Age of cichlids: New dates for ancient lake fish radiations
Age of cichlids: New dates for ancient lake fish radiations
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DOI：
10.1093/molbev/msm050
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发表时间：
2007-05-01
影响因子：
10.7
通讯作者：
Turner, Georg F.
中科院分区：
文献类型：
--
作者：
Genner, Martin J.;Seehausen, Ole;Turner, Georg F.
时间分歧事件使我们能够推断生物多样性进化的条件，并获得对驱动进化机制的重要见解。丽鱼科鱼是研究物种形成和适应性辐射的模型系统，然而，我们缺乏它们进化的可靠时间尺度。系统发育重建与冈瓦纳大陆破碎之前的慈鲷起源一致，时间为121-165 MYA，比第一个已知的慈鲷化石（始新世）早得多。我们使用宽松的分子钟检查了丽鱼科鱼进化的时间，该分子钟通过对 1) 冈瓦纳碎片和 2) 丽鱼科鱼化石年龄的地质估计进行了校准。从其他硬骨鱼的化石年代系统发育中得出的慈鲷进化的时间尺度与冈瓦纳分裂校准所建议的最接近，这表明慈鲷化石记录所暗示的始新世起源和海洋传播可能是由于其不完整。使用冈瓦纳校准，我们发现非洲马拉维湖、维多利亚湖和巴龙比姆博湖以及古马卡迪卡迪湖的辐射谱系内遗传多样性的积累开始于湖盆形成前后或之后。这些校准还表明坦噶尼喀湖曾被主要的辐射慈鲷部落独立殖民，此后这些部落开始积累遗传多样性。这些结果与广泛接受的理论形成鲜明对比，即坦噶尼喀盆地内发生了主要谱系的多样化。总之，这些证据表明，古代湖泊栖息地在辐射谱系内产生和维持多样性方面发挥了关键作用，而且湖泊可能从适应性辐射进化而来的多个来源捕获了先前存在的慈鲷多样性。
Timing divergence events allow us to infer the conditions under which biodiversity has evolved and gain important insights into the mechanisms driving evolution. Cichlid fishes are a model system for studying speciation and adaptive radiation, yet, we have lacked reliable timescales for their evolution. Phylogenetic reconstructions are consistent with cichlid origins prior to Gondwanan landmass fragmentation 121-165 MYA, considerably earlier than the first known fossil cichlids (Eocene). We examined the timing of cichlid evolution using a relaxed molecular clock calibrated with geological estimates for the ages of 1) Gondwanan fragmentation and 2) cichlid fossils. Timescales of cichlid evolution derived from fossil-dated phylogenies of other bony fishes most closely matched those suggested by Gondwanan breakup calibrations, suggesting the Eocene origins and marine dispersal implied by the cichlid fossil record may be due to its incompleteness. Using Gondwanan calibrations, we found accumulation of genetic diversity within the radiating lineages of the African Lakes Malawi, Victoria and Barombi Mbo, and Palaeolake Makgadikgadi began around or after the time of lake basin formation. These calibrations also suggest Lake Tanganyika was colonized independently by the major radiating cichlid tribes that then began to accumulate genetic diversity thereafter. These results contrast with the widely accepted theory that diversification into major lineages took place within the Tanganyika basin. Together, this evidence suggests that ancient lake habitats have played a key role in generating and maintaining diversity within radiating lineages and also that lakes may have captured preexisting cichlid diversity from multiple sources from which adaptive radiations have evolved.