ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld, Australia.
Lancaster Environment Centre, Lancaster University, Lancaster, UK.
Glob Chang Biol. 2018 Jul;24(7):3117-3129. doi: 10.1111/gcb.14119. Epub 2018 Apr 6.
Global climate change is altering community composition across many ecosystems due to nonrandom species turnover, typically characterized by the loss of specialist species and increasing similarity of biological communities across spatial scales. As anthropogenic disturbances continue to alter species composition globally, there is a growing need to identify how species responses influence the establishment of distinct assemblages, such that management actions may be appropriately assigned. Here, we use trait-based analyses to compare temporal changes in five complementary indices of reef fish assemblage structure among six taxonomically distinct coral reef habitats exposed to a system-wide thermal stress event. Our results revealed increased taxonomic and functional similarity of previously distinct reef fish assemblages following mass coral bleaching, with changes characterized by subtle, but significant, shifts toward predominance of small-bodied, algal-farming habitat generalists. Furthermore, while the taxonomic or functional richness of fish assemblages did not change across all habitats, an increase in functional originality indicated an overall loss of functional redundancy. We also found that prebleaching coral composition better predicted changes in fish assemblage structure than the magnitude of coral loss. These results emphasize how measures of alpha diversity can mask important changes in the structure and functioning of ecosystems as assemblages reorganize. Our findings also highlight the role of coral species composition in structuring communities and influencing the diversity of responses of reef fishes to disturbance. As new coral species configurations emerge, their desirability will hinge upon the composition of associated species and their capacity to maintain key ecological processes in spite of ongoing disturbances.
全球气候变化正在通过非随机物种更替改变许多生态系统的群落组成，这种更替通常表现为特化物种的丧失和生物群落在空间尺度上的相似性增加。由于人为干扰继续在全球范围内改变物种组成，因此越来越需要确定物种响应如何影响独特组合的建立，以便能够适当分配管理措施。在这里，我们使用基于特征的分析方法，比较了在经历了全系统热应激事件后，六个分类学上不同的珊瑚礁生境中五种补充的珊瑚鱼群落结构指数的时间变化。我们的研究结果表明，在大规模珊瑚白化之后，先前截然不同的珊瑚鱼群落的分类学和功能相似性增加，变化的特点是朝着小体型、藻类养殖生境的一般性专家的优势方向发生了微妙但显著的转变。此外，虽然所有生境的鱼类群落的分类学或功能丰富度都没有变化，但功能新颖性的增加表明功能冗余的整体丧失。我们还发现，在白化前的珊瑚组成可以更好地预测鱼类群落结构的变化，而不是珊瑚损失的程度。这些结果强调了衡量 alpha 多样性如何掩盖了生态系统结构和功能的重要变化，因为组合在重新组合。我们的研究结果还突出了珊瑚物种组成在构建群落和影响珊瑚鱼对干扰的响应多样性方面的作用。随着新的珊瑚物种结构的出现，它们的可取性将取决于相关物种的组成及其在持续干扰下维持关键生态过程的能力。
