Meeting Abstract

5.4  Jan. 4  Massive introgression of gamete recognition alleles in a blue mussel hybrid zone MCCARTNEY, Michael A.*; LIMA, Thiago G.; Univ of North Carolina, Wilmington mccartneym@uncw.edu

Earlier work in our laboratory examined evidence for reproductive character displacement of gamete compatibility between the blue mussels Mytilus edulis and M. trossulus inside and outside of their hybrid zone in the Gulf of Maine. We found a contrary result�M. trossulus males were actually more compatible with M. edulis females from within the hybrid zone that they were with M. edulis females from an allopatric population. We are now investigating evidence for introgression of alleles at M7 lysin, a gene coding for a sperm lysin that may control gamete compatibility in Mytilus. We have found that M. edulis M7 lysin alleles are unusually common in M. trossulus individuals that carry no M. edulis alleles at other marker loci. So far, this massive introgression of gamete recognition alleles seems to be confined to within the hybrid zone. Previous analyses of nucleotide substitutions in M7 lysin have shown evidence for positive, diversifying selection. The present result argues that balancing selection may also play a role in the evolution of M7 lysin.