Body Size and Its Relation to the Foraging Schedules of Social Wasps.

The foraging behavior of social wasps may vary throughout the day in response to different factors, including environmental variation and interspecific interactions. Body size is known to play a critical role in determining daily activity patterns in ecological communities. However, the body size characteristics of most species of social wasps is poorly known, as well the relationship between body size and foraging schedules. In this study, we evaluated the extent to which body size determines the patterns of daily activity in a community of social wasps. We found a high temporal overlap in most of the species pairs tested. The pattern of daily foraging activity fits a bimodal distribution for the majority of the species. Moreover, we found a relationship between body and foraging time; in general, smaller species tended to begin foraging in the early hours of the morning, in contrast to larger wasps, which began foraging later. These results suggest that patterns of foraging activity in social wasps are likely to be the result of complex interactions between many different factors, including body size.

Genetic diversity of Angiopolybia pallens (Lepeletier) (Hymenoptera, Vespidae, Polistinae) explained by the disjunction of South American rainforests.

Angiopolybia pallens is a swarm-founding wasp that occurs in Atlantic and Amazonian rainforests, which have been isolated from each other by a large arid corridor in central Brazil since the Tertiary. In this study, we used data from polymerase chain reaction-restriction fragment length polymorphism of 16S rDNA to infer some aspects of the genetic diversity and evolutionary history of this social wasp population. Samples collected across the species range in both rainforests showed remarkable differences that separated them into two distinct haplogroups. However, some samples from isolated areas in northeastern Bahia were more related to Amazonian lineages than to southern Bahia populations. Vicariant divergenc is discussed under South American rainforests biogeographical proposals.

Niche Overlap and Network Specialization of Flower-Visiting Bees in an Agricultural System.

Different resource use strategies manifest as differences in the realized niches of species. Niche segregation may involve several dimensions of the niche, such as diet, space, and time. We measured the level of redundancy and complementarity of a bee-plant interaction network in an agricultural system. Because flower resource diversity is high and resource abundance associated with flowering phenology varies throughout the year, we hypothesized that trophic overlap in the community would be low (i.e., high niche complementarity). In contrast, we expected a combination of physiological constraints and exploitation competition to create high temporal overlap, leading to high redundancy in the time of use of floral resources. Dietary overlap was low (NOih = 0.18): niches of 88% of species pairs had less than 30% overlap. In contrast, temporal overlap was intermediate (NOih = 0.49): niches of 65% of species pairs had 30% to 60% overlap. Network analysis showed that bees separated their dietary niches and had intermediate complementary specialization (H2' = 0.46). In terms of their temporal niches (H2' = 0.12), bees were generalists, with high temporal redundancy. Temperature was not a key factor in the determination of niche overlap, suggesting that environmental factors do not likely have a primary role in determining high redundancy in the temporal use of floral resources. Rather, temporal overlap is likely associated with the timing of nectar production by flowers. Our results suggest that bees partition a wide variety of available floral resources, resulting in low dietary overlap and intermediate temporal overlap.

Mitochondrial DNA variability in populations of Centris aenea (Hymenoptera, Apidae), a crop-pollinating bee in Brazil.

Centris spp are oil-collecting solitary bees that are valuable pollinators of crops such as Brazil nut, cashew, and acerola. We investigated the genetic variability of populations of C. aenea in the northeastern region of Brazil. Total DNA was extracted from 59 individuals from 6 locations in the States of Pernambuco and Bahia and a 600-650-bp fragment of the mitochondrial COI/COII region amplified by PCR, followed by digestion with the restriction enzymes DraI and SspI. PCR-RFLP analysis revealed eight different haplotypes among the populations. Haplotype A1, revealed by DraI, was the most frequent (50%), and haplotypes A3 and A4 were exclusive to Feira de Santana, Bahia and Morro do Chapéu, Bahia, respectively. Among the haplotypes revealed by SspI, B2 was the most frequent (37%) and B3 was exclusive to Feira de Santana. This information revealing high haplotype diversity will be useful for developing management strategies for Centris, especially because of increasing interest in the rearing and/ or relocation of these bees for crop pollination.

An adaptive view of caste differentiation in the neotropical wasp Polybia (Trichothorax) sericea Olivier (Hymenoptera: Vespidae).

The tribe Epiponini comprehends the swarm-founding Neotropical wasps, with several species endemic to Brazil, which are extremely important in studies of social evolution of wasps. The Epiponini diverge in several ways from the definitions of high eusociality, since caste syndromes range from species without morphological caste differentiation to those with complete caste dimorphism, and all species are polygynous. Frequently, indirect studies based on morphometry and physiology are the only solutions to collect data regarding the natural history and caste system in this tribe, since most species are extremely aggressive and build enveloped nests, usually in places of difficult access. We analyzed morphological parameters in seven colonies of the Epiponini species Polybia (Trichothorax) sericea Olivier in different phases of colonial development. Nine body variables were taken and females were classified according to their ovary development and spermathecal contents. The results showed that caste differences in this species are based on a contrast among variables: queens have larger mesosoma and abdomen, but are smaller in head width and wing length. These results suggest that morphological caste differentiation in this species is based mainly on body shape. We considered this combination of characters as being adaptive. We also showed that caste differences varied according to the colony cycle, with more conspicuous differences when queen number is reduced.