BALLARD, JR., HARVEY E.*, KEN INOUE, AND KENNETH J. SYTSMA. Department of Environmental and Plant Biology, Ohio University, Athens, OH 45701; Biological Institute and Herbarium, Shinshu University, Matsumoto, Nagano 390, Japan; and Department of Botany, University of Wisconsin, Madison, WI 53706. - Phylogenetic relationships and biogeography of Japanese violets (Viola) based on Internal Transcribed Spacer DNA sequences.
New Internal Transcribed Spacer (ITS) DNA sequences were generated for
most violet (Viola) species in Japan and eastern Asia.
Parsimony and maximum likelihood analyses of these and sequences for
other infrageneric groups worldwide (75 ingroup species total)
permitted us to address taxonomic problems in Asian species,
reevaluate group assignments, clarify phylogenetic relationships and
circumscription of groups, and make biogeographic inferences. Most
taxa often considered conspecific varieties (V. iwagawai/V.
tashiroi and V. chaerophyllum/V. eizanensis) or conspecific
populations (Beringian and Japanese V. langsdorffii)
encompassed as much ITS divergence as other accepted species pairs in
their respective subclades, encouraging future studies of these
complexes. Extensive deletions in the sequence of V.
stoloniflora of the Australasiaticae probably contributed
to its peculiar isolation in most analyses; however, its extant
sequence shared numerous synapomorphies with the Adnatae and
Stolonosae. Membership of V. raddeana in the
Bilobatae was confirmed, and V. okinawaensis and V.
utchinensis were segregated from other Australasiaticae and
inserted among the Rostratae in another clade. Three species
of Nudicaules of sect. Chamaemelanium were removed to an
isolated subclade consisting of sect. Dischidium--a group
sometimes subsumed in sect. Chamaemelanium. Inclusion of
numerous Asian Viola species maintained the paraphyletic grade
of intermingling Chamaemelanium and Plagiostigma groups
suggested by other recent studies but increased irresolution among
them and strengthened the case for drastic recircumscription of many
groups in the assemblage. The remaining species fell out according to
previous group assignments in the
Rostratae-Plagiostigma-Nosphinium clade, and Japanese V.
langsdorffii was placed basal to Beringian V. langsdorffii
+ Hawaiian sect. Nosphinium. The expanded data set amplified
biogeographic inferences for Viola worldwide from earlier
investigations using few Asian representatives, and prompted new
hypotheses of diversification and dispersal in certain eastern Asian
violet groups.
Key words: biogeography, Internal Transcribed Spacer, Japan, phylogenetic relationships, Viola