Twigs in the Leaf Litter as Ant Habitats in Different Vegetation Habitats in Southeastern Brazil

Abstract

Vegetation structure and microhabitat availability and diversity affect ant assemblage diversity, growth, and dispersal. In this study, we described assemblages of ants nesting in twigs found in the leaf litter, comparing nest characteristics and ant colony sizes among different vegetation habitats at a regional scale. Twigs were collected in urban parks, Eucalyptus plantations, and preserved areas of native Atlantic Forest. We measured the twigs, counted the number of ant colonies, and estimated canopy openness. A total of 51,213 ants from 22 genera and 61 species were recorded. We collected 74, 141, and 283 nests in urban parks, Eucalyptus plantations, and native forest areas, respectively. The richest genera were Pheidole, Camponotus, and Solenopsis. Linepithema neotropicum, Gnamptogenys striatula, and Solenopsis sp.2 were recorded in all study areas. We found only one invasive species, Cardiocondyla wroughtonii. Typically, the canopy in urban park areas was more open, and these areas had lower species richness, lower rate of twig occupancy, and smaller diameter twigs occupied by smaller colonies compared to Eucalyptus plantations or native forest. Ant assemblages were determined mainly by vegetation habitat, followed by twig characteristics. As many ant species use twigs as nest site, twigs are critical habitats for maintaining ant diversity in the leaf litter of areas with varying degrees of complexity in the vegetation structure. However, the availability of twigs as nest resource depended on vegetation structure. In addition, twigs may increase the area occupied by the colonies of some ant species, including Wasmannia auropunctata, which was very frequent in urban parks.

Ants that Frequently Colonize Twigs in the Leaf Litter of Different Vegetation Habitats

“…Of these, only L. neotropicum (Mann-Whitney = 1.7401; p = 0.0818) and P. sospes (Mann-Whitney = 0.0985; p = 0.9215) colonized similar-diameter twigs in different vegetation habitats (Fig 2), although the leaf litter in the native forest shelters a higher twig diversity (Murnen et al, 2013) compared to eucalyptus plantations (Pereira et al, 2007). Our study is the first to compare "common inhabitants" of twigs among different vegetation habitats in the Brazilian Atlantic domain, demonstrating that these communities are affected by habitat structure, as shown by Souza-Campana et al (2017) for other twig-colonizing ant species. By finding that 25% of the "common inhabitants" were arboreal ants, and that some species colonized similar twigs in different vegetation habitats, our results contribute to the knowledge of the biology of these ants in the leaf litter.…”

“…None species was recorded in urban parks in 864 m 2 of leaf litter; in the eucalyptus plantations, four species (33.3%) were observed in 57 twigs (= 0.06 twigs/ m 2 of leaf litter); and in the native forest, 11 species (91.7%) in 217 twigs (= 0.25 twigs/m 2 of leaf litter). Other studies on ants that colonize twigs in native forest and agroecosystems (Murnen et al, 2013;Souza-Campana et al, 2017) have also shown that the less the anthropogenic influence, for the best the ant diversity.…”

“…collected, and their size was described by three diameter measurements, one at each end of the twig and one in the middle. Diameter has been identified as the variable that is most strongly associated with ant species richness in twigs (Carvalho & Vasconcelos, 2002;Souza-Campana et al, 2017) or with events of bamboo traps occupation by arboreal ants (Cobb et al, 2006). Ants were identified based on Suguituru et al (2015).…”

“…Ant community diversity is limited in areas with few nesting resources (Fowler et al, 1991). However, resource quality is also important, because decayed and hollow twigs with higher moisture content (Carvalho & Vasconcelos, 2002) and larger diameters (Souza-Campana et al, 2017) are colonized more often. In eucalyptus plantations, twigs are very rigid and dense (Pereira et al, 2007), making it more difficult for "common inhabitant" species to colonize them; as a result, these communities are poorer (Table 1).…”

“…In eucalyptus plantations, twigs are very rigid and dense (Pereira et al, 2007), making it more difficult for "common inhabitant" species to colonize them; as a result, these communities are poorer (Table 1). Even when the eucalyptus plantations have a developed understory, the structure of the twigs is homogeneous (Souza-Campana et al, 2017). Therefore, "common inhabitants" colonize twigs of similar diameters (KW = 3.9113; df = 3; p = 0.2712), in contrast with the native forest, where "common inhabitants" exploit a greater diversity of twig sizes (KW = 27.9747; df = 10; p = 0.0018), especially Gnamptogenys striatula Mayr 1884, Linepithema neotropicum Wild, 2007, Pheidole sarcina Forel, 1912 and Solenopsis sp.2 (Table 1).…”