Having recently encountered the absurd criterion of whether a book will fit in a backpack as the first cut in a judgment of its worth, with size inversely proportional to value, I am both personally and professionally pleased to note that this new book written by Kent Wells will not fit in an ordinary backpack. Nor for that matter will it accommodate the schemata of narrow minds, short attention spans, or least publishable units (more on this below).
This is a book about the diversity of amphibian life and the ecological and behavioral features that have made amphibians successful components of global terrestrial and freshwater aquatic ecosystems. There are more than 6000 extant species of amphibians, and nearly everything you need to know about these animals is included in this volume. Kentwood D. Wells, a professor in the Department of Ecology and Evolutionary Biology at the University of Connecticut, traces his book's pedigree back to G. K. Noble's The Biology of the Amphibia (1931) and through Duellman and Trueb's Biology of Amphibians (1986) and Heatwole's Amphibian Biology series (1999–present). To this list I would add Stebbins and Cohen's A Natural History of Amphibians (1995).
Throughout the book Wells emphasizes variation. He points out that because modern amphibians consist of families at least 50 million to 100 million years old, they are as divergent as horses are from opossums, bats, and anteaters. He challenges the “uncritical use of…animals as model organisms, based on the assumption that [amphibians] chosen mainly for their suitability [for the] laboratory…are representative of amphibians as a whole.” And where there are differences of opinion, out of concern for fair play he recognizes all sides. Considering the evolutionary origin of amphibians, Wells writes: “We can only speculate about the selective pressures that led a group of fishes to emerge onto land.… Some authors have argued that the [selective force was] unexploited food resources in the emerging terrestrial communities and the absence of large predators.… Others have suggested [the requirement to leave low dissolved oxygen conditions in] warm, swampy environments.… Another theory is that…periodic drought favor[ed] the ability to leave drying pools to seek out other aquatic habitats” (p. 3).
Authors take heart: you may have thought not many people noticed that neat little paper you published in that midlevel journal, but Kent Wells did, and it's included in this book.
Where there are problems, such as with the paraphyly of the anuran (frog and toad) families Hylidae, Leptodactylidae, and Ranidae, he acknowledges the situation, suggests patience, and offers direction: “these families eventually will be divided into smaller families that are monophyletic” (p. 15). When considering Wells's words, I'm reminded of the compliment that legendary biologist Ed Ricketts paid to W. K. Fisher about one of his biogeographic papers. Ricketts wrote that it was “the work of a man who has too much integrity to make things fit for convenience what won't fit in fact” (Rodger 2006). And when Wells writes about the new and “radically revised” phylogeny of amphibians recently proposed by Daryl Frost and colleagues (2006), he notes the value of this new thinking, but then adds, “It seemed neither possible nor desirable [at this late date] to incorporate these changes into the book” (p. 2). We feel a little bad about this both for him and for us, because we want Kent Wells to be able to incorporate this new thinking, and we know that how he thinks about this issue will, to some extent, determine how we think about it.
Chapters are organized around biological themes, and Wells begins each with a quote, usually from a centuries-old source, that is quirky, naïve, or quaint, and often hostile. (My favorites include “These foul and loathsome animals,” “Amphibians are a defeated group,” “These hideous and disgusting reptiles,” and “Amphibia…remain slaves of their surroundings.”) These words make us smile but also give perspective on how far we've come in our understanding of “these fine beasts.” In each chapter, Wells provides a clear history of the topic, including citations of nearly all of the relevant literature. (Authors take heart: you may have thought not many people noticed that neat little paper you published in that midlevel journal, but Kent Wells did, and it's included in this book.) As mentioned above, Wells takes an even-handed, level-headed approach to nearly every topic considered, and in many cases suggests directions for future research.
