Manenti Raoul, Kristensen Nadiah, Cogliati Paola, Barzaghi Benedetta, Melotto Andrea, Ficetola Gentile Francesco
Department of Environmental Science and Policy, Università degli Studi di Milano, Milano, Italy.
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
J Evol Biol. 2023 Mar;36(3):529-541. doi: 10.1111/jeb.14155. Epub 2023 Feb 9.
Theory predicts that, in organisms with complex life cycles, if the earlier-stage limiting factor induces weak later-stage phenotypes, the development of the later-stage trait should evolve to reduce carry-over effects. Local adaptations could thus favour decoupling of later stages. However, decoupling is not always possible. In this study, we used a widespread amphibian, the European fire salamander (Salamandra salamandra), to assess the role of local adaptations to environmental stressful conditions experienced at the larval stage. We exposed 150 larvae from different altitudes to two conditions: rich food and poor food condition. Conditions in early life stages can affect an individual's traits, either as a direct effect or mediated through outcomes in successive life stages. To distinguish between effects of rearing conditions and local adaptation, we searched for a causal model. The causal model detected effects of both food treatment and population origin (altitude) on all life stages. Larvae reared under rich food condition metamorphosed earlier, had higher growth rates and reached smaller size at metamorphosis. Significant differences occurred between larvae of different origin: low-altitude individuals performed poorly under the poor food treatment. Moreover, larvae from higher altitudes were slower with rich food and faster with poor food compared to those from lower altitudes. Our results underline that environmental conditions and local adaptation can interplay in determining the plasticity of larval stages, still adaptations can maximize the growth efficiency of early stages in oligotrophic environments, leading to divergent pathways across populations and environmental conditions.
理论预测，在具有复杂生命周期的生物体中，如果早期阶段的限制因素诱导出较弱的后期阶段表型，后期阶段性状的发育应该进化以减少遗留效应。因此，局部适应性可能有利于后期阶段的解耦。然而，解耦并非总是可行的。在本研究中，我们使用了一种分布广泛的两栖动物——欧洲火蝾螈（Salamandra salamandra），来评估局部适应对幼体阶段所经历的环境压力条件的作用。我们将来自不同海拔高度的150只幼体暴露于两种条件下：丰富食物条件和贫乏食物条件。生命早期阶段的条件可以影响个体的性状，要么是直接影响，要么是通过连续生命阶段的结果介导。为了区分饲养条件和局部适应的影响，我们寻找了一个因果模型。因果模型检测到食物处理和种群来源（海拔）对所有生命阶段都有影响。在丰富食物条件下饲养的幼体更早变态，生长速度更快，变态时达到的体型更小。不同来源的幼体之间存在显著差异：低海拔个体在贫乏食物处理下表现较差。此外，与低海拔的幼体相比，高海拔的幼体在丰富食物条件下速度较慢，在贫乏食物条件下速度较快。我们的结果强调，环境条件和局部适应在决定幼体阶段的可塑性方面可以相互作用，适应性仍然可以在贫营养环境中最大化早期阶段的生长效率，导致不同种群和环境条件下的不同发育途径。
