Divergence estimates of Tetrachondra hamiltonii and T-patagonica (Tetrachondraceae) and their implications for austral biogeography

Citation
Sj. Wagstaff et al., Divergence estimates of Tetrachondra hamiltonii and T-patagonica (Tetrachondraceae) and their implications for austral biogeography, NZ J BOTANY, 38(4), 2000, pp. 587-596
Citations number
52
Categorie Soggetti
Plant Sciences
Journal title
NEW ZEALAND JOURNAL OF BOTANY
ISSN journal
0028825X → ACNP
Volume
38
Issue
4
Year of publication
2000
Pages
587 - 596
Database
ISI
SICI code
0028-825X(200012)38:4<587:DEOTHA>2.0.ZU;2-J
Abstract
The enigmatic genus Tetrachondra has been included variously in the Boragin aceae, Lamiaceae, Scrophulariaceae, or recognised as the distinct family Te trachondraceae. Two species with a disjunct distribution are included in th e genus: T. hamiltonii is confined to New Zealand, and T. patagonica is con fined to South America. New Zealand and South America once formed part of G ondwana, but separated approximately 80 million years ago. In a parsimony a nalysis of rbcL sequences, T. hamiltonii and T. patagonica form a distinct, well-supported clade that diverged early in the evolutionary history of th e large angiosperm order Lamiales. Polypremum procumbens emerges as their s ister group. While there are no known fossils of Tetrachondraceae, fossils from related families in the Lamiales suggest that the Tetrachondral/Polypr emum 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. Thu s, their present disjunct distribution reflects long-distance dispersal rat her than vicariance.