Patterns in the spatial distribution of organisms provide important information about mechanisms underlying biodiversity and the complexity of ecosystems. One of the most well-documented spatial patterns is the distance-decay relationship, which is a universal biogeographic pattern observed repeatedly for plant and animal communities, particularly for microorganisms in natural ecosystems such as soil, ocean, and salt marsh sediment. However, it is uncertain whether the microorganisms exhibit a distance-decay pattern in engineered ecosystems. Therefore, we measured the distance-decay relationship across various microbial functional and phylogenetic groups in 26 biological wastewater treatment plants (WWTPs) in China using a functional gene array (GeoChip 4.2). We found that microbial communities of activated sludge in WWTPs exhibited a significant but very weak distance-decay relationship. The taxon-area z values for different functional and phylogenetic groups were <0.0065, which is about 1 to 2 orders of magnitude lower than those observed in microbial communities elsewhere. Variation-partitioning analysis (VPA) showed that the relationships were driven by both environmental heterogeneity and geographic distance. Collectively, these results provided new insights into the spatial scaling of microbial communities in engineering ecosystems and highlighted the importance of environmental heterogeneity and geographic distance in shaping biogeographic patterns.
IMPORTANCEDetermining the distance-decay relationship of microbial biodiversity is important but challenging in microbial ecology. All studies to date are based on natural environments; thus, it remains unclear whether there is such a relationship in an engineered ecosystem. The present study shows that there is a very weak distance-decay relationship in an engineered ecosystem (WWTPs) at the regional-to-continental scale. This study makes fundamental contributions to a mechanistic, predictive understanding of microbial biogeography.A central goal of ecology is to understand how biodiversity is generated and maintained (1). Spatial patterns of species diversity offer insights into the mechanisms shaping biodiversity and are of practical importance for predicting the risk of biodiversity loss by environmental changes and consequently for setting up conservation priorities (2). Therefore, the spatial distribution patterns of species diversity have solicited substantial attention. Traditionally, the field of spatial distribution patterns of biodiversity has focused on plants and animals. For example, it has been well documented for plant and animal communities that community similarity decreased with geographic distance, known as the distance-decay relationship (3, 4). In recent years, a number of studies have been conducted to investigate biogeographic patterns of microorganisms, including bacteria, archaea, fungi, and other microbial eukaryotes (3,(5)(6)(7)(8)(9)(10). A growing body of research has shown that microorganisms, like plants and animals, exh...