Natural History of Ants: What We (do not) Know About Trophic and Temporal Niches of Neotropical Species

Our understanding of the natural history of Neotropical ants is still limited, both due to a lack of detailed descriptive efforts and the widespread use of morphospecies in community studies. Use of trophic resources and period of activity are two central niche aspects little explored for most species. This work aims to review the literature and provide empirical field data on these aspects for several species. The fieldwork was carried out in the Atlantic forest of southern Brazil. Trophic and temporal niches were assessed with pitfall traps and seven kinds of bait representing natural resources available to ants. Crushed insects were the preferred resource, whereas bird feces and living prey were less exploited overall. Most of the species occupied a broad trophic niche, using several resources, but with pronounced quantitative differences. Odontomachus chelifer (Latreille, 1802) and Pachycondyla striata Smith, 1858 were the only species that consistently used large prey, and avoided trisaccharides. Wasmannia auropunctata (Roger, 1863) differed remarkably from previous accounts, using feces as its sole trophic resource. Pheidole species had no previous records and use resources in different ways. Most species had no strong preference for period of activity. Camponotus zenon Forel, 1912 was nocturnal and Crematogaster nigropilosa Mayr, 1870, Linepithema iniquum (Mayr, 1870) and Linepithema pulex Wild, 2007 were diurnal. Complementary methods, context-dependence and descriptive studies have a central role in the understanding of ant natural history. Community assessments can contribute significantly to this knowledge if researchers also pay attention to the individual species involved.

Does body size of neotropical ant species influence their recruitment speed?

Ants are one of the most important animal groups in tropical forests because of its abundance and number of species. An important characteristic of the group is the eusociality, which allows the occurrence of a recruitment behavior when food resource is found. However, there are two main questions regarding this behavior: (i) the recruitment is a product of environmental or phylogenetic pressures, and (ii) the recruitment speed is related to the body size of the ant species. In this work we addressed these two questions using 17 species of neotropical ants, in the Amazonic lowland dense rain forest. According to results, recruitment behavior is related to ant size, where smaller species exhibit this trait when finding a protein resource. However, species size is not important in recruitment speed, which suggests that speed can be best explained by the type of food resources needed in the ant colony.

Associations of Two Ecologically Significant Social Insect Taxa in the Litter of an Amazonian Rainforest: Is There a Relationship between Ant and Termite Species Richness?

In spite of the ecological dominance of Neotropical ants and termites, little is understood about how their interactions influence their species richness and distribution. We surveyed ground-dwelling termite and ant species in a primary rainforest in Ecuador and analyzed ecological correlates of diversity. Termite richness was positively correlated with ant richness and abundance of twig-nesting ants. We found no evidence of competition for twigs between termites and ants. No ecological factors were correlated with termite diversity although elevation and twig and log abundance influenced ant diversity. When ant richness was compared to the richness of termites employing different predator defenses, a positive correlation was found with soldierless termites, but not genera employing chemical or mechanical defense. Our results suggest that multiple ecological factors influence ant and termite diversity, and that ant predation on termites may have a greater effect than competition between ant and termites for nest sites and food sources.

Intraspecific and Intracolonial Variation in the Profile of Venom Alkaloids and Cuticular Hydrocarbons of the Fire AntSolenopsis saevissimaSmith (Hymenoptera: Formicidae)

Fire ants are aggressive Neotropical ants that are extensively similar in general biology and morphology, making species identification difficult. Some fire ant species are top-rated pests spreading throughout the world by trade vessels. Many researchers attempted to sort between invasive and native species by using chemical characters, including patterns of venom alkaloids. The present study is the first to report intraspecific variation in some chemical characters, namely, cuticular hydrocarbons and venom alkaloids, within the Brazilian fire ant speciesSolenopsis saevissimaand also reports on within-nest variations among members of different castes. Two different haplotypes (cryptic species) ofS. saevissimawere clearly identified, one presenting a predominant combination of the venom alkaloidscis- andtrans-2-methyl-6-undecylpiperidine with the cuticular hydrocarbons C23, 3-Me-C23, 10-C25 : 1, C25, and 3-Me-C25, and the other a predominant combination ofcis- andtrans-2-methyl-6-tridecenylpiperidine with predominance of 12-C25 : 1, C25, 11-Me-C25, 3-Me-C25, 13-C27 : 1, C27, and 13-Me-C27. Intranest variations revealed that the proportions among these compounds varied sensibly among workers of different sizes, gynes, and males (no alkaloids were detected in the latter). Larva contained vestiges of the same compounds. The recorded chemical profiles are quite different from previous reports withS. saevissimasamples from São Paulo. The finds thus support other recent claims thatS. saevissimaincludes cryptic species; the study, moreover, adds the find that they can occur in the same geographical location.