Maintenacne of Parent-Species Reservoirs in a Complex Hybrid Zone

pi一直在对两种海洋贻贝（Mytilus edulis和M. galloprovincialis）之间的杂交区进行详细分析，这两种贻贝在欧洲是同域的。pi研究表明：1)在杂交种群中发生了强烈的定向选择，从而消除了Mytilus edulis和类似Mytilus edulis的杂种；2)定向选择被纯Mytilus edulis种群的迁移所抵消；3)分散和选择之间的平衡目前是稳定的；4)杂交是这些物种进化史上的一个重要特征。这些研究将未来的研究集中在一个新的方向上：了解这个杂交区动态的主要问题是确定毛竹纯种群是如何维持的。紫贻贝纯种群的维持是分散和定向选择之间动态平衡的重要因素，这种平衡维持和塑造了这个杂交区。PI将提出验证M. edulis具有优越的生理能力来应对其饮食中的淤泥，并且该物种的纯种群有选择地维持在淤泥浓度高的河口环境中。这一假设是由以下观察结果提出的：纯毛毛杆菌种群与泥沙负荷高的河口有关，并且独立研究的初步结果表明，毛毛杆菌在暴露于含有高浓度淤泥的饮食中时可能具有更高的吸收效率。PI还将提出实验室和实地实验相结合的方法来验证这一假设。实验室实验将测试拟议的毛利分枝杆菌和加洛省分枝杆菌之间的生理差异，而现场实验是必要的，以证明这些差异在自然界中具有重要的后果。

Hilbish 9708074 The PIs have been conducting a detailed analysis of a hybrid zone between two species of marine mussels, Mytilus edulis and M. galloprovincialis that are sympatric in Europe. The PIs' have shown that 1) strong directional selection occurs within hybrid populations that eliminates Mytilus edulis and M. edulis-like hybrids, 2) directional selection is offset by immigration from pure populations of M. edulis, 3) the balance between dispersal and selection is presently stable, and 4) hybridization has been an important feature in the evolutionary history of these species. These studies focus future research in a new direction: the primary issue in understanding the dynamics of this hybrid zone is to determine how pure populations of M. edulis are maintained. The maintenance of pure populations of Mytilus edulis is an essential element of the dynamic equilibrium between dispersal and directional selection that maintains and shapes this hybrid zone. The PI will propose to test the hypothesis that M. edulis has a superior physiological capacity to cope with silt in its diet and that pure populations of this species are selectively maintained in estuarine environments where silt concentrations are high. This hypothesis was suggested by the observation that pure populations of M. edulis are associated with estuaries that have high silt loads and preliminary results from separate studies that indicate that M. edulis may have a much greater absorption efficiencies when exposed to diet containing high concentrations of silt. The PI will also propose a combination of laboratory and field experiments to test this hypothesis. Laboratory experiments will test for the proposed physiological differences between M. edulis and M. galloprovincialis while the field experiments are necessary to demonstrate that these differ ences have significant consequences in nature.