White wood aster (Eurybia divaricata) COSEWIC assessment and status report: chapter 3

SPECIES INFORMATION

Name and Classification

Scientific Name:            Eurybia divaricata (L.) Nesom

Pertinent Synonyms:     Aster divaricatus L.

                                        Biotia macrophyllus (L.) DC. var. divaricata (L.) DC.

                                        Aster corymbosum Aiton

English Names:             White wood aster

                                         Heart-leaved Aster

                                         Serpentine Aster

Family Name:                 Asteraceae (Compositae)

English Family Name:   Aster

All species of Eurybia have been treated as members of Aster in North American floras.  The nomenclature is a significant shift in what had been standard, but it is strongly supported on the basis of morphology because the species are not genetically related to members of the Eurasian genus Aster.  Members of sect. Eurybia (Biotia) have heart-shaped basal leaves, while those of other sections have oblanceolate or obovate basal leaves.  Nesom divided subgenus Eurybia into five sections (Semple et. al, 1996). 

Description

Eurybia divaricata is a fall-flowering herbaceous perennial. It emerges from rhizomes (horizontal, underground stems), and grows in colonies. It is characterized by deeply serrated upper leaves and narrowly heart-shaped lower leaves (Figure 1).  Flat-topped clusters of small flower heads also distinguish it. The disk florets in the flower heads are yellow and purple with white rays surrounding.  For a more detailed description, please refer to The Asters of Ontario (Semple et. al, 1996), Manual of Vascular Plants of Northeastern United States and Adjacent Canada (Gleason and Cronquist, 1991) or to the original COSEWIC report (Sharp et al., 1995).

Traditional treatments place most asters in the genus Aster L. However, during the last decade analyses of morphology, chloroplast DNA restriction fragment length polymorphisms and ITS sequence data, and on going karyotype studies have all demonstrated that asters are polyphyletic and members of a number of very distinct phylads within the tribe (Nesom, 1994).

Figure 1.  Illustration of Eurybia divaricata (Semple et al., 1996).

Figure 1.  Illustration of Eurybia divaricata (Semple et al., 1996).

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