Snake diversity in floodplains of central South America: Is flood pulse the principal driver?

Abstract

Seasonal flood pulses drive important seasonal ecosystem changes, trigger ecological processes that control spatial and temporal distribution of organisms and their life-history strategies, and are considered a key ecological process shaping diversity in floodplains. We used generalized dissimilarity modelling (GDM) to analyse the relative importance of flooding as a driver of snake community composition in the Paraguay River Basin (PRB), which encompasses discontinuous seasonal flooded areas, including the Pantanal floodplain, one of the largest Neotropical wetland systems. We modelled the beta diversity of pairs of PRB snake communities (based on species occurrence and phylogenetic relationships) as a function of biogeographical and environmental dissimilarities between areas, considering predictors that represent distinct limitations of species’ ability to use an area. Annual flooding directly drives snake diversity, mainly when ancient evolutionary relationships between species were considered to calculate the phylogenetic diversity of the communities. Floods recurrently produce major changes in the environment and probably limit the persistency of species extremely specialized in habitat use. Despite the confirmation of the effect of flooding, the most important predictor of beta diversity between snake communities in the PRB was forest cover where communities were placed. Forest cover seems to constrain the occurrence of some species in both gradient extremities through the absence of suitable conditions for either specialized habitat use or thermoregulatory behaviours. Geographical distance was also an important predictor of beta diversity, highlighting the importance of neutral process in the assembly of local communities in systems such as seasonally flooded areas, where annual disturbances of varying intensities continually disassemble and reassemble biological communities. For the first time, we quantified the relative importance of flooding affecting patterns of biological communities in the Pantanal floodplain, compared to multiple factors also acting on species turnover in the area.