A New Genus, Hesperocyparis, for the Cypresses of the Western Hemisphere (cupressaceae)

Phylogenetic comparisons of three nuclear DNA gene regions (nrDNA(ITS), 4-coumarate: CoA ligase, abscisic acid-insensitive 3) and a chloroplast region (petN-psbM) show that the Western Hemisphere cypresses (Hesperocyparis) is a well-supported clade quite separated from the Eastern Hemisphere cypresses (Cupressus). Based on these new data and previous data, a new genus, Hesperocyparis, is erected for the Western Hemisphere species previously placed in the genus Cupressus (sensu lato). Hesperocyparis is most closely related to the northwestern North American Callitropsis nootkatensis and the southeast Asian Xanthocyparis vietnamensis. Morphological characters distinguishing Hesperocyparis from C. nootkatensis and X. vietnamensis, and from the Eastern Hemisphere cypresses (Cupressus), are presented. Phytologia 91(1):160-185 (April, 2009).