Chemical niche differentiation among sympatric species of orchid bees

Abstract

Abstract. Male Neotropical orchid bees (Euglossini ) collect volatile substances (fragrances) from flowers and other sources (e.g., decaying wood) and store them in specialized hind tibial pockets. The accumulated chemicals are later emitted during courtship display, presumably to lure conspecific females for mating. We analyzed tibial fragrances of males of 15 sympatric Panamanian species in the genus Euglossa to test whether communities of euglossine bees are chemically structured, and to elucidate whether male fragrance signals evolve to convey premating isolation. Our analysis revealed substantial chemical disparity among all lineages. Disparity was mediated by compounds that were exclusive to certain species but also by differences in relative quantity of shared compounds. We mapped tibial fragrance compounds present in each species on a DNA-based phylogeny (reconstructed using partial sequences of COI, EF1-a, ArgK, and Pol-II ) and found that most dominant compounds were highly homoplasious. In an analysis of chemical differentiation in relation to phylogenetic divergence through time, disparity was greater than expected from a null model at any point during evolutionary history, suggesting that diversifying selection has shaped fragrance phenotypes. Notably, chemical disparity was greater within recently diverged lineages than among them, suggesting that chemical preferences in orchid bees evolved rapidly in the early stages of species divergence. We postulate communication interference as the possible mechanism behind the observed fragrance differentiation, which may be the product of reproductive character (fragrance) displacement. Our findings are consistent with the hypothesis that male fragrance signals evolve to convey premating isolation.

Olfactory specialization for perfume collection in male orchid bees

“…In fact, a pattern consistent with diversifying selection in sympatry was found for male orchid bee perfumes (Zimmermann et al, 2009). The chemical composition of blends collected by 15 sympatric species of Euglossa from central Panama were more different from each other than expected under a model of neutral phenotypic evolution, and perfume disparity between species was particularly pronounced between closely related lineages (Zimmermann et al, 2009).…”

“…In fact, a pattern consistent with diversifying selection in sympatry was found for male orchid bee perfumes (Zimmermann et al, 2009). The chemical composition of blends collected by 15 sympatric species of Euglossa from central Panama were more different from each other than expected under a model of neutral phenotypic evolution, and perfume disparity between species was particularly pronounced between closely related lineages (Zimmermann et al, 2009). Based on these findings, we hypothesized that the outstanding divergence of fragrances observed among closely related species is mediated by an underlying species-specific sensory adaptation that evolved in response to reproductive character displacement at the sensory level.…”

“…The process of fragrance collection involves a range of morphological, biochemical and behavioral adaptations. Specialized hind-tibial pouches enable males to store volatile substances over long periods of time, ultimately accumulating complex blends of species-specific 'perfumes' (Eltz et al, 2005a;Zimmermann et al, 2009). Finally, the perfumes are actively exposed by males at the sites where mating takes place (Eltz et al, 2005b) and probably serve as pheromonal analogues (Zimmermann et al, 2006).…”

The Role of the Agricultural Matrix: Coffee Management and Euglossine Bee (Hymenoptera: Apidae: Euglossini) Communities in Southern Mexico

“…Orchid bees pollinate roughly 650 species of orchids, as well as other plant species in about 30 different families, including some economically important crops such as Brazil nuts and rubber trees (Dressler 1982;Ackerman 1983;Roubik & Hanson 2004;Ackerman & Roubik 2012;Briggs et al 2013). Males visit flowers to collect aromatic compounds or associated chemicals (Dodson et al 1969;Roubik & Hanson 2004) that appear to be associated with species recognition, competition, and mate choice (Zimmermann et al 2009). This behavior makes it possible to sample orchid bee males with aromatic compounds.…”

A Checklist of the Orchid Bees of Nicaragua (Hymenoptera: Apidae: Euglossini)

“…These fragrances appear to be associated with species recognition, competition, and mate choice (Zimmermann et al 2009). Orchid bees are best known for their associations with orchids, and are important pollinators of roughly 650 species in this plant family.…”