Data from: Field evidence for a rapid adaptive plastic response in morphology and growth of littoral and pelagic brook charr: a reciprocal transplant experiment

1. Phenotypic plasticity, a process by which individuals modify their morphology, physiology, or behaviour in response to environmental changes, can be seen as the first step in adaptive evolution. Phenotypic plasticity is adaptive if two conditions are met: (i) the phenotype is associated with an environment (plastic response) and (ii) the phenotype–environment association increases individual fitness (adaptive response). 2. Using a reciprocal transplant experiment, we tested the hypothesis that functional morphological responses are correlated with growth at two organizational levels (between and within ecotypes) in brook charr. 3. Four-month-old individuals from four littoral and four pelagic families raised in the laboratory were transferred into eight littoral (3 m × 4 m × 1.5 m depth) and eight pelagic (3 m × 4 m × 6 m depth) lake enclosures for a period of 12 weeks. 4. Fin length (the main discriminant trait of the littoral and pelagic ecotypes) was less plastic than body shape. Growth was higher in the pelagic than in the littoral habitat, but offspring from littoral and pelagic parental origins did not experience higher growth in their respective habitats (comparison between ecotypes). The body shape of most individuals transplanted to their reciprocal environment shifted toward the form expected in that environment. This plastic response in body shape was functionally correlated with growth within ecotypes, but only in the littoral habitat. Furthermore, the within-ecotype variance of both morphological traits and growth were higher in the littoral than in the pelagic habitat. 5. Small phenotypic differences could have direct consequences on fitness in the less favourable habitat, inducing higher inter-individual variance in growth and stronger phenotype–growth associations. We suggest that phenotypic accommodation and cryptic genetic variation, two mechanisms previously proposed as mechanisms involved in distinct situations, could be simultaneously involved to hasten the process of adaptive evolution in an unfavourable environment.1. 表型可塑性（Phenotypic plasticity）指个体响应环境变化而改变自身形态、生理或行为的过程，可被视为适应性进化的首要步骤。当满足两个条件时，表型可塑性便具有适应性：（i）表型与环境存在关联（即可塑性响应）；（ii）表型-环境关联能够提升个体适合度（即适应性响应）。 2. 本研究通过互易移植试验（reciprocal transplant experiment），验证了“溪红点鲑（brook charr）在两个组织层级（生态型间与生态型内）上，功能形态学响应与生长存在相关性”这一假说。 3. 本实验将实验室饲养的4月龄溪红点鲑个体，取自4个沿岸带（littoral）家系与4个远洋带（pelagic）家系，随后转移至8个沿岸带围隔（规格为3 m × 4 m × 1.5 m水深）与8个远洋带围隔（规格为3 m × 4 m × 6 m水深）中，饲养时长为12周。 4. 鳍长（沿岸带与远洋带生态型的主要判别性状）的可塑性弱于体型。远洋带生境中的生长速率高于沿岸带生境，但源自沿岸带与远洋带亲本的后代，并未在各自对应的生境中表现出更高的生长速率（生态型间比较结果）。大多数被移植到互易生境的个体，其体型会向该生境下的典型形态发生偏移。这种体型的可塑性响应在生态型内与生长存在功能相关性，但仅在沿岸带生境中显著。此外，沿岸带生境中形态性状与生长的生态型内方差均高于远洋带生境。 5. 在较不利生境中，微小的表型差异可能直接影响个体适合度，进而导致生长的个体间方差更高、表型与生长的关联更强。我们提出，表型调适（phenotypic accommodation）与隐性遗传变异（cryptic genetic variation）这两种此前分别被提出用于不同场景的机制，可共同参与作用，以加速不利环境下的适应性进化进程。