Biologia da nidificação de Tetrapedia Curvitarsis Friese (Apidae, Tetrapediini): fenologia, estrutura dos ninhos e nicho alimentar

Abstract

Solitary bees comprise a group of pollinators as important as the social species, but little is known about the biology of these insects due to its sparse population and therefore, the difficulty of locating the nesting sites. However, the abundance of these bees in areas of Cerrado and high attractiveness for trap-nests provides information that could support actions of conservation and management of this group. In this sense, the aims of this study were to describe the nests of Tetrapedia curvitarsis with respect to phenology and physical parameters of the nests and to verify the effect of seasonality in the production of brood cells, sex ratio, size of individuals (intertegular length and maximum head width), incidence of natural enemies, breadth and uniformity of food niche, and morphological characteristics of pollen grains. The study was conducted from April 2012 to March 2013, in an area of Cerrado in Uberlândia-MG (Experimental Station of Água Limpa). Females of Tetrapedia curvitarsis constructed their nests throughout the year (n= 45 collected nests), with no significant difference between seasons (U=12.50; n1=6, n2=6; p>0.05). The highest number of brood cells was observed in nests of greater length and diameter. The number of cells constructed per nest was constant between seasons (t=0.49; df= 43; p>0.05). The sex ratio did not differ significantly from 1:1 (χ2= 0.46; df= 1; p >0.05), indicating equal sexual allocation for both sexes throughout the year. The size of Tetrapedia curvitarsis had the effect on the season, i.e. males and females were significantly higher in the wet season. The females were significantly larger than males, only by the maximum head width. A low frequency of natural enemies in the nests was verified, prevailing Coelioxoides sp. in the dry season and Anthrax oedipus in the wet season. The analysis of larval food was performed for 22 nests, 11 nests provisioned in the dry season and 11 provisioned in the wet season. Pollen analysis of the larval food showed that Tetrapedia curvitarsis collected 22 pollen type of eight families (Asteraceae, Clusiaceae, Euphorbiaceae, Fabaceae, Lamiaceae, Malpighiaceae, Myrtaceae and Sapindaceae) as pollen sources, and used profusely the pollen type Kielmeyera in both seasons. Tetrapedia curvitarsis presented higher food niche breadth in the wet season (t = -43.947, df= 17516, p <0.05) and low similarity (39,05%) in the use of the pollen sources between seasons.The species used mainly pollen grains of medium and large sizes (H0,05, 22, 22, 22, 22= 42.488; p <0.001) and the collection of grains with the presence of spicules, staffs, maces or prismatic units was higher in the dry season (U= 99.50; n1= 11, n2= 11; p <0.05). In conclusion, verified that Tetrapedia curvitarsis is active throughout the year, has low rates of parasitism and that, although it explore different food sources, there was a predominance of pollen type Kielmeyera and use of grains from medium to large sizes, without spicules, staffs, maces and prismatic units.