Merilä J, Laurila A, Lindgren B
Department of Ecology and Systematics, Ecological Genetics Research Unit, University of Helsinki, Helsinki, Finland.
J Evol Biol. 2004 Sep;17(5):1132-40. doi: 10.1111/j.1420-9101.2004.00744.x.
Adaptive phenotypic plasticity in the form of capacity to accelerate development as a response to pond drying risk is known from many amphibian species. However, very little is known about factors that might constrain the evolution of this type of plasticity, and few studies have explored to what degree plasticity might be constrained by trade-offs dictated by adaptation to different environmental conditions. We compared the ability of southern and northern Scandinavian common frog (Rana temporaria) larvae originating from 10 different populations to accelerate their development in response to simulated pond drying risk and the resulting costs in metamorphic size in a factorial laboratory experiment. We found that (i) northern larvae developed faster than the southern larvae in all treatments, (ii) a capacity to accelerate the response was present in all five southern and all five northern populations tested, but that the magnitude of the response was much larger (and less variable) in the southern than in the northern populations, and that (iii) significant plasticity costs in metamorphic size were present in the southern populations, the plastic genotypes having smaller metamorphic size in the absence of desiccation risk, but no evidence for plasticity costs was found in the northern populations. We suggest that the weaker response to pond drying risk in the northern populations is due to stronger selection on large metamorphic size as compared with southern populations. In other words, seasonal time constraints that have selected the northern larvae to be fast growing and developing, may also constrain their innate ability for adaptive phenotypic plasticity.
许多两栖动物物种都具有以加快发育能力的形式表现出的适应性表型可塑性，以此作为对池塘干涸风险的一种反应。然而，对于可能限制这种可塑性进化的因素，我们知之甚少，而且很少有研究探讨可塑性在多大程度上可能受到因适应不同环境条件而产生的权衡取舍的限制。在一项析因实验室实验中，我们比较了来自10个不同种群的斯堪的纳维亚半岛南部和北部普通青蛙（林蛙）幼体对模拟池塘干涸风险做出反应来加快其发育的能力，以及由此导致的变态体型成本。我们发现：（i）在所有处理中，北部幼体发育得比南部幼体快；（ii）在测试的所有五个南部种群和所有五个北部种群中都存在加快反应的能力，但南部种群的反应幅度要比北部种群大得多（且变化较小）；（iii）南部种群存在显著的变态体型可塑性成本，即没有干燥风险时，具有可塑性的基因型的变态体型较小，但在北部种群中未发现可塑性成本的证据。我们认为，北部种群对池塘干涸风险的反应较弱，是因为与南部种群相比，对大型变态体型的选择更强。换句话说，选择北部幼体快速生长和发育的季节性时间限制，也可能限制它们适应性表型可塑性的先天能力。
