Environment and biotic associations jointly shape cross-taxon aquatic communities in southern South American ponds

Abstract

In southern South America the Patagonia region is experiencing a long-term drought that reduces water availability, underscoring the need to clarify how environmental gradients influence aquatic species occurrences and associations. We used occurrence, traits and phylogenetic relationships cross-taxon species data (13 macrophyte and 35 macroinvertebrate species) from 64 ponds distributed across Patagonia aridity and temperature gradients. We tested two hypotheses: (H1) macrophyte and macroinvertebrate occurrence and their traits are primarily driven by climatic variables; and (H2) macroinvertebrate species positively co-occur with macrophyte species. To capture species- and traits-environment relations, and species-to-species associations, we fitted a Bayesian Joint Species Distribution Model (JSDM) that explained 25.5% of the variation in community composition, with air temperature, aridity, and precipitation seasonality emerging as the main drivers of species occurrences and traits, thereby supporting our H1. Despite limited macrophyte-macroinvertebrate associations (rejecting our H2), species shared ecological niches which constitutes a stepping point to track regional alterations in their biotic associations. Our results indicate that intensifying drought threatens Patagonia eastern pond biodiversity, while western ponds may serve as species reservoirs. Rising temperatures and aridity could alter species distributions and wetlands ecosystem functions, highlighting the need for conservation strategies that account for regional variability under global change.