Phylogeny
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Tetrachondraceae

Viridiophytes: green plants -> Embryophytes: Land plants -> Angiosperms: flowering plants -> Eudicots: buttercups, peas, pinks, cotton, carrots, and sunflowers -> Lamiales: mints, figworts, and plantains

The enigmatic genus Tetrachondra has variously been placed in the Boraginaceae, Lamiaceae, Scrophulariaceae or most recently included along with Polypremum, in the distinct family Tetrachondraceae. Polypremum procumbens, the sole member of the genus, is widely distributed in northern South America, Central America, Mexico, the West Indies, and the southeastern United States. A single disjunct population is reported from Paraguay, but it is not know whether this is a recent introduction. Two species of Tetrachondra are recognized with a disjunct distribution, T. hamiltonii in New Zealand and T. patagonica in South America. They are small aquatic to semiaquatic herbs found along lake and river margins and damp grasslands from sea level to alpine. At various times during the year the plants are completely submerged and can be found at considerable depth. Estimates from DNA sequence variation suggest the two species of Tetrachondra diverged during the Pliocene, hence their disjunct distribution reflects long-distance dispersal rather than vicariance.

Indigenous or exotic to New Zealand.

NZ Flora Web Site Link to the Ngā Tipu o Aotearoa Database

 
References
Oxelman, B; Backlund, M.; Bremer, B. 1999. Relationships of the Buddlejaceae s.l. investigated using branch support analysis of chloroplast ndhF and rbcL sequence data. Systematic Botany 24: 164-182.
Wagstaff, S.J.; Martinsson, K.; Swenson, U. 2000: Divergence estimates of Tetrachondra hamiltonii and T. patagonica (Tetrachondraceae) and their implications for austral biogeography. New Zealand Journal of Botany 38(4): 587-596.
Wagstaff, S.J.; Olmstead, R. G. 1997: Phylogeny of Labiatae and Verbenaceae inferred from rbcL sequences. Systematic Botany 22(1): 165-179.
Last updated: 05-Mar-2013