Geographical background and dispersal ability may strongly influence assemblage dissimilarity; however, these aspects have generally been overlooked in previous large-scale beta diversity studies. Here, we examined whether the patterns and drivers of taxonomic beta diversity (TBD) and phylogenetic beta diversity (PBD) of breeding birds in China vary across (1) regions on both sides of the Hu Line, which demarcates China's topographical, climatic, economic, and social patterns, and (2) species with different dispersal ability. TBD and PBD were calculated and partitioned into turnover and nestedness components using a moving window approach. Variables representing climate, habitat heterogeneity, and habitat quality were employed to evaluate the effects of environmental filtering. Spatial distance was considered to assess the impact of dispersal limitation. Variance partitioning analysis was applied to assess the relative roles of these variables. In general, the values of TBD and PBD were high in mountainous areas and were largely determined by environmental filtering. However, different dominant environmental filters on either side of the Hu Line led to divergent beta diversity patterns. Specifically, climate-driven species turnover and habitat heterogeneity-related species nestedness dominated the regions east and west of the line, respectively. Additionally, bird species with stronger dispersal ability were more susceptible to environmental filtering, resulting in more homogeneous assemblages. Our results indicated that regions with distinctive geographical backgrounds may present different ecological factors that lead to divergent assemblage dissimilarity patterns, and dispersal ability determines the response of assemblages to these ecological factors. Identifying a single universal explanation for the observed pattern without considering these aspects may lead to simplistic or incomplete conclusions. Consequently, a comprehensive understanding of large-scale beta diversity patterns and effective planning of conservation strategies necessitate the consideration of both geographical background and species dispersal ability.
物种组成如何以及为何在空间上变化是生物地理学研究的核心问题之一，对生物多样性保护意义重大。物种分布与地理环境背景及其迁徙扩散能力密切相关。一方面不同地理环境背景下的物种分布可能受制于不同的生态过程（环境过滤或扩散限制），另一方面，不同扩散能力物种对这些生态过程的反应亦具差异。因此，对物种组成差异机制的深入理解需要我们同时考虑地理环境背景与迁徙扩散能力差异所带来的影响。胡焕庸线（又称黑河（爱辉）-腾冲线）是我国最为重要的地理分界线。胡焕庸线东侧以温暖、湿润的平原为特征，容纳了全国90%以上的人口。相比之下，西侧则以寒冷、干旱的高原为主，人口不足10%。已有研究显示，胡焕庸线两侧环境差异对中国社会、经济与生态格局影响深刻。然而，胡焕庸线两侧在生物多样性格局与机制上是否存在同样显著的差异，我们仍然知之甚少。该研究收集整理了1146种中国繁殖鸟类的地理分布数据与谱系发育信息，通过移动窗口法（moving window approach）计算了中国繁殖鸟类物种与谱系beta多样性及其周转与嵌套组分的地理格局，并利用气候、生境质量、生境异质性等因子以及空间距离评估环境过滤与扩散限制对beta多样性格局相对贡献。在此基础上，分析了繁殖鸟类群落的物种与谱系组成差异及其驱动因素在胡焕庸线东西两侧和不同扩散能力物种分组间的差异。研究发现，山地是中国繁殖鸟类群落的物种与谱系beta多样性主要热点区域，环境过滤是beta多样性格局形成的主要决定过程。胡焕庸线两侧的繁殖鸟类群落beta多样性有着截然不同的主导组分与环境驱动因子。在胡焕庸线以东，繁殖鸟类群落物种与谱系组成差异由气候驱动的物种周转所主导，在胡焕庸线以西，繁殖鸟类群落物种与谱系组成差异由生境异质性驱动的物种嵌套所主导。另一方面，扩散能力越强的鸟类受气候、生境异质性等环境过虑作用的影响越大，形成更匀质化的群落。研究结果不仅揭示了地理环境和扩散能力差异对中国繁殖鸟类组成差异地理格局与形成机制的重要影响，同时也为制定因种施策、因地制宜的生物多样性保护规划提供了非常有价值的参考。.
Keywords: Beta diversity; Breeding birds; Dispersal limitation; Environmental filtering; Hu Line; Species dispersal ability.