Exploitation of Floral Resources and Niche Overlap within an Oil-collecting Bee Guild (Hymenoptera, Apidae) in a Neotropical Savanna

Oil bees exploit host plants for resources to feed the adults and offspring, as well as for the construction of their nests. The aim of the current study is to investigate how the species in this guild distribute their foraging effort, and the range in their niche overlap levels. The bees were sampled for six months, during their visits to the flowers in a savanna (“cerrado”). These oil-bee species explored the floral resources provided by 13 plant species. The trophic niche of the most abundant species, Centris aenea Lepeletier, was relatively narrow, similarly to those of Epicharis species. Low overlap of trophic niches (TrNO≤30%) was most commonly found. The distribution of bee visits to the host plants revealed redundancy in the floral resource exploitation. However, the foraging concentration levels in some key plants were different for distinct oil-bee species, and it contributed to the low overlap of niches between many pairs of specie

Centris aenea (Hymenoptera, Apidae): a Ground-nesting Bee with High Pollination Efficiency in Malpighia emarginata DC (Malpighiaceae)

This study aimed to assess the efficiency of Centris aenea Lepeletier as pollinator of Malpighia emarginata DC. The pollination efficiency was determined according to three criteria: 1) the pollen deposition rate of M. emarginata and other plant species on the thorax ventral region of females, 2) the rate of M. emarginata fruit set after a single visit, and 3) the pollen deposition rate on the stigma after one single visit. 59% of the pollen grains deposited on the ventral region of C. aenea came from flowers of M. emarginata. The fruit set after a single visit by C. aenea (21%) was much higher than that reported previously for Centris tarsata Smith. We argue that pollination efficiency of C. aenea can be related to its body size, since that females of C. aenea can carry larger amounts of pollen grains of M. emarginata than C. tarsata, as well females of C. aenea are able to touch a larger stigma area, resulting in higher fruit sets after a single visit. Our study suggests that only one visit by C. aenea ensures fruit set in M. emarginata

Cavity Length Affects the Occupation of Trap-Nests by Centris analis and Tetrapedia diversipes (Hymenoptera: Apidae)

The ideal cavity dimensions for neotropical cavity-nesting bees with the potential to be managed as pollinators have not been getting proper attention. We investigated whether the occupancy of trap-nests by Centris analis Fabricius and Tetrapedia diversipes Klug, and other nesting aspects, are affected by different trap-nest length. The used trap-nests were cardboard tubes 5, 10, 15 and 20 cm in length, and Ø 8 mm. Occupation rates of 10-cm trap-nests by C. analis was higher than that of the 5-cm ones (χ2=11.17, gl=1, p<0.001). On the other hand, there was not difference between the occupation rates of 10 and 15-cm long trap-nests (χ2=0.51, gl=1, p=0.48), and between the ones measuring 15 and 20 cm long (χ2=1.36, gl=1, p=0.24). T. diversipes occupied a smaller number of 5-cm trap-nests than the 10-cm ones (χ2=1.52, gl=1, p=0.22), as well as that the 15-cm ones were more occupied than the 10-cm trap-nests (χ2=4.23, gl=1, p=0.04); moreover, there was not difference between the occupation of 15 and 20-cm trap-nests (χ2=0.28, gl=1, p=0.59). Both species showed higher rates of dead immatures in nests set in the shortest trap-nests, whereas these mortality rates were lower in the longest ones. By taking into consideration that there was not significant difference in many of the assessed parameters in comparison to values recorded for 15 and 20-cm long trap-nests, it seems likely to recommend the adoption of 10-cm long trap-nests for C. analis reproduction in agricultural sites that depend on the pollination service provided by this bees species

Special Issue on Stingless bees: Integrating basic biology and conservation

It is easy to see why stingless bees (Meliponini) were chosen for this special issue, entitled Stingless bees: Integrating basic biology and conservation. Interest in these bees is increasing each day, with their role as ecosystemservices providers in the pollination of wild and cultivated plants, and their fascinating biology and social behavior. Yet, despite having been kept by the Native Americans for hundreds of years for their honey, they remain much understudied compared to their better known relatives, the bumblebees and honeybees. This is in part due to their massive biodiversity, with known species now numbering over 500 – all with a tropical distribution. The diversity and rich social behavior of the stingless bees has often been compared to the knowledge of the other group of eusocial bees, including the bumblebees (Bombini) and honeybees (Apini). Yet, the development of new scientific techniques and research methods, and progress in deciphering their phylogeny, now allows for an updated interpretation of the evolution, biology and conservation of Meliponini bees

Morphometric Variability among Populations of Euglossa cordata (Hymenoptera: Apidae: Euglossini) from Different Phytophysiognomies

