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Intraspecific geographic variation of fragrances acquired by orchid bees in native and introduced populations.

Ramírez SR, Eltz T, Fritzsch F, Pemberton R, Pringle EG, Tsutsui ND - J. Chem. Ecol. (2010)

Bottom Line: We recorded a total of 292 fragrance compounds from hind-leg extracts, and found that overall perfume composition was different for each population.We detected a pronounced chemical dissimilarity between native (Mesoamerica) and naturalized (U.S.) populations that was driven both by proportional differences of common compounds as well as the presence of a few chemicals unique to each population group.By comparing incidence values and consistency indices across populations, we identify putative functional compounds that may play an important role in courtship signaling in this species of orchid bee.

View Article: PubMed Central - PubMed

Affiliation: Environmental Science, Policy & Management, University of California Berkeley, 137 Mulford Hall #3114, Berkeley, CA 94720, USA. sramirez77@berkeley.edu

ABSTRACT
Male orchid bees collect volatiles, from both floral and non-floral sources, that they expose as pheromone analogues (perfumes) during courtship display. The chemical profile of these perfumes, which includes terpenes and aromatic compounds, is both species-specific and divergent among closely related lineages. Thus, fragrance composition is thought to play an important role in prezygotic reproductive isolation in euglossine bees. However, because orchid bees acquire fragrances entirely from exogenous sources, the chemical composition of male perfumes is prone to variation due to environmental heterogeneity across habitats. We used Gas Chromatography/Mass Spectrometry (GC/MS) to characterize the perfumes of 114 individuals of the green orchid bee (Euglossa aff. viridissima) sampled from five native populations in Mesoamerica and two naturalized populations in the southeastern United States. We recorded a total of 292 fragrance compounds from hind-leg extracts, and found that overall perfume composition was different for each population. We detected a pronounced chemical dissimilarity between native (Mesoamerica) and naturalized (U.S.) populations that was driven both by proportional differences of common compounds as well as the presence of a few chemicals unique to each population group. Despite these differences, our data also revealed remarkable qualitative consistency in the presence of several major fragrance compounds across distant populations from dissimilar habitats. In addition, we demonstrate that naturalized bees are attracted to and collect large quantities of triclopyr 2-butoxyethyl ester, the active ingredient of several commercially available herbicides. By comparing incidence values and consistency indices across populations, we identify putative functional compounds that may play an important role in courtship signaling in this species of orchid bee.

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Overlaid total ion current chromatograms corresponding to hind-leg (black) and labial gland (grey) extracts from the same individual bee. Compounds present in both hind legs and labial glands were considered endogenous in origin and thus were excluded from the analysis. The Y axis indicates ion abundance
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Fig2: Overlaid total ion current chromatograms corresponding to hind-leg (black) and labial gland (grey) extracts from the same individual bee. Compounds present in both hind legs and labial glands were considered endogenous in origin and thus were excluded from the analysis. The Y axis indicates ion abundance

Mentions: Fragrance Extraction and Chemical Analysis Male bees were cold-anaesthetized either on ice or inside a freezer (−20°C) for 5 min immediately prior to dissection. Right hind tibiae were removed with clean dissecting scissors and deposited in 2 ml screw-cap autosampler vials (Agilent Technologies, Santa Clara, CA, USA), which contained 500 μl of hexane to extract the fragrances. To distinguish between exogenous volatiles and endogenous male-produced lipids, acetates, and straight-chain hydrocarbon compounds, labial glands were dissected, extracted, and analyzed from a subset of individuals (N = 43) using the same protocol described above. All compounds present in both leg extracts and labial glands were excluded from the analysis (Fig. 2). Extracted samples were stored at −20°C until subsequent GC/MS analysis. Voucher specimens of all samples were either pinned or deposited in 200 proof ethanol.Fig. 2


Intraspecific geographic variation of fragrances acquired by orchid bees in native and introduced populations.

Ramírez SR, Eltz T, Fritzsch F, Pemberton R, Pringle EG, Tsutsui ND - J. Chem. Ecol. (2010)

Overlaid total ion current chromatograms corresponding to hind-leg (black) and labial gland (grey) extracts from the same individual bee. Compounds present in both hind legs and labial glands were considered endogenous in origin and thus were excluded from the analysis. The Y axis indicates ion abundance
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908462&req=5

Fig2: Overlaid total ion current chromatograms corresponding to hind-leg (black) and labial gland (grey) extracts from the same individual bee. Compounds present in both hind legs and labial glands were considered endogenous in origin and thus were excluded from the analysis. The Y axis indicates ion abundance
Mentions: Fragrance Extraction and Chemical Analysis Male bees were cold-anaesthetized either on ice or inside a freezer (−20°C) for 5 min immediately prior to dissection. Right hind tibiae were removed with clean dissecting scissors and deposited in 2 ml screw-cap autosampler vials (Agilent Technologies, Santa Clara, CA, USA), which contained 500 μl of hexane to extract the fragrances. To distinguish between exogenous volatiles and endogenous male-produced lipids, acetates, and straight-chain hydrocarbon compounds, labial glands were dissected, extracted, and analyzed from a subset of individuals (N = 43) using the same protocol described above. All compounds present in both leg extracts and labial glands were excluded from the analysis (Fig. 2). Extracted samples were stored at −20°C until subsequent GC/MS analysis. Voucher specimens of all samples were either pinned or deposited in 200 proof ethanol.Fig. 2

Bottom Line: We recorded a total of 292 fragrance compounds from hind-leg extracts, and found that overall perfume composition was different for each population.We detected a pronounced chemical dissimilarity between native (Mesoamerica) and naturalized (U.S.) populations that was driven both by proportional differences of common compounds as well as the presence of a few chemicals unique to each population group.By comparing incidence values and consistency indices across populations, we identify putative functional compounds that may play an important role in courtship signaling in this species of orchid bee.

View Article: PubMed Central - PubMed

Affiliation: Environmental Science, Policy & Management, University of California Berkeley, 137 Mulford Hall #3114, Berkeley, CA 94720, USA. sramirez77@berkeley.edu

ABSTRACT
Male orchid bees collect volatiles, from both floral and non-floral sources, that they expose as pheromone analogues (perfumes) during courtship display. The chemical profile of these perfumes, which includes terpenes and aromatic compounds, is both species-specific and divergent among closely related lineages. Thus, fragrance composition is thought to play an important role in prezygotic reproductive isolation in euglossine bees. However, because orchid bees acquire fragrances entirely from exogenous sources, the chemical composition of male perfumes is prone to variation due to environmental heterogeneity across habitats. We used Gas Chromatography/Mass Spectrometry (GC/MS) to characterize the perfumes of 114 individuals of the green orchid bee (Euglossa aff. viridissima) sampled from five native populations in Mesoamerica and two naturalized populations in the southeastern United States. We recorded a total of 292 fragrance compounds from hind-leg extracts, and found that overall perfume composition was different for each population. We detected a pronounced chemical dissimilarity between native (Mesoamerica) and naturalized (U.S.) populations that was driven both by proportional differences of common compounds as well as the presence of a few chemicals unique to each population group. Despite these differences, our data also revealed remarkable qualitative consistency in the presence of several major fragrance compounds across distant populations from dissimilar habitats. In addition, we demonstrate that naturalized bees are attracted to and collect large quantities of triclopyr 2-butoxyethyl ester, the active ingredient of several commercially available herbicides. By comparing incidence values and consistency indices across populations, we identify putative functional compounds that may play an important role in courtship signaling in this species of orchid bee.

Show MeSH