Nidificação de abelhas e vespas solitárias e biologia reprodutiva de Megachile dentipes Vachal (Hymenoptera, Megachilidae) em ninhos-armadilha

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

25/02/2011

RESUMO

Terrestrial ecosystems, solitary bees and wasps play important roles as pollinators, predators and parasites. Most part of the life of these Hymenoptera is designed to aspects related to nesting, including the search of the nest site, nest construction and food collection to rear the larvae. However, in natural environments the nests of these insects are difficult to find. A solution to this problem, at least for some species, is the use of artificial burrows in the field (trap nests). Using trap nests it is possible to collect standardized samples and to study the biology of some species. Thus, the community of solitary bees and wasps, nesting in trap nests was evaluated using parameters such as richness, diversity and nest abundance in two different agroecosystems of the state of Pernambuco, northeastern Brazil: sugarcane monoculture and polyculture. Moreover, the natural history and nesting biology of a bee species (Megachile dentipes) collected in the trap nests was studied. In this study, the main aspects of life history (seasonality, diameter of the nests, sex ratio, parasitism, development time) and nesting biology (nest architecture, nesting behavior, larval diet) was studied. Insects were sampled using the technique of trap nests, which consisted of 1) cardboard tubes inserted into blocks of wood of different diameters (4, 6, 8 and 10 mm), and 2) wooden planks, drilled lengthwise (5, 6, 8, 10 and 12 mm in diameter) and covered with a transparent plastic sheet (observation-nests). In each agroecosystem 3.360 cardboard tubes were available for nesting during one year (June/2009 to May/2010) and 1000 holes of observationnests during five months (October/2009 to February/2010). In the monoculture a total of 259 nests, 86 (33.2%) build by bees and 173 (66.8%) by wasps were sampled. Five species of bees were sampled, and Megachile dentipes was the most abundant bee species in the sugarcane (n = 76; 85%). In the polyculture area, 411 nests were collected, being 254 (61.8%) of bees and 157 (38.2%) of wasps. In this environment, 14 spp. nesting bee species were recorded. The leaf-cutter bee Megachile dentipes was also the most abundant (n = 117 nests, 46%). The abundance of bee nests, species richness and diversity of bees and wasps was significantly higher in the polyculture area compared to monoculture area. It is suggested that plant richness is a determining factor in the occurrence of the species. However, other factors such as distance from forest fragments and the use of herbicides and burning, might have influence in the low richness and diversity of bees and wasps in the area with sugarcane monoculture. Regarding Megachile dentipes it was shown that it is an polilectic species, collecting pollen from a wide spectrum pollen from mainly five botanical families: Asteraceae, Rubiaceae, Euphorbiaceae, Mimosaceae and Scrophulariaceae. This species showed a clear preference for nesting in the dry periods of the year in both studied areas, with peaks in October and December. Furthermore, this species had several generations throughout the year (multivoltine). It was demonstrated experimentally that recognition of the cavities by females is determined by the nest position in the blocks. Probably, chemical signals (marking the cavity) are not used, at least in the initial recognition of the nests. Nest structure of M. dentipes differs from most species because the lining of the brood cell is made from chewed leaves unlike the other species that involve the brood cells with whole leaves not chewed.. Biological and ecological characteristics of M. dentipes, as e.g. abundance and poliletia, makes this species a good candidate for management programs aimed at pollination, but further studies are necessary for that purpose.

ASSUNTO(S)

megachilidae nidificação agroecossistemas plantas herbáceae canade- açúcar zoologia agroecosystems nesting megachilidae herbaceous plants sugarcane

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