Assembly processes of waterbird communities across subsidence wetlands in China: A functional and phylogenetic approach

Aim: Although assembly processes have been studied in a wide range of taxa, determining assembly rules remains controversial, particularly in assemblages consisted of species with strong dispersal capacities. Moreover, few studies focused on communities in recently human-created habitats. We tested two prevailing but opposing hypotheses, environmental filtering and limiting similarity, in waterbird communities across subsidence wetlands created by underground coal mining in China, with an aim to better understand assembly processes in communities composed of highly mobile species in human-dominated landscape. Location: The North China Plain. Methods: We quantified taxonomic, functional and phylogenetic diversity of the waterbird assemblages in different seasons and compared the mean pairwise distances (MPD) and the mean nearest taxon distances (MNTD) with null models to examine whether co-occurring species were clustered or overdispersed on the functional dendrogram or phylogenetic tree. Independent contributions of multi-scale habitat variables therein were determined using a hierarchical partitioning method. Results: We showed asynchronous patterns of seasonal dynamics among the multiple diversity metrics, with highest species diversity during autumn migration. Generally, the co-occurring species were functionally and phylogenetically clustered. Habitat variables had stronger effects on the functional structure than on the phylogenetic structure of the communities. The degree of functional clustering increased in older and larger wetlands, while the assemblages shifted from functional clustering to overdispersion with increasing habitat diversity, landscape connectivity and human disturbance. Main conclusions: The waterbird assemblages were mainly structured by environmental filtering, and the assembly processes were significantly affected by habitat variables, with stronger effects on functional diversity. Our study highlights the importance of environmental filtering and habitat variables in structuring assemblages dominated by species with high dispersal capacities and suggests that increasing habitat diversity and reducing disturbances will contribute to waterbird conservation in this human-dominated landscape.