Pale yellow dune moth (Copablepharon grandis) COSEWIC assessment and status report: chapter 4

Distribution

Global range

Copablepharon grandis is widely distributed in western North America but sampling records suggest it is most prevalent in the arid steppe of the Great Basin and the southern Rocky Mountains (Figure 2). It has been found from southern California in the southwest tocentral Texas in the southeast and as far north as Lloydminster, AB. Its global extent of occurence is 4,345,223 km². The species appears to have a range disjunction with one group of occurrences in the southwestern US, and a second group west of the Great Lakes and extending in to the southern Canadian prairies. More sampling is needed in the intervening portion of the Great Plains to ascertain C. grandis’ distribution more completely. The moth has been found at approximately 84 localities in North America since it was described in 1878.

Figure 2. Distribution of Copablepharon grandis in North America. The extent of occurrence is shown with the dark line.

Figure 2. Distribution of Copablepharon grandis in North America. The extent of occurrence is shown with the dark line.

Canadian range

Since 1902, C. grandis has been captured 36 times in ten localities in Canada (Figure 3): four in Alberta, five in Saskatchewan, and one in Manitoba. Three of the ten localities were found during the 2004–2005 sampling program (Appendix 1). Its Canadian extent of occurence is 184,590 km² based on a minimum convex polygon encompassing all known localities in Canada. Some additional populations are likely to occur in the Canadian prairies. Copablepharon grandis has not been captured in the active sand dunes of the Palliser Triangle, such as the Great Sand Hills or Middle Sand Hills. An additional record is noted in Strickland (1920, p. 82): “on May 9 [1913] a single larva of C. grandis was taken in a stubble field at Monarch, Alberta”. However, this specimen is not available for taxonomic review and cannot be verified. It is included in Figure 3 with a unique symbol. Monarch, AB is northwest of Lethbridge on the Oldman River and is an area of arid, sandy habitats. The Canadian range of C. grandis is in the aspen parkland ecoregion and moist mixed grassland of the prairie ecozone (Marshall and Schut, 1999).

The estimated maximum area of occupancy is 203 km² in Canada. This is based on area of occupancy encompassed by known or suspected presence in habitats within the Canadian range measured with a 1 km grid overlaid on Landsat satellite images obtained in 2000; grid squares with suitable habitat were considered occupied. The area of occupancy is less than 50 km² based on a 2X2 km² grid overlaid on actual occurrences.

Figure 3. Distribution of Copablepharon grandis in Canada. Black dots represent known localities. Open circles indicate sites with sparsely vegetated sandy habitats sampled in 2004–2005 in which C. grandis was not captured. An unverified record from Monarch, AB (Strickland, 1920) is shown with a black triangle.

Figure 3. Distribution of Copablepharon grandis in Canada.

Population structure

The population structure of C. grandis, including the boundaries of populations and the occurrence of subpopulations, is poorly understood. Sampling records indicate that C. grandis is found in sparsely vegetated, sandy habitats that are patchily distributed within a matrix of more densely vegetated grasslands, shrublands, and forests. This distribution suggests that populations may be composed of subpopulations that are connected through dispersal at a local scale (0.5–2 km), but are isolated at a regional-scale (Figure 3).

Page details

Date modified: