Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN 37996, USA.
J Evol Biol. 2010 Jul;23(7):1456-67. doi: 10.1111/j.1420-9101.2010.02004.x. Epub 2010 May 7.
The lower jaw (LJ) provides an ideal trophic phenotype to compare rates and patterns of macroevolution among cichlid radiations. Using a novel phylogeny of four genes (ND2, dlx2, mitfb, and s7), we examined the evolutionary relationships among two of the most phylogenetically disparate cichlid radiations: (i) the Central America Heroines; and (ii) the East African Lake Malawi flock. To quantify jaw morphology, we measured two LJ lever systems in approximately 40 species from each lineage. Using geologic calibrations, we generated a chronogram for both groups and examined the rates of jaw evolution in the two radiations. The most rapidly evolving components of the LJ differed between the two radiations. However, the Lake Malawi flock exhibited a much faster rate of evolution in several components of the LJ. This rapid rate of divergence is consistent with natural selection, promoting unparalleled trophic diversification in Lake Malawi cichlids.
下颚（LJ）提供了一个理想的营养表型，可用于比较丽鱼辐射之间的宏观进化速度和模式。利用四个基因（ND2、dlx2、mitfb 和 s7）的新系统发育，我们研究了两个在系统发育上差异最大的丽鱼辐射之间的进化关系：（i）中美洲女英雄；（ii）东非马拉维湖群。为了量化下颚形态，我们测量了来自每个谱系的大约 40 个物种的两个 LJ 杠杆系统。利用地质校准，我们为两个群体生成了一个时标，并检查了两个辐射中下颚进化的速度。LJ 的两个辐射之间的进化速度最快的组成部分不同。然而，马拉维湖群的 LJ 的几个组成部分的进化速度要快得多。这种快速的分化速度与自然选择一致，促进了马拉维湖慈鲷无与伦比的营养多样化。
