Horn Rebekah L, Marques Adam J D, Manseau Micheline, Golding Brian, Klütsch Cornelya F C, Abraham Ken, Wilson Paul J
Trent University Peterborough ON Canada.
Instituto Gulbenkian de Ciência Oeiras Portugal.
Ecol Evol. 2018 May 15;8(12):6053-6064. doi: 10.1002/ece3.4154. eCollection 2018 Jun.
The parallel evolution of phenotypes or traits within or between species provides important insight into the basic mechanisms of evolution. Genetic and genomic advances have allowed investigations into the genetic underpinnings of parallel evolution and the independent evolution of similar traits in sympatric species. Parallel evolution may best be exemplified among species where multiple genetic lineages, descended from a common ancestor, colonized analogous environmental niches, and converged on a genotypic or phenotypic trait. Modern North American caribou () originated from three ancestral sources separated during the Last Glacial Maximum (LGM): the Beringian-Eurasian lineage (BEL), the North American lineage (NAL), and the High Arctic lineage (HAL). Historical introgression between the NAL and the BEL has been found throughout Ontario and eastern Manitoba. In this study, we first characterized the functional differentiation in the cytochrome-b (cytB) gene by identifying nonsynonymous changes. Second, the caribou lineages were used as a direct means to assess site-specific parallel changes among lineages. There was greater functional diversity within the NAL despite the BEL having greater neutral diversity. The patterns of amino acid substitutions occurring within different lineages supported the parallel evolution of cytB amino acid substitutions suggesting different selective pressures among lineages. This study highlights the independent evolution of identical amino acid substitutions within a wide-ranging mammal species that have diversified from different ancestral haplogroups and where ecological niches can invoke parallel evolution.
物种内部或物种之间表型或性状的平行进化为深入了解进化的基本机制提供了重要线索。遗传学和基因组学的进展使得人们能够研究平行进化的遗传基础以及同域物种中相似性状的独立进化。平行进化在多个遗传谱系从共同祖先分化而来、占据相似环境生态位并在基因型或表型性状上趋同的物种中表现得最为典型。现代北美驯鹿起源于末次盛冰期（LGM）期间分离的三个祖先种群：白令 - 欧亚谱系（BEL）、北美谱系（NAL）和高北极谱系（HAL）。在安大略省和马尼托巴省东部发现了NAL和BEL之间的历史基因渗入现象。在本研究中，我们首先通过识别非同义变化来表征细胞色素b（cytB）基因的功能分化。其次，将驯鹿谱系作为评估谱系间位点特异性平行变化的直接手段。尽管BEL具有更高的中性多样性，但NAL内部的功能多样性更大。不同谱系中发生的氨基酸替换模式支持了cytB氨基酸替换的平行进化，表明不同谱系之间存在不同的选择压力。这项研究突出了同一氨基酸替换在一种广泛分布的哺乳动物物种中的独立进化，该物种从不同的祖先单倍群分化而来，且生态位可引发平行进化。
