Data from: Geographical barriers and dispersal propensity interact to limit range expansions of Himalayan birds

Range expansions are limited by two key factors. These are (1) dispersal, which includes a species’ intrinsic mobility, geographical barriers, and their interaction; and (2) the ability of a species to persist beyond its current range. I evaluate the role of these in affecting bird species distributions across the Himalayas, under a hypothesis that many species have recently expanded their range out of an eastern Pleistocene refuge. I measured wing shape as a proxy for dispersal ability and topographic complexity across the Himalayas as a proxy for dispersal barriers. As a factor affecting the potential for persistence in novel locations, I compared similarity of a species’ climatic envelope in the east, the hypothesized historical refuge, and the west, the location of recent colonization. Climatic similarity, wing shape, and the interaction of topographic complexity with wing shape all contribute significantly to the range extent of a given species. The result highlights the important interaction between morphological and landscape factors in affecting successful range expansions. The two dispersal-related parameters together explain two times the variance explained by climate, but I present additional evidence that other factors besides climate—notably biotic interactions—affect the ability of a species to persist beyond its range.

物种分布范围扩张受两大关键因素制约。其一为扩散（dispersal），涵盖物种固有移动能力、地理屏障及其交互作用；其二为物种在当前分布范围以外区域存续的能力。本研究基于“多数鸟类近期已从更新世（Pleistocene）东部避难所向外扩张分布范围”的假说，评估上述两大因素对喜马拉雅山脉区域鸟类物种分布的影响。本研究以翼形作为扩散能力的替代指标（proxy），以喜马拉雅山脉的地形复杂度作为扩散屏障的替代指标。作为影响物种在新区域存续潜力的因素，本研究对比了物种在东部（即假说中的历史避难所）与西部（近期殖民区域）的气候包络（climatic envelope）相似性。气候包络相似性、翼形以及地形复杂度与翼形的交互作用，均对特定物种的分布范围规模具有显著影响。本研究结果揭示了形态学与景观因子在推动物种成功实现分布范围扩张过程中的重要交互作用。与仅考虑气候因子的模型相比，这两个与扩散相关的参数共同解释的变异量是其两倍；此外本研究还提供了额外证据，表明除气候因子外，其他因素——尤其是生物交互作用——会影响物种在分布范围以外区域的存续能力。