Spatial patterns of zooplankton diversity in riverine floodplains

ZSÓFIA HORVÁTH; ROBERT PTACNIK; CHAPARRO, GRISELDA N.; THOMAS HEIN

Conferencia; 41st IAD Conference; 2016

IAD

Understanding the spatial distribution of species diversity is a main interest of ecology and its relevance is enhanced under the current scenario of progressive diversity loss and massive change of ecosystems. Despite the relevance of spatial scale is increasingly recognized in biodiversity studies, there is still a lack of understanding on how combined environmental variations at smaller and broader scales influence diversity in a certain region. We studied spatial patterns of zooplankton diversity (rotifers, cladocerans and cyclopoid copepods) in riverine floodplains from the Upper Danube River in Austria, with the aim to understand how regional diversity is composed and assess the association between beta-diversities, environmental heterogeneity and spatial processes at different scales. We performed a field sampling using a hierarchical multi-scale approach, with particular emphasis on distinct vegetated habitats as hosts of zooplankton diversity. The sampling design included: 1- different habitat patches (open waters, submerged, floating-leaved and emergent macrophytes) to account for the variability within water sections and 2- different water sections along a gradient of connectivity with the main river channel to account for the variability among water sections in the floodplain wetlands. We included three wetlands within the Donau Auen National Park area, where river flooding is operative and one isolated wetland in an impounded section of the river and compared the patterns among them. We performed the sampling once during summer 2014 after a flood event and once during dry summer 2015 when no flood occurred. Our results indicate that regional diversity was very high and similar at flooded and non-flooded conditions. We found similar patterns for rotifers and crustaceans, with beta-diversities among water sections and among wetlands as main contributors to zooplankton regional diversity and minor contribution of beta-diversities among habitats. These patterns were similar in flooded and non-flooded conditions and we did not detect relationships between beta diversities and environmental heterogeneity at the studied scales. We used variation partitioning analyses to disentangle the roles of local environmental and spatial factors. Significant spatial effects at medium and fine scales in both flooded and non-flooded conditions suggest that massive dispersal related to floods produce homogenization of the communities and that these effects are persistent through time. In the isolated wetland with no flooding effect, we found a more even contribution of alpha and beta diversities to regional diversity as a result of increased beta diversity among habitats (compared to flooded wetlands). Our study suggests that in wetland systems with no regular flooding the lack of homogenizing effect determines that fine scale species turnover is high and significantly contributes to regional diversity, while in dynamic wetlands affected by river flooding, only medium or large scale species turnover are sufficiently high to significantly contribute to regional diversity. These results highlight the releveance of the spatial extent of dynamic floodplain wetlands for the mainteinance of regional diversity.