Speciation in Birds and More

but then leaves us with the vague and unsatisfying conclusion: “The influence of temperature on unionoids is thus pervasive and complicated, so it is not easy to specify the optimal thermal regime for a unionoid” (p. 55). This is mostly a writing style issue, but it does tend to overstate somewhat the extent of our ignorance about several topics in mussel ecology. Part II also contains a number of original analyses and modeling exercises that further explore the relationship of specific factors to mussel abundance. Some of these analyses are very strong and bring out important new points or different ways of looking at problems. In particular, the epidemiological models for studying mussel–fish interactions (p. 76–84) and the models for evaluating potential food limitation (p. 98–103) make some interesting predictions and could be fruitful approaches for future research. Other model predictions are less novel (e.g., smaller populations are at higher risk of extinction than large ones) or are supported by so few data as to be of questionable value (e.g., Figure 16, based on parameters that are “entirely speculative”). Nevertheless, these analyses all set up testable hypotheses for future research, and this is one of the most important functions of the book. Part III, “Making the Monster Walk,” is the ostensible culmination of the model-building exercise. The first chapter in Part III (“Three Models for Mussel Ecology”) is a general discussion—although couched within the realm of freshwater mussel ecology—of different approaches to ecological modeling. The final chapter (“Is a Comprehensive Model Possible?”) attempts to reconcile these various approaches and propose some more concrete examples of what multifactor models for mussels might look like and what they might be expected to accomplish. Here, the book is somewhat schizophrenic, as if Strayer cannot quite bring himself to abandon the goal of a single, unifying theory. On page 141 he states, “I think that careful empirical analyses have good potential for predicting the distribution and abundance of unionoids from multiple controlling factors.” This is followed, one page later, by “I do not believe that any of the three popular approaches to integration [one being empirical analyses]. . .is likely to lead to a satisfactory predictive understanding of unionoid distribution and abundance.” Finally, he concludes (p. 154) “I believe that the construction of a comprehensive, mechanistic model is a hopeless enterprise” (whew!), but continues to grasp for “some sort of integrative framework.” Even though, in the end, the monster never walks, this book is illuminating and thought provoking. While reading it, I constantly found myself thinking, “Hey, that could be tested” or “That would make a great study.” In this way the book is a charge to biologists to conduct mussel research in a coordinated, focused way that will directly inform the major problems of mussel ecology and conservation. This kind of efficiency is critical given the desperate plight of these animals. Nevertheless, although it is true that mussel ecology lags behind other fields, Strayer is perhaps a bit too critical of its lack of progress and direction (p. 156). As in any collection of people, mussel researchers each have their own professional responsibilities and mandates to answer to as well as their own personal interests. But apart from the old notion of mussels being outside the scope of ecology (a notion Strayer effectively dispels), the major problem with mussel ecology is that the field has simply not had the critical mass of researchers to really get off the ground. But this is changing rapidly as more talented people catch the mussel bug. In Freshwater Mussel Ecology: a Multifactor Approach to Distribution and Abundance, David Strayer provides direction for this burgeoning field, and I hope this timely book will entice still more ecologists to study and help save these fascinating animals.