Frequency, density and binding-affinity interactions can describe gamete recognition protein polymorphism
Friday seminar by Maurizio Tomaiuolo.
Gamete recognition proteins determine if sperm and eggs are compatible at fertilization and often evolve rapidly. The source of selection driving the evolution of these proteins is still debated. It has been suggested that sexual conflict can result in proliferation of genetic variation and possibly linkage disequilibrium between sperm and egg proteins. Empirical evidence suggests that both male and female reproductive success can be predicted by their sperm bindin genotype, but why female success can be predicted by a protein only expressed in males is unknown.
Here we use mathematical modeling to investigate the outcome of the interaction between spawning behavior and sexual conflict, between sperm ligands and egg receptors. We consider a model with haploid and diploid expression in gametes under two possible ecological scenarios, monogamous and competitive spawning. Spawning behavior plays an important role in determining possible outcomes resulting from sexual conflict. Sperm limitation selects for common genotypes. Conversely sperm abundance promotes allelic variation. Under conditions of sperm abundance monogamous spawning does not promote allelic variation but allows invasion of mutants at either locus (ligand or receptor). Under the same conditions, competitive spawning provides conditions for persistence of allelic variation and gametic disequilibrium.