Phylogenetic Relationships of the Genus Taxus Inferred from Chloroplast Intergenic Spacer and Nuclear Coding DNA

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Abstract
A cladistic analysis of the medicinal plant Taxus, using the sequences of one chloroplast (trnS–trnQ spacer) and three nuclear taxadiene synthase (TS), 10-deacetylbaccatin III-10β-O-acetyltransferase (DBAT), and 18S rDNA) molecular markers, was carried out by distance, parsimony, likelihood, and Bayesian methods. Three of the four New World species (T. brevifolia, T. floridana and T. globosa) form a well-supported clade, whereas T. canadensis initially branches—appearing distantly related to both Old World taxa and New World species. In Asia, Taxus chinensis, T. mairei, T. sumatrana and T. wallichiana cluster together and are sister to a clade containing T. baccata and T. contorta. Taxus yunnanensis is more closely related to T. wallichiana than to four other Taxus species in our study from China; T. contorta is closer to the Euro-Mediterranean T. baccata than to the Asian species. This study provides a genetic method for authentication of economically important Taxus species and proposes a robust phylogenetic hypothesis for the genus. Using trnS–trnQ spacer sequences, we were able to distinguish T. mairei from all other species of Taxus.