Data from: Environmental and evolutionary drivers of diversity patterns in the tea family (Theaceae s.s.) across China

Subtropical forest is recognized as an important global vegetation type with high levels of plant species richness. However, the mechanisms underlying its diversity remain poorly understood. Here, we assessed the roles of environmental drivers and evolutionary dynamics (time-for-speciation and diversification rate) in shaping species richness patterns across China for a major subtropical plant group, the tea family (Theaceae s.s.) (145 species), at several taxonomic scales. To this end, we assessed the relationships between species richness, key environmental variables (minimum temperature of the coldest month, mean annual precipitation, soil pH) and phylogenetic assemblage structure (net related index) by using non-spatial and spatial linear models. We found that species richness is significantly related to environmental variables, especially soil pH, which is negatively related to species richness both across the whole family and within the major tribe Theeae (116 species). Family-level species richness is unrelated to phylogenetic structure, whereas species richness in tribe Theeae was related to phylogenetic structure with U-shaped relationship, a more complex relation than predicted by the time-for-speciation or diversification rate hypotheses. Overall, these results suggest that both environmental and evolutionary factors play important roles in shaping species richness patterns within this subtropical plant family across China, with the latter mainly important at fine taxonomic scales. Most surprisingly, our findings show that soils can play a key role in shaping macro-scale diversity patterns, contrary to often-stated assumptions.

亚热带森林作为全球重要的植被类型之一，拥有极高的植物物种丰富度。然而，其物种多样性背后的形成机制仍有待深入阐明。本研究以中国境内一类主要的亚热带植物类群——狭义茶科（Theaceae s.s.，共145个物种）为研究对象，在多个分类学尺度下，探究了环境驱动因子与进化动态（物种形成时间与分化速率）对物种丰富度分布格局的塑造作用。为此，我们通过非空间与空间线性模型，分析了物种丰富度与关键环境变量（最冷月最低温、年平均降水量、土壤pH值）以及系统发育群落结构（净亲缘指数（net related index））之间的关联。研究结果显示，物种丰富度与环境变量存在显著关联，其中尤以土壤pH值最为显著：无论是在整个茶科还是其主要类群茶族（Theeae，共116个物种）中，土壤pH值均与物种丰富度呈负相关关系。科水平的物种丰富度与系统发育群落结构无显著关联，但茶族的物种丰富度则与系统发育群落结构呈U型相关关系，这一关联比物种形成时间或分化速率假说的预测更为复杂。总体而言，本研究结果表明，环境与进化因子共同塑造了中国境内该亚热带植物类群的物种丰富度分布格局，其中进化因子在精细分类学尺度下的作用更为突出。尤为值得注意的是，本研究发现土壤因子对宏观尺度的多样性分布格局具有关键塑造作用，这与学界普遍持有的传统假设相悖。