Department of Genetics, Evolution & Environment, University College London, Wolfson House, 4, Stephenson Way, London NW1 2HE, UK.
BMC Evol Biol. 2010 Jun 19;10:188. doi: 10.1186/1471-2148-10-188.
Lake Tanganyika (LT) is the oldest of the African Rift Lakes and is one of the richest freshwater ecosystems on Earth, with high levels of faunal diversity and endemism. The endemic species flocks that occur in this lake, such as cichlid fishes, gastropods, catfish and crabs, provide unique comparative systems for the study of patterns and processes of speciation. Mastacembelid eels (Teleostei: Mastacembelidae) are a predominately riverine family of freshwater fish, occurring across Africa and Asia, but which also form a small species flock in LT.
Including 25 species across Africa, plus Asian representatives as outgroups, we present the first molecular phylogenetic analysis for the group, focusing particularly on the evolutionary history and biodiversity of LT mastacembelid eels. A combined matrix of nuclear and mitochondrial genes based on 3118 bp are analysed implementing different phylogenetic methods, including Bayesian inference and maximum likelihood.
LT Mastacembelus are recovered as monophyletic, and analyses reveal the rapid diversification of five main LT lineages. Relaxed molecular clock dates provide age estimates for the LT flock at approximately 7-8 Myr, indicating intralacustrine diversification, with further speciation events coinciding with periods of lower lake level. Our analyses also reveal as yet undescribed diversity of lacustrine and riverine species. A Southern-Eastern African clade, that is younger than the LT flock, is also recovered, while West African taxa are basal members of the African mastacembelid clade.
That the LT species flock of mastacembelid eels appears to have colonised and immediately diversified soon after the formation of the lake, supports the view of LT as an evolutionary hotspot of diversification. We find evidence for biogeographic clades mirroring a similar pattern to other ichthyological faunas. In addition, our analyses also highlight a split of African and Asian mastacembelid eels at approximately 19 Myr that is considerably younger than the split between their associated continents, suggesting a dispersal scenario for their current distribution.
坦噶尼喀湖（LT）是非洲裂谷湖中最古老的一个，也是地球上最富有的淡水生态系统之一，拥有高度的动物多样性和特有性。该湖中特有的鱼类群，如慈鲷鱼、腹足纲动物、鲶鱼和螃蟹，为研究物种形成的模式和过程提供了独特的比较系统。鳗鲡（硬骨鱼纲：鳗鲡科）是一种主要生活在河流中的淡水鱼类，分布于非洲和亚洲，但也在 LT 形成了一个小的物种群。
我们包括了来自非洲的 25 个物种，加上亚洲代表作为外群，首次对该组进行了分子系统发育分析，重点研究了 LT 鳗鲡的进化历史和生物多样性。基于 3118bp 的核和线粒体基因组合矩阵，采用不同的系统发育方法进行分析，包括贝叶斯推断和最大似然法。
LT 鳗鲡被证明是单系的，分析揭示了五个主要 LT 谱系的快速多样化。放松的分子钟日期为 LT 鱼群提供了约 7-8 百万年前的年龄估计，表明了湖泊内的多样化，进一步的物种形成事件与较低的湖泊水位时期相吻合。我们的分析还揭示了尚未描述的湖泊和河流物种的多样性。一个比 LT 鱼群年轻的东南非分支也被回收，而西非分类群是非洲鳗鲡分支的基础成员。
LT 鳗鲡物种群似乎在湖泊形成后不久就已经殖民并立即多样化，这支持了 LT 作为一个多样化的进化热点的观点。我们发现生物地理群的证据与其他鱼类区系相似。此外，我们的分析还突出了非洲和亚洲鳗鲡大约在 1900 万年前的分裂，这比它们相关大陆的分裂要年轻得多，这表明了它们目前分布的扩散情景。
