Data from: Reproductive isolation and local adaptation quantified for a chromosome inversion in a malaria mosquito

Chromosome inversions have long been thought to be involved in speciation and local adaptation. We have little quantitative information, however, about the effects that inversion polymorphisms have on reproductive isolation and viability. Here we provide the first estimates from any organism for the total amount of reproductive isolation associated with an inversion segregating in natural populations. We sampled chromosomes from 751 mosquitoes of the malaria vector Anopheles funestus along a 1421 km transect in Cameroon that traverses savannah, highland, and rainforest ecological zones. We then developed a series of population genetic models that account for selection, migration, and assortative mating, and fit the models to the data using likelihood. Results from the best-fit models suggest there is strong local adaptation, with relative viabilities of homozygotes ranging from 25% to 130% compared to heterozygotes. Viabilities vary qualitatively between regions: the inversion is underdominant in the savannah, while in the highlands it is overdominant. The inversion is also implicated in strong assortative mating. In the savannah, the two homozygote forms show 92% reproductive isolation, suggesting that this one inversion can generate most of the genetic barriers needed for speciation.长期以来，染色体倒位（chromosome inversions）一直被认为与物种形成及局部适应过程密切相关。然而，目前学界对倒位多态性（inversion polymorphisms）如何影响生殖隔离与生存适合度的定量研究仍较为匮乏。本研究首次在任一物种中，估算了自然种群中分离的染色体倒位所关联的生殖隔离总强度。 研究团队沿喀麦隆境内1421公里的样带开展采样，该样带横跨稀树草原、高地与热带雨林三类生态区，共采集了751只作为疟疾媒介的富氏按蚊（Anopheles funestus）的染色体样本。随后，研究团队构建了一系列涵盖选择、迁移与选型交配的种群遗传模型，并采用极大似然法将模型与实测数据进行拟合。 最优拟合模型的结果显示，该倒位存在显著的局部适应性：与杂合子（heterozygotes）相比，纯合子（homozygotes）的相对生存适合度介于25%至130%之间。不同区域的生存适合度存在质性差异：在稀树草原区域，该倒位表现为杂合劣势（underdominant），而在高地区域则表现为超显性（overdominant）。该染色体倒位还与强烈的选型交配显著相关。在稀树草原区域，两种纯合子类型间的生殖隔离率达92%，这表明单个染色体倒位即可产生物种形成所需的绝大多数遗传屏障。