Meeting Abstract
11.11 Sunday, Jan. 4 Sexual Conflict and the Development of Gamete Incompatibility in the Blue Mussel SCHMIDT, Victor*; MCCARTNEY, Michael; UNC, Wilmington ; UNC, Wilmington vts7867@uncw.edu
The blue mussel genus Mytilus contains four species with a rich biogeographic history typified by secondary contact and hybridization. In the Canadian Maritimes hybrid zone a strong yet incomplete block to fertilization exists between M. edulis and M. trossulus, which still permits high levels of hybridization and gene introgression. We are evaluating two main hypotheses for the development of incompatibility between these two species; the first states that cross species fertilizations lead to unfit hybrids, and thus selection to prevent hybridization (reinforcement) favors the evolution of gamete incompatibility. Results from cross population fertilizations (allopatric versus sympatric) so far indicate that this pattern does not hold. An alternative hypothesis is provided by sexual conflict as follows. Sperm competition should select for fast-fertilizing sperm, while eggs will evolve barriers to multiple sperm fertilizing an egg (polyspermy). This form of sexual conflict within species may coincidentally promote the evolution of blocks to fertilization between species. This process can operate without secondary contact and may explain cross species fertilization blocks found in allopatric females. For this hypothesis to hold true, females showing strong resistance to polyspermy (within species) must also show strong incompatibility with heterospecific sperm (between species) and vise versa. This relationship is currently under investigation using M. edulis females from Cobscook Bay, Maine, which show broad variation in the concentration of M. trossulus sperm required to fertilize 20% of their eggs(F20). These females were crossed with both homo and heterospecific males. Each female was scored for resistance to heterospecific fertilization by estimating F20, and for polyspermy resistance by calculating the concentration of sperm required to induce multiple sperm entry in 50% of eggs.
