GIS and Spatial Ecology Lab, Halmos College of Arts and Sciences, Nova Southeastern University, 8000 North Ocean Drive, Dania Beach, FL, 33004, USA.
School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, UK.
Sci Rep. 2024 Apr 3;14(1):7893. doi: 10.1038/s41598-024-58185-6.
The Anthropocene rise in global temperatures is facilitating the expansion of tropical species into historically non-native subtropical locales, including coral reef fish. This redistribution of species, known as tropicalization, has serious consequences for economic development, livelihoods, food security, human health, and culture. Measuring the tropicalization of subtropical reef fish assemblages is difficult due to expansive species ranges, temporal distribution shifts with the movement of isotherms, and many dynamic density-dependent factors affecting occurrence and density. Therefore, in locales where tropical and subtropical species co-occur, detecting tropicalization changes relies on regional analyses of the relative densities and occurrence of species. This study provides a baseline for monitoring reef fish tropicalization by utilizing extensive monitoring data from a pivotal location in southeast Florida along a known transition between tropical and subtropical ecotones to define regional reef fish assemblages and use benthic habitat maps to spatially represent their zoogeography. Assemblages varied significantly by ecoregion, habitat depth, habitat type, and topographic relief. Generally, the southern assemblages had higher occurrences and densities of tropical species, whereas the northern assemblages had a higher occurrence and density of subtropical species. A total of 108 species were exclusive to regions south of the Bahamas Fracture Zone (BFZ) (South Palm Beach, Deerfield, Broward-Miami) and 35 were exclusive to the north (North Palm Beach, Martin), supporting the BFZ as a pivotal location that affects the coastal biogeographic extent of tropical marine species in eastern North America. Future tropicalization of reef fish assemblages are expected to be evident in temporal deviance of percent occurrence and/or relative species densities between baseline assemblages, where the poleward expansion of tropical species is expected to show the homogenization of assemblage regions as adjacent regions become more similar or the regional boundaries expand poleward. Ecoregions, habitat depth, habitat type, and relief should be incorporated into the stratification and analyses of reef fish surveys to statistically determine assemblage differences across the seascape, including those from tropicalization.
全球气温在人类世的上升正促进热带物种向历史上非本地的亚热带地区扩张，包括珊瑚礁鱼类。这种被称为热带化的物种再分布对经济发展、生计、粮食安全、人类健康和文化都有严重的影响。由于物种分布范围广泛、与等温线移动相关的时间分布变化以及许多影响出现和密度的动态密度依赖性因素，因此，在热带和亚热带物种共存的地方，测量亚热带珊瑚礁鱼类组合的热带化程度具有挑战性。因此，在热带和亚热带物种共存的地方，检测热带化变化依赖于对物种相对密度和出现的区域分析。本研究利用佛罗里达州东南部关键地点的广泛监测数据，为监测珊瑚礁鱼类热带化提供了基线，该地点位于热带和亚热带生态交错带之间的已知过渡带，用于定义区域珊瑚礁鱼类组合，并使用底栖生境图在空间上表示它们的动物地理学。组合在生态区、生境深度、生境类型和地形起伏方面差异显著。一般来说，南部组合热带物种的出现率和密度较高，而北部组合亚热带物种的出现率和密度较高。共有 108 种鱼类仅存在于巴哈马断裂带（BFZ）以南地区（南棕榈滩、迪尔菲尔德、布劳沃德-迈阿密），35 种鱼类仅存在于北部（北棕榈滩、马丁），这支持 BFZ 作为一个关键位置，影响东大西洋热带海洋物种的沿海生物地理范围。预计未来珊瑚礁鱼类组合的热带化将在基线上出现百分比出现率和/或相对物种密度的时间偏差中显现，热带物种的极向扩张预计将使组合区域的同质化，因为相邻区域变得更加相似或区域边界极向扩展。生态区、生境深度、生境类型和地形起伏应纳入珊瑚礁鱼类调查的分层和分析中，以从统计学上确定整个海域的组合差异，包括热带化的影响。
