No abstract

Aggressive behaviour can ensure animal access to local resources. To reduce constant costs in the defence of territories, species could save energy with conflicts avoiding aggression with neighbour or in situations with abundance of resources. In the present study, we analysed the effect of distance among colonies and resource availability on the aggression level and responses to chemical cues of Nasutitermes aff. coxipoensis (Holmgren) (Termitidae: Nasutitermitinae). Manipulation of resource offer was conducted in the field, where nests with different distances were kept without addition of baits (control), with addition of three or 16 sugarcane baits/nest. After 3 months, aggressiveness, linear and Y-shaped trail-following bioassays were carried out with all pairwise combinations of colonies in each treatment. Our results showed that aggressive index of N. aff. coxipoensis was affected by the resource availability. However, individuals from colonies with 0 and 3 baits/nest showed a higher number of fighting with neighbours than those from non-neighbours colonies. Termite workers from colonies without baits (control) followed shorter distance in the linear trails compared to those from colonies with addition of baits. In all treatments, there was no preference of workers in relation to the choice of chemical cues from own or other colonies. The response of intercolonial aggressiveness in N. aff. coxipoensis seems to be resource-dependent. These results may contribute to the comprehension of the use of space by N. aff. coxipoensis and could be useful to explain patterns of termite co-occurrence at different spatial scales, from local (inside the nest-e.g. cohabitation of nests by inquilines) to regional (e.g. around the nest).

Constrictotermes sp. nests are frequently inhabited by colonies of Inquilinitermes microcerus. In this association, I. microcerus colonies usually establish their colonies spatially isolated from Constrictotermes colonies. Here, we investigated whether the apparent spatial isolation of I. microcerus colonies in Constrictotermes nests should be related to their needs (e.g. feeding) in relation to the central part of the nest or to a possible stress provoked by the presence of the host. For this, survival and walking behavior bioassays were performed to test the hypothesis that the survivorship of inquilines is: (i) reduced in the presence of host, mainly of those from different nests, (ii) increased in contact with inner walls compared with external walls; and that the distance walked and walking velocity of inquiline is: (iii) increased in the presence of the host and (iv) reduced in contact with the internal walls compared with external walls of host nest. The mean time to death of inquiline workers is lower in contact with host (independently from the same or different nest) compared with control and the mean time to death of inquiline workers is lower in contact with external walls of host nest compared with control group and the inner walls. The distance walked and walking velocity of inquiline workers in contact with their hosts (from the same or different nest) did not differ from control, however, these parameters were reduced when workers were in contact with inner and external walls compared with control. In general, our results showed that I. microcerus adopt behavioral strategies to avoid perception by its host.

No abstract

Symbiosis between plants and ants include examples in which the plant provides shelter and/or food for ants that, in turn, act in the defense or in the dispersion of seeds from the host plant. Although traditionally referred as mutualistic, the results of these interactions may vary with the ecological context in which patterns are involved. A range of species have facultative association with Turnera subulata (Turneraceae). Here, using behavioral bioassays, we investigated the effects of the most frequent ant species associated with T. subulata (Brachymyrmex sp.1, Camponotus blandus (Smith), Dorymyrmex sp.1, Crematogaster obscurata Emery, and Solenopsis invicta Buren) in the dispersion of plant host seeds and in the number of seedlings around the associated ant nests. We also evaluated the effects of these ant species in the germination of T. subulata seeds, in the consumption of elaiosome, and in the attractiveness to elaiosome odor. Our results showed that the ant species associated with T. subulata presented variation in the attraction by the odor and in the rate of consumption of the elaiosomes. However, none of the ant species studied contributed significantly to the increase of seed germination and seedling growth. Our results suggest that the consumption of the elaiosome by ant species is not a determinant factor to the success of germination of T. subulata. However, such species could contribute indirectly to seed germination by carrying seeds to sites more fertile to germination. In general, our results help to elucidate the results of ecological interactions involving ants and plants.