Dissertation Research: Analysis of Fitness Determinants in a Natural Hybrid Zone Between Rana blairi and Rana sphenocephala: The Evolutionary Potential of Natural Hybridization

Semlitsch9801125天然杂交在许多物种群的进化中发挥了重要作用。作为遗传变化的一种机制，自然杂交有可能产生新的和相对合适的杂交基因类型，而这反过来又可以影响杂交物种之间的进化模式。当代杂交区研究强调对杂交种和亲本基因型的相对适合性的实验测定，以及对环境和基因型之间相互作用的测量。两种两栖动物--黑林蛙和蝶头蛙在密苏里州至德克萨斯州的分布相遇并发生杂交。在密苏里州，这两个物种之间的杂交经常发生，但在德克萨斯州的种群中更有限。只有通过对这两个独特地理区域的相对亲本和杂交适合度的实验分析，我们才能理解这两个区域是否存在不同的进化过程来构建杂交区域。来自密苏里州地方的初步实验证据表明，与亲本基因相比，某些杂交基因具有同等或更高的适合度水平。因此，在某些环境中，某些杂交种可能比亲本保持相对的适合度优势，潜在地导致用重组的亲本替代亲本。杂交区分析的经验方法提供了直接测量亲本和杂交种的终身适合度的重要组成部分的方法。这些方法对于理解杂交对杂交区结构和进化模式的影响至关重要。

Semlitsch9801125 Natural hybridization has played a prominent role in the evolution of many species groups. Serving as a mechanism of genetic change, natural hybridization has the potential to produce novel and relatively fit hybrid genotypes which, in turn, can affect the pattern of evolution between hybridizing species. Contemporary hybrid zone studies emphasize experimental determination of the relative fitness of hybrid and parental genotypes and measurements of the interactions between the environment and genotype. The distributions of two amphibian species, Rana blairi and Rana sphenocephala, meet and hybridization occurs in a zone extending from Missouri to Texas. Hybridization frequently occurs between these two species in Missouri, but is more limited in Texas populations. It is only through experimental analysis of relative parental and hybrid fitness from these two unique geographic areas that we can understand if different evolutionary processes are structuring the hybrid zone in these two areas. Preliminary experimental evidence from Missouri localities suggests that certain hybrid genotypes posses equivalent or higher levels of fitness compared to parental genotypes. Thus, certain hybrid genotypes may maintain a relative fitness advantage over parental genotypes in some environments, potentially leading to the replacement of parental genotypes with recombinant ones. Empirical approaches to hybrid zone analyses provide direct methods of measuring important components of lifetime fitness for both parental and hybrid genotypes. These methods are critical for understanding the effect that hybridization can have on patterns of hybrid zone structure and evolution.