Molecular and fossil evidence place the origin of cichlid fishes long after Gondwanan rifting

Cichlid fishes are a key model system in the study of adaptive radiation, speciation and evolutionary developmental biology. More than 1600 cichlid species inhabit freshwater and marginal marine environments across several southern landmasses. This distributional pattern, combined with parallels between cichlid phylogeny and sequences of Mesozoic continental rifting, has led to the widely accepted hypothesis that cichlids are an ancient group whose major biogeographic patterns arose from Gondwanan vicariance. Although the Early Cretaceous (ca 135 Ma) divergence of living cichlids demanded by the vicariance model now represents a key calibration for teleost molecular clocks, this putative split pre-dates the oldest cichlid fossils by nearly 90 Myr. Here, we provide independent palaeontological and relaxed-molecular-clock estimates for the time of cichlid origin that collectively reject the antiquity of the group required by the Gondwanan vicariance scenario. The distribution of cichlid f...慈鲷科鱼类（Cichlid）是研究适应辐射、物种形成与进化发育生物学的核心模式系统。目前已有超过1600种慈鲷栖息于全球多个南部大陆块的淡水及近岸海洋环境中。这种分布格局，加之慈鲷系统发育与中生代大陆裂谷演化序列之间的相似性，催生了广为接受的假说：慈鲷是一类古老类群，其主要生物地理格局起源于冈瓦纳异域分化（Gondwanan vicariance）。尽管异域分化模型所提出的现生慈鲷类群在早白垩世（约1.35亿年前，ca 135 Ma）的分化事件，如今已成为硬骨鱼分子钟校准的关键节点，但这一推测的分化时间却比已知最古老的慈鲷化石早了近9000万年。本研究通过独立的古生物学方法与宽松分子钟模型，估算了慈鲷类群的起源时间，综合结果均不支持冈瓦纳异域分化假说所要求的该类群古老起源时间。慈鲷的分布...