Some chapters are books unto themselves. For example, chapter 1 begins with general characteristics of living amphibians. Wells then considers the origin and evolution of amphibians, morphological evolution, paedomorphosis, genome size, and the phylogeny and classification of anurans, urodeles (salamanders), and caecilians. Each of the phylogeny and classification sections includes lengthy synopses of each component family, followed by topics such as morphological evolution and ecology, habitat associations, body size, sensory systems, locomotion, body plans associated with burrowing, arboreal dwelling, gliding, and the evolution of lunglessness. The first chapter alone is worth the price of the book.
In the chapters addressing physiology, Wells pays attention to ecological and life history differences. For example, in addressing water relations (chapter 2), he regards ground-dwelling, arboreal, and burrowing species separately. When considering temperature relations (chapter 3), he addresses life-history stages separately and includes an extensive section on freeze tolerance. In the chapters on behaviors, he emphasizes species differences. For example, addressing movements and orientation (chapter 6), he presents separate, lengthy tables first on movement distances, then on home-range sizes for salamanders and anurans. Considering anuran vocal communication (chapter 7), he offers a text appropriate for a short course in neural systems and behavior.
The numerous photographs accompanying chapters on reproduction (chapter 10) and parental care (chapter 11) demonstrate differences in mating, egg-mass shape, nests, egg guarding, brood pouches, and egg and tadpole transport. The reader is left with a conscious impression of variation in these traits, and the data shown in the many tables and figures reinforce this understanding. The chapters on ecology and behavior of larvae (chapter 12) and complex life cycles and metamorphosis (chapter 13) continue Wells's emphasis on variation as he addresses the morphology, physiology, ecology, and behavior of larval life histories and their trajectories. Chapters on predators (14) and communities (15) reinforce the notion that amphibians occupy midlevel trophic positions in most ecosystems (i.e., one ecological role of amphibians is to transfer insect biomass into avian and mammal biomass—that is, these amphibians are meant to eat and be eaten).
Wells provides figures demonstrating mortality rates, survivorship, and longevity. His first table in chapter 14 is an internal reference to other sections in the book where predation is shown to influence specific behaviors or ecological factors. In chapter 15, Wells provides a conceptual framework for amphibian community studies that defines spatial scale, species composition, processes that structure communities, and global and regional patterns. He then addresses communities of adult anurans, terrestrial salamanders, pond-dwelling salamanders, and tadpoles.
Because of how Wells sets up the first 15 chapters of his book—with theme and variations, and a stunning attention to species-specific detail—his last chapter (16) has something that almost no other argument for amphibian conservation has: the implicit notion that if a large percentage of amphibian species become extinct, what the earth loses forever are big chunks of the biology just described. In this chapter, all known causes of amphibian declines are addressed, and there is a large section on the relatively new phenomenon of chytridiomycosis and emerging infectious diseases.
So, the question everyone posits when they contemplate this book (and one that, as a neurobiologist, I naturally gravitate to) is: how can one person know all this stuff? The answer, of course, is they just do. To paraphrase Norman Maclean, there is something in them that's not in the rest of us. Ted Parker's brain knew 4000 species of Neotropical birds by their song alone; Al Gentry's brain could recognize 6000 species of Neotropical woody plants (one sixth of the world's woody plant species) on sight in the field. When Parker and Gentry were killed in a 1993 plane crash in Ecuador, these skills were gone and could not be replaced. (Perhaps by teams of people and technology, yes, but not at that time by individuals with the same aptitude.) Add to this list of exceptional biological talent the ability of Kent Wells's brain to synthesize literature.
Any book is a direct extension of its author. In The Ecology and Behavior of Amphibians, the University of Chicago Press notes in its description that Wells's book synthesizes 70 years of research on amphibian biology, and this is true. It is also true that “the reports of biologists are the measure, not of the science, but of the men themselves” (Steinbeck and Ricketts 1941, p. 73). As we contemplate the future and the growing challenges to the survival of amphibian diversity (and therefore to amphibian biology), let us not forget that while individual papers, or series of papers, give us our knowledge, it is uniquely talented people like Kent Wells, with that rare ability to fully assimilate large numbers of facts—measured, I guess, in clusters called backpack units—who give us, in their own inimitable way, our understanding.