Defining Habitat Use by the Parabiotic Ants Camponotus femoratus (Fabricius, 1804) and Crematogaster levior Longino, 2003

Ant-garden ants have a strong relationship with epiphytes that need light to grow, for these reason, it has been previously documented in forest gaps. Moreover, larger gaps have more available area for nesting and habitats for use as forage. Thus we hypothesize that 1) canopy openness influence the presence of ant´s gardens in gaps, and 2) greater gaps will have more nests, and 3) both openness canopy and area determine the colony size in forest gaps. Furthermore, it is known that parabiotic ants foraging on the ground and in vegetation, the nests are arboreal. So, we also hypothesize that 4) parabiotic ants are more often sampled in arboreal strata and 5) increasing vegetation connectivity and the volume of accumulated litter in the soil increase the foraging of the ants in vegetation and ground, respectively, with the increase in canopy openness increasing the activity of the two species in both strata. Presence, number of Ant-gardens, as colony size, was affected by area and locality, but not by canopy openness. Nevertheless, there was not overall difference in the use of strata by Camponotus femoratus, neither by Crematogaster levior. On the other hand, frequency of C. femoratus on the ground decreases with canopy openness but is not affected by the vegetation connectivity. Also, C. levior frequency on the ground also decreases with the increase of complexity of vegetation and canopy openness. In addition, neither vegetation connectivity, or canopy openness influence the frequency of foraging of these ants in understory.

The role of parabiotic ants and environment on epiphyte composition and protection in ant gardens

Ant gardens (AGs) are a multi-partner specialized ant-plant interaction involving several ant and epiphyte species. Although studies on AGs have reported possible roles for some species in this system, there are unanswered questions regarding the process of epiphyte incorporation in the AGs and the role of less aggressive ant species in AG protection. In this study, we used AGs in the Brazilian Amazon forest formed by two parabiotic ant species to test a set of hypothesis regarding two main questions: 1) How is AG plant community composition affected by the surrounding environment? 2) Does Crematogaster levior play a role in the chemical detection of herbivory in the AGs? After identifying epiphytes occurring at AGs at the forest edge and in the interior, we found that ant gardens in each environment exhibited different compositions, and that plant species bearing oil or extrafloral nectar glands were more frequent in AGs located in the forest interior than in those at the forest edge. By performing experiments with volatile compounds emitted from injured epiphytes, we detected that only Camponotus femoratus was responsive, responding almost eight times faster in response to plant extracts than water treatments. Our results support the idea that environmental conditions affect ant preference for feeding resources provided by epiphytes and consequently shape the structure of the epiphyte community in AGs. On the other hand, the role of C. levior in AGs remains unknown, since it seems to play no direct or indirect role in AG protection.

Proximity shapes similarity in epiphytic composition of Neotropical ant gardens

Ant gardens (AGs) are specialized ant-plant associations where arboreal ants build their carton nests in association with epiphytes that use the carton as a substrate. Most of the epiphytes are planted by ants; therefore, seed selection by ants is a key driver of the epiphyte composition of AGs. However, deterministic post-dispersal factors, such as the surrounding environmental conditions and plant succession, may also influence epiphyte composition. Here we ask whether epiphyte composition on a local scale is associated with dispersal constraints, local environmental conditions (light availability, number of branches and nest height) or AG successional stage. We sampled all epiphyte species in 18 AGs formed by Camponotus femoratus and Crematogaster levior in Central Amazon, Brazil. AGs were located within a range of 1 km and at a maximum of 20 m from the edges of a dirt road within a primary forest. Epiphytic composition showed strong spatial structure, decreasing in similarity with increasing distance. Environmental conditions and AG successional stage were not related to AG floristic composition, suggesting a key role of stochastic processes related to seed dispersal. A combination of seed abundance and attractiveness in neighbouring AGs seems to drive the higher similarity in epiphyte composition among closer AGs.

Jardins de formigas na Amazônia Central: um experimento de campo utilizando cupins vivos como iscas

Jardins de formigas são um tipo especial de associação entre formigas e epífitas, em que duas ou mais espécies de formigas podem compartilhar o mesmo ninho por parabiose. Essa associação que ocorre em florestas tropicais ainda foi pouco estudada. O objetivo deste trabalho foi avaliar jardins de formigas na Amazônia Central determinando se as formigas identificam e removem potenciais herbívoros que estejam visitando as árvores hospedeiras de jardins de formigas ocupados pelas espécies Camponotus femoratus e Crematogaster levior. No estudo foram observadas 42 árvores contendo jardins de formigas. Em cada árvore foi colocado um cupim, como isca, a diferentes distâncias do ninho, contabilizado o tempo para sua remoção e observado se havia recrutamento de outras formigas para realizar a remoção da isca. Os resultados evidenciaram que ambas as espécies examinam as árvores hospedeiras para forragear. Durante a captura da isca, C. levior foi mais eficiente para detectar o cupim, não tendo sido observado recrutamento para carregá-lo ao ninho. Em alguns casos, indivíduos de C. femoratus identificaram a isca e indivíduos de C. levior a carregaram ao ninho. A relação entre árvore hospedeira e formigas beneficiam ambas, pois a árvore recebe proteção indireta contra cupins e fornece apoio para o ninho das formigas.