The midpoint attractor (MPA) models of species richness integrate a unimodal environmental favourability gradient and neutral effects forced by geometric constraints and thus extend the ecologically neutral mid-domain model. However, both alternative MPA algorithms assume that underlying environmental favourability peaks within the modelling domain. Here, we used elevational distribution data for 1054 plant species occurring in northwest Himalaya to explore species richness gradients and MPA performance in species groups defined by biogeography, taxonomy and life-form. MPA models achieved an excellent fit, but the two MPA algorithms produced contrasting estimates of MPA location, especially for species groups with richness originating in lowlands. Therefore, we propose a modification of the MPA model accounting for the environmental favourability peak outside the study domain to reflect these situations. Biogeographic origin was more decisive for MPA location than taxonomic or life-form classification, indicating relatively low climatic niche conservatism in plants.

中文翻译：

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中点吸引子模型解决了喜马拉雅植物物种丰富度的中海拔峰值

物种丰富度的中点吸引子 (MPA) 模型整合了单峰环境有利梯度和几何约束强制的中性效应，从而扩展了生态中性中域模型。然而，这两种替代 MPA 算法都假设潜在的环境有利性在建模域内达到峰值。在这里，我们使用喜马拉雅西北部发生的 1054 种植物物种的海拔分布数据来探索由生物地理学、分类学和生命形式定义的物种群的物种丰富度梯度和 MPA 性能。MPA 模型实现了极好的拟合，但两种 MPA 算法产生了对 MPA 位置的对比估计，特别是对于起源于低地的丰富物种群。所以，我们建议对 MPA 模型进行修改，以反映研究领域外的环境有利性峰值，以反映这些情况。与分类学或生命形式分类相比，生物地理起源对 MPA 的位置更具决定性，表明植物的气候生态位保守性相对较低。