Limited evidence of interspecific competition despite high niche overlap among Ectatomma Smith, 1858 (Hymenoptera: Formicidae: Ectatomminae) ants in the Brazilian Cerrado

Niche partitioning is a key mechanism to explain species coexistence. However, congeneric species are expected to display high niche overlap due to shared evolutionary history. We evaluated the extent of niche differentiation among six Ectatomma species, a prevalent ant genus in the Brazilian Cerrado. We found that habitat specialization had limited influence on coexistence, as most species occurred in savannas rather than in dry forest habitats. There was large overlap in daily time of foraging as most species were active throughout the day and night, except notably for E. opaciventre which was a predominantly diurnal forager. The range of thermal tolerances was positively correlated with body size, as larger Ectatomma were both more heat and cold tolerant. However, interspecific differences in thermal tolerances were relatively small and did not fully explain the differences in daily foraging schedules. Mean trophic position was similar for most species, except between those that forage on the ground and in trees. In agreement with the limited niche differences, patterns of species co-occurrences did not differ from the random expectation. We suggest that the coexistence of Ectatomma species in the Cerrado savannas is facilitated by their solitary foraging behavior which reduces resource monopolization and agonistic encounters.