The largely endemic cichlid species flocks of the East African Great Lakes are among the prime examples for explosive speciation and adaptive radiation. Speciation rates differ among cichlid lineages, and the propensity to radiate has been linked to intrinsic and extrinsic factors such as sexual selection and ecological opportunity. Remarkably, only one cichlid tribe—the Boulengerochromini—comprises just a single species, Boulengerochromis microlepis, a predominantly piscivorous endemic of Lake Tanganyika and the world’s largest cichlid. While the lineage diverged from its closest relatives at the onset of the Lake Tanganyika radiation >8 MYA, mitochondrial control region sequences collected in this study dated the most recent common ancestor of B. microlepis to ~60–110 KYA. There was no evidence of phylogeographic structure in the lake-wide sample. Patterns of genetic diversity and demographic analyses were consistent with slow and steady population growth throughout the reconstructed timescale. Additionally, the shallow divergence within the species may be related to a possibly large variance in reproductive success in this highly fecund species. Trophic niche space restriction by sympatric piscivores, lack of geographic structure, low potential for sexual selection arising from the monogamous mating system and extinction may have contributed to keeping the lineage monotypic.

中文翻译：

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大鱼，小分歧：坦噶尼喀湖巨型慈鲷的系统地理学，Boulengerochromis microlepis

东非五大湖的主要地方性慈鲷物种群是爆炸性物种形成和适应性辐射的主要例子之一。慈鲷谱系的物种形成率不同，辐射倾向与性选择和生态机会等内在和外在因素有关。值得注意的是，只有一个慈鲷部落 - Boulengerochromini - 仅包含一个物种，即 Boulengerochromis microlepis，这是坦噶尼喀湖的主要食鱼特有种，也是世界上最大的慈鲷。虽然该谱系在坦噶尼喀湖辐射 >8 MYA 开始时与其最近的亲属发生分歧，但本研究中收集的线粒体控制区序列将 B. microlepis 的最新共同祖先定为约 60-110 KYA。在整个湖泊的样本中没有系统地理结构的证据。在整个重建的时间尺度上，遗传多样性和人口统计分析的模式与缓慢而稳定的人口增长一致。此外，物种内的浅差异可能与这种高度繁殖的物种的繁殖成功率可能存在很大差异有关。同域食鱼动物对营养生态位空间的限制、缺乏地理结构、由一夫一妻制交配系统引起的性选择潜力低以及灭绝可能有助于保持谱系的单一性。物种内的浅差异可能与这种高度繁殖的物种的繁殖成功率可能存在很大差异有关。同域食鱼动物对营养生态位空间的限制、缺乏地理结构、由一夫一妻制交配系统引起的性选择潜力低以及灭绝可能有助于保持谱系的单一性。物种内的浅差异可能与这种高度繁殖的物种的繁殖成功率可能存在很大差异有关。同域食鱼动物对营养生态位空间的限制、缺乏地理结构、由一夫一妻制交配系统引起的性选择潜力低以及灭绝可能有助于保持谱系的单一性。