Geometric morphometrics is a tool capable of measuring the response of organisms to different environmental pressures. We tested the hypothesis that E. cordata wing morphometry, as an indicator of response to environmental pressure, it would vary depending on habitat changes, in the Atlantic Forest, Savanna and dry forest (Caatinga). For analysis of wing shape and size, 18 landmarks were digitized at the intersections of the wing veins 348 individuals. Except for the two populations sampled in Chapada Diamantina, the wing shape had significant statistical variations among the populations (p < 0.05). The wing size variation was also statistically significant among populations (p < 0.05).  Although E. cordata is a species tolerant to different environments, the observed morphometric variability may be related to population adaptations to the conditions of each phytophysiognomy

Centris aenea (Hymenoptera, Apidae): a Ground-nesting Bee with High Pollination Efficiency in Malpighia emarginata DC (Malpighiaceae)

This study aimed to assess the efficiency of Centris aenea Lepeletier as pollinator of Malpighia emarginata DC. The pollination efficiency was determined according to three criteria: 1) the pollen deposition rate of M. emarginata and other plant species on the thorax ventral region of females, 2) the rate of M. emarginata fruit set after a single visit, and 3) the pollen deposition rate on the stigma after one single visit. 59% of the pollen grains deposited on the ventral region of C. aenea came from flowers of M. emarginata. The fruit set after a single visit by C. aenea (21%) was much higher than that reported previously for Centris tarsata Smith. We argue that pollination efficiency of C. aenea can be related to its body size, since that females of C. aenea can carry larger amounts of pollen grains of M. emarginata than C. tarsata, as well females of C. aenea are able to touch a larger stigma area, resulting in higher fruit sets after a single visit. Our study suggests that only one visit by C. aenea ensures fruit set in M. emarginata.</em

Bee Life in the City: an Analysis of the Pollen Provisions of Centris (Centris) flavifrons (Centridini) in an Urban Area

Due to deforestation and fragmentation of ecosystems, the management of bee populations targeting pollination services is increasingly urgent. Because urban environments are stressful, the dietary knowledge in such areas can help to cope with this issue in the near future. Using palynological analysis the floral resources used by Centris flavifrons, an important pollinator of crops and native plants was studied in an urban area. Byrsonima sericea type, Solanum paniculatum type, Cestrum type, and Myrcia type 1 together accounted for more than 93% of pollen grains foraged by females. It is noteworthy that this bee population depends on few plant species both for pollen and for oil. Furthermore, females showed flexibility to replace the primary pollen source in different breeding seasons, as well as one female could provision different cells in the same nest with different predominant pollen types. It is highlighted the importance of wastelands for keeping bee populations in urban areas

The Similar Usage of a Common Key Resource Does Not Determine Similar Responses by Species in A Community of Oil-collecting Bees

Variations in abundance and species richness among communities are often determined by interactions between biotic and abiotic factors. However, for communities composed of species that share a common specialization (such as similar foraging adaptations) it may be a key ecological factor involved in the common specialization that affects community variations. To evaluate this possibility, we characterized the guild of oil-collecting bees of a Neotropical savanna in Brazil and tested whether differences in Byrsonima abundance and availability of floral oil explain differences in species richness and abundance of oil-collecting bees of different tribes. Both the number of species and total abundance of Centridini species increased with the abundance of Byrsonima. One plausible explanation for the stronger adjustment between the abundance of Centridini and Byrsonima is that the abundance of these plants affects not only the availability of floral oil, but also of pollen. These findings indicate that the existence of a common specialization among different species does not homogenize their response to variations in a common explored resource

Species Richness and Diversity in Bee Assemblages in a Fragment of Savanna (Cerrado) at Northeastern Brazil

The conservation of the fauna of bees inhabiting the Brazilian savanna is threatened due to changes in land use in the last decades. We investigated the composition, species richness and abundance of a bee assemblage in the vicinity of the Chapada Diamantina National Park. In addition, we compiled data on composition and diversity from another bee assemblage located in the same portion of the Cerrado, which was previously investigated by one of us almost 30 years ago, in order to produce a more complete panorama on beta diversity of bees in this region. We used a non-metric multidimensional scaling ordination analysis (NMDS) to compare composition of bee assemblages from diff erent types of open vegetation. We recorded 77 bee species (H’ = 2.95; J = 0.68), 42% of them were singletons. We collected slightly more than half of the species and 60% of the genera recorded in the bee assemblage studied three decades ago. H’ was signifi cantly lower in our area than in the previous study (t = 8.588, p &lt;0.001), but equitability (J) was very similar. Several factors may contribute to these diff erences, including local diff erences in bee assemblage composition, diff erences in the probability of capturing the diff erent species (many rare species), factors affecting the sampling itself, and perhaps species loss over the three decades separating the two studies. The magnitude of species loss is difficult to assess because the two studies were not carried out exactly in the same area and there were differences in sampling time and sampling effort