Species richness, endemism, and abundance patterns: tests of two fractal models in a serpentine grassland

From Ecology Letters: Although scaling relationships that characterize fractal species distributions offer an exciting potential for unification in biogeography, empirical support for fractal theory remains the subject of debate. We synthesize and test multiple predictions of two interrelated fractal models and a null model of random placement using Californian serpentine grassland data describing the spatial location of over 37 000 individually identified plants. The endemics–area relationship and species‐abundance distribution recently derived from a community‐level fractal property performed poorly because of an inaccurate assumption of homogeneity among species. In contrast, a species‐level fractal model that incorporates species‐level differences predicted abundances well, but systematically overestimated endemism and predicted a species–area relationship that violated the observed power law. These findings indicate that in order to make predictions based on the existence of a p...选自《生态学通讯》（Ecology Letters）：尽管用以表征分形（fractal）物种分布的尺度关系为生物地理学（biogeography）领域的统一化研究带来了令人振奋的潜力，但分形理论的实证支撑至今仍饱受争议。本研究基于描述超37000株经个体识别的植物空间位置的加利福尼亚蛇纹石草原（serpentine grassland）数据集，整合并检验了两个相关分形模型与一个随机放置零模型（null model）的多项预测结果。近期基于群落水平分形特性（community-level fractal property）推导得出的特有种-面积关系（endemics–area relationship）与物种-多度分布（species‐abundance distribution）表现不佳，原因在于其对物种间同质性的假设并不准确。与之相对，纳入了物种间差异的物种水平分形模型（species‐level fractal model）能够较好地预测物种多度，但却系统性高估了特有种比例，且其所预测的物种-面积关系违背了观测到的幂律（power law）。上述研究结果表明，若要基于某一...的存在性做出预测