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（lineage）遭遇大范围开放生态位空间（即生态机遇，ecological opportunity）时触发，此类生态机遇主要源于三类成因：其一，开拓新区域；其二，竞争者灭绝；其三，产生关键创新。其中最广为人知的生态机遇类型，是通过地理扩散或侵入全新生态栖息地来开拓新区域的过程。然而，生态机遇中一个极少被研究的维度是：潜在竞争者的存在是否会限制新定殖的适应带（adaptive zones）内的演化分化。本研究显示，在海洋海鲶科（Ariidae）多次独立地从海洋重新入侵淡水生境的案例中，其演化分化速率（以形态差异度（morphological disparity）和分支发生（cladogenesis）为估算依据）受到了已存在的高多样性淡水演化支的约束。仅有澳大利亚-新几内亚这一区域例外——该区域的淡水动物群原本极度贫乏，海鲶科的入侵在此获得了显著的扩张成效。这一结论在区域和群落两个尺度上均成立，表明竞争限制或许是影响适应辐射的重要因素。