Biophysical and Behavioral Agents of Natural Selection in a Hybrid Zone

杂交带的结构取决于自然选择和扩散的相互作用。利用不同形式的自然选择产生了简单的模型来解释杂交带的结构和维持。然而，实地研究表明，自然选择可能非常复杂，不能通过简单的模型来理解杂交带。为了理解杂交带是如何形成和维持的，有必要确定自然选择的作用及其作用的生态环境。本研究提出确定在两种海洋贻贝之间形成的杂交区中操作的选择力。先前的一项研究结果表明，这两个物种在忍受淤泥升高的生理能力上存在差异。一种可能的适应淤泥淤积的方式是增加机动性，这样动物就可以移动，避免窒息。在淤泥浓度低的开阔海岸环境中，这种适应可能是有害的，贻贝可能因暴露于增加的波浪作用而被移走。如果贻贝迁移到贻贝床的顶部或其他更容易被移动的地方，那么流动性更强的贻贝可能会受到更大的波浪作用。这项研究将验证这两种贻贝对淤泥的行为适应不同的假设，这些差异导致了对开放海岸环境中更灵活的物种的强烈自然选择。

The structure of hybrid zones depends on the interaction of natural selection and dispersal. Simple models using different forms of natural selection have been generated to explain the structure and maintenance of hybrid zones. However, field studies have shown that natural selection can be very complex and that an understanding of hybrid zones cannot be obtained through simple models. It is necessary to determine the agent of natural selection and the ecological circumstances under which it operates to understand how hybrid zones are formed and maintained. This study proposes to determine the selective forces operating in a hybrid zone formed between two species of marine mussels. Results from a previous grant demonstrated that the two species differed in their physiological capacity to tolerate elevated silt. One possible adaptation to elevated silt is increased mobility so that the animal can move and avoid smothering. This adaptation may be detrimental in open coast environments where silt concentrations are low and mussels may be dislodged by exposure to increased wave action. Mussels that are more mobile may be exposed to greater wave action if they migrate to the top of mussel beds or into other locations where they are more likely to be dislodged. This study will test the hypothesis that these two species of mussels differ in their behavioral adaptations to silt and that these differences result in strong natural selection against the more mobile species in open coast environments.