Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Spain.
Heredity (Edinb). 2013 Jun;110(6):520-9. doi: 10.1038/hdy.2012.118. Epub 2013 Jan 16.
Gene flow (defined as allele exchange between populations) and gene flux (defined as allele exchange during meiosis in heterokaryotypic females) are important factors decreasing genetic differentiation between populations and inversions. Many chromosomal inversions are under strong selection and their role in recombination reduction enhances the maintenance of their genetic distinctness. Here we analyze levels and patterns of nucleotide diversity, selection and demographic history, using 37 individuals of Drosophila subobscura from Mount Parnes (Greece) and Barcelona (Spain). Our sampling focused on two frequent O-chromosome arrangements that differ by two overlapping inversions (OST and O(3+4)), which are differentially adapted to the environment as observed by their opposing latitudinal clines in inversion frequencies. The six analyzed genes (Pif1A, Abi, Sqd, Yrt, Atpα and Fmr1) were selected for their location across the O-chromosome and their implication in thermal adaptation. Despite the extensive gene flux detected outside the inverted region, significant genetic differentiation between both arrangements was found inside it. However, high levels of gene flow were detected for all six genes when comparing the same arrangement among populations. These results suggest that the adaptive value of inversions is maintained, regardless of the lack of genetic differentiation within arrangements from different populations, and thus favors the Local Adaptation hypothesis over the Coadapted Genome hypothesis as the basis of the selection acting on inversions in these populations.
基因流（定义为种群之间的等位基因交换）和基因通量（定义为异核雌性减数分裂期间的等位基因交换）是降低种群间遗传分化和倒位的重要因素。许多染色体倒位受到强烈选择，其减少重组的作用增强了它们遗传独特性的维持。在这里，我们使用来自希腊帕纳塞斯山（Mount Parnes）和西班牙巴塞罗那（Barcelona）的 37 只果蝇 subobscura 个体，分析核苷酸多样性、选择和种群历史的水平和模式。我们的采样集中在两种常见的 O 染色体排列上，它们通过两个重叠的倒位（OST 和 O(3+4)）而有所不同，这两个倒位由于其在反转频率上的相反纬度梯度而对环境表现出不同的适应性。分析的六个基因（Pif1A、Abi、Sqd、Yrt、Atpα 和 Fmr1）是根据它们在 O 染色体上的位置和它们在热适应中的作用而选择的。尽管在倒位区域外检测到广泛的基因通量，但在该区域内发现了两种排列之间的显著遗传分化。然而，当比较不同种群中相同排列的所有六个基因时，发现基因流水平很高。这些结果表明，反转的适应性价值得到了维持，尽管来自不同种群的排列内部缺乏遗传分化，因此支持局部适应假说而不是共适应基因组假说作为这些种群中反转选择的基础。
