John C. Semple WAT

Oclemena E.L. Greene

BOG AND WHORLED WOOD ASTERS

Oclemena is a small northeastern North American genus of 2 distinct species of pink to rose-violet rayed asters with a chromosome base number of x=9 . The genus is defined on the basis of fruit and phyllary traits; achenes are glandular and have a double pappus of two long whorls of bristles, one with clavate tips; phyllaries are narrow and have a chlorophyllous zone restricted to narrow bands along the raised midrib.

This small group of asters were thought to be related to Doellingeria (Jones 1980; Semple and Brouillet 1980), but cpDNA analysis revealed that the two genera were not closely related within the tribe (Brouillet, Allen, Semple and Ito 2001).

Semple, Chmielewski and Leeder (1990) included a fourth species (O. reticulata) in Doellingeria (Aster sect. Triplopappus). However, Brouillet, Allen, Semple and Ito (2001) found support for Nesom's (1994) placement of the species within Oclemena. They also found that Oclemena was the basal genus in the clade that included Nesom's subtribes Conyzinae, Chaetopappinae, Astranthiinae, and the genus Euthamia and other genera.

Illustrations

Oclemena acuminata (syn: Aster acuminatus); habit
Oclemena × blakei (acuminata × nemoralis)
Oclemena nemoralis; habit; head
Oclemena reticulata; habit, heads