Environmental variation and biotic interactions limit adaptation at ecological margins: lessons from rainforest Drosophila and European butterflies

Models of local adaptation to spatially varying selection predict that maximum rates of evolution are determined by the interaction between increased adaptive potential owing to increased genetic variation, and the cost genetic variation brings by reducing population fitness. We discuss existing and new results from our laboratory assays and field transplants of rainforest Drosophila and UK butterflies along environmental gradients, which try to test these predictions in natural populations. Our data suggest that: (i) local adaptation along ecological gradients is not consistently observed in time and space, especially where biotic and abiotic interactions affect both gradient steepness and genetic variation in fitness; (ii) genetic variation in fitness observed in the laboratory is only sometimes visible to selection in the field, suggesting that demographic costs can remain high without increasing adaptive potential; and (iii) antagonistic interactions between species reduce local pro...

针对空间异质选择的局部适应模型预测，进化的最大速率由两种因素的相互作用所决定：一是遗传变异增加带来的适应性潜力提升，二是遗传变异因降低种群适合度而产生的适应性代价。我们将讨论针对沿环境梯度分布的热带雨林果蝇（Drosophila）与英国蝴蝶开展的实验室测定与野外移植实验的已有及最新研究结果，这些实验旨在检验自然种群中的上述理论预测。我们的研究数据显示：(i) 沿生态梯度的局部适应在时间与空间维度上并非总能被观测到，尤其是当生物与非生物交互同时影响梯度陡度与适合度相关的遗传变异时；(ii) 实验室中观测到的适合度遗传变异，在野外环境中仅部分会受到选择作用的影响，这提示种群适合度代价可能在未提升适应性潜力的情况下仍维持在较高水平；(iii) 物种间的拮抗交互作用会降低局部...