New Zealand Journal of Botany abstracts
B99055Received 9 November 1999; accepted 1 May 2000
Divergence estimates of Tetrachondra hamiltonii and T.
patagonica (Tetrachondraceae) and their implications for austral
biogeography
STEVEN J. WAGSTAFF
Landcare Research
P.O. Box 69
Lincoln 8152, New Zealand
email: WagstaffS@landcare.cri.nz
KARIN MARTINSSON
Botanical Garden
Uppsala University
Villavägen 8
752 36 Uppsala, Sweden
ULF SWENSON
Department of Botany
Stockholm University
106 91 Stockholm, Sweden
Abstract The enigmatic genus
Tetrachondra has been
included variously in the Boraginaceae, Lamiaceae, Scrophulariaceae, or
recognised as the distinct family Tetrachondraceae. Two species with a disjunct
distribution are included in the genus:
T.
hamiltonii is confined
to New Zealand, and
T.
patagonica is confined to South America.
New Zealand and South America once formed part of Gondwana, but separated
approximately 80 million years ago. In a parsimony analysis of
rbcL
sequences,
T.
hamiltonii and
T.
patagonica form
a distinct, well-supported clade that diverged early in the evolutionary
history of the large angiosperm order Lamiales.
Polypremum
procumbens emerges as their sister group. While there are no known
fossils of Tetrachondraceae, fossils from related families in the Lamiales
suggest that the
Tetrachondra/
Polypremum lineage may have evolved
during the Paleocene. The
rbcL sequences of
T. hamiltonii
and
T.
patagonica are virtually identical, however, suggesting a
more recent divergence during the Pleistocene for these two species. Thus,
their present disjunct distribution reflects long-distance dispersal rather
than vicariance.
Keywords divergence estimates; Lamiales; phylogenetic
relationships; Tetrachondra; Polypremum; austral distribution
New Zealand Journal of Botany, 2000, Vol. 38: 595-606
0028-825X/00/3804-0595 $7.00 (c) The Royal Society of New Zealand 2000
PDF file of entire paper: medium quality (754K); (scanned from paper original: notes about this process)
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