Data from: Drivers of contemporary lacustrine fish species richness in the glacial Lake Agassiz basin

Aim: Biological communities are the result of a stepwise spatiotemporal filtering process, driven by large-scale historical and local contemporary determinants. The biogeographical pattern and species richness of North American fishes are predominantly determined by historical processes of past glaciations and postglacial dispersal and by contemporary environmental and ecological processes. Here, we evaluate the effects of postglacial dispersal through glacial Lake Agassiz and habitat heterogeneity, as represented by lake surface area, on contemporary freshwater fish species richness patterns of northwestern Ontario lakes. Location: Northwestern Ontario, Canada Taxon: Freshwater fishes Methods: We applied the theory of island biogeography and species-area curves to examine the effects of isolation from the past dispersal corridor of glacial Lake Agassiz and habitat heterogeneity on species richness across 264 contemporary lakes in northwestern Ontario, Canada. While controlling for correlations among the predictor variables, generalized linear models were constructed between species richness, as the response variable and the explanatory variables of lake elevation and surface area and connection to the dispersal corridor of Lake Agassiz. Results: Differential cover by glacial Lake Agassiz led to variation in fish species richness across contemporary lake basins and species richness is higher in lakes that were covered by Lake Agassiz relative to basins remaining outside of the boundaries of the glacial lake. Lake surface area is the strongest predictor of species richness, while lake elevation is the strongest factor predicting isolation as species richness decreases with increasing altitudes. Main Conclusions: Habitat heterogeneity and postglacial colonization have led to differences in fish richness within the same geographical region. Fish species richness increases with lake surface area and decreases with elevation, likely driven by greater niche diversity facilitating the assembly of more diverse communities and isostatic rebound and fluctuating levels of Lake Agassiz isolating lakes at high elevations from the dispersal route earlier during the colonization process, respectively. These patterns underscore the importance of incorporating historical and environmental community determinants in biodiversity studies.

研究目的：生物群落是由大规模历史因子与当代局部驱动因子共同塑造的逐步时空过滤过程的产物。北美淡水鱼类的生物地理格局与物种丰富度，主要受古冰期历史过程、冰消期扩散事件，以及当代环境与生态过程调控。本研究旨在评估通过阿加西斯冰湖（glacial Lake Agassiz）的冰消期扩散，以及以湖泊表面积表征的生境异质性，对加拿大安大略省西北部湖泊当代淡水鱼类物种丰富度格局的影响。
研究区域：加拿大安大略省西北部
研究类群：淡水鱼类
研究方法：本研究基于岛屿生物地理学理论与种-面积曲线，探究与阿加西斯冰湖古扩散廊道的隔离程度，以及生境异质性，对加拿大安大略省西北部264个当代湖泊的物种丰富度的调控作用。在控制预测变量间相关性的前提下，以物种丰富度为响应变量，构建以湖泊海拔、表面积及与阿加西斯冰湖扩散廊道的连通性为解释变量的广义线性模型。
研究结果：阿加西斯冰湖的覆盖差异导致当代湖盆间鱼类物种丰富度存在异质性；相较于位于该冰湖边界之外的湖盆，曾被阿加西斯冰湖覆盖的湖泊物种丰富度更高。湖泊表面积是物种丰富度最强的预测因子，而湖泊海拔则是调控隔离程度的核心因子：物种丰富度随海拔升高而降低。
主要结论：生境异质性与冰消期定植过程共同导致了同一地理区域内鱼类丰富度的差异。鱼类物种丰富度随湖泊表面积增大而升高，随海拔升高而降低——前者可能源于更丰富的生态位多样性促进了更多样的群落组装，后者则可能因冰后均衡回弹与阿加西斯冰湖水位波动，使得高海拔湖泊在定植早期便与扩散廊道产生了隔离。本研究结果凸显了在生物多样性研究中纳入历史与环境群落调控因子的重要性。