MEUDT, HEIDI M.* and BERYL B. SIMPSON. Section of Integrative Biology and the Plant Resources Center, The University of Texas, Austin, Texas, 78712. - Austral biogeography: the evolution of subalpine Ourisia (Veronicaceae/Scrophulariaceae s.l.) in a phylogenetic context.
The austral biogeographic pattern refers to the presence of congeneric
organisms in South America, Australasia and/or Africa and is generally
considered to be a classic vicariant scenario associated with the
breakup of Gondwana. Results from phylogenetic studies and fossil
record evidence of Nothofagus and Araucaria, both woody
forest genera, are congruent with this hypothesis. However, the same
history may not apply to all genera in austral areas. It has been
hypothesized that higher elevation herbaceous taxa may be of more
recent origin, suggesting that long-distance dispersal may have played
a role in their historical biogeography. An extensive phylogenetic
study of austral, subalpine Ourisia (Veronicaceae/
Scrophulariaceae s.l.) based on molecular and morphological data is
currently underway to investigate the biogeography and evolution
within the genus. The approximately 30 species of Ourisia are
distributed equally between the South American Andes (Venezuela to
Tierra del Fuego) and the New Zealand Southern Alps. One species is
also endemic to high-elevation habitats in Tasmania, Australia.
Historically, Ourisia has been divided into two subgenera (each
with a bihemispheric distribution) based on calyx symmetry and corolla
tube curvature. Our current data sets include the nuclear Internal
Transcribed Spacer (ITS1, 5.8S, ITS2) and chloroplast
matK-3’trnK sequences for 22 species and subspecific
entities of Ourisia. The inferred phylogenies from both
separate and combined data sets show that: 1) Ourisia is
monophyletic, 2) the subgenera as currently circumscribed are not
monophyletic, 3) three suffruticose Andean taxa are sister to the rest
of Ourisia, and 4) the New Zealand taxa form a monophyletic
clade embedded within the Andean Ourisia. These findings
suggest that it is highly unlikely that a vicariant event is
responsible for the current biogeography of the genus, and instead
long-distance dispersal from South America to New Zealand is a more
plausible explanation.
Key words: Andes, biogeography, New Zealand, Ourisia, Scrophulariaceae, Tasmania