SYSTEMATIC IMPLICATIONS OF POLLEN MORPHOLOGY IN SUBFAMILIES LAMIOIDEAE AND POGOSTEMONOIDEAE (LABIATAE)

Pollen morphology was surveyed in 57 of the 60 genera of Lamioideae and Pogostemonoideae sensu Cantino et al. and two genera of uncertain subfamilial affinities: Anisomeles and Eurysolen. Pollen in all Pogostemonoideae, most Lamioideae, Anisomeles, and Eurysolen is tricolpate with suprareticulate sculpturing. Variants found in a few genera of Lamioideae include tetracolpate and hexapantocolpate pollen and psilate, granulate, and rugulate sculpturing. Most species in which pollen was examined in section have simple columellae, but seemingly branched columellae were observed in Gomphostemma, Chelonopsis, and one species of Stenogyne. With regard to the genera of uncertain affinities, the findings presented here support a relationship between Anisomeles and Pogostemon; the position of Eurysolen remains unclear. Within subfamily Lamioideae, pollen morphology supports the segregation of Lamiophlomis, Lagopsis, and Phlomidoschema from Phlomis, Marrubium, and Stachys, respectively. Hexapantocolpate pollen is hypothesized to be a synapomorphy of Sideritis section Empedoclea. Similarities in pollen sculpturing were noted between Brazoria, Macbridea, and Physostegia, and between Galeopsis and Synandra.