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

[00:73846]希尔比什&吉尔在英格兰西南部，两种贻贝，Mytilus edulis和M. galloprovincialis，杂交并产生可育的杂交后代。在这一区域内，与加洛省支原体亲缘关系较近的个体成虫存活率高于与毛利支原体亲缘关系较近的个体。虽然你会预测这种优势会导致加洛省分枝杆菌胜过毛蕊分枝杆菌并占领该地区，但这一杂交区以两种相同比例保持在同一位置至少20年了。本研究将确定是什么进化因素稳定了杂交区，并抵消了有利于黄花栗鼠的定向选择。两个潜在的因素是基因流动和自然选择有利于贻贝在幼虫期。在杂交区定居的幼虫可能主要来自纯毛竹种群，这种涌入可能抵消了自然选择。将收集在该地区定居的幼虫，并利用遗传标记确定其可能的原始种群。这些信息将决定贻贝幼虫通常会游多远以及朝哪个方向游。也有可能是在幼虫阶段发生了有利于毛蕊支原体的自然选择。这可以通过在实验室中饲养贻贝幼虫和确定幼虫基因组成的变化来确定。

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.