Data from: Flight loss linked to faster molecular evolution in insects

The loss of flight ability has occurred thousands of times independently during insect evolution. Flight loss may be linked to higher molecular evolutionary rates because of reductions in effective population sizes (Ne) and relaxed selective constraints. Reduced dispersal ability increases population subdivision, may decrease geographical range size and increases (sub)population extinction risk, thus leading to an expected reduction in Ne. Additionally, flight loss in birds has been linked to higher molecular rates of energy-related genes, probably owing to relaxed selective constraints on energy metabolism. We tested for an association between insect flight loss and molecular rates through comparative analysis in 49 phylogenetically independent transitions spanning multiple taxa, including moths, flies, beetles, mayflies, stick insects, stoneflies, scorpionflies and caddisflies, using available nuclear and mitochondrial protein-coding DNA sequences. We estimated the rate of molecular evolution of flightless (FL) and related flight-capable lineages by ratios of non-synonymous-to-synonymous substitutions (dN/dS) and overall substitution rates (OSRs). Across multiple instances of flight loss, we show a significant pattern of higher dN/dS ratios and OSRs in FL lineages in mitochondrial but not nuclear genes. These patterns may be explained by relaxed selective constraints in FL ectotherms relating to energy metabolism, possibly in combination with reduced Ne.

在昆虫演化历程中，飞行能力的丧失已独立发生过数千次。飞行能力丧失可能与更高的分子演化速率相关，这源于有效种群大小（effective population size, Ne）的缩减以及选择性约束的松弛。扩散能力减弱会加剧种群分化，可能缩小物种的地理分布范围，并增加（亚）种群的灭绝风险，进而导致预期中的有效种群大小缩减。此外，鸟类的飞行能力丧失已被证实与能量相关基因更高的分子演化速率相关，这可能是由于能量代谢相关的选择性约束松弛。本研究利用已公开的核基因与线粒体蛋白编码DNA序列，针对涵盖蛾类、蝇类、甲虫、蜉蝣、竹节虫、石蝇、蝎蛉与毛翅目昆虫在内的多个类群的49次系统发育独立的飞行能力丧失事件，通过比较分析检验了昆虫飞行能力丧失与分子演化速率之间的关联。本研究通过非同义替换与同义替换的比值（non-synonymous-to-synonymous substitution ratio, dN/dS）以及总替换速率（overall substitution rates, OSRs），估算了无飞行能力（flightless, FL）类群及其近缘有飞行能力支系的分子演化速率。在多次飞行能力丧失事件中，我们发现线粒体基因中无飞行能力支系的dN/dS比值与总替换速率均显著更高，而核基因中未观察到该模式。该模式可通过无飞行能力外温动物能量代谢相关的选择性约束松弛来解释，这可能与有效种群大小缩减共同作用。