COSEWIC assessment and update status report on the American Columbo in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements and Authorities Contacted and Information Sources
- Biographical Summary of Report Writers and Collections Examined
American columbo (Frasera caroliniensis) is a taprooted perennial herb of the gentian family (Gentianaceae). Plants exist most of their lives as a basal rosette of leaves that may be as large as 40 cm long. When flowering stems are produced they have sets of whorled leaves that become progressively smaller toward the top of the plant. Flower clusters are produced from the upper leaf axils. Populations tend to flower synchronously, with individuals producing a single flowering stem 2-3 m tall after 7-15+ years in a vegetative state. Plants die after their first and only flowering season and are, therefore, said to be monocarpic.
Frasera caroliniensis is widely distributed in eastern North America, ranging from southern Ontario to northern Alabama and adjacent states. It is not common or abundant anywhere in its range. In Canada, it is known from a total of 22 documented populations of which 12 are extant.
Frasera caroliniensisis most commonly associated with open forested slopes, but can also be found in thickets and clearings. Its long lifespan may allow it to persist temporarily in sub-optimal habitats.
Little detail on the biology of Frasera caroliniensis is known except for its floral ecology, which has been well-studied; basic questions regarding the initiation of flowering remain to be answered.
Population Sizes and Trends
Of a total of 22 known populations nine appear to be extirpated with 7 of these being quite old historic sites. Twelve populations are extant and the status of one other population is uncertain. Of the extant populations, ten are large enough to be considered secure in the short term. Of these, two may be increasing, and four appear to be stable. Changes in population size cannot be inferred from the remaining extant populations due to the limited data available. Only five of the large populations are in permanently protected habitats, and three face possible or likely eradication due to development. The historic loss of nine populations represents about a 41% decline over the past century. More recent trends are difficult to determine due to the lack of previous population estimates. Because the species grows in a vegetative state as leafy rosettes for a number of years before flowering and subsequently dying, it is difficult to estimate the number of relatively mature individuals in a population when no plants are in flower in a given season when surveys are conducted. This was the case in 2004. A total of 3919 vegetative rosettes were counted in 2004. Only a few flowering stalks from the previous season were observed. In 2005, however, a total of 70 flowering shoots were counted at five of six populations visited. The six sites visited in 2005 yielded an additional count of 419 rosettes (updated information). These were found at two new sites (#21 and #22) and at a new subpopulation (#9B). Approximately the same numbers of rosettes as estimated in 2004 at the largest population in Short Hills Provincial Park were confirmed in 2005. Rosettes were too withered and difficult to count at one other site (#12). The estimated total number of plants in 2005 is in the order of perhaps 4200, with all but a few being vegetative.
Limiting Factors and Threats
Ongoing loss of habitat in southern Ontario and the encroachment of exotic invasive species are the primary threats identified for Frasera caroliniensis. As already noted, planned development of several of the largest populations will cause further losses in the medium term.
Special Significance of the Species
Frasera caroliniensis has been valuable in investigations of the biogeography of the eastern deciduous forest.
The species is listed as Threatened in New York and Endangered in Pennsylvania. It is regarded as special concern by COSSARO (Committee on the Status of Species at Risk in Ontario).
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