Metabolic plasticity in response to different environmental conditions is widespread across taxa. It is reasonable to expect that such plasticity should be adaptive, but only few studies have determined the adaptive significance of metabolic plasticity by formally estimating selection on metabolic rate under different environmental conditions. We used a model marine colonial invertebrate, Bugula neritina to examine selection on metabolic rate in a harsh and a benign environment in the field, then tested whether these environments induced the expression of different metabolic phenotypes. We conducted two experimental runs and found evidence for positive correlational selection on the combination of metabolic rate and colony size in both environments in one run, whereas we could not detect any selection on metabolic rate in the second run. Even though there was no evidence for different selection regimes in the different environments, colonies expressed different metabolic phenotypes depending on the environment they experienced. Furthermore, there was no relationship between the degree of plasticity expressed by an individual and their subsequent fitness. In other words, we found evidence for phenotypic plasticity in metabolic rate, but there was no evidence that this plasticity was adaptive. In the absence of estimates of performance, changes in metabolic rate should not be assumed to be adaptive.

中文翻译：

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可塑性但不适应性：尽管栖息地之间的选择没有差异，但栖息地驱动的代谢率差异

响应不同环境条件的代谢可塑性在整个分类群中广泛存在。预期这种可塑性应该具有适应性是合理的，但只有少数研究通过正式估计不同环境条件下代谢率的选择来确定代谢可塑性的适应性意义。我们使用了一个模型海洋殖民地无脊椎动物，Bugula neritina检查在野外恶劣和良性环境中对代谢率的选择，然后测试这些环境是否诱导了不同代谢表型的表达。我们进行了两次实验运行，并在一次运行中发现了两种环境中代谢率和菌落大小组合正相关选择的证据，而在第二次运行中我们无法检测到代谢率的任何选择。尽管没有证据表明在不同环境中存在不同的选择机制，但菌落会根据它们所经历的环境表达不同的代谢表型。此外，个体表达的可塑性程度与其随后的适应度之间没有关系。换句话说，我们发现了代谢率表型可塑性的证据，但没有证据表明这种可塑性是适应性的。在缺乏表现估计的情况下，不应假设代谢率的变化是适应性的。