Turko Andy J, Rossi Giulia S, Blewett Tamzin A, Currie Suzanne, Taylor D Scott, Wright Patricia A, Standen Emily M
Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G 2W1.
Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2M9.
J Exp Biol. 2022 Apr 15;225(8). doi: 10.1242/jeb.243372. Epub 2022 Apr 22.
Understanding the mechanisms that create phenotypic variation within and among populations is a major goal of physiological ecology. Variation may be a consequence of functional trade-offs (i.e. improvement in one trait comes at the expense of another trait) or alternatively may reflect the intrinsic quality of an organism (i.e. some individuals are simply better overall performers than others). There is evidence for both ideas in the literature, suggesting that environmental context may mediate whether variation results from trade-offs or differences in individual quality. We tested this overarching 'context dependence' hypothesis by comparing the aquatic and terrestrial athletic performance of the amphibious fish Kryptolebias marmoratus captured from two contrasting habitats, a large pond and small burrows. Overall, pond fish were superior terrestrial athletes but burrow fish were better burst swimmers, suggestive of a performance trade-off at the population level. Within each population, however, there was no evidence of a performance trade-off. In burrow fish, athletic performance was positively correlated with muscle content and body condition, consistent with the individual quality hypothesis. In pond fish, there was only a relationship between glycolytic white muscle and aquatic burst performance. Notably, pond fish were in better body condition, which may mask relationships between condition and athletic performance. Overall, our data highlight that population-level trends are insufficient evidence for the existence of phenotypic trade-offs in the absence of similar within-population patterns. Furthermore, we only found evidence for the individual quality hypothesis in one population, suggesting that patterns of phenotypic covariance are context dependent.
理解在种群内部和种群之间产生表型变异的机制是生理生态学的一个主要目标。变异可能是功能权衡的结果（即一个性状的改善是以另一个性状为代价的），或者也可能反映了生物体的内在品质（即一些个体总体表现比其他个体更好）。文献中对这两种观点都有证据支持，这表明环境背景可能会调节变异是由权衡还是个体品质差异导致的。我们通过比较从两个截然不同的栖息地（一个大池塘和小洞穴）捕获的两栖鱼类红树鳉的水生和陆地运动表现，来检验这个总体的“背景依赖性”假设。总体而言，池塘鱼是更优秀的陆地运动员，但洞穴鱼是更好的爆发式游泳者，这表明在种群水平上存在表现权衡。然而，在每个种群内部，没有表现权衡的证据。在洞穴鱼中，运动表现与肌肉含量和身体状况呈正相关，这与个体品质假设一致。在池塘鱼中，只有糖酵解白肌与水生爆发表现之间存在关系。值得注意的是，池塘鱼的身体状况更好，这可能掩盖了身体状况与运动表现之间的关系。总体而言，我们的数据强调，在没有类似的种群内模式的情况下，种群水平的趋势不足以作为存在表型权衡的证据。此外，我们只在一个种群中发现了个体品质假设的证据，这表明表型协方差模式是依赖于背景的。
