LINDQVIST, CHARLOTTE, TIMOTHY J. MOTLEY, AND VICTOR A. ALBERT.* 1,3. Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487; 2. The Lewis B. & Dorothy Cullman Program for Molecular Systematics Studies, The New York Botanical Garden, Bronx, NY 10458. - A North American closest relative for the Hawaiian endemic mints (Lamiaceae): implications for pollination syndrome and fruit evolution.
Our previous phylogenetic studies on the Hawaiian endemic mints
(Haplostachys, Phyllostegia, and Stenogyne)
suggested their close relationship to Gomphostemma, an Asian
labiate bearing fleshy fruits. Phyllostegia and
Stenogyne are also fleshy-fruited, but differences in pericarp
structure cast doubt on the homology of fleshiness among the Hawaiian
taxa and other lamioid mints. Further sequencing of rbcL and the 5S
rDNA non-transcribed spacer region (5S-NTS) has identified a closer
relative to the Hawaiian mints, Stachys coccinea. Stachys
coccinea is not only representative of a distinct and mostly
insect-pollinated North American group within Stachys, but it
is also characterized by dry nutlets and bird-pollinated flowers. With
rbcL, Stachys coccinea plus the Hawaiian mints form a
monophyletic group separate from Eurasian Stachys species and
Gomphostemma. These findings have implications for reproductive
character evolution among the diverse Hawaiian mints, which, like the
silverswords (Asteraceae), appear to have derived once from a North
American lineage. Phylogenetic analysis of 5S-NTS reveals that
Haplostachys, which bears dry nutlets, is the sister genus to
all other Hawaiian taxa. Because Stachys coccinea shares the
same nutlet state, the ancestral condition for the Hawaiian species
could be dry rather than fleshy. Additionally, bird pollination in
Stachys coccinea raises the possibility that the ancestral
condition for Hawaiian taxa, many of which (especially
Stenogyne spp.) have classic, bird-pollinated flowers, could be
likewise. Haplostachys is enigmatic because its nutlets are dry
but its flowers are insect-pollinated. Tendencies toward evolution of
fruit fleshiness and bird pollination may exist among the lamioid
mints, which could confound interpretation of ancestral states until
more taxa can be studied phylogenetically. Such tendencies may in turn
be manifest by narrow genetic differences between character states, as
has been demonstrated for pollination syndromes in the scroph
Mimulus.
Key words: 5S rDNA non-transcribed spacer, Hawaiian endemic mints, Lamiaceae, rbcL, Stachys coccinea