Goat‐driven land degradation reduces richness and reshapes the functional composition of an ant community in a tropical dry forest

Abstract Tropical dry forests are among the world's most threatened ecosystems, having lost over 60% of their original extent due to agricultural expansion and livestock grazing. In the Neotropical region, overgrazing by domestic livestock poses particularly severe threats to ecosystem structure and function. Ant communities, due to their sensitivity to habitat disturbance and their central roles in nutrient cycling, seed dispersal and predation, provide a powerful framework for understanding these changes. We sampled ant communities across a goat grazing gradient in a Tumbesian dry forest in Loja, Ecuador. Nine sampling clusters were distributed across a 20 × 25 km landscape on three levels of grazing degradation (low, moderate and high). Within each cluster, we established three 60 × 60 m plots, which were separated by at least 250 m from each other. Eighteen pitfall traps were deployed per plot. Ant community responses to the goat grazing gradient were assessed using abundance‐ and incidence‐based analyses and related to satellite‐derived vegetation cover (normalized difference vegetation index [NDVI]). We collected 47,473 individuals (abundance) in 1871 collection events (incidence) representing 22 ant species in six ant subfamilies. Species richness declined with grazing degradation (low = 20 spp.; moderate = 15; high = 13), and generalist forager species dominated the more degraded landscape. Beta diversity decomposition revealed a shift from turnover‐dominated dissimilarity at the low moderate degradation transition to nestedness‐dominated dissimilarity at the moderate high transition, indicating increasing habitat simplification with higher land degradation. While categorical differences in ant community composition among land degradation levels were not statistically clear, NDVI was associated with abundance‐based ant community composition. Our trait‐based analysis revealed a contraction of the functional space occupied by ants: communities under high degradation were characterized by smaller, less sculptured ant species, and community‐weighted coloration changed along the gradient as species composition shifted. These findings underscore the conservation value of low‐degradation forests and support grazing exclusion as a management tool for limiting biodiversity loss. Because the mechanisms linking the loss of vegetation cover to ant community change operate across tropical dry forests globally, our results contribute to the broader understanding of how livestock grazing reshapes invertebrate communities in threatened tropical ecosystems.