Drought drives fish disassembling in a Neotropical coastal plain

With the aim to assess how environmental heterogeneity affect fish assembly patterns, we evaluated species co-occurrence and nestedness in 16 lentic environments in a drying coastal plain of Southeast Brazil. We calculated the frequency of co-occurrence and nestedness for 13 quarterly campaigns exclusively for fish species tolerant to a narrow range of low water salinity (stenohaline) and to wider range of water salinity (euryhaline) and for all species together, and assessed its significance with null models. We employed a Principal Component Analysis (PCA) to explore temporal trends in physical and chemical parameters of water and to detect those that most influenced environmental heterogeneity. Linear regressions assessed the potential effect of each parameter that most influenced the PCA on co-occurrence. Few campaigns presented nonrandom patterns of community composition, and only for euryhaline or for all species considered together. Communities shifted to anti-nested and negative species co-occurrence with the increase of environmental heterogeneity. Parameters related to desiccation (salinity and depth) affected euryhaline species co-occurrence. Together, these results revealed group-dependent responses to drought according to physiological tolerances. This study improves our understanding of how the predicted increase in precipitation anomalies may disassembled aquatic communities of coastal plains in the face of climatic changes.