The aromatic pink-flowered Phebalium complex is comprised by P. nottii Maiden & Betche, P. speciosum I. Telford and the very similar but mostly white-flowered P. woombye (F.M.Bailey) Domin. Phebalium nottii, as currently circumscribed, includes several geographically disjunct populations that have been segregated at the N.C.W. Beadle Herbarium as putatively distinct species, several of high conservation value. To study volatiles sustainably, large-scale hydrodistillation was aborted and only single leaves were removed from herbarium vouchers, extracted into solvent and analysed by GC–MS. Unlike other species of Phebalium, volatiles in pink-flowered Phebalium are mostly dominated by spathulenol and bicyclogermacrene. Multivariate analysis of the chemistry of volatiles clearly demonstrated good agreement between chemotypes and putative taxa in central Queensland populations. Southern taxa, and the true P. nottii sensu stricto from northern Queensland, express high levels of volatile coumarins. Thus, morphological relationships are mostly reflected in morphometric clusters. As with other members of Phebalium, most taxa can be distinguished on chemistry alone, using only GC–MS analysis of herbarium material. These results corroborate several new species and reveal relationships within the heterogeneous species aggregate of P. nottii.
Reference: Sadgrove, N. J., et al. (2020). “GC–MS ‘chemophenetics’ on Australian pink-flowered Phebalium (Rutaceae) using herbarium leaf material demonstrates phenetic agreement with putative new species.” Phytochemistry Letters 38: 112-120