Floral structure, histochemistry and volatile compounds in Bulbophyllum species of the ‘Cirrhopetalum alliance’ (Orchidaceae)

Davies, Kevin L., Stpiczyńska, Małgorzata, Ludlow, Richard, Wheaton, Louise, Aros, Danilo, Hailer, Frank ORCID: https://orcid.org/0000-0002-2340-1726, Muller, Carsten ORCID: https://orcid.org/0000-0003-0455-7132 and Rogers, Hilary ORCID: https://orcid.org/0000-0003-3830-5857 2024. Floral structure, histochemistry and volatile compounds in Bulbophyllum species of the ‘Cirrhopetalum alliance’ (Orchidaceae). Botanical Journal of the Linnean Society 10.1093/botlinnean/boae029

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Abstract

Bulbophyllum is the most species-rich orchid genus. Recent molecular data groups certain of its species into a monophyletic ‘Cirrhopetalum alliance’. Within this alliance are a monophyletic section Cirrhopetaloides and a non-monophyletic section Cirrhopetalum. Floral morphology and scent are partially conserved phylogenetically compared to the molecular data. Here, floral morphology, histochemistry, anatomy, and floral volatile organic compounds (VOCs) of selected Bulbophyllum species are analysed to assess whether there are structural or chemical differences that support separation into the two sections, to update available VOC data from this genus, and to consider evolutionary adaptations in the ‘Cirrhopetalum alliance’. We found that ‘Cirrhopetalum alliance’ flowers differ from some sections of Bulbophyllum in the structure of cells lining the longitudinal groove on the labellum or lip and report, for the first time in Bulbophyllum, a type of atypical oleiferous trichome probably involved in VOC production. We show a clear difference in floral VOC profiles between B. bicolor (sect. Cirrhopetaloides) and four other Bulbophyllum species, three previously assigned to sect. Cirrhopetalum, but VOC profiles do not support separation into the two sections. The lack of congruence between already established molecular phylogeny, floral anatomy, and VOC data suggests that VOC differences are due to recently and independently evolved pollinator specificity. We therefore show that there is no clear separation of these sections based on floral anatomy, histochemistry, or VOC profiles.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Biosciences Earth and Environmental Sciences
Publisher:	Oxford University Press
ISSN:	0024-4074
Date of First Compliant Deposit:	30 April 2024
Date of Acceptance:	27 April 2024
Last Modified:	17 Jun 2024 11:24
URI:	https://orca.cardiff.ac.uk/id/eprint/168509

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