Meeting Abstract
52.2 Tuesday, Jan. 5 Hybrid sterility limits introgression between invasive and endemic blue mussels BRANNOCK, Pamela M*; HILBISH, Thomas J; University of South Carolina; University of South Carolina pamela.m.brannock@gmail.com
The mechanisms of speciation in marine ecosystems have interested scientists for decades. Since many marine species spawn gametes into the water column and fertilization occurs externally, there is relatively little opportunity to develop pre-mating reproductive barriers based upon mate recognition. A majority of the research on speciation in marine systems has focused on pre-mating reproductive isolation mechanisms and very seldom have post-mating reproductive isolating mechanisms been examined. Marine mussels in the Mytilus edulis complex (M. edulis, M. trossulus, and M. galloprovincialis) are emerging as a model system for examining the role of post-mating reproductive isolation in limiting hybridization and introgression. Mytilus gallorprovincialis and M. trossulus are sympatric and hybridize on both coasts of the North Pacific. Hybridization levels differ among geographic locations, but in all regions introgression beyond the F1 generation is either rare or absent. While assessing gender of mussels in the summer of 2008 for another study, we documented a noticeably low ability to determine gender of individuals in both hybrid zones in Hokkaido, Japan. Eighty percent of individuals where gender could not be determined utilizing traditional field methods had a hybrid multi-locus genotype. Histological examination of the gonad tissue revealed unusual cell types present in hybrid individuals that appeared to be arrested in a meiotic phase. The arrest of gametogenesis in both male and female individuals results in very low fertility and thus represents a formidable level of post-zygotic reproductive isolation between these species. This is the first report of reduced fertility as a result of hybridization among any of the species in the blue mussel species complex.
