Telmatochromis temporalis is a cichlid fish endemic to Lake Tanganyika. Two morphs of this species, normal and dwarf, form a good model for the study of ecological speciation through divergent natural selection on body size. This study reports a third morph of this species, slender morph, which was collected from deep waters off Kasenga, Zambia, whereas the normal morph inhabits shallow waters of the same locality. This study examined morphological characters and mitochondrial DNA sequences in 18 populations of the three T. temporalis morphs and two closely related species. The slender morph was morphologically similar to the normal and dwarf morphs of the same species, but clearly differed from closely related species. Genetic analyses showed that the slender morph was closest to but significantly different from the parapatric normal morph, suggesting reproductive isolation between them. Due to the lack of colour differences between morphs and of obvious geographical barriers between habitats, reproductive isolation between these morphs may be attributed to ecological factors, rather than sexual or geographical segregation. Further studies examining the evolution of the slender morph may deepen our knowledge of initial stages of speciation, like in the dwarf morph.

中文翻译：

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坦噶尼喀湖的一种新形态的颞叶鱼（慈鲷科；慈鲷）

Telmatochromis temporalis 是坦噶尼喀湖特有的一种慈鲷鱼。该物种的两个变体，正常和矮化，通过对体型的不同自然选择形成了生态物种形成研究的良好模型。这项研究报告了该物种的第三种变体，细长变体，它是从赞比亚卡森加附近的深水中收集的，而正常变体则栖息在同一地区的浅水区。这项研究检查了三个 T. temporalis 变形和两个密切相关物种的 18 个种群的形态特征和线粒体 DNA 序列。细长的变种在形态上与同一物种的正常和矮化变种相似，但与密切相关的物种明显不同。遗传分析表明，细长型与旁系正常型最接近，但有显着差异，暗示他们之间存在生殖隔离。由于变种之间没有颜色差异，栖息地之间没有明显的地理障碍，这些变种之间的生殖隔离可能归因于生态因素，而不是性别或地理隔离。进一步研究细长变形的进化可能会加深我们对物种形成初始阶段的了解，就像在矮变形中一样。