CHUMLEY, TIMOTHY W.1*, STERLING C. KEELEY2, JOSE L. PANERO1, and ROBERT K. JANSEN1. 1Section of Integrative Biology, School of Biological Sciences, University of Texas at Austin, Austin, TX 78712; 2Dept. of Botany, University of Hawaii, 3190 Maile Way, Honolulu, HI 96822-2279. - A phylogeny of Lipochaeta (Asteraceae) inferred from the internal and external transcribed spacers of nuclear ribosomal DNA.
Lipochaeta is a small genus of 20 species endemic to the
Hawaiian Islands. Two sections with differing chromosome numbers and
morphological traits are recognized, Aphanopappus (n =
15, five-merous disk corollas) and Lipochaeta (n = 26,
four-merous disk corollas). Several hypotheses of the origin of the
genus have been proposed, with evidence providing support for the
close relationship of Wollastonia biflora and an allopolyploid
origin for section Lipochaeta. In order to test the monophyly
of the genus, sequence data for the internal transcribed spacer (ITS)
and the external transcribed spacer (ETS) of nuclear ribosomal DNA
were utilized in reconstructing a phylogeny. A parsimony analysis of
ITS for the subtribe Ecliptinae (Heliantheae) demonstrated
Lipochaeta to be a monophyletic group, and sister to a clade
containing Wollastonia and Melanthera. A maximum
likelihood analysis also identified the latter genera as sister to
Lipochaeta, and produced well-supported clades that correspond
to the two sections, but provided little resolution of species
relationships within the two groups. Maximum likelihood analysis of
the ETS data produced a single tree that appears largely incongruent
with the ITS data, though soft polytomies and weak branch support
overall do not preclude combining the datasets. Melanthera is
basal to a paraphyletic Lipochaeta clade that includes
Wollastonia in a polytomy with L. micrantha and L.
kamolensis. The combined data produce a single most likely tree in
which Melanthera and Wollastonia are again sister taxa
to a monophyletic Lipochaeta. Three major clades within
Lipochaeta can be recognized, but their relative positions are
unresolved. Section Lipochaeta is weakly supported as a
monophyletic group in which L. lobata is basal, but this is
sister to a species pair (L. waimeaensis - L. faurei) of sect.
Aphanopappus in a well supported clade. This preliminary
evidence thus supports the view of a single introduction and
subsequent polyploid speciation of Lipochaeta within the
islands.
Key words: Asteraceae, Ecliptinae, Hawaii, Heliantheae, Lipochaeta, Melanthera, Wollastonia