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：其一为扩散能力，涵盖物种固有移动性、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。本研究以“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”为核心假说，评估上述两大因素对喜马拉雅山脉鸟类物种分布的影响。本研究分别以翼形作为扩散能力的替代指标、喜马拉雅山脉地形复杂度作为扩散屏障的替代指标。针对影响物种在新生境中存续潜力的因素，本研究比较了物种气候生态位（climatic envelope）在作为假说中历史避难所的东部区域，与近期发生殖民扩张的西部区域之间的相似性。研究发现，气候相似性、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扩张程度具有显著影响。本结果揭示了形态学因子与景观因子之间的关键交互作用，其对物种成功实现分布范围扩张具有重要意义。两大与扩散相关的参数共同解释的变异量是气候因子的两倍，但本研究同时提供了额外证据：除气候因子外，其他因素——尤其是生物交互作用——同样会影响物种在分布范围以外区域的存续能力。