Impacts of oxygen deficiency on embryo life-history traits of migratory locust Locusta migratoria from low and high altitudes

Hypoxia challenges aerobic organisms in numerous environments,and hypoxic conditions may become more severe under future climate-change scenarios.The impact of hypoxia on the development of terrestrial insect embryos is not well understood.Here,to address this gap,embryonic life-history traits of migratory locust Locusta migratoria from low-altitude and high-altitude regions were compared under 2 oxygen levels:normoxia(i.e.,21 kPa oxygen partial pressure and mild hypoxia(i.e.,10 kPa oxygen partial pressure).Our results demonstrated that,whether reared under normoxia or mild hypoxia,L.migratoria from high-altitude populations had longer developmental times,reduced weight,and lower mean relative growth rate as compared with those from low-altitude populations.When transferred from normoxia to mild hypoxia,nearly all the tested lifehistory traits presented significant negative changes in the low-altitude populations,but not in the high-altitude populations.The factor'strain'alone explained 18.26%-54.59%of the total variation for traits,suggesting that the phenotypic differences between L.migratoria populations from the 2 altitudes could be driven by genetic variation.Significant genetic correlations were found between life-history traits,and most of these showed differentiation between the 2 altitudinal gradients.G-matrix comparisons showed significant structural differences between L.migratoria from the 2 regions,as well as several negative covariances(i.e.,trade-offs)between traits in the low-altitude populations.Overall,our study provides clear evidence that evolutionary divergence of embryonic traits between L.migratoria populations from different altitudes has occurred.