An Experimental Investigation of Ecological Character Displacement in Polyphenic Species

9873633 pfeni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差异大于异域种群之间的差异时，就会发生生态特征位移。尽管字符位移在生态学理论中占有重要地位，但大多数支持字符位移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状进化。显示多表型的生物体，在不同的环境刺激下由单一基因型产生不同的表型，非常适合于性状位移的研究。这样的系统是理想的，因为如果通过移除或添加竞争对手，多表型物种分化或不分化成多种形态，那么竞争对手存在或不存在与特征变化之间的因果关系就可以明确确立。本研究将通过继续开展和正在进行的对两种沙漠掌足蟾蜍营养多表型的调查来探索特征位移。这项研究的具体目标是：(1)利用实验室实验来确定异种物种的存在是否会影响食肉动物的产生，如果是，如何影响；(2)采用普通的花园实验来确定同域种群中食肉动物形态产生的物种差异是否比异域种群中更大。(3)通过野外实验确定南方蟾蜍是否比平原蟾蜍具有竞争劣势，从而确定特征位移的进化原因。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。宽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.