1. The invasion of new environments can be a key instigator of adaptive diversification, but the likelihood of such invasions succeeding can depend on the attributes of would‐be invaders. Chief among these seems to be a generalist or ‘jack‐of‐all‐trades’ phenotype.
2. Yet, despite the obvious link between habitat transitions and adaptation, we know surprisingly little about how phenotypes that might initially allow taxa to transition between habitats subsequently evolve or influence post‐invasion differentiation.
3. We tested how a generalist phenotype of a broad diet and behavioural plasticity in marine blenny fish has facilitated the repeated invasion of extreme environments—particularly land—and how the conditions post‐invasion have impacted that generalist phenotype and associated trophic morphology.
4. Our data show that a wide diet and plasticity in being able to shift between environments freely have been instrumental in the progressive invasion of land by amphibious blennies. Once established, however, terrestrial blennies have experienced strong stabilizing selection for a restricted diet, little to no plasticity and a highly specialized morphology. Instead of promoting diversification, the invasion of land appears to offer only a limited niche for survival, constraining descendent blennies to a specific adaptive phenotype.
5. While our study supports the view that generalism facilitates invasion and that habitat transitions instigate adaptation, it also shows a generalist strategy is not optimal for successful establishment and new environments may offer fewer (not more) opportunities for diversification. This has broad implications for how taxa might be expected to respond or adapt to abrupt environmental change more generally.

中文翻译：

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跨越极端栖息地边界：万事通促进入侵，但由于适应万能大师而受到侵蚀

1. 新环境的入侵可能是适应性多样化的关键诱因，但是这种入侵成功的可能性可能取决于潜在入侵者的属性。其中最主要的似乎是通才或“万事通”表型。
2. 然而，尽管栖息地过渡与适应之间有着明显的联系，但我们对最初可能允许分类群在栖息地之间过渡的表型随后如何进化或影响入侵后分化的信息知之甚少。
3. 我们测试了海洋粘鱼中广泛饮食的通配表型和行为可塑性如何促进极端环境（尤其是陆地）的反复入侵，以及入侵后的状况如何影响通配表型和相关的营养形态。
4. 我们的数据表明，能够在环境之间自由转换的广泛饮食和可塑性对两栖性泥炭逐渐侵占土地起了作用。然而，一旦建立起来，陆生薄脆犬就经历了针对稳定饮食的强烈稳定选择，几乎没有甚至没有可塑性和高度专业的形态。入侵土地并没有促进多样化，而只是为生存提供了一个有限的利基市场，将后代脆弱性限制在特定的适应性表型上。
5. 虽然我们的研究支持通才主义促进入侵并且栖息地过渡促进适应的观点，但它也表明通才主义者的策略并非成功建立的最佳选择，而新的环境可能提供更少（而不是更多）的多样化机会。这对于预期如何更广泛地响应分类群或对突然的环境变化做出适应具有广泛的意义。