Data from: Habitat change and its consequences on reef fish specialization in biogeographic transition zones

Aim Reef fishes are commonly recognized as sentinels of the ongoing tropicalization in biogeographic transition zones between temperate and tropical areas. Despite the reliance of these marine ectotherms on the benthos, the importance of benthic habitat has rarely been considered as a factor constraining fish distribution. Therefore, our study aims at examining the consequences of both temperature and benthic variations on the fish fauna and diagnosing potential sentinels of these environmental changes. Location Taiwan, West Pacific. Taxon Teleostei (184 species). Methods We examined how the partitioning of habitats can influence the specialization of fish fauna along a latitudinal gradient. We diagnosed 'specialist' and 'generalist' fishes in this partitioning. For each specialist, we further evaluated whether its distribution is constrained by temperature, benthic habitat, or both factors combined. The change in sea surface temperature over the last three decades was also monitored. Results Fish fauna showed the highest specialization when tropical and subtropical partitions of habitat were considered. Fifty-one tropical specialists, seven subtropical specialists, and 21 possible generalists were identified. Among specialists, 13 species were associated with temperature, 19 with habitat, and 26 with both factors. Steady warming occurred across latitudes but was accentuated in the winter of subtropical habitat. Main conclusions Our results suggested that the distribution of some specialist fishes was constrained only by temperature while the distribution of some others also depended on the availability of benthic habitats. Consequently, under global warming, the distribution of some specialists might shift in a manner that follows the movement of isotherms, while the distribution of others might also be conditioned by the poleward shifts of benthos. A temporal mismatch between the emergence of suitable thermal environments and the arrival of some specialists may exist. Therefore, the tropicalization of high-latitude areas may be characterized by different waves of colonization.

靶标礁区鱼类（Aim Reef Fishes）通常被认定为温带与热带区域之间生物地理过渡带（biogeographic transition zones）内当前热带化（tropicalization）进程的指示生物（sentinels）。尽管这类海洋变温动物（marine ectotherms）依赖底栖生物，但底栖生境（benthic habitat）的重要性极少被视为限制鱼类分布的因素。因此，本研究旨在探究温度与底栖生境变化对鱼类区系（fish fauna）的影响，并甄别这些环境变化的潜在指示生物。
研究区域：西太平洋中国台湾海域。研究类群：硬骨鱼纲（Teleostei），共计184种。
方法：本研究探究了生境分区如何沿纬度梯度（latitudinal gradient）影响鱼类区系的特化程度，并甄别了该分区下的‘特化种（specialist）’与‘广适种（generalist）’。针对每一种特化种，本研究进一步评估其分布是否受温度、底栖生境，或二者共同限制。此外，本研究还监测了近30年的海表温度（sea surface temperature）变化。
结果：当以热带与亚热带生境分区进行分析时，鱼类区系表现出最高的特化程度。本研究共甄别出51种热带特化种、7种亚热带特化种以及21种潜在广适种。在特化种中，13种的分布仅受温度限制，19种受底栖生境限制，26种受二者共同限制。全纬度带均出现持续变暖现象，而亚热带生境冬季的变暖幅度更为显著。
主要结论：本研究结果表明，部分特化鱼类的分布仅受温度限制，而另一些特化鱼类的分布则还依赖底栖生境的可获得性。因此，在全球变暖背景下，部分特化种的分布可能随等温线（isotherms）迁移而发生位移，而另一些特化种的分布则可能受底栖生物向极迁移（poleward shifts）的制约。适宜热环境出现的时间与部分特化种的抵达时间可能存在时间错配（temporal mismatch）。因此，高纬度区域（high-latitude areas）的热带化可能表现为多波次的物种迁入过程。