Wetland genesis rules invertebrate spatial patterns at Patagonian ponds (Santa Cruz, Argentina): A multiscale perspective

Abstract

Ecological regions are areas of similar nature in terms of environmental features. Examination of the correspondence between organismal assemblage structure and function at different levels of spatial scale is crucial regarding pond conservation, especially in unexplored areas as continental austral Patagonia, where the extensive sheep breeding has been the historical land use. We assessed relationships between invertebrate assemblages and environmental characteristics at local (hydrogeomorphology and genesis) and landscape scale (phytogeographical and biozones) on 20 isolated wetland ponds (Southern Patagonia, Argentina). Additionally, we recognized best environmental predictors of invertebrate community attributes using generalized linear models (GLM). Most ponds displayed low anthropogenic stress since most of them were far from urban and rural settlements. Even though a few sites showed strong oxygen depletion (n = 3), most were well oxygenated (>85%, >11 mg/l). Also, ponds had low ammonia and soluble reactive phosphorus contents (>60%, 25 µg/l). A total of 80 invertebrate taxa were found, with Insecta and Oligochaeta displaying the highest richness. Cyanallagma interruptum (Anisoptera), Parapsectrocladius sp. and Parachironomus sp. (Chironomidae) were the most abundant taxa. Redundancy Analysis (RDA) showed that local environmental factors greatly explained the abundance patterns of invertebrates. In addition, variance partitioning analyses displayed that taxa responded more strongly to pond genesis (7% of variation) than to the other levels of spatial scale analyzed. Structural and functional attributes of communities (metrics) also showed that genesis (local scale) resulted a reliable predictor. Thus, the community composition changed according to fluvial, glacigenic, mass removal or anthropogenic origin of the ponds. Our results suggest that ponds across the austral continental Patagonia area appeared as crucial reservoirs of invertebrate biodiversity sustaining several endemic taxa. However, the expansion of new agricultural and land use practices in surrounding areas could impact negatively on pond integrity. Conservation programs should include major constrains at both, local and landscape scale, in which part of the physical complexity is driving by pond origin.