Data from: Phenotypic rate and state are decoupled in response to river-to-lake transitions in cichlid fishes

Geographic access to isolated ecosystems is an important catalyst of adaptive radiation. Cichlid fishes repeatedly colonized rift, crater, and volcanic lakes from surrounding rivers. We test the "lake effect" on the phenotypic rate and state across 253 cichlid species. The rate of evolution was consistently higher (~10-fold) in lakes, and consistent across different dimensions of the phenotype. Rate shifts tended to occur coincident with or immediately following river-to-lake transitions, generally resulting in 2- to 5-fold faster rates than in the founding riverine lineage. By contrast, river- and lake-dwelling cichlids exhibit considerable overlap in phenotypes, generally with less disparity in lakes, but often different evolutionary optima. Taken together, these results suggest that lake radiations rapidly expand into niches largely already represented by ancestral riverine lineages, albeit in different frequencies. Lakes may provide ecological opportunity via ecological release (e.g., from predators/competitors), but need not be coupled with access to novel ecological niches.

地理可达性对孤立生态系统而言，是适应性辐射的重要驱动因子。慈鲷科鱼类多次从周边河流迁入裂谷湖、火山口湖及火山湖。我们针对253种慈鲷，检验了‘湖泊效应’对表型演化速率与表型状态的影响。湖泊生境中的演化速率始终更高（约为河流生境的10倍），且在表型的不同维度上均保持这一趋势。演化速率的转变往往发生在从河流迁入湖泊的节点或紧随该节点之后，通常使演化速率较起源的河流支系提升2至5倍。相较而言，栖息于河流与湖泊的慈鲷在表型上存在大量重叠，湖泊生境中的表型差异通常更小，但二者往往具有不同的演化最适值。综合来看，这些结果表明湖泊适应性辐射会快速拓展至祖先河流支系已占据的生态位空间，只是各生态位的占据频率有所差异。湖泊可通过生态释放（例如摆脱捕食者与竞争者）提供生态机遇，但未必需要伴随新生态位的开拓。