Data from: Land colonisation by fish is associated with predictable changes in life history

The colonisation of new environments is a central evolutionary process, yet why species make such transitions often remains unknown because of the difficulty in empirically investigating potential mechanisms. The most likely explanation for transitions to new environments is that doing so conveys survival benefits, either in the form of an ecological release or new ecological opportunity. Life history theory makes explicit predictions about how traits linked to survival and reproduction should change with shifts in age-specific mortality. We used these predictions to examine whether a current colonisation of land by fishes might convey survival benefits. We found that blenny species with more terrestrial lifestyles exhibited faster reproductive development and slower growth rates than species with more marine lifestyles; a life history trade off that is consistent with the hypothesis that mortality has become reduced in younger life stages on land. A plausible explanation for such a shift is that an ecological release or opportunity on land has conveyed survival benefits relative to the ancestral marine environment. More generally, our study illustrates how life history theory can be leveraged in novel ways to formulate testable predictions on why organisms might make transitions into novel environments.向新环境的定殖是演化过程中的核心环节，但由于难以通过实证研究探索其潜在机制，物种为何会完成这类环境转变的原因至今仍不明确。对于向新环境转变的最合理解释是，这类转变能带来生存优势，具体表现为生态释放（ecological release）或新生态机会（new ecological opportunity）两种形式。生活史理论（Life history theory）可针对与生存和繁殖相关的性状如何随年龄特异性死亡率（age-specific mortality）的变化而改变作出明确预测。我们依托这些预测，验证当前鱼类向陆地定殖的过程是否能带来生存优势。我们发现，相较于海洋生活型物种，陆生生活特征更显著的鳚鱼（blenny）种群展现出更快的生殖发育速度与更缓慢的生长速率；这类生活史权衡现象与“陆地环境中幼龄阶段的死亡率有所降低”的假说相符。对于这类转变的一个合理解释是，相较于祖先所处的海洋环境，陆地环境带来的生态释放或生态机会为种群带来了生存优势。从更广泛的意义上来说，本研究展示了我们可以如何以新颖的方式运用生活史理论，针对生物体为何会向新环境转变提出可检验的预测。