IS THERE A UNIFYING THEORY OF SEX ALLOCATION

Review of: West, S. 2009. Sex Allocation. Princeton University Press, New Jersey. 482 pp. ISBN 978-1-4008-3201-9. $99.50 (cloth), $45.00 (paper). Within evolutionary biology, the field of sex allocation is often heralded as one of the great successes, where simple and elegant theory can explain and predict the patterns we observe in the natural world. Perhaps even more impressive is the accumulated evidence that organisms from parasitic flatworms to red deer exhibit subtle patterns of sex allocation, biasing their relative production of gametes or sons and daughters in response to a variety of environmental variables and individual conditions. For those of us who watch the field closely, however, we know that lurking beyond that true sense of achievement there is also a plaguing amount of overlooked biological complexity and unexplained empirical variation. As such, I recently found myself wondering aloud whether there was or ever could be a unifying theory of sex allocation? I do not mean to imply that we do not know a great deal about sex allocation in terms of both theoretical expectations and empirical patterns. Instead, what I would argue is that we have a lot of really wonderful, but slightly myopic, understanding of observed patterns and that research often sets out to examine overlapping hypotheses without a clear sense of how (or whether) we can truly distinguish between them, independent of any specific set of results. This means that we end up being both a little bit right and a little bit wrong most of the time. To be fair, this problem is not limited to our understanding of sex allocation. The question is whether this is the inevitable outcome of biological complexity or whether one might actually hope for a general theory of sex allocation or at least some testable and mutually exclusive hypotheses that apply as well to plants as they do to mammals. I may be an optimist, but I was personally hoping for the latter as I sat down to read Stuart West’s recent book titled “Sex Allocation” (2009). I also could not help but compare it with Charnov’s (1982) book on “The Theory of Sex Allocation.” In my defense, in case you are thinking these were unrealistically high expectations for any one book, it is precisely the need to update Charnov (1982) and a desire to unify this large but fractured field that Stuart West gives as his reasons for “Why this book is needed” (p. 8, West 2009). Putting aside those lofty goals for the moment, there is a lot to like about this book. First, I found it surprisingly easy and interesting to read. It is serious and rigorous, yet interspersed with just enough humor and personal notes to be enjoyable without being cute. My personal favorites were the suggested reading plans for (among others) “those already familiar with sex allocation and aged >30” (Table 1.1, which for the record I ignored) and the assertion that “only a loony would use a multilocus model to solve a sex allocation problem that could be addressed with ESS theory” (page 360–361, which you may admittedly have to be a game theorist to appreciate). Each chapter includes a rigorous presentation of key theoretical and empirical results, and the book represents an impressive synthesis of what is a large and complex field. For those new to the subject, they will likely find certain explanations incomplete and will need to go to the primary literature for enlightenment. This task should, however, be relatively easy as the text is well-referenced throughout (though those