Geometric morphometrics of the wings of Amazonian species of Melipona (Illiger, 1806) (Hymenoptera: Apidae).

Identifying and classifying species of stingless Neotropical bees is not a trivial task and requires the help of taxonomists and substantial study and training time. Also, there is a lack of taxonomically useful characters to differentiate among the megadiverse Neotropical group of stingless bees, and to recognize variation. Based on that, we have been testing alternatives to a character-based, efficient taxonomic determination of stingless bees, and herein we performed exploratory analyses of wing shape variation using geometric morphometrics. Thus, we built a data set of photographs of the right anterior wing of 1628 individuals belonging to 11 species in the genus Melipona (Illiger 1806) taken from collection material deposited in entomological collections. We then conducted a Procrustes analysis, followed by a Principal Component Analysis (PCA) and by a Canonical Variable Analyses (CVA). The two first principal components of the PCA accounted for 68% of the variation of the wing shape, and the ordination displayed by the first component separated species of the subgenus Melikerria from the others. In the CVA, the first two canonical axes explained 88% of the wing shape variation found among species, and Melikerria appears as a separate group, apart from the other subgenera in the first canonical axis. Along the second axis species belonging to Eomelipona and Michmelia, and among the Michmelia species, and its species group fuliginosa formed well-separated clusters. The wing shape variation of Melipona supports the recognition of subgenera as currently proposed for Melipona.

Queens remate despite traumatic mating in stingless bees.

Males can control female reproduction using genital plugs to impede access by rivals. In social bees, ants, and wasps, plugging may involve traumatic mating, with females being harmed. In stingless bees, chances are that plugs may promote ovarian activan, and are thought to ensure single mating-a general tendency among the social Hymenoptera. However, understanding on relationships between mating plugs, traumatic mating, and mating systems in stingless bees remains limited. To address this, we (1) compared mated queens of 7 Neotropical species to understand the patterns of copulatory marks in females and (2) compared pre- and post-mating genitalia of males and females in Melipona fasciculata to depict plug functional morphology. Data revealed an unprecedented consequence of mating in stingless bees: the characteristic marks left by mating plugs on female abdomens and the inferences that can be made from them. To our surprise, in 1 species M. fasciculata we found that queens retain the plug long after mating, and may carry it for the rest of their lives. All the other 6 species retained the plug for only a short period. Remated queens were only found in M. seminigra, whose multiple copulatory marks match previous findings of polyandry in this species. Our study shows that queens can remate, and suggests that male genital morphology may determine in part the time persistence of plugs. We conclude that traumatic mating plugs do not fully prevent remating in stingless bees and that mating systems are not uniform in this group. Nonetheless, exceptional cases of facultative polyandry in social insects-for example, when mating plugs fail-may confirm a general tendency for single mating in close link with efficient mating plugs.

Everything you always wanted to know about gene flow in tropical landscapes (but were afraid to ask).

The bulk of the world's biodiversity is found in tropical regions, which are increasingly threatened by the human-led degradation of natural habitats. Yet, little is known about tropical biodiversity responses to habitat loss and fragmentation. Here we review all available literature assessing landscape effects on gene flow in tropical species, aiming to help unravel the factors underpinning functional connectivity in the tropics. We map and classify studies by focus species, the molecular markers employed, statistical approaches to assess landscape effects on gene flow, and the evaluated landscape and environmental variables. We then compare qualitatively and quantitatively landscape effects on gene flow across species and units of analysis. We found 69 articles assessing landscape effects on gene flow in tropical organisms, most of which were published in the last five years, were concentrated in the Americas, and focused on amphibians or mammals. Most studies employed population-level approaches, microsatellites were the preferred type of markers, and Mantel and partial Mantel tests the most common statistical approaches used. While elevation, land cover and forest cover were the most common gene flow predictors assessed, habitat suitability was found to be a common predictor of gene flow. A third of all surveyed studies explicitly assessed the effect of habitat degradation, but only 14 of these detected a reduced gene flow with increasing habitat loss. Elevation was responsible for most significant microsatellite-based isolation by resistance effects and a single study reported significant isolation by non-forested areas in an ant. Our study reveals important knowledge gaps on the study of landscape effects on gene flow in tropical organisms, and provides useful guidelines on how to fill them.

Insights into the role of age and social interactions on the sexual attractiveness of queens in an eusocial bee, Melipona flavolineata (Apidae, Meliponini).

The attraction of sexual partners is a vital necessity among insects, and it involves conflict of interests and complex communication systems among male and female. In this study, we investigated the developing of sexual attractiveness in virgin queens (i.e., gynes) of Melipona flavolineata, an eusocial stingless bee. We followed the development of sexual attractiveness in 64 gynes, belonging to seven age classes (0, 3, 6, 9, 15, 18 days post-emergence), and we also evaluated the effect of different social interactions (such as competition between queens and interactions with workers) on the development of attractiveness in other 60 gynes. We used the number of males that tried to mate with a focal gyne as a representative variable of its sexual attractiveness. During the essays, each gyne was individually presented to 10 sexually mature males, and during 3 min, we counted the number of males that everted their genitalia in response to the presence of a gyne. Here, we show that M. flavolineata gynes are capable to (i) maintain their sexual attractiveness for long periods through adult life, (ii) they need a minimum social interaction to trigger the development of sexual attractiveness, and (iii) that gynes express this trait only within a social context. We conclude that the effective occurrence of matings is conditional on potential social interactions that gynes experienced before taking the nuptial flight, when they are still in the nest. These findings bring insights into the factors determining reproductive success in social insects.