Next-generation studies of mating system evolution.

The specificity of mate selection can vary from wantonly indiscriminate to extraordinarily choosy, and depends in large part on molecules expressed on the surfaces of sperm and eggs. Understanding the evolution of this specificity of gamete recognition leads to important insights into the evolution of reproductive isolation and speciation. One productive area of research has focused on genes that encode gamete recognition proteins in broadcast-spawning marine invertebrates. These gene products are relatively accessible to biochemical and cellular analyses of expression and function, and they mediate almost all of the elements of mate selection and specificity between males and females of such species. However, genetic analyses of their evolution are currently limited to a few combinations of molecules and taxa, and may miss the broader view of adaptive responses to selection on mating specificity across many genes and many types of mating systems. A transcriptomic study shows how next-generation sequencing methods and analyses could relatively easily broaden such studies to more clades, deepen those studies to include more of the interacting molecular parts that mediate gamete recognition, and eventually lead to a more complete understanding of the molecular basis for mating system variation and its evolutionary response to selection.