Population genetic structure of orchid bees (Euglossini) in anthropogenically altered landscapes

Abstract

Habitat degradation and fragmentation are widespread phenomena in tropical regions. Negative effects on the biota are numerous, ranging from interruption of gene flow among populations, to the loss of genetic diversity within populations, to a decline in species richness over time. Orchid bees (Hymenoptera: Apidae: Euglossini) are of major conservation interest due to their function as pollinators of numerous orchid species and other tropical plants. Here, we used microsatellite markers to investigate the effects of geographic distance and habitat fragmentation on gene flow among populations. Populations of Euglossa dilemma in three geographic regionsthe Yucatán peninsula (Mexico), Veracruz (Mexico), and Florida (USA)-were genetically structured predominantly across the regions, with the strength of differentiation among populations being positively correlated with geographic distance. Within geographic regions only little substructure was found, suggesting that dispersal is substantial in the absence of geographic or ecological barriers. In a second study, patterns of genetic differentiation among eight species of Euglossa were not related to habitat fragmentation following deforestation in southern Mexico (Veracruz). Specifically, most bee populations in the 9,800 ha forest remnant of Los Tuxtlas (Volcano San Martin) were neither differentiated from, nor had less genetic diversity than, populations in near-continuous forest separated from Los Tuxtlas by 130 km of agricultural land. Either occasional long distance dispersal across open areas has buffered the expected genetic effects of fragmentation, or the history of fragmentation in southern Mexico is too recent to have caused measurable shifts in allelic composition.

Population genetics of orchid bees in a fragmented tropical landscape

“…championi are consistent with previous population genetic data on bees in the genus Euglossa. Zimmermann et al (2011) found low differentiation for eight species of Euglossa between sites separated by over 130 km of agricultural land, a much larger area than our study, in which the furthest forest fragments were 14 km apart. This study did not investigate levels of differentiation for any species in the genus Eulaema, a genus in which bees tend to be much larger.…”

“…A recent population genetic study of orchid bees in Mexico sought to tease apart the influences of habitat fragmentation and distance on genetic diversity and gene flow (Zimmermann et al 2011). These authors found low levels of genetic differentiation between sites separated by 130 km of agricultural land, and no difference in levels of differentiation between sites separated by forest or by agricultural land.…”

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

“…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.…”

“…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. Based on their findings, Suni and Brosi (2011) suggest that the mobility of orchid bees differs significantly among species.…”

“…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.…”