Unravelling the role of determinism and stochasticity in structuring the phytoplanktonic metacommunity of the Paraná River floodplain

DEVERCELLI M; SCARABOTTI P; MAYORA G; SCHNEIDER B; GIRI F

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2015

0018-8158

One of the ongoing debates around metacommunityecology is to what extent stochastic anddeterministic processes act on community assembly.We explored the influence of both determinism,mediated by environmental filters, and stochasticity,mediated by dispersal and ecological drift, on phytoplanktonassembly in a floodplain river. A probabilisticco-occurrence model revealed the presence of94.1% random and 5.9% non-random species pairwiseassociations. The latter were higher at both hydrologicallyisolated (4.42%) and connected environments(2.2%). Variation partitioning analysis showed similarsignificant explanations by the unique environmental(7.7%, Secchi, conductivity, vegetation, phosphorous)and spatial (7.2%, watercourse distance, longitude)components. Temporal variability was poorly represented(2.4%) because we only considered two lowwaterperiods. Species co-occurrence patterns showedthat most taxa coexist randomly. The environmentalexplanation is in line with niche-assembly models(species sorting), but the similar proportion explainedby spatial organisation related to random dispersalguides the evidence to both deterministic and stochasticprocesses. The higher percentage of random cooccurrenceand the larger assemblage variabilityobserved in isolated environments suggests that randomdispersal, ecological drift, and priority effectscould promote stochasticity. We concluded that bothprocesses affect the structure of phytoplankton metacommunitiesin a floodplain system and suggest thepreponderance of stochastic organisation.