Shall we dance or shall we fight? Using DNA sequence data to untangle controversies surrounding sexual selection.

Population and evolutionary genetics studies have largely benefitted from advances in DNA manipulation and sequencing, as well as DNA data analysis techniques. Molecular evolution studies of male reproductive genes show a pattern of rapid evolution shaped, in some cases, by an adaptive selective process. Despite the large body of data on male reproductive genes, the female side of the story has remained unexplored. The few cases of female egg receptors analyzed also show rapid evolution. However, to disentangle between competing hypotheses on how selection operates on male x female molecular interaction leading to fertilization, we need to find male and female molecules that are partners in fertilization. A conflict model of sexual selection (similar to a host-parasite model) assumes a male-driven system where females are being forced under suboptimal conditions. This predicts that the amount of divergence at a female receptor depends on the amount of divergence among the male reproductive proteins that it binds (i.e., males are leading). Under a classical model of runaway sexual selection, female protein receptors might be the key to the rapid molecular changes observed in male reproductive proteins and higher divergence should be expected among female receptors than among their respective male binding proteins.