YOO, KI-OUG*, P. P. LOWRY, J. L. WALCK, AND JUN WEN. *Department of Biology, Colorado State University, Fort Collins, CO 80523-1878, , **Missouri Botanical Garden P.O. Box 299, St. Louis, Missouri 63166, ***Department of Biology, Middle Tennessee State University, P.O. Box 60, Murfreesboro, TN 37132. - A Phylogenetic and Biogeographic Analysis of OSMORHIZA (Apiaceae) Based on ITS and ndhF Sequences.
Osmorhiza Raf. (Apiaceae) consists of ten species disjunctly
distributed in temperate Asia (1 sp.) and the Americas (9 spp.).
Osmorhiza berteroi DC. and O. depauperata Philippi are
disjunct between North and South America. Within North America, these
two species are disjunctly distributed in eastern and western North
America and the Great Lakes regions. Phylogenetic analysis was
conducted to clarify the interspecific and intraspecific relationships
of based on sequences of the ITS regions of nrDNA and ndhF
chloroplast gene. With Myrrhis as the outgroup, the monophyly
of Osmorhiza is strongly supported. The ITS phylogeny suggests
the basal position of the Asiatic O. aristata and the monophyly
of the nine New World species. Osmorhiza aristata is relatively
divergent from other species even though it is morphologically similar
to the eastern North American O. claytonii and O.
longistylis. Osmorhiza claytonii and O. longistylis
form a clade. Osmorhiza brachypoda, O. depauperata,
O. occidentalis and O. purpurea constitute a
monophyletic group. The seven populations of the widespread O.
berteroi form a clade, which showed no or little sequence
divergence, suggesting recent colonization of these widely separated
regions by this species. Disjunct populations of O. depauperata
from the Rocky Mountains and eastern North American have similar ITS
profile and form a clade. Osmorhiza occidentalis, however shows
a high level of infraspecific sequence divergence. The sequence
divergence of ndhF gene within Osmorhiza is low.
Congruent with the ITS data set, the ndhF phylogeny suggests
that O. aristata from Asia is basal within the genus. The
remaining nine from the New World form a monophyletic group.
Osmorhiza glabrata and O. depauperata form a subclade,
whereas the ITS phylogeny places O. glabrata basal to the New
World clade. The ITS and ndhF phylogenies suggest rapid
diversifications of Osmorhiza in western North America.
Key words: Biogeography, ITS, Monophyly, ndhF sequences, Osmorhiza, Phylogeny