Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, 35 Stirling Highway, Crawley, 6009, WA, Australia.
Department of Biological Sciences (E8C 209), Macquarie University, Eastern Road, Sydney, 2109, NSW, Australia.
Sci Rep. 2020 Feb 11;10(1):2311. doi: 10.1038/s41598-020-59254-2.
Extreme differences between the sexes are usually explained by intense sexual selection on male weapons or ornaments. Sexually antagonistic genes, with a positive effect on male traits but a negative effect on female fitness, create a negative inter-sexual correlation for fitness (sexual conflict). However, such antagonism might not be apparent if sexually selected male traits are condition-dependent, and condition elevates female fitness. Here we reveal a surprising positive genetic correlation between male weaponry and female fecundity. Using mite lines that had previously been through 13 generations of selection on male weapons (fighting legs), we investigated correlated evolution in female fecundity. Females from lines under positive selection for weapons (up lines) evolved higher fecundity, despite evolving costly, thicker legs. This is likely because male mites have condition-dependent weaponry that increases our ability to indirectly select on male condition. Alleles with positive effects on condition in both sexes could have generated this correlation because: the up lines evolved a higher proportion of fighters and there were positive correlations between weapon size and the male morph and sex ratios of the offspring. This positive inter-sexual genetic correlation should boost the evolution of male weapons and extreme sex differences.
性别的极端差异通常可以用雄性武器或装饰物的强烈性选择来解释。具有正向影响雄性特征但负向影响雌性适合度的性拮抗基因，为适合度创造了负的两性间相关性（性冲突）。然而，如果受性选择的雄性特征是条件依赖的，并且条件提高了雌性适合度，那么这种拮抗作用可能不明显。在这里，我们揭示了雄性武器和雌性繁殖力之间惊人的正向遗传相关性。使用先前经过 13 代雄性武器（战斗腿）选择的螨系，我们调查了雌性繁殖力的相关进化。尽管武器（上系）进化出了更昂贵、更厚实的腿，但来自正选择武器的系的雌性进化出了更高的繁殖力。这可能是因为雄性螨虫具有条件依赖性的武器，这增加了我们间接选择雄性条件的能力。在两性中都具有正向影响条件的等位基因可能产生了这种相关性，因为：上系进化出了更高比例的斗士，武器大小与雄性形态以及后代的性别比例之间存在正相关。这种正向的两性间遗传相关性应该会促进雄性武器和极端性别差异的进化。
