Distribution and coexistence patterns of phytoplankton in subtropical shallow lakes and the role of niche-based and spatial processes

Phytoplankton is an important microbial component in many ecosystems, and thus, knowing the predictive variables of its distribution is very valuable. In this study, we evaluated the roles of niche-based and spatial processes on phytoplankton communities of nine lakes in southern Brazil (spatial distance covered of 220 km). Variation partitioning analysis was employed to determine the relative contributions of environmental and spatial variables on the distribution of prokaryotic (PRP) and eukaryotic (EUP) components of phytoplankton at multispatial extents. C-score analysis was carried out, at intra- and interlake scales, to examine whether phytoplankton species coexist less or more than expected by chance (taxa segregation and aggregation, respectively). Our results showed that, at broader spatial scales, both PRP and EUP distributions are mainly influenced by pure space, while at finer spatial scales, the two groups are mainly influenced by pure environment. PRP distribution at broader spatial scales was also significantly influenced by spatially structured environment, and was in general more affected by spatial variables than by EUP. Finally, a taxa segregation pattern was observed at the interlake scale. In general, our results suggest that niche-based processes are more important in structuring phytoplankton on the local scale while spatial processes on the regional scale.