Desenvolvimento do mosaico de formigas arborícolas dominantes e sua importância no controle biológico natural dos insetos associados ao cacaueiro (Theobroma cacao L.)

Abstract

Agroforests contribute to the survival of many native species. The cocoa plantations inserted in the Atlantic Forest biome in Southeast Bahia contribute to the conservation of a large amount of organisms, including ants. The evaluation of the ontogenetic succession of ants can help understanding the mosaic dynamics of the arboreal ants. Since this mosaic can play a role in suppressing cocoa pests, it is important to conduct studies on the organization of cocoa plantations of different ages. This will help to verify the organization of ants that are biological control agents throughout time. The purpose of this study was to investigate if there is a relation to investigate if there a relation between the cocoa developmental cycle and the richness and diversity of ant species. Furthermore, it also aimed to investigate in which cocoa development phase the mosaic structure becomes more complex and if this complexity occurs gradually. At last, this work evaluated if there is a period when the mosaic is in better conditions to influence the impact of the main insect pests of this crop. The experiment was conducted in 50 plants of cocoa plantations of three, four, eight, 15 and 33 years of age the experimental areas of the Cocoa Research Center, Ilhéus, Bahia. The methods used were: hand collecting, honey baits and tuna fish baits, sheet and pitfall. A total of 1500 samples was taken. The evaluation of damage types caused by the main cocoa pests was conducted with the evaluation of the ants ability for predation. The following analyses were performed frequency, calculations of diversity and richness indices; unbiased correspondence analyses and principal component analysis (PCA); Berger-Parker dominance index, analysis of co-occurrence and niche overlapping, multivariate analysis of Restrict Seriation and predation indeces. Mean values of the diversity and richness indeces did not show either growth or reduction. 15-year old cocoa plantation had the highest score value in the PCA. Ant species had fluctuations in their dominance indeces, but values for Wasmannia Auropunctata were the highest. Monomorium floricola had the highest behavioral dominance. Co-occurrence was detected only in cocoa plantations of three to 15-years of age. Niche overlappings occurrence most frequently in older cocoa plantations. Ants were mostly associated with low levels or absence of damage by pests. The oldest cocoa plantations had the highest damage level. Linepithema neotropicum showed the highest predation level. There was no species diversity and richness gradient in the sucession of the ant community as the plant grew older. Changes in species distribution and regulation among ant populations were detected as the mosaic gets organized during plant development. This probably contributed to the uneven variation in species diversity and richness. The complexity of the mosaic of arboreal ants in cocoa is more evident in plantations of intermediate ages. However, the degree of complexity during plant development did not change progressively. The mosaic had fluctuations in its species territories. There was a great influence of invading ant species. It can not be said that successive changes in the mosaic organization structure influence the control of the main cocoa pests, but the presence of some particular species play a certain role in this pest control.