Data from: Adaptive phenotypic plasticity contributes to divergence between lake and river populations of an East African cichlid fish

Adaptive phenotypic plasticity and fixed genotypic differences have long been considered opposing strategies in adaptation. More recently, these mechanisms have been proposed to act complementarily and under certain conditions jointly facilitate evolution, speciation and even adaptive radiations. Here we investigate the relative contributions of adaptive phenotypic plasticity vs. local adaptation to fitness, using an emerging model system for studying early phases of adaptive divergence, the generalist cichlid fish species Astatotilapia burtoni. We tested direct fitness consequences of morphological divergence between lake and river populations in nature by performing two transplant experiments in Lake Tanganyika. In the first experiment we used wild-caught juvenile lake and river individuals, while in the second experiment we used F1 crosses between lake and river fish bred in a common garden setup. By tracking the survival and growth of translocated individuals in enclosures in the lake over several weeks, we revealed local adaptation evidenced by faster growth of the wild-caught resident population in the first experiment. On the other hand, we did not find difference in growth between different types of F1 crosses in the second experiment, suggesting a substantial contribution of adaptive phenotypic plasticity to increased immigrant fitness. Our findings highlight the value of formally comparing fitness of wild-caught and common-garden-reared individuals and emphasize the necessity of considering adaptive phenotypic plasticity in the study of adaptive divergence.长期以来，适应性表型可塑性（adaptive phenotypic plasticity）与固定基因型差异一直被视作适应过程中相互对立的两种策略。近年来，学界提出这两种机制可协同发挥作用，在特定条件下共同推动演化、物种形成乃至适应性辐射。本研究以作为适应性分化早期阶段研究新兴模式系统的广食性慈鲷物种伯顿慈鲷（Astatotilapia burtoni）为研究对象，探究适应性表型可塑性与本地适应对适合度的相对贡献。我们通过在坦噶尼喀湖开展两项移植实验，验证了自然环境中湖泊与河流种群间的形态分化对适合度的直接影响：第一项实验采用野外捕获的湖泊与河流幼体个体，第二项实验则使用在同质园（common garden）环境中繁育的湖泊与河流种群个体的F1杂交后代。通过连续数周追踪湖内围隔中移植个体的存活与生长情况，我们在第一项实验中发现野外捕获的本地种群生长更快，这一结果证实了本地适应的存在。而在第二项实验中，我们未观测到不同类型F1杂交后代的生长差异，这表明适应性表型可塑性对迁入个体适合度的提升具有显著贡献。本研究结果凸显了对比野外捕获与同质园繁育个体适合度的重要价值，并强调在适应性分化研究中纳入适应性表型可塑性考量的必要性。