Acquisition of species-specific perfume blends: influence of habitat-dependent compound availability on odour choices of male orchid bees (Euglossa spp.)

Abstract

Male orchid bees (Euglossini, Apidae, Hymenoptera) expose species-specific blends of volatile chemicals (perfume bouquets) during their courtship display. The perfumes are acquired by collecting fragrant substances from environmental sources, which are then accumulated in specialised hind leg pouches. To balance the perfume composition, the males need to find and collect the required substances in specific relative amounts while facing seasonal, local or habitat-dependent differences in compound availability. Experience-dependent choice of odours, i.e. 'learned avoidance' of recently collected components, has been proposed as the mechanism that mediates the accumulation of the stereotypical compound ratios. In the present study, we used the presence of certain compounds in male hind leg pouches as proxy for the respective local compound availability, and investigated whether differences in content are correlated with differences in chemical choice assays. Our results suggest that volatile availability differs between localities (n = 16) as well as habitats (n = 2; coastal vs. inland) across the Yucatán peninsula, Mexico, for both studied species. Male Euglossa dilemma showed a pronounced preference for benzyl benzoate and eugenol at locations where those compounds were rare in hind leg extracts, as predicted by the learned avoidance model. No equivalent correlations were found for Euglossa viridissima. This is the first study to combine chemical analyses of perfumes with bioassays of odour choice. It strengthens the view that negative feedback from collected odours modifies future chemical choice and helps males to acquire specific perfume blends.

Macroevolution of perfume signalling in orchid bees

“…) and similarity to the species centroid increases with the number of compounds included (Pokorny et al . ). Additionally, because within‐species variability is required for sexual selection to act on male traits (e.g.…”

Olfactory specialization for perfume collection in male orchid bees

“…Species-specific preferences for collecting certain compounds are evident (Ackerman, 1989), resulting in distinct tibial blends (Eltz et al, 2005a). There is, however, broad overlap in the range of chemicals collected by different species (Ackerman, 1983a;Janzen et al, 1982;Pearson and Dressler, 1985) as well as geographical and seasonal shifts of preferences (Ackerman, 1989;Pokorny et al, 2013).…”

Perfume production in flowers of Angelonia salicariifolia attracts males of Euglossa annectans which do not promote pollination

“…This finding reinforces the idea that Euglossini are generalists regarding the available source (floral or non-floral source), but some species may be specialists regarding the kind of perfume they are attracted to or forage. Recently, Pokorny et al (2013) reported by means of perfume attraction assays that two species of Euglossa reacted differently to specific extract compounds. The experiments showed that only co-specific males were attracted when those volatiles were offered.…”

“…Recently, Cappellari et al (2009) included the family Plantaginaceae in the group of scent flowers visited by the male orchid bees. Other aromatic sources reported as perfume attractants for the Euglossini include tree trunks (Rebêlo and Garófalo 1991), rotting wood (Whitten et al 1993), roots (Ramírez et al 2002), fungi (Pearson and Dressler 1985;Cappellari and Harter-Marques 2010), leaf surfaces (Pemberton and Wheeler 2006) and also the hind leg of conspecific males (Carvalho Filho 2010, Pokorny et al 2013.…”