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和与资源利用相关的表型特征的进化比异地种群之间的差异更大时，就会发生生态特征置换。尽管字符移位在生态学理论中占有重要地位，但大多数支持字符移位发生的例子都依赖于相关数据。因此，通常很难确定种间竞争是否以及如何导致性格进化。表现出多表现性的生物体非常适合于性格置换的研究。在这种情况下，单一的基因对不同的环境刺激会产生不同的表型。这样的系统是理想的，因为如果通过移除或添加竞争对手，多种多样的物种分化成或不形成多个变体，就可以明确地建立竞争对手的存在或不存在与特征变化之间的因果联系。这项研究将通过对两种荒漠黑脚蟾蜍营养多物性的持续和发展以及正在进行的调查，来探索特征的置换。这项研究的具体目标将是：(1)使用实验室实验来确定异种生物的存在是否影响食肉动物的产量，如果是的话，如何影响；(2)使用普通的花园实验来确定同域种群中的肉食动物形态产量是否比异地种群中的物种之间存在更大的差异；以及(3)通过野外实验来确定特征置换的进化原因，方法是确定南部铲足蟾蜍是否在竞争性上逊于平原铲足蟾蜍。总之，这些研究将增加我们对资源竞争如何促进表型差异的理解。铲足蝌蚪是研究替代表型如何存在以及为什么存在的理想工具，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.