Flavonoid Variation in North American Menziesia (Ericaceae)

Abstract

The flavonoids of Menziesia ferruginea and M. pilosa are based, mainly, on flavonols. Menziesia ferruginea accumulates derivatives of kaempferol, 7-0-methylkaempferol, quercetin, 7-0methylquercetin, myricetin, and gossypetin, although some individual plants do not have all compounds. The compounds occur as a complex mixture of mono-, di-, and triglycosides some of which occur as acetylated derivatives. Very polar derivatives of kaempferol and quercetin also occur. Triglycosides are of seldom and scattered distribution. Menziesia pilosa has a simpler flavonoid profile; it lacks 7-0-methylated flavonols, triglycosides, and gossypetin. The two species are further distinguished by the presence of an unidentified flavanone in M. ferruginea and dihydromyricetin in M. pilosa. Differences in flavonoid profile were found between material collected from several areas within the range of M. ferruginea but these differences do not correlate with infraspecific taxa that were recognized by earlier workers. The pattern of variation in occurrence of flavonoids is more complex in M. ferruginea than in M. pilosa. ANOVA of principal components analysis axis scores showed that geographical differences are most significant; between-year and within-year variation are less significant. The amount of variation accounted for by these factors, however, is comparatively small; principal components analysis showed that only about 30% of the total variation is accounted for by the first two axes. With respect to infraspecific flavonoid variation, Menziesia resembles the situation described for species of Phlox by Levy and coworkers. Menziesia Smith (Ericaceae) is represented in North America by two species (Fernald 1950); an additional four occur in Japan (Ohwi 1965). The eastern North American species, M. pilosa (Michaux) A. L. Juss., occurs in the Appalachian Mountains from Pennsylvania and Maryland south through Virginia, West Virginia, North Carolina, and Tennessee to extreme northern Georgia. Menziesia ferruginea Smith occurs in the Rocky Mountains from Alberta and British Columbia south to Wyoming and along the coast from Alaska to northern California as well as on the Queen Charlotte Islands and Vancouver Island (Hitchcock et al. 1959). The Rocky Mountain form has been recognized as a separate taxon, M. glabella A. Gray [=M. ferruginea var. glabella (A. Gray) Peck]. As part of our continuing study of Ericaceae, we undertook an investigation of the flavonoid chemistry of North American Menziesia. Preliminary sampling of plants from distantly separated sites in the range of M. ferruginea showed widely different two-dimensional thin-layer chromatograms. Trial chromatograms of M. pilosa showed a simpler pattern. We felt that a detailed study of the flavonoid profiles would enable us: 1) to compare the overall pattern of the two species with a view toward assessing their relationships; 2) to examine the question of recognition of infraspecific taxa within M. ferruginea from a different perspective; and 3) to comment on the phenomenon of infraspecific flavonoid variation. MATERIALS AND METHODS Ninety-seven collections from individual M. ferruginea plants were made; these represented the entire geographic range of the species. An additional 26 collections were made from seven of the southwestern British Columbia plants at different times during the 1982 growing season. Material was collected from 78 individuals of M. pilosa from throughout its range. Sitedata are summarized in table 1. A map of the collection areas is presented in figure 1. For M. ferruginea six areas are identified to which reference will be made in the discussions below: 1) Alaska and Queen Charlotte Islands; 2) southwestern British Columbia, Vancouver Island, and Washington Cascades; 3) Oregon; 4) California; 5) northern mountains of Alberta and British Columbia; and 6) southern Rocky Mountains. The range of distribution of M. pilosa was divided roughly into equal halves: 1) Pennsylvania, Maryland, West Virginia, and Virginia (area 7 in fig. 1) and 2)