Ant communities and urbanization: insights from tropical territories in French overseas regions

Abstract Urbanization is a rapid ecological process that fundamentally reshapes biodiversity. As urban areas expand, species distributions and biotic interactions are altered, leading to biodiversity loss and biotic homogenization. This study investigates the impact of urbanization on ant communities across three tropical territories with distinct ecological histories: French Guiana, Guadeloupe, and Martinique. We hypothesized that increasing urbanization would decrease native species richness while facilitating the establishment of exotic species. Using citizen science initiatives to collect ant samples, we analyzed species richness, community composition, and co-occurrence patterns along urbanization gradients. Results showed that in French Guiana and Guadeloupe, urbanization significantly decreased species richness while the proportion of exotic species increased. Martinique exhibited no significant effect of urbanization on species richness or exotic species proportion. The patterns of beta diversity were driven by both nestedness and spatial turnover among urbanization levels within territories. Negative co-occurrences were predominantly observed between invasive species in all territories, particularly involving Pheidole megacephala , which showed exclusionary interactions with both native and other introduced species. Our findings underscore the complex, context-dependent effects of urbanization on biodiversity, highlighting biotic homogenization as a key consequence. These results provide valuable insights into the role of urbanization in shaping ant communities in tropical ecosystems.