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）与固定遗传差异（fixed genotypic differences）被视作适应演化中的两种对立策略。近年来，有研究提出二者可协同发挥作用，在特定条件下共同推动演化、物种形成乃至适应性辐射（adaptive radiation）。本研究以用于探究适应性分化早期阶段的新兴模式类群——广食性慈鲷（cichlid）伯顿丽体鱼（Astatotilapia burtoni）为研究对象，剖析适应性表型可塑性与局部适应（local adaptation）对适合度（fitness）的相对贡献。我们通过在坦噶尼喀湖（Lake Tanganyika）开展两项移植实验，检验了自然界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幼龄湖泊种群与河流种群个体，第二项实验则使用共同花园（common garden）繁育环境下培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（enclosures）中移植个体的存活与生长情况，我们发现第一项实验中野外捕获的土著种群生长更快，这一结果证实了局部适应的存在；而第二项实验中，不同组合的F1杂交后代并未出现生长差异，这表明适应性表型可塑性对提升移民适合度具有显著贡献。本研究结果凸显了对比野外捕获个体与共同花园繁育个体适合度的研究价值，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。