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The seeds and fleshy fruits consumption by ants in the Atlantic forest : natural history, ecology and spatial variation of a prominent interaction

Author(s):
Claudia Bottcher
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
Defense date:
Examining board members:
Alexander Vicente Christianini; André Victor Lucci Freitas; Marco Aurélio Pizo Ferreira; Paulo Sávio Damásio da Silva
Advisor: Paulo Sérgio Moreira Carvalho de Oliveira
Abstract

The large number of fleshy fruits and the diversity and abundance of ants in tropical environments makes the ant-diaspore interaction very common. Currently it is known that these interactions involve a large number of plants and ants species in an ecological community. Among the ant species interacting with diaspores, Pachycondyla striata and Odontomachus chelifer stand out as main dispersers of seeds encountered on the forest ground. Moreover, the physical and chemical characteristics of their nests often promote the establishment of seedlings. However, despite the recognized importance of these ants for some species of plants, nothing is known about the influence of the consumption of fleshy diaspores in the development and reproduction of the ant colonies. Based on this scenario, this thesis was divided into two related parts. In the first part, Chapter I, we investigated the interactions between ants and nonmyrmecochorous diaspores in three different physiognomic forest of Cardoso Island (sandy, lowland and hillside), southeastern Brazil. During two years of monthly samples 517 interactions involving 53 ant species and 48 species of seeds were observed. Most interactions occurred in lowland Forest (54.62%), and less than half occurred in the two other areas, hillside (31.33%) and sandy Forest (14.06%). Myrmicinae had the highest species number in interaction (39 species), totaling 436 interactions (82.20%). The six species of the Ponerinae subfamily were observed exploring diaspores accounted for 33 interactions (6.4%). Myrtaceae was the most numerous plant family in interactions (14 species). In the second part of this thesis, Chapter II and III, we emphasized two species of Ponerinae (Pachycondyla striata and Odontomachus chelifer), investigating the importance of fruits in their foraging ecology and the development of their colonies. In Chapter II we studied how nest structure, colonies demography, daily activities, diet and home range of these two species vary spatially and seasonally in sandy and lowland forest. Odontomachus chelifer and Pachycondyla striata workers hunt opportunistically including a wide variety of food items. They forage more intensively during the wet season when alates are more abundant and environmental conditions are more favorable. The foraging activity showed variation among the ant species, which could be associated with physical factors and food availability, showing that the foraging behavior of O. chelifer and P. striata correspond to temporal and spatial variability of the Atlantic Forest. To test the hypothesis that the consumption of non-myrmecochorous diaspores benefit ant colonies, in Chapter III we tested the effect of consumption of seeds of Cabralea canjerana, with lipid-rich arils, in colonies of O. chelifer under controlled laboratory conditions. We found that ant larvae fed with diaspores of C. canjerana were on average larger and grew better than control larvae. In conclusion, the data presented here reinforce the importance of secondary dispersal by ants for seeds primarily dispersed by vertebrates. Our results also indicate the importance of studying the foraging ecology and the influence of fruit consumption on survival and growth of colonies of ants. (AU)