The adaptive value of correlations among phenotypic traits depends on the prevailing environmental conditions. Differences in selection pressures during species range expansions may therefore shape phenotypic integration. In this study, we assessed variation in behavioral and morphological traits, as well as their covariations, in replicated southern and northern European populations of the northward expanding dragonfly Crocothemis erythraea. Larvae from northern populations were, on average, darker in color, and therefore, better camouflaged than larvae from southern populations. However, there was no difference in activity level. Darkness and activity were positively correlated in larvae from northern populations, whereas this trait covariation was missing in southern populations. This suggests the emergence of alternative strategies in time-limited northern populations, a higher activity level that required better camouflage through darker coloration, while less active larvae benefited from an energy-saving strategy by reducing the investment in costly traits, such as body darkness. We further found that larger larvae emerged into larger adults, with a higher investment in flight morphology. Our findings imply that phenotypic integration is associated with the northward range shift, potentially differentially shaping fitness consequences, and ecological interactions in southern versus northern populations.

中文翻译：

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范围扩展会改变性状协变吗？研究向北扩展的蜻蜓。

表型性状之间的相关性的适应性值取决于主要的环境条件。因此，物种范围扩展期间选择压力的差异可能会影响表型整合。在这项研究中，我们评估了向北扩展的蜻蜓番红花（Crocothemis erythraea）的复制的南欧和北欧人口中行为和形态特征的变异以及它们的协变。平均而言，北部种群的幼虫颜色较深，因此比南部种群的幼虫伪装得更好。但是，活动水平没有差异。北方种群幼虫的黑暗度和活性呈正相关，而南方种群缺少这种性状的协变。这表明在有时间限制的北方人群中出现了替代策略，较高的活动水平需要通过深色着色来更好地伪装，而活动较少的幼虫则通过减少对人体黑暗等昂贵特性的投资而受益于节能策略。我们进一步发现，较大的幼虫出现在较大的成年动物中，对飞行形态的投资更高。我们的发现表明，表型整合与北移，潜在的差异适应度后果以及南部和北部人口的生态相互作用有关。例如身体黑暗。我们进一步发现，较大的幼虫出现在较大的成年动物中，对飞行形态的投资更高。我们的发现表明，表型整合与北移，潜在的差异适应度后果以及南部和北部人口的生态相互作用有关。例如身体黑暗。我们进一步发现，较大的幼虫出现在较大的成年动物中，对飞行形态的投资更高。我们的发现表明，表型整合与北移，潜在的差异适应度后果以及南部和北部人口的生态相互作用有关。