Selection in the Rapid Evolution of Gamete Recognition Proteins in Marine Invertebrates
- 1Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0202
- 2Department of Genome Sciences, University of Washington, Seattle, Washington 98195-7730
- Correspondence: vvacquier{at}ucsd.edu
Abstract
Animal fertilization is governed by the interaction (binding) of proteins on the surfaces of sperm and egg. In many examples presented herein, fertilization proteins evolve rapidly and show the signature of positive selection (adaptive evolution). This review describes the molecular evolution of fertilization proteins in sea urchins, abalone, and oysters, animals with external fertilization that broadcast their gametes into seawater. Theories regarding the selective forces responsible for the rapid evolution driven by positive selection seen in many fertilization proteins are discussed. This strong selection acting on divergence of interacting fertilization proteins might lead to prezygotic reproductive isolation and be a significant factor in the speciation process.
Since only a fraction of all eggs are fertilized and only an infinitesimal fraction of male gametes succeed in fertilizing
an egg, gametes are obviously a category of entities subjected to intense selection. It is curious that this is never mentioned
in the literature dealing with selection, perhaps because we know so little about fitness differences among gametes.
(ErnstMayr, 1997)
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