Genetic differentiation of the Euglossini (Hymenoptera, Apidae) populations on a mainland coastal plain and an island in southeastern Brazil

Abstract

Euglossini bees are among the main pollinators of plant species in tropical and subtropical forests in Central and South America. These bees are known as long-distance pollinators due to their exceptional flight performance. Here we assessed through microsatellite loci the gene variation and genetic differentiation between populations of four abundant Euglossini species populations sampled in two areas, Picinguaba (mainland) and Anchieta Island, Ubatuba, São Paulo State, southeastern Brazil. There was no significant genetic differentiation between the island and mainland samples of Euglossa cordata (Fst = 0.008, P = 0.60), Eulaema cingulata (Fst = 0.029, P = 0.29) and Eulaema nigrita (Fst = 0.062, P = 0.38), but a significant gene differentiation between mainland and island samples of Euglossa stellfeldi (Fst = 0.028, P = 0.016) was detected. As expected, our results showed that the water body that separates the island from the mainland does not constitute a geographic barrier for these Euglossini bees. The absence of populational structuring of three out the four species studied corroborates previous reports on those bees, characterized by large populations, with high gene diversity and gene flow and very low levels of diploid males. But the Eg. stellfeldi results clearly point that dispersal ability is not similar to all euglossine bees, what requires the development of different conservationist strategies to the Euglossini species.

Mitochondrial DNA of Euglossa iopoecila (Apidae, Euglossini) reveals two distinct lineages for this orchid bee species endemic to the Atlantic Forest

“…The pattern of isolation by distance exhibited by E. iopoecila differs from that found for most euglossine species studied so far (Freiria et al 2012;Rocha-Filho et al 2013;Boff et al 2014;Suni et al 2014). Only Zimmermann et al (2011) and Suni and Brosi (2011), in their respective studies of Euglossa dilemma populations in Mexico and E. bombiformis in Costa Rica, detected a significant positive correlation between genetic distance and geographical distance for these species.…”

“…Considering our results, the pattern of isolation by distance exhibited by E. iopoecila also suggests that this orchid bee species shows limited dispersal ability when compared with other euglossine species. Despite this, the estimates of F ST and D est for E. iopoecila revealed by microsatellite markers did not differ conspicuously from those reported for populations of other euglossine species (Zimmermann et al 2011;Freiria et al 2012;Rocha-Filho et al 2013;Boff et al 2014;Suni et al 2014). These authors also used microsatellite markers to assess the population structure of different euglossine species and detected either a lack of genetic differentiation in the populations or levels of differentiation ranging from low to moderate.…”

“…Additional information on the study sites can be found in Ramalho et al (2009), Rocha-Filho et al (2013 and Boff et al (2014). …”

“…These authors proposed several possible causes for the discrepant cyto-nuclear patterns found for the three orchid bee species studied, including a longterm male-biased dispersal resulting in panmixia in the nuDNA and genetic structure in the mtDNA. Indeed, different authors have already pointed out males as the disperser sex in euglossine bees (Cerântola et al 2011;Rocha-Filho et al 2013). For this reason, it was suggested that dispersal differences between both sexes is a matter that should be better investigated by comparing genetic differentiation among Euglossini populations based on both nuclear and mitochondrial genomes (Cerântola et al 2011).…”

“…Actually, the latter author reports what may be the first documented local extinction for an orchid bee species, endemic to Atlantic Forest (AF) and dependent on forest areas. However, contrary to what would be expected of bees considered sensitive to habitat disturbance, most population genetic studies on euglossine bees have shown that the majority of the species investigated exhibit high levels of genetic diversity and, at most, modest genetic structuring (Zimmermann et al 2011;Rocha-Filho et al 2013;Boff et al 2014;Suni et al 2014). In all these studies, genetic analyses were based mainly on nuclear markers.…”