Phylogeny and biogeography of the genus Lycium (Solanaceae):: Inferences from chloroplast DNA sequences

Lycium comprises approximately 70 species and is disjunctly distributed in temperate to subtropical regions in: South America, North America, southern Africa, Eurasia, and Australia. Among them, only Lycium sandwicense A. Gray sporadically occurs widely on oceanic-islands in the Pacific Ocean. To investigate phylogenetic and biogeographic relationships of the genus with emphasis on L. sandwicense, the coding region,of matK; the two intergenic spacers trnT (UGU)-trnL (UAA) and trnL (UAA)-trnF (GAA), and the trnL (UAA) intron of chloroplast DNA (cpDNA) were sequenced. A strict consensus tree resulting from the phylogenetic analysis indicates the following: (1) New World species comprise a potentially paraphyletic assemblage; (2) southern African, Australian, and Eurasian species together are monophyletic; (3) southern African species are a paraphyletic assemblage; and (4) L. sandwicense is in a clade with certain New World species. The estimated biogeographic events based on: the cpDNA analysis indicate that (1) Lycium originated in the New World, (2) all southern African, Australian, and Eurasian species have a common ancestor from the New World, (3) Australian and Eurasian species originated once from a southern African progenitor, and (4) L. sandwicense differentiated from the New World species. (C) 2001 Academic Press.