Spatial Variations in Water Beetle Communities in Arid and Semi-Arid Patagonian Wetlands and Their Value as Environmental Indicators

To evaluate spatial variations in aquatic beetle assemblages, 26 Patagonian ponds were sampled during late spring (Dec.). The hydroperiod, hydrology, abiotic features, precipitation, aridity, and aquatic plant richness of the study sites differed. Fifteen physicochemical features were measured, and aquatic plants were collected to determine taxonomic richness. Sampling of the 26 ponds produced 21 aquatic beetle taxa in 6 families. All aquatic beetles (adults and larvae) were assigned to functional feeding groups. A canonical correspondence analysis (CCA) was run to assess relationships between aquatic beetle assemblages and environmental variables. Of the variance in aquatic beetle taxa abundances, 23% was accounted for by the 1st 3 ordination axes. Moreover, the 1st 2 canonical axes respectively accounted for 38.2% and 28.4% of the variations attributable to environmental variables (i.e., annual precipitation, elevation, pond area, aquatic plant richness, pH, and conductivity), with conductivity and elevation being the most important. A parsimony analysis was performed to establish which species could define and/or group some of the communities (with sampling sites treated as taxa and species treated as characters). Results of the parsimony analysis suggested that some taxa (Haliplus subseriatus, Gymnochthebius sp., Enochrus darwini, Cyphon sp., Luchoelmis sp., and Rhantus validus) were useful in defining some ponds or groups of ponds. These species can be used as indicators since beetle distributions are not considered to randomly occur. Our findings show that aquatic beetle assemblages can be utilized for wetland conservation planning since in arid and semiarid Patagonia, they are important as water reservoirs and for cattle rearing.