The Origin and Phylogenetic Relationships of the Californian Chaparral ‘Paleoendemic’ <I>Pickeringia</I> (Leguminosae)

Abstract

Abstract Pickeringia, a monotypic genus of the Leguminosae endemic to the xerophytic sclerophyllous chaparral vegetation of the California Floristic Province, has been considered a “relict” of legume diversity in the North American flora and an example of the classic “paleoendemics” in the flora of California. Evidence is presented for the phylogenetic relationships of this genus, inferred from nucleotide sequence variation in the internal transcribed spacers of nuclear ribosomal DNA and the plastid matK gene. Phylogenies derived from maximum parsimony and Bayesian analyses both strongly support a close relationship of Pickeringia to the temperate to subtropical, deciduous genera Cladrastis and Styphnolobium of tribe Sophoreae consistent with morphological and cytogenetic evidence rather than to members of tribe Thermopsideae where the genus has been treated taxonomically. Cladrastis is resolved as paraphyletic while Styphnolobium is strongly supported as a monophyletic group. These results, plus an estim...