, New Haven: Yale University Press. The latter Ryan, W. Wilczynski, T. E. Hetherington, and W. Walkowiak (eds,) , 1988, The Evo- reference also is pertinent to biogeography (Chapter 18). On a smaller, but far more lution of the Amphibian Auditory System, New York: John Wiley and Sons. in-depth, scale is the thorough work by N_G. Hairston, 1987, Community Ecology and Salamander Guilds, Cambridge: Cambridge University Press, in which the au- The biology of larval amphibians (Chapter 6) continues to be an exciting field. thor emphasizes different dynaamonmg ciommcunitsies of pond-breeding, stream- By defining a dichotomy between the sources of used during larval side, and terrestrial salamanders. development—endotrophy and exotrophy—R. Altg and G. Johnson (1988, Guilds of anuran larvae: relationships among developmental modes. morphologies, and Readers interested in the morphology of amphibians (Chapters 13 and 14) are habits, Herpetol. Monogr., 3:81-109) contributed significantly to our understand- directed to The Skull( J. Hanken and B. Hall (eds. |, 1993, Chicago: The University ing of the bioloof glayrva l anurans. Based on their comprehensive survof eanyura n af Chicago Press); the three volumes that comprise the series (Volume 1: Develop: larvae, these authors offered speculative scenarios and hypotheses concerning the ment; Volume 2: Patterns of Structuraalnd Systematic Diversity: Volume 3; Func- functional adaptations of different larval morphologies and the relationships of tional and Evolutionary Mechanisms) represent a synthesis of the comparative mor- traphic structures to the ecology of the tadpoles. phology, development, evolution and functional biology of the vertebrate skull. A great deal of valuable information on fossil and recent amphibians is integrated into Chapter 7 provides fundamental information on the complex mechanisms gov- many of the chapters. eming metamorphosis in amphibians. The ecological and evolutionary implications of amphibian metamorphosis, along with processes of its control, are bur- There are several useful supplements and updates to the discussion of primitive geoning fields of contemporary research that, as yet, have not been reviewed tetrapods and their relationships (Chapter 15). J. A. Gauthier, A. G. Kluge, and synthetically, However, the evolution of metamorphosis in amphibians with respect T. Rowe (1988, "The early evolution of the Amniota” in M. J. Benton (ed. ], Am- fo the brain stem, inner ear, and lateral-line system, was reviewed in the context of phibians, Reptiles, Birds, The Phylogeny and Classification of Tetrapods, Vol. 1. adaptive changes by B.Fritzsch (1990, The evolution of metamorphosis in amphib- Oxford: Clarendon Press.) examined which taxa among extinct tetrapods are re- ians, J. Neurobiol. 21:1011—1021). Fritesch arqued persuasively that changes trans- lated most closely to the Amnicta. In another chapter of the sare work, A. Milner forming tadpoles into froglets evolved within amphibians and, contrary to popular (“The relationships and origin of living amphibians") reviewed the statofu esach of wisdom, that the process of metamorphosis in amphibians does not reflect the the orders of living amphibians. The most recent treatment of the relationships of water-to-land transition of ancient ammniotes, primitive tetrapods is Section | of a book edited by H. P Schultze and L. Trueb (1991, Origins of the Higher Groups of Tetrapods: Controversy and Consensus, The material on relations with the environment (Chapter 8) should be augmented Ithaca, New York: Cornell University Press.); seven authors contributed five chap- by the excellent reviews of ecological and developmental physiology included in ters dealing with the origin of tetrapods. The systematic status and relationships of M. E. Feder and W. W. Burggren (eds.), 1992, Environmental Physiology of the living amphibians are extensively dealt with by three authors in two chapters in the Amphibians, Chicago: University of Chicago Press. Much new material is presented same volume (op, cit.). John R. Bolt reinvestigated the positions of the dissoraphids in the section on energetics and locomotion, and the section on development and and the microsaur Hapsidopareion with respect to the Lissamphibia, and, in a major reproduction is also pertinent to Chapter 2 (reproductive strategies) and Chapter 5 phylogenetic study based on osteological features and soft-anatomical characters, (eggs and development). L. Trueb and R. Cloutier attempted to document the monophyly of the Lissam- phibia and hypothesized relationships between this group and primitive tetrapods The major new information that bears on population biology (Chapter 11) is the observation by biologists that populations of many species of amphibians through- Persons interested in cytogenetic, molecular, and genomic evolution (Chapter out the world have declined since the mid-1980s. Muchof this decline can be attrib- 16) should consult the volume, Amphibian Cytogenetics and Evolution, edited by uted to destruction or modification of habitats, but the decline of populations in D. M. Green and S. K. Sessions (1991, New York: Academic Press, Inc.). This book, pristine areas suggests that more subtle (and as yet, unidentified) causes are respon- which consists of 17 chapters contributed by 24 authors, |s a vital source that largely sible, Declining populations are not evident in alll taxa in all locations, nor is there supersedeosur treatment of the subjects. Also, the material on chromosome com- evidence of a single global causal factor. The issue was addressed at a workshop plements has been expanded by M. Kuramoto, 1990, A list of chromosome num- sponsored by the National Research Council, USA, in February 1990. A summary bers of anuran amphibians, Bull. Fukuoka Univ, Education, 39:83-127. was published as “Declining amphibian populations—a global phenomenon? Findings and recommendations,” Alytes, 9:33—42. Subsequently, the Species Sur- Significant advances have been made in our understanding of the phylogenetic vival Commission of the International Union for the Conservation of Nature estab- relationsohf ispomse groups of amphibians (Chapter 17), Use of molecular data has lished the Declining Amphibian Populations Task Force, which is coordinating re- resulted in the formulation of alternate hypotheses of the relationships of the fam- search on monitoring amphibian populations. ilies of salamanders (A. Larson, 1991, A molecular perspectivoen the evolutionary xvi xvii