Microbial metacommunity assembly and interaction networks in floodplain lakes

DEVERCELLI, M.; METZ, S.; UNREIN, F.; SCARABOTTI, P.; DI PASQUALE, V.; ROJAS MOLINA, F.; PAGGI, J. C. ; ALVARENGA, P.; MAYORA, G.; CHINGOLANI, G.; SCHNEIDER, B.; GIRI, F.; MARCHESE, M.

Workshop; 18th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP); 2017

The planktonic microorganisms of floodplain lakes constitute a complex assemblage for which metacommunity framework emerges as appropriate to unveil their diversity and assembly. The beauty of this approach is that it assumes the influence of environmental filters within the interconnected dynamic of local communities. Besides environmental conditions, microbes are integrated in interaction networks that in turn are influenced by spatial factors that dampen the destabilizing oscillations of strong associations. Within this frame, we aim to glimpse the assembly of microbial community in floodplain lakes. We analyse the relative importance of environmental and spatial factors, and interactions, and if spatial dynamic (by means of environmental connectivity) affects community attributes and interactions strength. We sampled connected and disconnected lakes (n=14) during drought and flood periods (November2013, September2015). We quantified bacterioplankton, picocyanobacteria, picoeukariotes, heterotrophic and autotrophic nanoflagellates (flow cytometer, epifluorescence microscope), and phytoplankton >8 μm (inverted microscope). We measured spatial, physical, chemical, and morphometric variables of lakes, as well as macrophytes, zooplankton and planktivorous fish composition and abundances. To characterise and compare microbial structure among connected/disconnected lakes, and drought/flood periods, we performed PERMANOVA and SIMPER analyses. We applied mantel correlograms and pRDA to dissect the relationships among spatial, environmental, and biological factors driving the different microbial assemblages. We performed co- occurrence analyses to species and trophic functional groups to approximate biological interactions. We used path analysis to test the fit of different interaction models. With this work we expect to incorporate the effect of species interactions and the role of spatial dynamic in networks to the current hypotheses of microbial assembly. We discuss differences in the driving factors for each assemblage (from the smallest heterotrophic bacterioplankton to the largest autotrophic phytoplankton). We hypothesize that connectivity maintains the high floodplain diversity due to recruitment and exchange of organisms among environments, and by dampening interactions strength.