Full text
| |
| Author(s): |
Sebastian Felipe Sendoya Echeverry
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2012-08-27 |
| Examining board members: |
Paulo Sergio Moreira Carvalho de Oliveira;
Sérvio Pontes Ribeiro;
Martin Francisco Pareja;
Paulo Inácio Prado;
Lucas Augusto Kaminski
|
| Advisor: | André Victor Lucci Freitas; Paulo Sergio Moreira Carvalho de Oliveira |
| Abstract | |
Ants are dominant organisms in tropical ecosystems such as Cerrado savanna. It is well known that most ants in forest canopy are highly dependent on liquid food sources derived from plants (such as extrafloral nectaries and secretions from honey-dew producing insects), being functionally considered as herbivores. The high abundance of those resources in Cerrado is an incentive for ants to visit the foliage, although, we still do not know how dependent the ant community is on those resources. While foraging on plants, some ants can behave as generalist predators, thereby, for some Cerrado plants it has been proved that ant presence may reduce infestation levels of phytophagous insects. In the present study we evaluated the importance of ants visitation for lepidopteran larvae, for both host plant use as well as for the defense strategies. In laboratory tests we showed that shelter construction was the more frequent and most efficient defense of Lepidoptera larvae to avoid ant attack. Other traits such as larval body size were important to predict ant attack, but its effect varied with ant species. Larvae may negatively respond to the presence of some aggressive ant groups and not be affected by innocuous ants, but this response may be affected by the specific defensive set of larvae. We also carried out field samplings of both lepidopteran larvae and foraging ants in four fragments of Cerrado (southeastern Brazil), and we found that the foraging intensity of ants had a negative effect on the probability of finding larvae on plants. We show here that interactions between ants and plants vary across space both in how ants use resources present on plants but also in how they affect herbivorous presence. Localities with higher ant density were also places with low larval abundance. The presence of liquid food resources on plants may be a factor mediating ant effects, and the groups of ants that better responded to those resources were also the ones with higher effect on caterpillar presence. However, ant response to liquid food resources on plants are dependent on local conditions and vary across space. Which ants are present locally and the way that they use plant resources may affect host plant use by lepidopteran larvae, as well as the defensive sets that those larvae may present. This evidence suggest that the importance of the ant-plant mutualism in terms of benefits for both organisms is highly dependent on the characteristics of local communities and vary on space. As consequence, the outcome of ant-plant interaction and specifically the function of ants as plant body guards and the potential benefits for plants of herbivory reduction may highly in some communities and small or even null in others (AU) | |