Bastide Héloïse, Lange Jeremy D, Lack Justin B, Yassin Amir, Pool John E
Laboratory of Genetics, University of Wisconsin-Madison, Wisconsin 53706.
Laboratory of Genetics, University of Wisconsin-Madison, Wisconsin 53706
Genetics. 2016 Nov;204(3):1307-1319. doi: 10.1534/genetics.116.192492. Epub 2016 Sep 16.
Unraveling the genetic architecture of adaptive phenotypic divergence is a fundamental quest in evolutionary biology. In Drosophila melanogaster, high-altitude melanism has evolved in separate mountain ranges in sub-Saharan Africa, potentially as an adaptation to UV intensity. We investigated the genetic basis of this melanism in three populations using a new bulk segregant analysis mapping method. We identified 19 distinct QTL regions from nine mapping crosses, with several QTL peaks overlapping between two or all populations, and yet different crosses involving the same melanic population commonly yielded distinct QTL. The strongest QTL often overlapped well-known pigmentation genes, but we typically did not find wide signals of genetic differentiation (F) between lightly and darkly pigmented populations at these genes. Instead, we found small numbers of highly differentiated SNPs at the probable causative genes. A simulation analysis showed that these patterns of polymorphism were consistent with selection on standing genetic variation. Overall, our results suggest that, even for potentially simpler traits like pigmentation, the complexity of adaptive trait evolution poses important challenges for QTL mapping and population genetic analysis.
揭示适应性表型分化的遗传结构是进化生物学的一项基本探索。在黑腹果蝇中，高海拔黑化现象已在撒哈拉以南非洲的不同山脉中独立进化，这可能是对紫外线强度的一种适应。我们使用一种新的混合分离群体分析法，研究了三个种群中这种黑化现象的遗传基础。我们从九个定位杂交中鉴定出19个不同的数量性状基因座（QTL）区域，其中几个QTL峰值在两个或所有种群之间重叠，然而，涉及同一黑化种群的不同杂交通常产生不同的QTL。最强的QTL通常与著名的色素沉着基因重叠，但我们通常在这些基因的浅色和深色色素沉着种群之间没有发现广泛的遗传分化信号（F）。相反，我们在可能的致病基因处发现了少量高度分化的单核苷酸多态性（SNP）。模拟分析表明，这些多态性模式与对现存遗传变异的选择一致。总体而言，我们的结果表明，即使对于色素沉着这样可能更简单的性状，适应性性状进化的复杂性也给QTL定位和群体遗传分析带来了重要挑战。
