Simpson Kyle M, Spalink Daniel
Ecology and Evolutionary Biology Interdisciplinary Degree Program, Texas A&M University 2258, College Station, TX 77843-2258, USA.
Department of Ecology and Conservation Biology, Texas A&M University 2258, College Station, TX 77843-2258, USA.
Ann Bot. 2025 May 9;135(5):935-948. doi: 10.1093/aob/mcae226.
Quantifying niche similarity among closely related species offers myriad insights into evolutionary history and ecology. In this study, our aim was to explore the interplay of geographical and niche space for rare, endemic plant species and to determine whether endemic habitats were environmentally similar or unique.
We characterized the niche of all Leavenworthia species, a genus of rare plants endemic to rocky glades in the eastern USA, using WorldClim data, surface geology, elevation and slope. We calculated the area of range overlap and estimated niche similarity between pairs of species in their total occupied niche space and the subset of niche space shared by both species. We used linear discriminant analyses to determine which niche dimensions differed the most between species. We used niche dimensions with consistently high discriminatory power to perform a random forest classification analysis and principal component analysis. Using a linear model, we related geographical distance to distance in niche space.
Most species comparisons concluded that species niches had diverged, with niche similarity increasing linearly with range overlap. Temperature variation, precipitation amount and seasonality, and surface geology were the most divergent niche dimensions among all species comparisons. Geographical distance explained 42 % of the variation in niche space distance. Sites that were closer in niche space than expected were oriented east-west owing to the strong correlation between latitude and scores on the first principal component.
Despite being endemic seemingly to very similar habitat, niche similarity is low among Leavenworthia species. Low niche similarity, combined with low geographical overlap, suggests that this lineage of rare plants potentially diversified in isolation but across a very small geographical area. The correlation between geographical space and niche space has received considerable attention, but our results suggest that geographical distance is a weak predictor of distance in niche space.
量化近缘物种间的生态位相似性有助于深入了解进化历史和生态学。在本研究中，我们旨在探究珍稀特有植物物种的地理空间与生态位空间之间的相互作用，并确定特有栖息地在环境上是相似还是独特。
我们利用世界气候数据、地表地质、海拔和坡度，对美国东部岩石裸露地特有的珍稀植物属——莱文沃思草属所有物种的生态位进行了特征描述。我们计算了分布范围重叠的面积，并估计了成对物种在其总占据生态位空间以及两个物种共有的生态位空间子集中的生态位相似性。我们使用线性判别分析来确定哪些生态位维度在物种间差异最大。我们使用具有持续高判别力的生态位维度进行随机森林分类分析和主成分分析。利用线性模型，我们将地理距离与生态位空间距离相关联。
大多数物种比较得出结论，物种生态位已经分化，生态位相似性随分布范围重叠呈线性增加。温度变化、降水量和季节性以及地表地质是所有物种比较中差异最大的生态位维度。地理距离解释了生态位空间距离变异的42%。由于纬度与第一主成分得分之间的强相关性，在生态位空间中比预期更接近的地点呈东西向分布。
尽管莱文沃思草属物种似乎特有于非常相似的栖息地，但它们之间的生态位相似性较低。低生态位相似性与低地理重叠相结合，表明这一珍稀植物谱系可能在隔离状态下但在非常小的地理区域内实现了多样化。地理空间与生态位空间之间的相关性已受到相当多的关注，但我们的结果表明，地理距离对生态位空间距离的预测能力较弱。
