Drivers of phytoplankton diversity in tropical artificial ponds

Understanding the origin and maintenance of microbial diversity patterns, and the relative importance of local and landscape processes for determining biodiversity is still challenging. We investigated the influence of environmental factors acting at local and landscape scales on several facets of phytoplankton diversity. We conducted standardized surveys in 45 artificial ponds in an agricultural landscape of the Brazilian Cerrado, measuring several local (i.e. limnological variables) and landscape characteristics, and phytoplankton abundance, species richness and functional diversity. Structural Equation Models were used to decompose the multiple relationships that local and landscape factors can have between each other and with phytoplankton diversity. Abundance was determined by pond connectivity and limnological variables (water conductivity, transparency, and ammonia), while species richness was positively related to abundance, but negatively affected by pond age. Further, species richness shows a direct negative relationship with functional evenness, so species-poor communities tended to be overdispersed in the functional space. This complex set of relationships highlights the importance of decomposing environmental, morphometric and spatial factors and considering multiple facets of biodiversity to understand community dynamics. These results provide valuable insights on how artificial pond configuration and management in farmstead strategies can allow maintaining high levels of phytoplankton diversity and other aquatic communities in tropical regions.