Rao Mide, Steinbauer Manuel J, Xiang Xiaoguo, Zhang Minggang, Mi Xiangcheng, Zhang Jintun, Ma Keping, Svenning Jens-Christian
Key Laboratory of Biodiversity Sciences and Ecological Engineering, Ministry of Education, College of Life Sciences Beijing Normal University Beijing China.
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany Chinese Academy of Sciences Beijing China.
Ecol Evol. 2018 Nov 8;8(23):11663-11676. doi: 10.1002/ece3.4619. eCollection 2018 Dec.
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.
亚热带森林被认为是一种重要的全球植被类型，拥有高度丰富的植物物种。然而，其多样性背后的机制仍知之甚少。在这里，我们在几个分类学尺度上评估了环境驱动因素和进化动态（物种形成时间和多样化速率）在中国主要亚热带植物类群——茶科（狭义茶科，145种）物种丰富度模式形成中的作用。为此，我们使用非空间和空间线性模型评估了物种丰富度、关键环境变量（最冷月最低温度、年平均降水量、土壤pH值）和系统发育组合结构（净亲缘指数）之间的关系。我们发现，物种丰富度与环境变量显著相关，尤其是土壤pH值，它在整个科以及主要的山茶族（116种）内均与物种丰富度呈负相关。科级水平的物种丰富度与系统发育结构无关，而山茶族的物种丰富度与系统发育结构呈U形关系，这种关系比物种形成时间或多样化速率假说所预测的更为复杂。总体而言，这些结果表明，环境和进化因素在中国这个亚热带植物科内物种丰富度模式的形成中都起着重要作用，其中进化因素主要在精细的分类学尺度上起重要作用。最令人惊讶的是，我们的研究结果表明，与通常的假设相反，土壤在塑造宏观尺度的多样性模式中可以发挥关键作用。
