Bog and Whorled Wood Asters

OclemenaOclemena E.L. Greene is a small northeastern North American genus of three distinct species of pink to rose-violet rayed asters and a white to pink rayed species  native to the SEUS.  All have a chromosome base number of x=9 (2n=18). The genus is defined on the basis of fruit and phyllary traits; cypselae (fruits) are glandular and have a quadruple pappus of two short and two long whorls of bristles, the inner most with narrow clavate tips (Semple and Hood 2005); 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.  In Brouillet et al. (2009), the phylogenetic position of Oclemena in the North American Clade was unresolved.  The treatment here follows Brouillet (2006 Flora North America) who summarized the literature on the species and hybrid.

Brouillet, L.  2006. Oclemena Greene. pp. 78--81. In Flora North America Editorial Committee, North America. Vol. 20. Asteraceae, Part 2. Astereae and Senecioneae. Oxford University Press, New York.

Last updated 13 April 2023 by J.C. Semple

© 2013, 2014, 2023 J.C. Semple, including all photographs unless otherwise indicated