Stochastic and deterministic processes shaping the testate amoeba communities across different biotopes of urban parks in Moscow and Xiamen cities

Global urbanization has resulted in local habitat fragmentation, influencing ecological processes and biodiversity conservation. However, little is known about the diversity and distribution of microbial communities across urban biotopes. Here, we compared testate amoeba communities in Moscow (63 samples from five urban parks) and Xiamen (69 samples from six urban parks) across four biotopes (tree hole, moss, soil, and sediment) to better understand microbial diversity and ecological processes shaping microbial communities. A total of 116 morphospecies (31 genera), corresponding to 90 in Moscow and 84 in Xiamen, were identified using light microscopy. The species richness per sample (mean ± standard error) was higher in Moscow parks (14 ± 1 species, n = 63) than Xiamen parks. The mean species richness per biotope was highest in the mosses (13 ± 1 species, n = 33). 13–26% of the total species richness was shared by all biotopes, indicating the ubiquitous distribution of testate amoeba morphospecies. The community composition in different biotopes markedly differed in both Moscow and Xiamen regions. Community connectivity varied among biotopes, and community complexity and dynamics were substantially stronger in soil and sediment. The stochastic processes explained a significantly high percentage of community composition in all biotopes (57–81%) in 11 parks. The standardized effect size for C-score in all biotopes changed from 1.48 to 6.92, indicating the enhanced significance of deterministic processes for the testate amoeba communities. The different relative importance of stochastic or deterministic processes in four studied biotopes suggests that factors influencing the testate amoeba communities greatly vary across heterogeneous urban environments.