Dusky dune moth (Copablepharon longipenne) COSEWIC assessment and status report: chapter 6

Distribution

Global Range

The distribution of Copablepharon longipenne is associated with the Great Plains, a geologically defined region running through the centre of North America (Trimble, 1990). Copablepharon longipenne is found from southern Manitoba, Saskatchewan, and Alberta, to western Texas and southern New Mexico (Figure 2). The most northern locality is near Saskatoon, Saskatchewan, and the most southern is near Paducah in north central Texas. The estimated extent of occurrence is 1 258 285 km2 globally.


Figure 2: Distribution of Copablepharon longipenne in North America

Figure 2. Distribution of Copablepharon longipenne in North America.

Occurrences are shown as black dots and the extent of occurrence is depicted with the black line.


Canadian Range

The estimated extent of occurrence in Canada is 164 480 km2 based on a minimum convex polygon encompassing all known localities in Canada. Except for the population near Brandon, MB, all known populations are found in the Palliser Triangle, a region of dry, shortgrass prairie that extends from the southwestern corner of Manitoba to south central Alberta and as far north as Lloydminster, SK (Barendregt et al., 1988). The Palliser Triangle is the driest region in the Canadian prairies.Copablepharon longipenne was not captured in more northern dune areas near North Battleford, SK and Wainwright, AB despite repeated light-trapping surveys. It has, however, been recorded historically from nearby Rivercourse, AB. More formally, most of the Canadian range of C. longipenne is in the mixed grassland ecoregion of the prairie ecozone (Marshall and Schut, 1999). The population in Manitoba occurs in the aspen parkland ecoregion of the prairie ecozone. The estimated maximum area of occupancy is 126 km2 in Canada. Area of occupancy encompassed known or suspected presence in open dune habitats within C. longipenne’s Canadian range measured using a 1 km grid overlaid on Landsat satellite imagery from 2000; grid squares with open sand dunes were considered occupied habitat. However, the species is definitely absent from some apparently suitable areas. For known populations, the AO is estimated to be less than 50 km2.

Copablepharon longipenne has been recorded at 12 localities in Canada since 1922, representing 12 populations (Figure 3; Appendix 1): five in Alberta, six in Saskatchewan, and one in Manitoba. Three of the 12 localities were discovered in southern Saskatchewan (Dundurn, Cramersburg, and Seward sand hills) by N.A. Page in 2004–2005 and one new population was recorded at Dune Point in southern Alberta by B.C. Schmidt (Appendix 1). Additional sites in the southern Canadian prairies may support C. longipenne. Figure 3 shows the location of four suspected localities based on the presence of active sand dunes. It is not known if C. longipenne has been extirpated from any sites in Canada. Active sand dunes no longer occur in the Lethbridge area, and it is unlikely that the population recorded there in 1922 is still present. Vegetation stabilization of sand dunes in the Middle Sand Hills and elsewhere may have caused extirpation of some populations or subpopulations.


Figure 3: Distribution of Copablepharon longipenne in Canada

Figure 3. Distribution of Copablepharon longipenne in Canada.

Black dots represent known localities and open dots indicate dune or dry grasslands sites sampled in 2004–2005 in which C. longipenne was not captured. Triangles represent suspected localities identified during field work or through air photo interpretation; other sites may exist.


Population Structure

Copablepharon longipenne is associated with sparsely vegetated active sand dunes or blowouts that generally occur as spatially isolated patches within larger areas of dry, sandy grassland. Active dunes are often clustered because of shared substrate conditions and physical processes. The largest area of active sand dunes in Canada is the Great Sand Hills in southwestern Saskatchewan where four clusters of active dunes occur.

The population structure of C. longipenne reflects the spatial patterns of sand dune features at both the regional and local scale. Populations likely occur across multiple active sand dunes within a landscape of stable, semi-stable, and active dunes. Dispersal between nearby sand dunes (e.g., 250–1000 m apart) is likely but unsubstantiated, but dispersal between regionally isolated dune fields is likely very rare. However, that C. longipenne recolonized the southern Canadian prairies after the last glacial period may suggest long-distance dispersal to be possible. Figure 4 shows the distribution of dune fields and sandy habitats in southwestern Saskatchewan and the distribution of active sand dunes in a representative area of the Great Sand Hills. Areas between the sand dune areas are likely inhospitable to C. longipenne because of different soils and agricultural activity.


Figure 4: Regional and Local Scale Distribution of Sand Dunes in Southwestern Saskatchewan

Figure 4. Regional and local scale distribution of sand dunes in southwestern Saskatchewan.

Landsat image from 2000. The inset box shows active sand dunes (white patches) in a portion of the Great Sand Hills near Liebenthal, SK (Straw Road dune cluster). The juxtaposition of the sandy habitats (dark patches) amongst the heavily developed agricultural landscape is clear.

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