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

自然杂交在许多种群的进化中发挥了突出的作用。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型，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杂交和亲本基因型相对适合度的实验测定以及环境与基因型相互作用的测量。两种两栖动物的分布，布拉利蛙和蝶头蛙，相遇和杂交发生在从密苏里州延伸到德克萨斯州的区域。在密苏里州这两个物种之间经常发生杂交，但在德克萨斯州的种群中比较有限。只有通过对这两个独特地理区域的相对亲本和杂交适应度的实验分析，我们才能了解这两个区域的杂交区是否由不同的进化过程构成。来自密苏里地区的初步实验证据表明，某些杂交基因型与亲本基因型相比具有同等或更高的适应度。因此，某些杂交基因型可能在某些环境中保持相对于亲本基因型的适应度优势，可能导致亲本基因型被重组基因型取代。杂交区分析的经验方法为亲本和杂交基因型的终生适合度的重要组成部分提供了直接的测量方法。这些方法对于理解杂交对杂交带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.