Data from: Extra molting and selection on nymphal growth in the desert locust

In insects, extra-molting has been viewed as a compensatory mechanism for nymphal growth that contributes to optimize body weight for successful reproduction. However, little is known on the capacity of extra-molting to evolve in natural populations, which limits our understanding of how selection acts on nymphal growth. We used a multi-generational pedigree, individual monitoring and quantitative genetics models to investigate the evolution of extra-molting and its impact on nymphal growth in a solitarious population of the desert locust, Schistocerca gregaria. Growth compensation via extra-molting was observed for 46% of the females, whose adult weight exceeded by 4% that of other females, at a cost of a 22% longer development time. We found a null heritability for body weight threshold only, and the highest and a strongly female-biased heritability for extra molting. Our genetic estimates show that (1) directional selection can act on growth rate, development time and extra-molting to optimize body weight threshold, the target of stabilizing selection, (2) extra-molting can evolve in natural populations, and (3) a genetic conflict, due to sexually antagonistic selection on extra-molting, might prevent its fixation. Finally, we discuss how antagonistic selection between solitarious and gregarious environments and/or genetic correlations between growth and phase traits might also impact the evolution of extra-molting in locusts.

在昆虫中，额外蜕皮（extra-molting）向来被视为若虫生长的一种补偿机制，有助于优化成虫体重以保障成功繁殖。然而，学界对额外蜕皮在自然种群中的演化潜力尚所知甚少，这限制了我们对选择如何作用于若虫生长的认知。本研究以散居型沙漠蝗（Schistocerca gregaria）种群为研究对象，采用多代谱系分析、个体监测与定量遗传学模型，探究额外蜕皮的演化历程及其对若虫生长的影响。研究发现，46%的雌性个体通过额外蜕皮实现生长补偿，其成虫体重较其他雌性高出4%，但代价是发育时长增加22%。本研究仅发现体重阈值不存在遗传力，而额外蜕皮的遗传力最高，且呈现极强的雌性偏倚特征。我们的遗传估算结果表明：其一，定向选择可作用于生长速率、发育时长与额外蜕皮，以优化作为稳定选择靶标的体重阈值；其二，额外蜕皮可在自然种群中发生演化；其三，由于额外蜕皮受到性拮抗选择作用，可能存在遗传冲突，从而阻碍其在种群中完全固定。最后，本研究还讨论了散居与群居环境间的拮抗选择，以及生长与型态性状间的遗传相关，可能如何影响蝗虫额外蜕皮的演化。