Evaluating Conservation Corridor Success for Rare and Common Dragonflies Using Zeta Diversity.

Conservation corridors connect natural areas, aiming to mitigate the effects of land transformation. However, their influence on biodiversity, particularly species turnover, remains poorly understood. This study evaluates the impact of conservation corridors on riverine ecosystems and their associated dragonfly assemblages. We assessed species richness and applied the zeta diversity framework to evaluate species turnover across multiple sites, thereby providing insights into how these corridors influence dragonfly community composition relative to natural areas. The research was conducted in the KwaZulu-Natal Midlands of South Africa, covering 104 freshwater sites within natural grasslands and timber plantation corridors. At each site, a 100 m transect adjacent to a river was sampled twice, focusing on recording adult male dragonflies and six environmental variables. Drivers of species richness were analysed using generalised additive models and generalised linear models. Multi-site generalised dissimilarity models were run to examine changes in zeta diversity along environmental gradients and to partition the contributions of different factors to compositional turnover. A total of 37 species were recorded, with one species exclusive to natural areas and four unique to corridors. Dragonfly assemblages were influenced more by stochastic processes than by environmental gradients. Although factors such as site distance, differences in water temperature, dissolved oxygen, shade and rock cover affected turnover, they explained little variation in both rare and common species. Species richness was higher in corridors and consistently declined with increasing shade cover. Neither the presence of corridors nor invasive alien vegetation influenced species turnover, indicating that corridors function similarly to natural habitats. This study demonstrates the crucial role of conservation corridors in preserving dragonfly diversity in altered landscapes. Our findings support continued investment in corridor implementation and management for biodiversity conservation and demonstrate the utility of the zeta diversity framework for understanding species turnover dynamics.