Nevado B, Koblmüller S, Sturmbauer C, Snoeks J, Usano-Alemany J, Verheyen E
Department Vertebrates, Royal Belgian Institute of Natural Sciences, 1000 Brussels, Belgium.
Mol Ecol. 2009 Oct;18(20):4240-55. doi: 10.1111/j.1365-294X.2009.04348.x. Epub 2009 Sep 25.
We used nuclear and mitochondrial DNA (mtDNA) sequences from specimens collected throughout Lake Tanganyika to clarify the evolutionary relationship between Lamprologus callipterus and Neolamprologus fasciatus. The nuclear data support the reciprocal monophyly of these two shell-breeding lamprologine cichlids. However, mtDNA sequences show that (i) L. callipterus includes two divergent and geographically disjunct (North-South) mtDNA lineages; and that (ii) N. fasciatus individuals cluster in a lineage sister group to the northern lineage of L. callipterus. The two mtDNA lineages of L. callipterus diverged c. 684 kya to 1.2 Ma, coinciding with a major water level low stand in Lake Tanganyika, which divided the lake into isolated sub-lakes. This suggests that the two mtDNA lineages originated as the result of the separation of L. callipterus populations in different sub-basins. The incongruent phylogenetic position of N. fasciatus can best be explained by an ancient unidirectional introgression from L. callipterus into N. fasciatus. Remarkably, our data indicate that this event resulted in the complete mtDNA replacement in N. fasciatus. Our data suggest that hybridization occurred soon after the divergence of the two L. callipterus mtDNA lineages, probably still during the water level low stand, and that subsequently the invading mtDNA lineage spread throughout the lake.
我们使用了从坦噶尼喀湖各地采集的标本中的核DNA和线粒体DNA（mtDNA）序列，以阐明美丽扇丽鱼（Lamprologus callipterus）和带纹新亮丽鲷（Neolamprologus fasciatus）之间的进化关系。核数据支持这两种在贝壳中繁殖的丽鱼科鱼类的相互单系性。然而，mtDNA序列显示：（i）美丽扇丽鱼包括两个不同且地理上不连续（南北）的mtDNA谱系；以及（ii）带纹新亮丽鲷个体聚集在一个谱系姐妹群中，该姐妹群与美丽扇丽鱼的北部谱系相邻。美丽扇丽鱼的两个mtDNA谱系大约在68.4万至120万年前分化，这与坦噶尼喀湖一次主要的低水位期相吻合，当时该湖被分成了孤立的子湖。这表明这两个mtDNA谱系是美丽扇丽鱼种群在不同子流域分离的结果。带纹新亮丽鲷不一致的系统发育位置可以最好地用美丽扇丽鱼向带纹新亮丽鲷的古老单向基因渗入来解释。值得注意的是，我们的数据表明，这一事件导致带纹新亮丽鲷的mtDNA完全被替换。我们的数据表明，杂交发生在美丽扇丽鱼的两个mtDNA谱系分化后不久，可能仍处于低水位期，随后入侵的mtDNA谱系扩散到了整个湖泊。
