Does Seasonality Influence the α and β-diversity of Soil Fauna? A Case Study of Terrestrial Isopods (Isopoda, Oniscidea) Assemblage in the Colombian Caribbean Tropical Dry Forest

Terrestrial isopods are important to forest soils, breaking down decaying plant material and aiding in nutrient recycling. Despite their ecological significance, studies on their diversity and dynamics in Neotropical dry forests are limited. This research investigated the seasonality of the alpha and beta diversity of terrestrial isopod assemblages in a protected fragment of Tropical Dry Forest in the Colombian Caribbean. We sampled isopods in 1 m2 units of litter, and recorded soil and litter temperatures, and moisture during twelve field trips conducted between June 2018 and March 2019 in rainy, transition, and dry climatic seasons. A total of 867 individuals belonging to four families, six genera, and eight species were collected. Alpha diversity did not show significant differences across seasons. However, abundance was significantly influenced by seasonality, soil temperature, litter temperature, and soil moisture. Moreover, species richness was affected by soil moisture and litter temperature. Our results highlight pronounced seasonality in the isopod assemblage, characterized by balanced variation in beta diversity, with higher abundance during the transition and rainy seasons. The observed increase in the variables, correlated with higher total beta diversity, underscores their role as drivers of seasonal dynamics in assemblage structure. Soil temperature and moisture significantly influenced balanced variation component of beta diversity. The identified seasonal pattern likely results from the historical adaptive processes of these species to the conditions of the tropical dry forest. Nonetheless, effective conservation strategies are essential to mitigate the impacts of climate change on edaphic arthropod assemblages in this ecosystem.