Macrophytes as drivers of pleustonic Ostracoda (Crustacea) in tropical floodplain lakes

Abstract

Aquatic plants communities, known as macrophytes, are diverse in floodplains and play the role of structuring agents in such habitats, providing availability of food resources, shelter and foraging habitat to several communities. Worldwilde, several studies have approached macrophytes and its structure effects on biodiversity, although, most of them do not take in account macrophytes distinct ecologic groups. We used Generalized Linear Mixed Models, to focus on free-floating macrophytes and its effects on pleustonic Ostracoda assemblages. We test two variables as predictors of Ostracoda richness and density. The first is free-floating macrophytes species, representing interspecific relationship, and root system volume, as a habitat structure measure. This study was carried in two lakes in Pandeiros floodplain, a São Francisco River tributaire. Total diversity registered is considerably high compared to tropical floodplains (31 species - which at least four species and also two genera are possibly new to science). Higher roots volume values supported higher richness, however, even amongst freefloating macrophytes there are differences be yond habitat structure provided. For density, macrophytes species effect was independent of habitat structure measure. P. stratiotes and Salvinia spp. were able to host high organism densities than E. crassipes, even though root volumes did not differ amongst them. Low E. crassipes density was found and a negative effect of this macrophyte on Ostracoda density is outstanding. Our results reveal the existence of important trophic links in an endangered and high priority ecorregion. We call attention to the undiscovered biodiversity inhabiting wetlands in Cerrado biome and suggest further studies at Pandeiros floodplain targeting ostracods and their specific requirements of resources and conditions provided by macrophytes.