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

导致物种形成(一个物种进化分裂成多个新物种)的生态机制是综合生态学和宏观进化的一般理论的核心。尽管长期以来，对资源的竞争一直被视为自然选择导致生物特征差异的主要机制，但竞争促进物种形成的确凿例子很少。这项拟议的研究将为生态物种形成假说提供一个罕见而有力的检验。具体而言，它将测试共同出现的黑脚蟾蜍幼虫之间的竞争是否会导致生态物种形成。这项研究将评估这样一种普遍假设，即由于其幼虫面临的不同竞争压力，与双管藻一起发生的和不发生的多重链球藻种群正在变得相互生殖隔离。目标是检验以下三个预测：(1)由于对杂交后代的选择，来自不同群体之间的杂交应该比来自群体内交配的后代更不适合；(2)在不同环境之间进行差异选择的特征应该影响配偶选择，从而形成生殖隔离的基础；以及(3)在经历类似选择压力的不同群体中，这些特征的差异应该平行进化。该项目将形成对生态物种形成的决定性测试，并将加深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.