Can floral volatile organic compounds contribute to the taxonomy of the Rhamnus sect. Alaternus?

The chemistry of plants represents a taxonomic and phylogenetic value. Researchers have recently used volatile organic compounds (VOCs) for taxonomic studies. The present work analysed and determined, for the first time, the usefulness of floral volatile compounds in the taxonomy of two species of Rhamnus sect. Alaternus, as well as the hybrid between these taxa. The two species show significant quantitative and qualitative differences. The terpenes linalool, ocimene, caryophyllene, and green volatiles are exclusive to Rh. alaternus, while farnesene (terpene), methyl salicylate and methyl benzoate (benzoids) are obtained from Rh. ludovici-salvatoris. Both volatilomes were attractive to Hymenoptera pollinators; therefore, these pollinators could serve as the main hybridisation vector. In addition, Rh. alaternus shows greater chemical and genetic heterogeneity than Rh. ludovici-salvatoris. Hybrids between the two species, Rh. × bermejoi, are closer in chemical similarity to Rh. alaternus than Rh. ludovici-salvatoris.