Meeting Abstract
34.1 Friday, Jan. 4 Selection and gene flow in gamete recognition molecules: daughters of immigrants meet sons of locals in a sexual conflict HART, M*; SUNDAY, J; POPOVIC, I; LEARNING, K; KONRAD, C; Simon Fraser Univ. mwhart@sfu.ca
Conflict between male and female reproductive interests can lead to a local arms race between male adaptations and female countermeasures within populations. Divergence between populations in male and female traits can lead to reproductive isolation and speciation, unless this outcome of the arms race is diluted by immigration and gene flow. Gamete recognition proteins (GRPs) of broadcast spawning marine animals are promising targets for selection, sexual conflict, and reproductive isolation, but few studies have looked at population-level divergence. We recently found strong positive selection that produces population divergence (and partial reproductive isolation) in the sperm acrosomal protein bindin between northern and southern populations of the bat star Patiria miniata. Here we analyze GRPs expressed in eggs. We modelled both positive selection and gene flow for these loci (as well as background rate of gene flow for loci not involved in sex). We found high amino acid substitution rates (a response to selection favoring new or rare or better alleles) for egg surface proteins. However, selection acts differentially on immigrant alleles for male- and female-expressed GRPs. Bindin gene flow is zero (less than background), but gene flow for the egg bindin receptor is high and asymmetrical: in the population that experiences the strongest selection for high rates of bindin evolution, immigration of egg bindin receptor alleles is ~80-fold higher than background. We conclude that selection in this system favors the daughters of immigrants (and their egg-expressed alleles) as a response to selection created by fast bindin evolution among the sons of locals. The evolutionary outcome of selection in such a system (and the potential for speciation) may be hard to predict.
