Soapweed (Yucca glauca) COSEWIC assessment and status report 2013: chapter 2

COSEWIC
Assessment Summary

Assessment Summary – May 2013

Common name
Soapweed

Scientific name
Yucca glauca

Status
Threatened

Reason for designation
This long-lived perennial is known from only three sites in southeastern Alberta and southwestern Saskatchewan, where it occurs mainly on south-facing coulee slopes. Plants are pollinated exclusively by Yucca Moth, which lays eggs in the flowers. In Canada, the species reproduces almost exclusively by vegetative spread. Seed production is limited by low numbers of Yucca Moth pollinators, while seedling establishment is negatively impacted by lack of natural disturbance, including fire suppression. Herbivory of flowering stalks by native ungulates also limits seed set. Despite improved management to limit the impact of threats, this perennial is designated Threatened. It is the only host for Yucca Moth, Non-pollinating Yucca Moth and Five-spotted Bogus Yucca Moth, all of which were assessed as Endangered.

Occurrence
Alberta, Saskatchewan

Status history
Designated Special Concern in April 1985. Status re-examined and designated Threatened in May 2000 and May 2013.

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