EVIDENCE FOR A POLYPHYLETIC ORIGIN OF THE LABIATAE

A preliminary cladistic analysis suggests that the Labiatae are polyphyletic as presently circumscribed. The gynobasic-styled Labiatae emerge as a clade, nested within a larger group characterized by suprareticulate pollen and a fruit composed of nutlets. The latter includes the bulk of the Labiatae plus the verbenaceous genera Garrettia and Holmskioldia; its closest relatives are in tribe Viticeae (Verbenaceae). In contrast, Teucrium and five other genera of Ajugeae (Labiatae) belong to a large clade characterized by pollen with branched to granular columellae, most members of which are currently assigned to tribes Clerodendreae and Caryopterideae (Verbenaceae). Another group traditionally placed in the Labiatae, tribe Prostanthereae, appears to be most closely related to subfamily Chloanthoideae (Verbenaceae). The hypothesis that the gynobasic-styled Labiatae evolved in southern China or Indomalaysia (Wu & Li, 1982) is supported by this analysis. An Australian origin is hypothesized here for the cosmopolitan genus Teucrium based on the distributions of its closest relatives.