Tall bugbane (Cimicifuga elata) COSEWIC assessment and status report: chapter 9

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Special Significance of the Taxon

Cimicifuga elata populations in British Columbia represent the northern-most limit of the species in its overall distribution in the Pacific Northwest. A genetic study currently being undertaken in which British Columbia specimens, in addition to United States specimens, will be analyzed may reveal that populations in the north are distinct from populations in the center of the distribution of this species. A genetic study done on seven populations of C. elata in Washington and Oregon revealed that the population representing the most southern extent of this species was genetically distinct from the rest of the localities (Evans, 1993).  Populations of C. elata are relatively small and sporadically distributed, so that the possibility of low genetic diversity and in-breeding depression remain a threat to the long-term persistence of this species. Concern about this issue led to a study on allozyme variation (Evans, 1993). However, Evans (1993) found that allozyme variation was not as low as suggested by principles of genetic theory.

As is the case with other species of Cimicifuga being investigated pharmacologically (Shibata et al., 1980), C. elata apparently contains active medicinal ingredients. ‘Western black cohosh,’ as it is known in the herbal trade, is considered one of the most useful medicinal plants of the Pacific Northwest (Moore, 1993). It is used as an anti-inflammatory, a peripheral vasodilator, an antispasmodic, a sedative, and an estrogenic. Cimicifuga elata is known in the horticultural trade, from a limited number of sources; two nurseries, one in Salem, Oregon, and the other one in Clinton, Washington are selling seed.

From an evolutionary standpoint, Cimicifuga species represent a relatively primitive and taxonomically isolated genus within the Ranunculaceae (Pellmyr, 1985a). Studies on the plant and pollinator interactions in Cimicifuga species can help reveal some information on the evolution of the earliest, herbaceous flowering plants. Cimicifuga elata was likely part of the flora of the Pacific Northwest in the Miocene Epoch, 7 to 26 million years before present (Alverson, 1986). Within the genus, Cimicifuga, C. elata is one of the four nectarless American species (Pellmyr, 1985a). To lack nectar is an ancestral characteristic. The ancestor to this subgrouping was likely similar to C. elata, however, it would not have been geitonogamous (selfing). Both out-crossing and selfing characteristics are present in C. elata, however, the overall evolutionary trend appears to be toward selfing.