Data from: Cross-sex genetic correlations and the evolution of sex-specific local adaptation: insights from classical trait clines in Drosophila melanogaster

Natural selection varies widely among locations of a species’ range, favouring population divergence and adaptation to local environmental conditions. Selection also differs between females and males, favouring the evolution of sexual dimorphism. Both forms of within-species evolutionary diversification are widely studied, though largely in isolation, and it remains unclear whether environmental variability typically generates similar or distinct patterns of selection on each sex. Studies of sex-specific local adaptation are also challenging because they must account for genetic correlations between female and male traits, which may lead to correlated patterns of trait divergence between sexes, whether or not local selection patterns are aligned or differ between the sexes. We quantified sex-specific divergence in five clinally variable traits in Drosophila melanogaster that individually vary in their magnitude of cross-sex genetic correlation (i.e., from moderate to strongly positive). In all five traits, we observed parallel male and female clines, regardless of the magnitude of their genetic correlation. These patterns imply that parallel spatial divergence of female and male traits is a reflection of sexually concordant directional selection imposed by local environmental conditions. In such contexts, genetic correlations between the sexes promote, rather than constrain, local adaptation to a spatially variable environment.

自然选择在物种分布范围的不同区域间差异显著，可推动种群分化并使其适应局部环境条件。此外，雌雄个体间的选择压力亦存在分化，进而促进性二态性（sexual dimorphism）的演化。尽管这两类种内进化分化形式均得到广泛研究，但二者大多独立开展，目前仍不清楚环境异质性通常会对两性产生相似还是截然不同的选择模式。
针对性别特异性局部适应的研究同样颇具挑战，因为这类研究必须考量雌雄性状间的跨性遗传相关（cross-sex genetic correlation）——无论局部选择模式在两性间是一致还是存在差异，这种遗传相关都可能导致两性间的性状分化呈现协同格局。
我们以黑腹果蝇（Drosophila melanogaster）为研究对象，对其5种渐变可变性状的性别特异性分化进行了量化分析。这些性状的跨性遗传相关程度跨度较大，从中度到强正相关不等。在全部5种性状中，无论其遗传相关强度如何，我们均观察到雌雄个体呈现出平行的渐变群（clines）模式。
上述结果表明，雌雄性状的平行空间分化，实则是局部环境条件施加的性别协同定向选择的直观体现。在此类情境中，两性间的遗传相关非但不会制约局部适应，反而会推动种群适应空间异质性的环境。