FLORAL VOLATILES FROM CLARKIA-BREWERI AND C-CONCINNA (ONAGRACEAE) - RECENT EVOLUTION OF FLORAL SCENT AND MOTH POLLINATION

Clarkia breweri (Onagraceae ucene) is the only species known in its ge nus to produce strong floral fragrance and to be pollinated by moths. We used gas chromatography-mass spectrometry (GC-MS) to identify 12 ab undant compounds in the floral headspace from two inbred lines of C. b reweri. These volatiles are derived from two biochemical pathways, one producing acyclic monoterpenes and their oxides, the other leading fr om phenylalanine to benzoate and its derivatives. Linalool and linaloo l oxide (pyran form) were the most abundant monoterpenoids, while lina lool oxide (furan form) was present at lower concentrations. Of the ar omatic compounds detected, benzyl acetate was most abundant, whereas b enzyl benzoate, eugenol, methyl salicylate, and vanillin were present as minor constituents in all floral samples. The two inbred C. breweri lines differed for the presence of the additional benzenoid compounds isoeugenol, methyleugenol, methylisoeugenol, and veratraldehyde. We a lso analyzed floral headspace from C. concinna, the likely progenitor of C. breweri, whose flowers are odorless to the human nose. Ten volat iles (mostly terpenoids) were detected at low concentrations, but only when headspace was collected from 20 or more flowers at a time. Trans -beta-ocimene was the most abundant floral compound identified from th is species. Our data are consistent with the hypothesized recent evolu tion of floral scent production and moth pollination in C. breweri.