BEARDSLEY, PAUL M.*, STEVE SCHOENIG, and RICHARD G. OLMSTEAD. Botany Department, University of Washington, Seattle, WA, 98195. - Radiation of Mimulus (Phrymaceae) in western North America: evolution of polyploidy, woodiness, and pollination syndromes.
Species in Mimulus in western North America have become model
systems for the study of evolutionary processes in nature. As
currently described, Mimulus contains approximately 120
species, of which 75 percent occur only in western North America.
Mimulus contains species with different ploidy levels,
reproductive strategies, and pollination syndromes. Molecular
phylogenetic studies in Mimulus have redefined Phrymaceae and
indicate that at least six genera have been derived from within
Mimulus. One clade recovered in these analyses contains all of
the species of Mimulus in western North America, plus
Hemichaena, Berendtiella, and Leucocarpus. A
phylogenetic hypothesis for 82 species was estimated using ITS, ETS
and trnL sequences. These analyses indicate that polyploidy has
evolved independently at least six times, woody plants have evolved
from herbaceous ancestors twice, self-pollination has possibly evolved
10 times and hummingbird pollination has evolved at least three times.
These results also indicate that Mimulus has established twice
in Asia and once in South America from ancestors in western North
America. Within sect. Eunanus patterns of genetic
diversification better match geographic distribution (Sierra Nevada
versus the Pacific Northwest) than taxonomic circumscription.
Mimulus nanus is not monophyletic in two distinct ways. First,
individuals from the Sierra Nevada are distinct from those in the
Cascade and Rocky Mountains. Second, Mimulus nanus in the
Pacific Northwest is paraphyletic, because three currently recognized
species, M. cusickii, M. jepsonii, and M. clivicola have
been derived from within it.
Key words: Mimulus nanus, Mimulus, Phrymaceae, pollination biology, polyploidy