Dissertation Research: Maladaptive Gene Flow and Counter Selection in a Blue Mussel Hybrid Zone

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0073846Hilbish & GilgIn Southwest England two mussel species, Mytilus edulis and M. galloprovincialis, interbreed and produce fertile hybrid offspring. Within this region individuals that are more closely related to M. galloprovincialis have better survival as adults than individuals that are more closely related to M. edulis. While you would predict that this advantage would result in M. galloprovincialis out-competing M. edulis and taking over the region, this hybrid zone has remained in the same location with the same proportions of the two species for at least 20 years. This study will determine what evolutionary factors are stabilizing the hybrid zone and offsetting the directional selection favoring M. galloprovincialis. Two potential factors are gene flow and natural selection favoring Mytilus edulis in the larval stage. It is possible that larvae that settle in the hybrid zone are predominantly coming from pure M. edulis populations and that this influx could offset natural selection. Larvae that settle in this region will be collected and their probable population of origin will be determined using genetic markers. This information will determine how far mussel larvae generally travel and in what direction. It is also possible that natural selection favoring M. edulis is occurring in the larval stage. This can be determined by raising larval mussels in the laboratory and determining changes in the genetic composition of the larvae.