An Experimental Investigation of Ecological Character Displacement in Polyphenic Species

当共存物种之间的竞争导致同域种群之间的资源利用以及与资源利用相关的表型特征比异域种群之间的差异更大时，就会发生生态特征置换。尽管在生态学理论中的突出的性格位移，大多数例子支持性格位移的发生依赖于相关数据。因此，通常很难确定种间竞争是否以及如何导致性状进化。显示多型性的生物体，其中替代表型是从一个单一的基因型，以响应不同的环境刺激，是非常适合的性格位移的研究。这样的系统是理想的，因为竞争者的存在或不存在与性状变化之间的因果关系可以明确地建立，如果通过去除或添加竞争者，多型物种分化或不分化成多个变体。本研究将通过对两种沙漠铲足蟾蜍营养多型性的持续、发展和持续调查来探索特征置换。研究的具体目标是：（1）使用实验室实验来确定异种的存在是否会影响食肉动物的生产，如果是这样，如何影响;（2）使用普通的花园实验来确定同域种群中食肉动物形态生产的物种之间是否存在比异域种群更大的差异，（3）通过野外实验确定南方铲足蟾蜍是否在竞争力上劣于平原铲足蟾蜍，从而确定性状置换的进化原因。总之，这些研究将增加我们对资源竞争如何促进表型分化的理解。铲足蟾蜍蝌蚪是研究如何以及为什么存在替代表型的理想选择，这是现代生物学家面临的最具挑战性的问题之一。

9873633PfennigEcological character displacement occurs when competition among coexisting species results in the evolution of greater differences in resource use, and in phenotypic features associated with resource use, between sympatric populations than between allopatric ones. Despite the prominence of character displacement in ecological theory, most examples supporting the occurrence of character displacement rest on correlational data. Thus, it is often difficult to establish whether and how interspecific competition causes character evolution. Organisms that display polyphenism, where alternative phenotypes are produced from a single genotype in response to different environmental stimuli, are well-suited for studies of character displacement. Such systems are ideal, because a causal link between the presence or absence of competitors and character change can be unequivocally established if by removing or adding competitors the polyphenic species differentiates or not into multiple morphs. This research will explore character displacement by continuing and developing and ongoing investigation of trophic polyphenism in two desert spadefoot toads. The specific goals of the research would be to (1) use laboratory experiments to determine whether the presence of heterospecifics influences the production of carnivores, and if so, how, (2) employ a common garden experiment to determine if there are greater differences between species in carnivore morph production in sympatric populations than in allopatric ones, and (3) use field experiments to determine the evolutionary cause of character displacement by establishing if southern spadefoot toads are competitively inferior to plains spadefoot toads. Together, these studies will add to our understanding of how resource competition may promote phenotypic divergence. Spadefoot toad tadpoles are ideal for investigating how and why alternative phenotypes exist, which is among the most challenging issues facing modern biologists.