Fish reproduction: patterns, puzzles, principles, and possibilities

Abstract

Robert (Bob) Wootton passed away in March 2014 while this book was going to press. He and Carl Smith spent five years writing it, and Bob was ill the whole time. It’s a great book, a big book (400 text pages and 1500 references, in round numbers), and a fine tribute to Bob’s life’s work. I am sorry to have never met Bob, but over the years I met several pieces of his work (as well as Carl’s). For example, in 1994 Bob wrote a paper that used the classic Smith/Fretwell model for optimal size of an offspring to predict egg size in pelagic fishes; the model/theory is deceptively simple in pictorial form, but that which generates the tradeoff curve is not simple. Guided by the model, Bob carefully assembled all the pieces and the predicted answer fell squarely in the range of observed egg sizes. I mention this particular paper because I used it for years in my graduate evolutionary ecology class, and found it quite impressive. So, how to begin describing the book? The topic is vast and first chapter lays out the landscape. The dual themes of phylogenetic history and adaptive significance (natural selection carefully applied to all aspects of life history) form the big structure. Here we get an overview of the reproductive modes of the teleost fishes (~30,000 species; not all discussed), and hints of what is to come. In all chapters a few exemplar case histories receive special attention because they allow us to resolve key issues with hard data. Some of them point to key gaps in our knowledge; they point to the future. Males and females often differ greatly in all elements of reproduction, so the second chapter delves into how sex is determined in the first place. Genotype alone can determine sex (GSD; by far the most common in fish), or sex can be set by the developmental environment, often temperature (ESD). Wootton and Smith tell us what the patterns are, point toward the unknowns, and discuss some of the ideas about why natural selection favors this or that mode of sex determination. There are many puzzles here, particularly why closely-related species often have very different forms of GSD, a pattern repeated in many other taxa, too (e.g., Bull 1983). This discussion is very well done, and is a fine gateway to broader, and more population genetic intensive (a nice phrase for= lots of math) treatments (Bull 1983; Beukeboom and Perrin 2014). This chapter has what we will find in all the chapters: patterns (mapped to phylogeny and environment), puzzles (unknowns big and small), principles (often insightful adaptation arguments, with limitations noted), and possibilities (i.e., where would all we just discussed point to next?). The Atlantic Silverside [Menidia menidia; work of David Conover] is an exemplar here. Those fish populations have a mixture of ESD and GSD, and show that ESD phases out as one looks at populations that reside at increasingly northern latitudes along the Atlantic coast of North America. Conover shows both how and why this is predicted by sex ratio theory. When ESD goes Environ Biol Fish (2015) 98:1727–1728 DOI 10.1007/s10641-015-0391-7