Sturmbauer C, Meyer A
Department of Ecology and Evolution, State University of New York, Stony Brook 11794-5245.
Mol Biol Evol. 1993 Jul;10(4):751-68. doi: 10.1093/oxfordjournals.molbev.a040042.
Of the three cichlid species flocks in eastern Africa, Lake Tanganyika harbors the oldest species assemblage, which is also the most diverse morphologically and behaviorally. For 12 species (20 individuals) of 12 genera of the tribe Ectodini, 852 bp from two segments (cytochrome b and control region) of the mitochondrial genome were sequenced. In addition, orthologous sequences were obtained from eight species (11 individuals) representing other mouthbrooding lineages from Lake Tanganyika. Comparisons of sequence divergences revealed that the single Tanganyikan tribe Ectodini appears to be approximately five times older than the whole Lake Malawi cichlid species flock, suggesting that the radiation of the Tanganyikan mouthbrooding lineages took place long before the species flocks of Lakes Malawi and Victoria evolved. Seven of nine surveyed tribes of Tanganyikan cichlids appear to be approximately equally divergent, and this seems to corroborate the hypothesis of a rapid simultaneous formation of lineages at an early stage in the history of the Lake Tanganyika species flock. The close genetic relationship between the endemic Tropheus lineage and a nonendemic "Haplochromine," Astatotilapia burtoni, indicates that members of the tribe Tropheini may be the sister group of the cichlid flocks of Lakes Malawi and Victoria. The phylogenetic analyses demonstrate the monophyly of the Ectodini and identify the Cyprichromini as their sister group among the Tanganyikan cichlids. Within the tribe Ectodini the molecular data suggest both a branching pattern different than that previously proposed and a subdivision of the Ectodini into four clades, instead of the two originally described. The previously postulated model of morphological transformations believed to be responsible for the drastically different types of ecological specialization found among the Ectodini might therefore be in need of reinterpretation. Characters immediately related to foraging and nutrition seem to be particularly prone to homoplasy, even among members of a single lineage of cichlid fishes.
在东非的三个丽鱼科物种群中，坦噶尼喀湖拥有最古老的物种组合，在形态和行为上也是最多样化的。对Ectodini族12个属的12个物种（20个个体），测定了线粒体基因组两个片段（细胞色素b和控制区）的852个碱基对序列。此外，还从代表坦噶尼喀湖其他口育谱系的8个物种（11个个体）中获得了直系同源序列。序列差异比较显示，坦噶尼喀湖的单一Ectodini族似乎比整个马拉维湖丽鱼科物种群大约早五倍，这表明坦噶尼喀湖口育谱系的辐射发生在马拉维湖和维多利亚湖物种群进化之前很久。坦噶尼喀湖丽鱼科九个被调查族中的七个似乎具有大致相同的分化程度，这似乎证实了在坦噶尼喀湖物种群历史早期谱系快速同时形成的假说。特有属Tropheus谱系与非特有属“Astatotilapia burtoni”之间的密切遗传关系表明，Tropheini族的成员可能是马拉维湖和维多利亚湖丽鱼科物种群的姐妹群。系统发育分析证明了Ectodini族的单系性，并确定Cyprichromini族是坦噶尼喀湖丽鱼科中它们的姐妹群。在Ectodini族内，分子数据表明分支模式与先前提出的不同，并且Ectodini族可细分为四个分支，而不是最初描述的两个。因此，先前假定的形态转变模型，被认为是造成Ectodini族中发现的截然不同的生态特化类型的原因，可能需要重新解释。即使在丽鱼科鱼类的单个谱系成员中，与觅食和营养直接相关的特征似乎也特别容易出现同形现象。
