Tropicalization of temperate reef fish communities facilitated by urchin grazing and diversity of thermal affinities

Aim: Global declines in structurally complex habitats are reshaping both land and seascapes in directions that affect biological communities’ responses to warming. Here, we test whether widespread loss of kelp habitats through sea urchin overgrazing systematically changes sensitivity of fish communities to warming. Location: Global temperate latitudes Time period: Modern Major taxa studied: Fishes Methods: Community thermal affinity shifts related to habitat were assessed by simulating and comparing fish communities from 2,271 surveys across 15 ecoregions. Results: We find that fishes in kelp and urchin barrens differ in realized thermal affinities and range sizes, but only in regions where species pools have high variability in species’ thermal affinities. Barrens on warm-temperate reefs host relatively more warm-affinity fish species than neighbouring kelp beds, highlighting acceleration of tropicalization processes facilitated by urchin herbivory. By contrast, proporti...研究目的：全球结构性复杂栖息地的衰退正重塑陆海景观格局，进而改变生物群落对气候变暖的响应。本研究旨在检验：由海胆过度啃食引发的大范围海藻床（kelp）栖息地丧失，是否会系统性改变鱼类群落对气候变暖的敏感性。 研究区域：全球温带纬度带 研究时段：现代 研究类群：鱼类 研究方法：通过模拟并对比15个生态区2271次调查获取的鱼类群落数据，评估与栖息地类型相关的群落热亲和性（thermal affinity）变化。 研究结果：本研究发现，海藻床与海胆荒滩（urchin barrens）中的鱼类在实际热亲和性及分布范围规模上存在差异，但该差异仅出现在物种库内物种热亲和性变异程度较高的区域。相较于相邻的海藻床，暖温带礁体上的海胆荒滩所栖息的暖亲和性鱼类物种比例更高，凸显出海胆植食作用可加速热带化进程。相较而言，proporti...