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COSEWIC assessment and update status report on the American Columbo in Canada

Distribution

Global Range

The historic range of Frasera caroliniensis is from south-eastern Oklahoma and north-eastern Louisiana east to north-western South Carolina, north to southern Ontario and southern Michigan, as shown in Figure 2 (Threadgill et al., 1979; Crins and Sharp, 1993). It may have been extirpated from Louisiana (Reid, 2004).


Figure 2: Global Range of Frasera caroliniensis

Global range of Frasera caroliniensis (after Crins and Sharp, 1993)

After Crins and Sharp, 1993.


Canadian Range

In Canada, Frasera caroliniensis is restricted to extreme southern Ontario, where 22 populations have been documented, as shown in Figure 3. Seven of these populations have not been seen in more than 49 years, suggesting a 1/3 decline in the Canadian range of the species. This is largely due to the loss of one historic population near Sarnia. The largest of these populations occupies at most 1 ha, so that the area of occupancy (AO) for this species is no more than 13 ha. While the total geographic area of the Canadian population spans hundreds of square kilometres, most of this area has been developed for urban or agricultural use. The historical extent of occurrence (EO) is estimated at 8000 km2, while the current EO is closer to 2000 km2, mainly due to the presumed extirpation of the Sarnia population. Detailed location data for all populations are on file at the Ontario Natural Heritage Information Centre.


Figure 3: Canadian Range of Frasera caroliniensis

 Canadian range of Frasera caroliniensis

Squares represent populations verified since 1986, triangles represent historic populations not seen since 1956; numbers refer to sites listed in Table 1.