Individuals of large or dark-colored ectothermic species often have a higher reproduction and activity than small or light-colored ones. However, investments into body size or darker colors should negatively affect the fitness of individuals as they increase their growth and maintenance costs. Thus, it is unlikely that morphological traits directly affect species' distribution and abundance. Yet, this simplification is frequently made in trait-based ecological analyses. Here, we integrated the energy allocation strategies of species into an ecophysiological framework to explore the mechanisms that link species' morphological traits and population dynamics. We hypothesized that the effects of morphological traits on species' distribution and abundance are not direct but mediated by components of the energy budget and that species can allocate more energy towards dispersal and reproduction if they compensate their energetic costs by reducing mobility costs or increasing energy uptake. To classify species' energy allocation strategies, we used easily measured proxies for the mobility costs and energy uptake of butterflies that can be also applied to other taxa. We demonstrated that contrasting effects of morphological traits on distribution and abundance of butterfly species offset each other when species' energy allocation strategies are not taken into account. Larger and darker butterfly species had wider distributions and were more abundant if they compensated the investment into body size and color darkness (i.e., melanin) by reducing their mobility costs or increasing energy uptake. Adults of darker species were more mobile and foraged less compared to lighter colored ones, if an investment into melanin was indirectly compensated via a size-dependent reduction of mobility costs or increase of energy uptake. Our results indicate that differences in the energy allocations strategies of species account for a considerable part of the variation in species' distribution and abundance that is left unexplained by morphological traits alone and ignoring these differences can lead to false mechanistic conclusions. Therefore, our findings highlight the potential of integrating proxies for species' energy allocation strategies into trait-based models not only for understanding the physiological mechanisms underlying variation in species' distribution and abundance, but also for improving predictions of the population dynamics of species.

中文翻译：

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流动成本和能量吸收调节形态特征对物种分布和丰度的影响

大型或深色变温物种的个体通常比小型或浅色物种具有更高的繁殖和活动。然而，对体型或深色的投资应该会对个体的健康产生负面影响，因为它们会增加他们的成长和维持成本。因此，形态特征不太可能直接影响物种的分布和丰度。然而，这种简化经常在基于特征的生态分析中进行。在这里，我们将物种的能量分配策略整合到一个生态生理框架中，以探索将物种形态特征与种群动态联系起来的机制。我们假设形态特征对物种的影响 分布和丰度不是直接的，而是由能量预算的组成部分调节的，如果物种通过降低流动成本或增加能量吸收来补偿其能量成本，则它们可以将更多的能量分配给扩散和繁殖。为了对物种的能量分配策略进行分类，我们使用了易于测量的蝴蝶移动成本和能量吸收代理，这些代理也可以应用于其他类群。我们证明，当不考虑物种的能量分配策略时，形态特征对蝴蝶物种分布和丰度的对比影响相互抵消。更大和更黑的蝴蝶物种分布更广，如果它们补偿对体型和颜色黑暗的投资（即，黑色素）通过降低他们的移动成本或增加能量吸收。与浅色物种相比，如果对黑色素的投资通过与体型相关的移动成本降低或能量吸收增加来间接补偿，则深色物种的成虫移动性更强，觅食更少。我们的研究结果表明，物种能量分配策略的差异占物种分布和丰度变化的很大一部分，这些变化仅由形态特征无法解释，忽略这些差异可能导致错误的机械结论。因此，我们的研究结果强调了将物种能量分配策略的代理整合到基于特征的模型中的潜力，这不仅是为了理解物种变异背后的生理机制。