A Comparison of Social Bee-Plant Networks between Two Urban Areas.

In the last decade, several studies demonstrated the effectiveness of ecological network analysis to a better understanding of the structure bee-plant interaction networks; however, such approaches involving urban areas are still scarce. Here, we analyzed two assemblages of corbiculate bees (Apoidea, Apidae) in two geographically distinct urban areas in Brazil. In both study areas, apid bees visiting flowers were captured with an insect net. Surveys were performed biweekly and alternately in each area, over a 1-year period. Both urban areas were very similar for most indices. The two social bee-plant networks were significantly nested, a pattern usually described for bee-plant networks and somehow expected in our study, considering the recognized behavior of social apid bees in exploring a wide range of plant species. The modularity measures were low and very similar for the networks of both urban areas, a finding that could be due at least in part to the low phylogenetic distance between corbiculate bees and the broad dietary habits of the social apid bees. Network-level indices showed that both bee assemblages had a relatively low niche overlap, indicating that the set of social apid species studied exploited differently the arrays of plants available. Species level index (resource range) showed that in both urban areas, Trigona spinipes (Fabr.) and Apis mellifera L. showed the higher number of interactions, a result that demonstrates the importance of these species in social bee-plant interaction networks in urban areas. Similarly to other ecosystems, these two apid species behaved as super-generalists in the two urban areas surveyed herein.

Pollination of tomatoes by the stingless bee Melipona quadrifasciata and the honey bee Apis mellifera (Hymenoptera, Apidae).

The pollination effectiveness of the stingless bee Melipona quadrifasciata and the honey bee Apis mellifera was tested in tomato plots. The experiment was conducted in four greenhouses as well as in an external open plot in Ribeirão Preto, SP, Brazil. The tomato plants were exposed to visits by M. quadrifasciata in one greenhouse and to A. mellifera in another; two greenhouses were maintained without bees (controls) and an open field plot was exposed to pollinators in an area where both honey bee and stingless bee colonies are abundant. We counted the number of tomatoes produced in each plot. Two hundred tomatoes from each plot were weighed, their vertical and transversal circumferences were measured, and the seeds were counted. We collected 253 Chrysomelidae, 17 Halictidae, one Paratrigona sp, and one honey bee from the flowers of the tomato plants in the open area. The largest number of fruits (1414 tomatoes), the heaviest and largest tomatoes, and the ones with the most seed were collected from the greenhouse with stingless bees. Fruits cultivated in the greenhouse with honey bees had the same weight and size as those produced in one of the control greenhouses. The stingless bee, M. quadrifasciata, was significantly more efficient than honey bees in pollinating greenhouse tomatoes.

Bee communities (Hymenoptera: Anthophila) of the "Cerrado" ecosystem in São Paulo State, Brazil.

Five surveys of the bee communities in four "Cerrado" ecosystem reserves in São Paulo State were compared for species richness and similarity. These areas are fragment vegetation reser-ves located in the Cerrado Corumbataí Reserve (Corumbataí), Jataí Ecological Park (Luiz Antônio), Cajuru (Cajuru), and Vassununga State Park - "Gleba de Cerrado de Pé-de-Gigante" (Santa Rita do Passa Quatro). The methodology consisted of capturing bees foraging on flowers along transects, though with small differences between surveys. These "cerrado" areas have a large number of species of native bees, which are important pollinators in several Brazilian ecosystems. The community of bees varied among these different fragments. Based on 500 individuals (standardized by rarefaction), Cajuru, Corumbataí 1 and Corumbataí 2 were the areas with highest species richness, and Jataí and Pé-de-Gigante had the lowest species richness in the bee communities. The bee faunas of Corumbataí 2 and Pé-de-Gigante had the highest similarity, forming a group with the bee fauna of Cajuru. The bee faunas of Corumbataí 1 and Jataí were isolated from this group. We found that the bee species richness and similarity found in these "cerrado" areas cannot be explained by general factors such as the size of the fragment, the species richness of plants and the distance between the areas. Therefore, we suppose that local factors that differ among areas, such as interactions between populations, and competition and interference from surrounding areas influence and determine bee species richness and similarity in these reserves.

Intrinsic colony conditions affect the provisioning and oviposition process in the stingless bee Melipona scutellaris.

The cell provisioning and oviposition process (POP) is a unique characteristic of stingless bees (Meliponini), in which coordinated interactions between workers and queen regulate the filling of brood cells with larval resources and subsequent egg laying. Environmental conditions seem to regulate reproduction in stingless bees; however, little is known about how the amount of food affects quantitative sequences of the process. We examined intrinsic variables by comparing three colonies in distinct conditions (strong, intermediate and weak state). We predicted that some of these variables are correlated with temporal events of POP in Melipona scutellaris colonies. The results demonstrated that the strong colony had shorter periods of POP.

Differences between the quality of strawberries (Fragaria x ananassa) pollinated by the stingless bees Scaptotrigona aff. depilis and Nannotrigona testaceicornis.

We investigated the success of two stingless bee species in pollinating strawberries in greenhouses. Three greenhouses and one open field area were used; one greenhouse had only strawberry plants (control), another (G1) had three colonies of Scaptotrigona aff. depilis and another (G2) had three colonies of Nannotrigona testaceicornis. In the open field area, the flowers could be visited by any bee. The total production of fruits was counted and a random sample (N = 100) from each area was used to measure weight, length, circumference, and achenes number (N = 5). The percentages of deformed strawberries were: 23% (no bees); 2% (greenhouses with bees) and 13% (open field). The strawberries from the greenhouse with N. testaceicornis and the open field were heavier than those from the greenhouses with no bees and with S. depilis. The fruit circumference was largest in the greenhouses with bees. The achenes number did not differ among the experimental areas. The strawberries produced in the greenhouses with stingless bees had more quality and greater commercial value than the fruits produced in the open field area and the greenhouse without bees. We conclude that stingless bees are efficient pollinators of strawberry flowers cultivated in greenhouses.