Numerical analysis of generic relationships in Thelypodieae (Brassicaceae)

Numerical methods were used to evaluate phenetic similarities and hypotheses of phylogenetic relationships among the ten genera of Thelypodieae, considered by some to be the most primitive tribe in Brassicaceae. The complementary phenetic methods of cluster analysis and ordination with a nearest neighbor directed network indicated why the genera are sometimes difficult to delimit. Several of these genera are close and nearly equidistant from each other. Three phylogenetic hypotheses were tested by assuming different hypothetical ancestors for the tribe or for the nine genera that occur in North America. Given data available at present, we suggest that the phylogenetic tree that uses a Cleome-like ancestor most reliably represents the evolutionary relationships among the nine genera restricted to North America. The tenth genus, Macropodium, remains an enigma because of its restriction to temperate eastern Asia.