Flavonoid variation in the Senecio streptanthifolius complex

Abstract

Flavonoid characters are presented for seven "phases" (sensu Barkley 1962) of Senecio streptanthifolius Greene and four related species, Seneciopauperculus Michx., Senecio multilobatus T. & G., Senecio canus Hook., and Senecio neomexicaiius A. Gray. Evidence from the study of flavonoid characters supports the division of S. streptanthifolius into two subgroups; the subgroup composed of the suksdorfii and laetiflorus phases is apparently related to S. pauperculus. In the other subgroup, three of five phases have apparently arisen through a combination of hybridization and polyploidy or introgression. While the two subgroups are thought to have originated during the Pliocene, the within-subgroup hybridization events are hypothesized to have occurred in Pleistocene or post-Pleistocene times.