Vespas sociais (Hymenoptera, Vespidae) amostradas no Parque Estadual do Ibitipoca-MG: estrutura, composição e visitação floral

Abstract

In Minas Gerais, areas of the Atlantic Forest, Rupestre fields and the Riparian Forest have been highlighted due to their importance for Conservation Biology, presenting high diversity and including social wasps. This group of insects, which is represented by Polistinae in Brazil, causes considerably high damage on ecosystems, since they are important predators and floral visitors. The objective of this work was to study the structure and taxocenosis composition of social wasps during the hot/humid and cold/dry seasons, and to observe the efficiency of the collection methods used to capture these insects at Ibitipoca State Park. The work also estimated richness, diversity, abundance, niche amplitude and evenness of the flower-visiting social wasps. In three phytophysiognomies (Rupestre fields, the Riparian Forest and an Atlantic Forest fragment), 12 collections were carried out from November 2007 to October 2008. Three collection methods were used: the active search, with the aid of an entomological net; the punctual method, with plants in the flowering periods being visited by wasps, and attractive traps with passion fruit juice or broth of sardines (sardines preserved and water). A total of 926 social wasp individuals were collected, and distributed among 21 species and eight genera in the active search (18 species), in the punctual method (15 species), in traps with passion fruit juice (seven species) and sardines (five species). The Riparian Forest presented the highest species richness (19), followed by Rupestre fields (14) and the Atlantic Forest (5), though Rupestre fields showed higher diversity (H’= 2.16) than the Riparian Forest (H’= 1.43) and the Atlantic Forest (H’= 0.18). The regular rate calculation of the species showed that 38.08 % were accidental (C<25%), 38.08% accessories (25% <C< 50%), and 23.84% constant (C>50%). In the cold/dry and hot/humid seasons, considering the three areas of study, the Spearman test showed that there was no significant correlation between richness and abundance and the climatic variables temperature and pluviosity. A total of 103 individuals were obtained, belonging to 15 species and seven genera, visiting flowers of 27 species of plants (14 families). The families with the highest number of visitors were Erythroxylaceae (10 species) and Asteraceae (10 species), which also stood out with the highest values for abundance of individuals (55). Mischocyttarus confusus, Mischocyttarus drewseni and Polybia sp2 were the most abundant in the Riparian Forest, and Polybia sp2 in Rupestre fields. The diversity of flower-visiting social wasps in the Riparian Forest (H’= 0.78 and J’= 0.75) was higher than in Rupestre fields (H’= 0.30 and J’= 0.39), and there were no significant differences between the Shannon-Wiener indices for the two locations studied 12 (Z(U)= 1.84 (p)= 0.064. The amplitude index of trophic niche showed variations from 0.63 to 2.42, with M. drewseni visitors present in 12 among the 27 species of plants at Ibitipoca State Park, being recorded during the study period with the highest amplitude index of trophic niche (2,42) Polybia sp2 visited nine of the 27 vegetable species, and showed higher abundance during the collection period. It may be concluded that no sampling method alone captured all the species recorded in the present study, a fact that indicates the use of all methods combined. In addition, richness and diversity varied according to phytophysiognomic characteristics of each location, with available resources and places for nidification. Wasps were regular floral visitors in the present study, showing the importance of these insects in search of nectar in different flowers at Ibitipoca State Park.