Guillaumet A, Crochet P-A, Godelle B
Laboratoire Génome, Populations, Interactions, Adaptation, CNRS UMR 5171, Université Montpellier II, C.C. 63, 34095 Montpellier cedex 5, France.
Mol Ecol. 2005 Oct;14(12):3809-21. doi: 10.1111/j.1365-294X.2005.02696.x.
The relative influences of history, natural selection and hybridization in shaping phenotypic variation in closely related taxa is a crucial issue in current evolutionary biology. In this study, we used as a model two sibling but paradoxically highly variable species of larks (Galerida theklae and Galerida cristata) of Morocco to separate the impacts of these evolutionary forces. In the former species, variation is manifested mainly in colouration, while in the latter, variation also encompasses bill size and shape. Mitochondrial and nuclear DNA sequencing were used to identify the historical relationships among the subspecies and species. According to our analyses, G. cristata and G. theklae diverged about 3.7 million years ago (Ma), and we found no evidence for a role of hybridization in maintaining their similarity. In G. theklae, there was no further subdivision, while in G. cristata two major mtDNA groups were identified (divergence approximately 1.1 Ma). These two lineages are parapatric and regroup, respectively, the three short-billed subspecies [G. (cristata) cristata] and the two long-billed subspecies [G. (cristata) randonii]. Patterns of morphological variation were then contrasted to this pattern of neutral relationships: we found that G. (c.) cristata was morphologically more similar to G. theklae than to G. (c.) randonii. Overall, these results point towards the prominent role of (i) natural selection and/or phenotypic plasticity in adapting the plumage to local conditions and (ii) natural selection in combination with historical isolation in driving the divergence in size and bill morphology in the crested larks.
历史、自然选择和杂交在塑造近缘分类群表型变异中的相对影响是当前进化生物学中的一个关键问题。在本研究中，我们以摩洛哥的两种亲缘关系相近但具有高度变异的云雀（泰氏云雀和凤头云雀）作为模型，以区分这些进化力量的影响。在前一个物种中，变异主要表现在羽色上，而在后一个物种中，变异还包括喙的大小和形状。线粒体和核DNA测序被用于确定亚种和物种之间的历史关系。根据我们的分析，凤头云雀和泰氏云雀大约在370万年前分化，并且我们没有发现杂交在维持它们相似性方面发挥作用的证据。在泰氏云雀中，没有进一步的细分，而在凤头云雀中，鉴定出了两个主要的线粒体DNA组（分化时间约为110万年前）。这两个谱系分别是邻域分布且重新组合了三个短喙亚种[凤头云雀指名亚种]和两个长喙亚种[凤头云雀兰氏亚种]。然后将形态变异模式与这种中性关系模式进行对比：我们发现凤头云雀指名亚种在形态上与泰氏云雀比与凤头云雀兰氏亚种更相似。总体而言，这些结果表明（i）自然选择和/或表型可塑性在使羽毛适应当地条件方面发挥着重要作用，以及（ii）自然选择与历史隔离相结合在推动凤头云雀的大小和喙形态差异方面发挥着重要作用。
