The Elevational Distribution Patterns of Plant Diversity and Phylogenetic Structure Vary Geographically Across Eight Subtropical Mountains

Mountains have been recognized as biodiversity hotspots and possess strong elevational gradients. Whether these gradients exhibit similar characteristics in the multidimensional diversity patterns across different mountain ranges is a subject of inquiry. Exploring the elevational patterns of the diversity and phylogenetic information of plant species in the different subtropical mountains is necessary. Here, we compiled the elevational patterns of plant diversity occurring in the eight subtropical mountains of China and focused on the assessment of the patterns and determinants of the multi-dimensional diversity and phylogenetic structure in different mountains. We also detected the elevational patterns and their relationship between different groups. The results indicate two main patterns of multi-dimensional diversity: monotonic decrease and hump-shaped, along with the area effect on the species diversity. There is a strong positive link between the non-native and native species of species richness, and significant differences in phylogenetic structure's elevational distribution. We did not find the same rule in the mountains that the plant species in the lowlands indicate phylogenetic overdispersion, and the species in the higher elevation regions indicate phylogenetic clustering. We found that the plants' diversity peak is related to the mountains size, and this result showed that we should pay more attention to the conservation of plant communities in the higher elevation regions for the higher mountains. This study suggested that we should take different protective measures for the subtropical mountains: the lowland regions should be paid more attention in Mt. Lushan (LS), Mt. Guanshan (GS), Mt. Huanggang (HG), and Mt. Fanjing (FJ), and the middle-altitude regions should be of concern for other mountains. This study helps to better understand the elevational gradients of species diversity on different scales and provides supporting scientific basis for biodiversity conservation in the subtropical mountain regions.