Ants are a conspicuous biotic component within the tropical dry forest, due to their great diversity both at the species and functional level. Of all the ants, those of the genus Pheidole (Formicidae: Myrmicinae) stand out, which have been categorized as a hyperdiverse group due to the high number of species. The latter has made this group a taxonomic challenge during the development of diversity and ecology studies, therefore, local studies that offer information on the identity of the Pheidole species of a given area becomes an important resource for the decision making. The ants of the genus Pheidole in different formations of tropical dry forest in Santa Marta were studied. Thirteen species are registered, of which Pheidole guajirana extends its distributional range to the department of Magdalena, while P. impressa and P. leptina are registered for the first time in the country. The diagnosis and description of the new species P. urbana is also offered and its morphological features are compared with similar species of the “ flavens ” informal group. The species richness of the genus in the different sampling sites is evaluated and discussed. Distinctive morphological characteristics are offered for each of the species. Moreover, morphological variability is discussed, and multifocal color images are included for the soldiers (major worker) and workers (= minor worker) of each of the registered species.

There have been few advances in understanding the organization and dynamics of ants in tropical dry forests. The latter are a seriously threatened ecosystem, and ants are important indicators of diversity, disturbance, and restoration in forest ecosystems. Using diversity data and morphofunctional traits, we evaluated the spatial and temporal variation of taxonomic and functional ant groups; in addition, we explored the variation in functional traits and diversity among communities. Ants were sampled during the dry and rainy seasons using mini-Winkler bags. A total of 9 subfamilies, 57 genera, and 146 species were collected. Ant species composition and richness varied both spatially (75 to 119 species) and temporally (121 and 127 species). The fragments from N2 and N3 showed higher diversity than those from N1. The dissimilarity among all areas was moderate (50–60%), mainly attributable to species turnover processes (77%). Twenty functional groups were identified. The N3 fragments had the highest functional diversity, with lower resistance to species loss, while the N1 and N2 fragments reduced functional diversity and increased similarity among species. Our results highlight the importance of integrating a functional analysis with the taxonomic assessment of ants as an important contribution to understanding the organization and dynamics of this community of insects that inhabit the tropical dry forest.