Competition and the Origins of Diversity: An Empirical Test of the Ecological Speciation Hypothesis

导致物种形成（一个物种进化成多个新物种）的生态机制是综合生态学和宏观进化的一般理论的核心。尽管对资源的竞争一直被认为是自然选择导致生物特征分化的主要机制，但很少有竞争促进物种形成的确凿例子。本研究将为生态物种形成假说提供一个罕见而有力的测试。具体来说，它将测试是否竞争的幼虫，spa bombifrons和S. multiplicata，导致生态物种的形成。本研究将评估一种普遍的假设，即由于其幼虫所面临的竞争压力的差异，与庞氏棉铃虫发生或不发生的多重棉铃虫种群正变得彼此生殖隔离。目标将是验证以下三个预测：(1)由于对杂交的选择，种群间杂交的后代应该比种群内交配的后代更不适合；(2)环境差异选择下的性状会影响交配选择，从而形成生殖隔离的基础；(3)在经历相似选择压力的不同种群中，这些特征的分化应该是平行进化的。这个项目将对生态物种形成形成一个决定性的测试，并将增强我们对竞争如何促进适应性辐射的理解。因此，这项研究将有助于解释多样性的起源，这是生物学家面临的最具挑战性的问题之一。

Ecological mechanisms that lead to speciation (the evolutionary splitting of one species into multiple new species) are central to general theory synthesizing ecology and macroevolution. Although competition for resources has long been viewed as the major mechanism by which natural selection would lead to divergence of organism traits, there are few conclusive examples of competition promoting speciation. The proposed research will provide a rare and strong test of the ecological speciation hypothesis in a system of co-occurring spadefoot toad species.Specifically, it will test whether competition among larvae of the spadefoot toads, Spea bombifrons and S. multiplicata, is leading to ecological speciation. This research will evaluate the general hypothesis that populations of S. multiplicata that do and do not occur with S. bombifrons are becoming reproductively isolated from one another because of contrasting competitive pressures faced by their larvae. The goals will be to test the following three predictions: (1) hybrids from crosses between populations should be less fit than offspring from matings within populations because of selection against hybrids; (2) traits under divergent selection between environments should influence mate choice and thereby form the basis of reproductive isolation; and (3) divergence in these traits should evolve in parallel in different populations that experience similar selective pressures. This project will form a decisive test of ecological speciation and will enhance our understanding of how competition promotes adaptive radiation. This study will, therefore, help explain the origins of diversity, which is one of the most challenging issues confronting biologists.