Institut de Recherche pour le Développement, UR016 CCPV, Montpellier, France.
Mol Biol Evol. 2011 Jan;28(1):745-58. doi: 10.1093/molbev/msq248. Epub 2010 Sep 13.
Chromosomal polymorphisms, such as inversions, are presumably involved in the rapid adaptation of populations to local environmental conditions. Reduced recombination between alternative arrangements in heterozygotes may protect sets of locally adapted genes, promoting ecological divergence and potentially leading to reproductive isolation and speciation. Through a comparative analysis of chromosomal inversions and microsatellite marker polymorphisms, we hereby present biological evidence that strengthens this view in the mosquito Anopheles funestus s.s, one of the most important and widespread malaria vectors in Africa. Specimens were collected across a wide range of geographical, ecological, and climatic conditions in Cameroon. We observed a sharp contrast between population structure measured at neutral microsatellite markers and at chromosomal inversions. Microsatellite data detected only a weak signal for population structuring among geographical zones (F(ST) < 0.013, P < 0.01). By contrast, strong differentiation among ecological zones was revealed by chromosomal inversions (F(ST) > 0.190, P < 0.01). Using standardized estimates of F(ST), we show that inversions behave at odds with neutral expectations strongly suggesting a role of environmental selection in shaping their distribution. We further demonstrate through canonical correspondence analysis that heterogeneity in eco-geographical variables measured at specimen sampling sites explained 89% of chromosomal variance in A. funestus. These results are in agreement with a role of chromosomal inversions in ecotypic adaptation in this species. We argue that this widespread mosquito represents an interesting model system for the study of chromosomal speciation mechanisms and should provide ample opportunity for comparative studies on the evolution of reproductive isolation and speciation in major human malaria vectors.
染色体多态性，如倒位，可能参与了种群对当地环境条件的快速适应。在杂合子中，替代排列之间的重组减少可能会保护一组适应局部的基因，促进生态分化，并可能导致生殖隔离和物种形成。通过对染色体倒位和微卫星标记多态性的比较分析，我们在非洲最重要和分布最广的疟疾媒介之一的疟蚊 Anopheles funestus s.s 中提供了生物学证据，支持了这一观点。标本采集自喀麦隆广泛的地理、生态和气候条件。我们观察到中性微卫星标记和染色体倒位测量的种群结构之间存在明显的对比。微卫星数据仅检测到地理区域之间的种群结构存在微弱信号（F(ST) < 0.013，P < 0.01）。相比之下，染色体倒位揭示了生态区域之间的强烈分化（F(ST) > 0.190，P < 0.01）。使用标准化的 F(ST)估计值，我们表明倒位的行为与中性预期不符，强烈表明环境选择在塑造它们的分布中起作用。我们通过典型对应分析进一步表明，在标本采样地点测量的生态地理变量的异质性解释了 A. funestus 中 89%的染色体方差。这些结果与染色体倒位在该物种生态适应中的作用一致。我们认为，这种广泛分布的蚊子是研究染色体物种形成机制的一个有趣模型系统，应该为主要人类疟疾媒介的生殖隔离和物种形成进化的比较研究提供充足的机会。
