HOGGARD, GLORIA, RON HOGGARD, MIA MOLVRAY, AND PAUL KORES.* Department of Botany-Microbiology and Oklahoma Biological Survey, University of Oklahoma, Norman, OK 73019. - A phylogenetic analysis of Gaura (Onagraceae) based on ITS sequence data.
Gaura is a small genus found in southern Canada, eastern and
central United States, Mexico and Guatemala. Its center of
distribution is within Texas. Raven and Gregory's monograph of the
genus (1972) formed the basis for a cladistic analysis by Carr, Crisci
and Hoch in 1990. In these treatments the 21 species of Gaura
were assigned to eight sections. Four of these sections,
(Campogaura, Gauridium, Schizocarya, Xenogaura) were monotypic.
The remaining four sections (Gaura, Pterogaura, Stipogaura,
Xerogaura) encompassed 17 species. In the cladistic analysis by
Carr et al., section Gauridium is sister to the other seven
sections within the genus, and the sections Xerogaura and
Gaura are not monophyletic. We compared this
morphologically-based phylogeny to one based on DNA sequence data from
the nuclear ribosomal internal transcribed spacer region (ITS). A
total of four outgroup taxa and 18 species of Gaura were
included in this analysis. Our molecular phylogeny of Gaura
supports five of the sections proposed by Raven & Gregory
(Campogaura, Pterogaura, Schizocarya, Stipogaura, and
Xerogaura), but the remaining three sections are problematic.
Section Xenogaura is embedded within section Gaura, and
the status of section Gauridium is uncertain. Our results
indicate that this section is either sister to section Gaura or
should be included within it. Thus, Gaura mutabilis, the sole
representative of section Gauridium, may actually be one of the
more derived species within Gaura and not the most basal member
of the genus as suggested by Carr et al.
Key words: Gaura, ITS, molecular systematics, Onagraceae, phylogeny