Variation in Callistemon viminalis (Myrtaceae): New evidence from leaf essential oils

Abstract

Analysis of leaf essential oils in Callistemon viminalis (Sol. ex Gaertner) G.Don ex Loudon was used to determine the validity of infraspecific taxa recognised in the taxon. The leaf essential oils obtained, in 0.08–0.63% yield, have been found to be qualitatively similar over the wide geographic distribution of the species (from 12°28′S to 29°43′S) but to differ quantitatively over this range. All oils contained α-pinene, β-pinene, myrcene and 1,8-cineole as their major compounds and traces of the β-triketones, leptospermone and flavesone. Overall the essential oils that contained the most 1,8-cineole (60–82%) came from the more southern latitudes (29°14′S to 20°16′S) while those oils with less 1,8-cineole (0.5–47%) came from the more northerly latitudes (12°53′S to 25°18′S). There was overlap in the region 25° S to 22° S, although the majority of samples from this region contained high 1,8-cineole values. Partial least squares analysis allowed the latitude to be calibrated by the leaf oil concentrations. These data would lend only equivocal support for the establishment of two intraspecific taxa of C. viminalis.