Rapoport’s rule explains the range size distribution of butterflies along the Eastern Himalayan elevation gradient

Understanding elevational range size distribution of organisms can provide valuable insights on biogeographic pattern of species and their conservation. Rapoport’s rule posits that the elevational range size of species increases with increasing elevation. However, the validity of this rule is often questioned due to variations in methodologies across studies and inconsistencies among different groups of organisms. In this study we examined the elevational range size distribution of butterflies in the Eastern Himalaya, and assessed the applicability of Rapoport’s rule using different approaches, which perhaps is the first of its kind in the Himalaya. We sampled butterflies along the elevational gradient of 16 elevational bands (300 – 3,300 m) using point count method along the transect. The sampled butterflies were grouped into various sub-groups based on family, biogeographic affinity, and larval feeding pattern. We found that the majority of the butterfly species (total as well as sub-groups) had small range sizes, and their elevational range distribution showed support for the Rapoport’s rule. Increase in variation in temperature as measured by temperature seasonality and mean annual temperature range were the most important predictors of range size distribution pattern of the overall butterfly community. However, the relationship between range size and climatic variability differed among various sub-groups implying that the perceived pattern may vary even within the species of the same taxon.

Methods
All details have been provided in the Manuscript published in Biotropica.

探明生物的海拔分布幅大小分布特征，可为物种生物地理格局及其保护工作提供重要参考依据。拉波波特法则（Rapoport’s rule）认为，物种的海拔分布幅随海拔升高而增大。然而，由于不同研究采用的方法存在差异，且不同生物类群间的结果并不一致，该法则的有效性常受到质疑。本研究以东喜马拉雅地区的蝴蝶为研究对象，分析其海拔分布幅大小分布特征，并采用多种方法评估拉波波特法则的适用性——这或许是喜马拉雅地区同类研究中的首次尝试。研究人员沿样带采用点计数法，在16个海拔梯度带（300~3300米）内开展蝴蝶采样。依据类群科、生物地理亲缘关系以及幼虫取食习性，将采样得到的蝴蝶划分为多个亚组。研究结果显示，多数蝴蝶物种（包括整体类群及各亚组）的分布幅较小，其海拔分布格局支持拉波波特法则。以温度季节性和年平均温度变幅衡量的温度变异程度升高，是影响整个蝴蝶群落分布幅大小分布格局的最关键预测因子。不过，分布幅与气候变异性之间的关联在不同亚组间存在差异，这表明即便同一分类单元内的物种，其观测到的分布格局也可能有所不同。
方法
所有详细信息已发表于《Biotropica》期刊的论文中。