Subtle Chemical Variations with Strong Ecological Significance: Stereoselective Responses of Male Orchid Bees to Stereoisomers of Carvone Epoxide

The Neotropical orchid genus Sarcoglottis comprises ~40 species, which emit strong floral scents, presumably involved in pollinator attraction. Information on basic aspects of its natural history is scant, with the few studies available so far pointing to nectar‐seeking orchid bees as pollinators. Here, we investigated the reproductive biology of Sarcoglottis acaulis, addressing the ecological meaning of its floral scent. In Atlantic Forest fragments of NE Brazil, we described the floral biology, determined the breeding system and recorded the pollinators of S. acaulis. Additionally, we chemically characterized its floral scent and assessed its role on pollinator attraction. Although self‐compatible, S. acaulis depends on pollinators to boost fruit set. Male orchid bees of Eulaema atleticana and E. niveofasciata were the only recorded pollinators. They foraged for nectar only, in spite of the strong scent emitted by S. acaulis flowers. The floral scent is composed of six compounds, of which geraniol and nerol elicited electroantennographic responses in Eulaema bees. A synthetic mixture of these compounds attracted Eulaema bees in field assays but did not trigger the stereotyped scent‐gathering behaviour. The floral scent of S. acaulis acts in signalling and nectar is the sole reward for pollinators. Despite the low pollinator frequency, S. acaulis shows a high fruit set (77%), particularly when compared to other orchids. Attributes such as pollinia that release small pollen loads, allowing a single pollinia‐carrying bee to pollinate several flowers, low amount of nectar, steady‐state flowering and traplining behaviour of pollinators, might act together to assure this outstanding fruit set.

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“…In general, the compounds which depolarize the bees’ antennae play a behavioural role (Brandt et al . 2019).…”

Section: Methodsmentioning

confidence: 99%

Pollination of the strongly scented Sarcoglottis acaulis (Orchidaceae) by male orchid bees: nectar as resource instead of perfume

et al. 2021

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“…The trapped compounds were eluted with 1 mL acetone (pro analysi, Merck, Germany). Aliquots of 1 μL of this sample, as well as of (5S,7S)-trans-conophthorin and (5R,7R)-trans-conophthorin (both available in the stock collection of WF) were injected, following Brandt et al (2019), at a temperature of 250 °C into an Agilent 7890A gas chromatograph (Santa Clara, California, USA) equipped with a fused silica capillary column (30 m × 0.23 mm i.d. ), coated with a 0.23 µm film of 0.4 % heptakis(2,3di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (DIME-beta-CD) (30 %) in SE-52 (70 %).…”

Section: Scent Collection and Analysesmentioning

confidence: 99%

Chemical Attraction of Gall Midge Pollinators (Cecidomyiidae: Cecidomyiinae) to Anthurium acutangulum (Araceae)

et al. 2022

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Flowering plants often use chemical signals to attract their pollinators, and compounds that elicit attraction are known for several groups of pollinators. For other pollinators such as gall midges, however, compounds responsible for their attraction to flowers are largely unknown. Here, we describe the pollination biology of Anthurium acutangulum, a Neotropical aroid species found to be attractive to gall midges. We collected and analyzed its floral scent by dynamic headspace collections and gas chromatography coupled to mass spectrometry, and identified compounds responsible for pollinator attraction. The inflorescences were almost exclusively visited by gall midges (females; Cecidomyiidae: Cecidomyiinae) and released a strong scent reminiscent of freshly cut cucumber, mainly (5S,7S)-trans-conophthorin, (E2,Z6)-2,6-nonadienal, and cis-conophthorin. Behavioral assays with the two most abundant compounds identified (E2,Z6)-2,6-nonadienal as being highly attractive to the female gall midge pollinators, whereas (5S,7S)-trans-conophthorin was not attractive. Overall, we introduce a new specialized gall midge pollination system and identify the chemical mediating communication between the pollinators and their host plants.

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“…Flowers of Catasetum species, known to be pollinated through PFPS by different Eulaema species, also contain trans-carvone oxide (Gerlach & Schill, 1991;Milet-Pinheiro & Gerlach, 2017;Whitten et al, 1986). Hence, this compound most likely evolved in perfumerewarding plant species as an attractant for Eulaema pollinator species (Brandt et al, 2019;Whitten et al, 1986). The specific role of the other identified compounds and their interaction with the Eulaema attractant trans-carvone oxide could be explored further since studies have demonstrated that appropriate compound blends filter out certain bee pollinator species (Whitten et al, 1986;Williams & Dodson, 1972).…”

Section: The Dual Pollinator Attraction Hypothesismentioning

confidence: 99%

Trick or treat? Pollinator attraction in Vanilla pompona (Orchidaceae)

et al. 2021

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Subtle Chemical Variations with Strong Ecological Significance: Stereoselective Responses of Male Orchid Bees to Stereoisomers of Carvone Epoxide

Cited by 14 publications

References 46 publications

Pollination of the strongly scented Sarcoglottis acaulis (Orchidaceae) by male orchid bees: nectar as resource instead of perfume

Pollination of the strongly scented Sarcoglottis acaulis (Orchidaceae) by male orchid bees: nectar as resource instead of perfume

Chemical Attraction of Gall Midge Pollinators (Cecidomyiidae: Cecidomyiinae) to Anthurium acutangulum (Araceae)

Trick or treat? Pollinator attraction in Vanilla pompona (Orchidaceae)

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