Data from: Apparent signal of competition limits diversification after ecological transitions from marine to freshwater habitats

Adaptive radiations are typically triggered when a lineage encounters a significant range of open niche space (ecological opportunity), stemming from i) colonization of new areas, ii) extinction of competitors, or iii) key innovations. The most well-known of these is the colonization of new areas, either through geographic dispersal or the invasion of a novel ecological habitats. One aspect of ecological opportunity that has rarely been studied, however, is whether the existence of potential competitors may act to limit evolutionary diversification in newly colonized adaptive zones. Here, we show that in multiple geographically independent reinvasions of freshwaters by marine Sea Catfishes (Ariidae), rates of diversification (estimated as a function of morphological disparity and cladogenesis) have been constrained by pre-existing high diversity freshwater lineages. Only one region (Australia-New Guinea), characterized by an otherwise-depauperate freshwater fauna, has an ariid invasion gained any substantial traction. This is true at both regional and community scales, suggesting that competitive constraints may be an important factor for adaptive radiation.

适应辐射（Adaptive radiation）通常在某一演化支接触到大范围开放生态位空间（即生态机遇）时被触发，此类生态机遇源自三大成因：i）新区域殖民，ii）竞争者灭绝，或iii）关键创新。其中最广为人知的生态机遇类型，是通过地理扩散或入侵全新生态栖息地来实现新区域殖民。然而，鲜有研究探讨的一类生态机遇相关议题是：潜在竞争者的存在是否会限制新定殖适应带内的演化多样性。本研究证实，在海鲇科（Ariidae）海洋类群多次独立地理再度入侵淡水生境的案例中，多样化速率（以形态差异度与分支发生为函数进行估算）受到了已存在的高多样性淡水演化支的约束。仅澳大利亚-新几内亚这一区域，其本土淡水动物群原本物种匮乏，使得海鲇科的入侵获得了可观的发展势头。这一现象在区域与群落尺度上均成立，表明竞争约束可能是影响适应辐射的重要因素。