Taxocenoses de meliponina, seus recursos florais e sítios de nidificação em áreas da caatinga, no Seridó Nordestino.

Abstract

The Seridó is a semiarid region in the Northeastern Brazil that presents a generalized picture of anthropogenic disturbance and a reduction in the range of distribution of stingless bees, native eusocial species of the Meliponina subtribe. The discovery of an area with remnants of natural populations of these bees allowed us to study nesting aspects and the use of flower resources in conditions closer to the original one, more than had been done before. The general objective was to study the Meliponina fauna in areas with different meliponine conservation states within the Seridó region to evaluate their conditions of existence. It was studied the meliponine fauna in three areas with vegetation preserved for at least 30 years, and similar caatinga (scrub) phytophysionomies: "Morada das Jandaíras" Farm (FMJ) and Seridó Ecological Station (ESEC), both in the Rio Grande do Norte state, and "Tamanduá" Farm (FT), in the Paraíba state. Two of them have no meliponine or just one species, while FMJ presents a high abundance of stingless bees nests. A phytosociological survey of trees and shrubs at FMJ was undertaken, in order to compare the forest structure with previously taken data from the other areas. It was investigated the efficiency baits use during the dry period, as alaternative to complement the diagnosis of meliponine species richness and evaluate the possibility of an alternative way of quick survey. The characteristics of trees used for nesting and the density of nests were evaluated, as well as nest tree availability considering only trees of Commiphora leptophloeos (Burseraceae) and Poincianella pyramidalis (Fabaceae Caesalpinoidea), previously recognized as preferred for nesting by these bees in the caatinga region. To evaluate the use of flower resources during dry season, a monthly survey of woody plants and cacti that visited by stingless bees and Apis mellifera L. was carried out. Euphorbiaceae, Fabaceae Caesalpinoidea and Fabaceae Mimosoidea were the plant families with the higher number of species in the phytosociological survey at FMJ. The dominance (total basal area was higher at FMJ than that of other areas. The family Burseraceae, represented only by C. leptophloeos, showed a quite high relative dominance, reaching more than 44 % of total one. The nest and flower visiting bees survey at FMJ resulted in the record of five species. The sampling with sugar solutions and scent baits was not efficient even in the dry period, and can not be used to survey of stingless bees in the caatinga region. 190 meliponine nests were found and analised, confirming the importance of C. leptophloeos e P. pyramidalis as nesting sites. A density of 1.56 nests/ ha was found. The absence of nest within the plots sistematically set for the phytosociological study demonstrate that this methodology is an inefficient way to estimate the nest density within the caatinga, considering the low number of plots. As an alternative, another criterion for setting the plots was used, considering as reference selected higher trees within transects. In this way, we get an ecological density of 20 nests/ha. A correction factor applied to the total number of nests found within 120 ha resulted in a corrected density of 3.12 nests/ha. The record of A. mellifera nests within the same plots confirm the possibility of coexistence of this exotic species with native stingless bees in similar natural areas of caatinga, at least for the two more abundant species, Frieseomelitta doederleini and Melipona subnitida. But this do not imply that there is no negative competitive effects on these native bees. In relation to the flower resources at FMJ, the woody plants and cacti provided flower resources throughout the year, but the abundance is lower during the dry season. With few exceptions, the woody species recorded at FMJ are also present at ESEC and FT, according to phytosociological studies in these areas, and so, there is still no evidence of strong differences in the provision of flower resources, especially during the dry season, between the three areas. But the analysis of the availability of nest trees showed a high total basal area at FMJ, determined by the presence of large individuals of C. leptophloeos, what serve as indicative of possible restriction for recolonization by stingless bees at ESEC and FT due to the scarcity of nesting sites. The abundance and diversity of stingless bees at FMJ can be considered an indicative of its good conservation status, allowing us to stress the importance of its maintenance for the study of the ecology of these bees at the region. Besides their ecological importance, its preservation will allow their continued use in programs of sustainable explotation.