Predation of top predators: cane toad consumption of bullet ants in a Panamanian lowland wet forest

Despite a clear consensus about the major roles that predators play in shaping ecological communities, descriptive studies of interactions between ecologically important top predator species are underreported. Native cane toad consumption of predatory bullet ant nests was verified through multiple, independent observations taken on Pipeline Road, Panama. Cane toad predation led to the extirpation of 42% of the nests within a 1.05 km2 area that is characterized as a late-successional wet forest. This predation pressure could be significant given the high rate of predation events and low bullet ant nest density observed here (0.12 nests ha−1). Implications of this interaction for the local bullet ant population, possible top-down effects and trophic cascades resulting from this top predator interaction are discussed.

Distribution and dietary regulation of an associated facultative Rhizobiales-related bacterium in the omnivorous giant tropical ant, Paraponera clavata

We document a facultative Bartonella-like Rhizobiales bacterium in the giant tropical ant, Paraponera clavata. In a lowland tropical rainforest in Costa Rica, 59 colonies were assayed for the prevalence of the Bartonella-like bacterium (BLB), 14 of which were positive. We addressed three questions: First, how does the prevalence of BLB within colonies vary with environmental conditions? Second, how does diet affect the prevalence of BLB in P. clavata? Third, how does the distribution of BLB among colonies reflect ambient differences in food resources and foraging habits? A variety of environmental variables that may be predictive of the presence of BLB were measured, and diet manipulations were conducted to test whether the prevalence of BLB responded to supplemental carbohydrate or prey. The ambient frequency of BLB is much higher in young secondary forests, but is nearly absent from older secondary forests. The prevalence of BLB inside field colonies increased over the duration of a 2-week carbohydrate supplementation; however, water and prey supplementation did not alter the prevalence of BLB. The diets of the colonies located in young secondary forest, compared to other habitats, have a diet richer in carbohydrates and lower in prey. The abundance of carbohydrate, or the relative lack of N, in a colony's diet influences the occurrence of the BLB microbe in P. clavata. As experimental diet manipulations can affect the facultative presence of an N-cycling microbe, a consistent diet shift in diet may facilitate the emergence of tighter symbioses.

A predictive distribution map for the giant tropical ant, Paraponera clavata

Paraponera clavata (Fabricius 1775) (Formicidae: Paraponerinae) is a widely distributed Neotropical ant whose large size has attracted the attention of numerous collectors. Working from museum specimens, a georeferenced database of collection localities was developed. This database then served as the source for computer generated predictive distribution maps. Annual rainfall was the most important variable chosen by the computer model to predict the distribution of P. clavata, both on the scale of the neotropics and at a finer scale at the northern end its distribution in Costa Rica and Nicaragua. When the model was forced to use vegetation as the first predictive variable, the Neotropical model used temperature and rainfall variance as additional variables, while the Mesoamerican model used both climatic and soils variables. Overall, the modeling suggests that P. clavata is more sensitive to abiotic factors (rainfall, temperature, soils) than to biotic factors (vegetation type) in its distribution, although this conclusion comes with the caveat that the vegetation types used in the model are quite generalized. Predictive distribution mapping holds great promise for generating more precise representations of insect distributions, thereby allowing better tests of the extent of distribution overlaps and other community relationships.