SCHUETTPELZ, ERIC J.* and SARA B. HOOT. Department of Biological Sciences, University of Wisconsin, Milwaukee, 53201. - Phylogenetic and biogeographic relationships of Caltha (Ranunculaceae) based on DNA sequence data and morphology.
Caltha consists of ten species of perennial herbs found in the
moist temperate and cold regions of both hemispheres. Past treatments
had divided the genus into two sections based primarily on the
presence of distinctly inflexed leaf auricles in the Southern
Hemisphere species. Through a cladistic analysis of three DNA sequence
data sets and morphology, we evaluate this classification as well as
biogeographical implications and character evolution. We find that
Caltha natans (N. America, Asia) is sister to all other
species; Caltha palustris (circumboreal) and Caltha
scaposa (Asia) are well supported as sister; and Caltha
leptosepala (western N. America) and the Southern Hemisphere
species together form a well supported group. We suggest a historical
dispersal event from North to South America, with a subsequent
dispersal event to New Zealand and Australia. A reexamination of leaf
morphology supports this hypothesis.
Key words: biogeography, Caltha, Ranunculaceae