Regional climate contributes more than geographic distance to beta diversity of copepods (Crustacea Copepoda) between caves of Italy

Despite the study of subterranean biodiversity facing harsh sampling and mapping challenges, the huge diversity of taxa, ecological adaptations and evolutionary trajectories in subterranean environments is gaining increasing attention. Yet, the spatial and environmental factors driving the composition of groundwater communities are still poorly understood. To partially fill this knowledge gap, we collected copepod crustaceans from 12 caves along the Italian peninsula between 2019 and 2022, sampling each cave twice. The resulting presence-absence data were analysed to assess: (i) between-cave taxonomic beta diversity, also partitioning between turnover and nestedness-resultant dissimilarity; (ii) the relative weight of geographic distance and climatic differences in shaping observed beta diversity. Seventy-one species of copepods were collected overall. Pairwise beta diversity was high for most pairs of caves, with turnover being the major component. Geographic distance-decay models partially explained total beta diversity and turnover patterns. However, in Generalized Dissimilarity Models (GDM), including surface climatic conditions as predictors, the contribution of seasonal temperature averages was generally higher than that of geographic distance. Further, the explanatory and predictive performance of the GDMs notably increased, along with temperature contribution, when widening the spatial extent from which climate data were gathered. Our results confirmed a high spatial turnover in groundwater copepods' assemblages and strengthened the link between regional climate and subterranean biodiversity.

Some like it hot: Thermal preference of the groundwater amphipod Niphargus longicaudatus (Costa, 1851) and climate change implications

Groundwater is a crucial resource for humans and the environment, but its global human demand currently exceeds available volumes by 3.5 times. Climate change is expected to exacerbate this situation by increasing the frequency of droughts along with human impacts on groundwater ecosystems. Despite prior research on the quantitative effects of climate change on groundwater, the direct impacts on groundwater biodiversity, especially obligate groundwater species, remain largely unexplored. Therefore, investigating the potential impacts of climate change, including groundwater temperature changes, is crucial for the survival of obligate groundwater species. This study aimed to determine the thermal niche breadth of the crustacean amphipod species Niphargus longicaudatus by using the chronic method. We found that N. longicaudatus has a wide thermal niche with a natural performance range of 7-9 °C, which corresponds to the thermal regime this species experiences within its distribution range in Italy. The observed range of preferred temperature (PT) was different from the mean annual temperature of the sites from which the species has been collected, challenging the idea that groundwater species are only adapted to narrow temperature ranges. Considering the significant threats of climate change to groundwater ecosystems, these findings provide crucial information for the conservation of obligate groundwater species, suggesting that some of them may be more resilient to temperature changes than previously thought. Understanding the fundamental thermal niche of these species can inform conservation efforts and management strategies to protect groundwater ecosystems and their communities.