Effects of Hydrological Management and Ivermectin Use on the Diversity of Dung Beetles in Wetlands of the Lower Paraná River Delta, Argentina

Cattle farming is a major activity in the Lower Paraná River Delta of Argentina, a wetland of high biodiversity and ecological importance. This study assessed the effects of hydrological management and ivermectin use on dung beetle (Coleoptera: Scarabaeidae and dung associated taxa) communities in cattle fields, considering seasonal variation. Beetles were sampled in fields with low (LHM) and high (HHM) hydrological management, with and without reported ivermectin application to cattle, and across seasons over the course of a year. Taxonomic and functional diversity metrics were compared, and community composition was evaluated. Species richness and abundance were higher in LHM fields, indicating that maintaining natural flood regimes benefits dung beetle assemblages. Paracoprid specialists declined in HHM fields, while generalist species were more prevalent under HHM. Although ivermectin application did not show statistically significant effects, trends suggested lower abundance of dung specialists but higher abundance and richness of predatory taxa in treated fields. Seasonal effects were strong, with diversity peaking in spring-summer and declining in winter, interacting with management practices to influence community structure. Results highlight the role of dung beetles as bioindicators of environmental change in wetlands and the potential ecological alterations of hydrological management and ivermectin use in cattle farming. Sustainable practices, such as maintaining hydrological connectivity and minimizing antiparasitic use during seasonal reproductive periods, are essential to preserve wetland integrity, support dung beetle diversity, and sustain the ecosystem services they provide.