Sea star populations diverge by positive selection at a sperm‐egg compatibility locus

• Published in: Ecology and evolution Vol. 3; no. 3; pp. 640 - 654
• Main Authors: Sunday, Jennifer M., Hart, Michael W.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-03-2013; Blackwell Publishing Ltd; Wiley
• Subjects: Amino acids; Animal behavior; Animal reproduction; Bindin; Compatibility; Divergence; Domains; Evolution; Fertilization; gamete compatibility loci; Immunology; Loci; Original Research; Pathogens; Polymorphism; Population; Population number; Populations; Positive selection; Proteins; Reproductive isolation; sea star; sexual conflict; Sexual selection; Spawning; Sperm; Ultrasonic testing; Queen Charlotte Sound; sea star; Bindin; positive selection; gamete compatibility loci; sexual conflict; sexual selection
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.487

Fertilization proteins of marine broadcast spawning species often show signals of positive selection. Among geographically isolated populations, positive selection within populations can lead to differences between them, and may result in reproductive isolation upon secondary contact. Here, we test for positive selection in the reproductive compatibility locus, bindin, in two populations of a sea star on either side of a phylogeographic break. We find evidence for positive selection at codon sites in both populations, which are under neutral or purifying selection in the reciprocal population. The signal of positive selection is stronger and more robust in the population where effective population size is larger and bindin diversity is greater. In addition, we find high variation in coding sequence length caused by large indels at two repetitive domains within the gene, with greater length diversity in the larger population. These findings provide evidence of population‐divergent positive selection in a fertilization compatibility locus, and suggest that sexual selection can lead to reproductive divergence between conspecific marine populations.
Fertilization proteins of marine broadcast spawning species often show signals of positive selection, and it has been postulated that such divergent selection across isolated populations may lead to reproductive isolation. Here, we test for positive selection in the reproductive compatibility locus, bindin, in two populations of a sea star on either side of a phylogeographic break. We find evidence for positive selection in both populations, with different sites under positive selection in either population, suggesting they are responding to different evolutionary processes which may lead to reproductive isolation.