Urban Environmental Filtering Explains Variation in Plant Phylogenetic Diversity in Shanghai, China (Completed and under modifying)

Abstract Urbanization has profoundly altered the distribution patterns and community composition of plant diversity. Phylogenetic diversity is a crucial aspect of plant diversity, contributing to a comprehensive understanding of the effects of urban environment and land use changes on urban plant community structure. However, the current understanding of the impact of urbanization on the plant phylogenetic diversity and its distribution patterns remain unclear. Shanghai was selected as the research area and surveyed 134 sample points along urban-rural gradients. Five phylogenetic diversity indices were calculated at each sample point, namely: Faith’s PD (PD), Mean pairwise distance (MPD), Mean nearest taxon distance (MNTD), Net relatedness index (NRI), and Net nearest taxon index (NTI). 17 indicators in four categories, including habitat transformation, habitat fragmentation, urban environment, and human preferences, obtained from field measurements and remote sensing data, were considered as influencing factors. Redundancy analysis and structural equation modeling were used to analyze the relative importance and pathways of each influencing factor on plant phylogenetic diversity. Four categories of influencing factors affect the richness of phylogenetic diversity of plant assemblages. They could explain the variation of plant phylogenetic richness, dispersion, and structure changes in 39.8%, 21.8%, and 10.0%, respectively, among the human preferences are the most significant factor. Habitat transformation and habitat fragmentation have the greatest impact on the structure of plant phylogenetic diversity, leading to a more clustered phylogenetic structure of plant communities in transformed and fragmented urban habitats, indicating closer phylogenetic relationships among species in these habitats, which may result in unstable community structures. Temperature, precipitation, and soil pH in urban environmental factors significantly affect plant phylogenetic diversity. The findings of the research can provide insights into the understanding of mechanisms of urbanization impacts on plant diversity and the ecosystem stability of plant assemblage in urban green spaces, and provide guidelines for improving and optimizing urban plant diversity, urban greening, ecological restoration, and urban ecosystem management.

Keyword：Environmental filtering, Phylogenetic diversity, Urban vegetation, Urbanization index, Plant diversity, Structural equation modeling