Data from: Does plasticity enhance or dampen phenotypic parallelism? A test with three lake-stream stickleback pairs.

Parallel (and convergent) phenotypic variation is most often studied in the wild, where it is difficult to disentangle genetic versus environmentally-induced effects. As a result, the potential contributions of phenotypic plasticity to parallelism (and non-parallelism) are rarely evaluated in a formal sense. Phenotypic parallelism could be enhanced by plasticity that causes stronger parallelism across populations in the wild than would be expected from genetic differences alone. Phenotypic parallelism could be dampened if site-specific plasticity induced differences between otherwise genetically-parallel populations. We used a common-garden study of three independent lake-stream stickleback population pairs to evaluate the extent to which adaptive divergence has a genetic or plastic basis, and to investigate the enhancing versus dampening effects of plasticity on phenotypic parallelism. We found that lake-stream differences in most traits had a genetic basis, but that several traits also showed contributions from plasticity. Moreover, plasticity was much more prevalent in one watershed than in the other two. In most cases, plasticity enhanced phenotypic parallelism, whereas in a few cases plasticity had a dampening effect. Genetic and plastic contributions to divergence seem to play a complimentary, likely adaptive, role in phenotypic parallelism of lake-stream stickleback. These findings highlight the value of formally comparing wild-caught and lab-reared individuals in the study of phenotypic parallelism.平行（及趋同）表型变异（parallel and convergent phenotypic variation）的相关研究多依托野外环境展开，此时难以厘清遗传效应与环境诱导效应的边界，因此表型可塑性（phenotypic plasticity）对表型平行性（及非平行性）的潜在贡献极少被置于正式框架下开展评估。若表型可塑性使得野外种群间的平行程度高于仅由遗传差异所能预期的水平，则可强化表型平行性；若位点特异性可塑性导致原本遗传背景一致的种群间产生表型差异，则会削弱表型平行性。本研究针对3组独立湖-溪棘鱼（stickleback）种群对开展共同花园实验（common-garden study），旨在评估适应性分化（adaptive divergence）的遗传与可塑性基础，并探究可塑性对表型平行性的强化与削弱效应。研究发现，多数性状的湖-溪差异具有遗传基础，但部分性状同时存在可塑性贡献；此外，可塑性在其中一个流域（watershed）中的普遍性远高于另外两个流域，多数情况下可塑性可强化表型平行性，仅少数场景下会产生削弱作用。遗传与可塑性对分化的贡献似乎在湖-溪棘鱼的表型平行性中发挥了互补且大概率具有适应性的作用，本研究结果凸显了在表型平行性研究中，正式比较野外捕获（wild-caught）与实验室饲养（lab-reared）个体的重要价值。