Ecological generalism and physiology mediate species biogeographic ranges under ocean warming

Climate-driven species redistributions are often facilitated by niche modifications that increase a species’ chances of establishment in novel ecological communities. It is relatively well-understood how range-extending species adjust individual niche traits when entering novel environments, yet it remains unclear how modification of ecological niche traits collectively may alter the pace of species range-extensions or contractions. Here, we quantified habitat niche width, species abundance, and physiological performance of range-extending coral reef fishes and co-existing local temperate coastal fishes along a 2,000-km latitudinal gradient from tropical to temperate reefs in a global warming hotspot. We then assessed the dietary and behavioural niches and establishment potential of the same species to understand whether ecological generalism facilitates successful range-extension of coral reef fishes. At its temperate cold-range edge, one coral reef species (Abudefduf vaigiensis) that increased their habitat, dietary and behavioural niches collectively showed stronger establishment, but experienced decreased physiological performance (increased oxidative stress) compared to its core tropical range. Contrastingly, the three other coral reef species that showed unmodified habitat, dietary or behavioural niches showed lower establishment potential in their novel ranges. One temperate species showed decreased abundance, habitat niche width, and physiological performance at their warm-trailing edge compared to their core temperate range, while the other two temperate species showed contrasting responses. We conclude that ecological generalists might be more successful than ecological specialists during the initial stages of climate change, with increasing future warming further strengthening this pattern by physiologically benefitting tropical generalists but disadvantaging temperate specialists.

气候驱动的物种重新分布往往得益于生态位调整，从而提升物种在新型生态社区中定居的可能性。关于范围扩展物种进入新环境时如何调整个体生态位特征，已有相对充分的认识，然而生态位特征集体调整如何影响物种范围的扩展或收缩速度，尚存疑虑。本研究中，我们量化了从热带到温带珊瑚礁的全球变暖热点地区，沿2000公里纬度梯度上，范围扩展的珊瑚礁鱼类和共存的本地温带沿海鱼类的栖息地生态位宽度、物种丰度和生理性能。随后，我们评估了同一物种的饮食和行为的生态位以及其定居潜力，以探究生态泛化是否促进了珊瑚礁鱼类的成功范围扩展。在温带冷范围边缘，一种珊瑚礁物种（Abudefduf vaigiensis）通过共同扩大其栖息地、饮食和行为生态位，表现出更强的定居能力，但与其核心热带分布区相比，生理性能（氧化应激增加）有所下降。相反，表现出未改变的栖息地、饮食或行为生态位的另外三种珊瑚礁物种，在其新分布区中显示出较低的定居潜力。一种温带物种在其核心温带分布区的暖尾端，丰度、栖息地生态位宽度和生理性能均有所下降，而另外两种温带物种则表现出相反的反应。我们得出结论，生态泛化者在气候变化初期可能比生态专业化者更成功，随着未来变暖的加剧，这一模式将进一步通过生理上对热带泛化者的益处和对温带专业化者的不利影响而得到强化。