Gold-edged gem (Schinia avemensis) COSEWIC assessment and status report: chapter 4

Distribution

Global range

The global range of the Gold-edged Gem extends from Spruce Woods Provincial Park in southwestern Manitoba west to eastern Alberta, and south to southern Colorado (Figure 2). The maximum global extent of occurrence (EO) encompasses approximately 340,600 km². Within the global range, Gold-edged Gems occur as four disjunct populations, two in Canada and two in Colorado, USA.

Canadian range

The Canadian range, both current and historical, extends from southwestern Manitoba to southeastern Alberta. The extent of occurrence (EO) in Canada is approximately 70,500 km². The known area of occupancy (AO) encompasses only four small areas of active sand dunes or blow-outs, an area of about 1.5 km² in total (G. Anweiler, unpublished; C. Schmidt, personal communication, 2004). There are a number of additional smaller areas of potential Gold-edged Gem habitat scattered throughout the EO in southeastern Alberta and southwestern Saskatchewan. In total these are estimated to not exceed an additional 3-5 km² of poorer quality habitat, i.e., extremely fragmented and of small size individually.

Figure 2. Collection sites for the Gold-edged Gem

Figure 2. Collection sites for the Gold-edged Gem.

The sites where Gold-edged Gems were found in Saskatchewan and Alberta are separated by approximately 50 km, and these two sites are each approximately 180 km from the third occupied Alberta site (Pakowki Lake). The Alberta-Saskatchewan and Manitoba populations are separated by about 750 km.

There are extensive dune formations in southwestern Saskatchewan (i.e., Bigstick – Crane Lake Sand Hills, Great Sand Hills, Burstall Sand Hills) and southern Alberta (i.e., Middle Sand Hills, Empress dunes) that contain active dunes and blow-outs (David, 1977; G. Anweiler, unpublished data), and it is highly probable that additional colonies of Gold-edged Gems occur therein.

The historic range of the Gold-edged Gems is essentially the same as the current range. Although the presence of the Gold-edged Gem in southern Saskatchewan and Alberta was unsuspected prior to 2004, a previously unidentified museum specimen collected at Medicine Hat in southwestern Alberta in 1939 indicates they have been there for many years (C. Schmidt, personal communication, 2004).

All Canadian populations of Gold-edged Gems are located within the Prairie National Ecological Area (COSEWIC, 2003). The Manitoba site is within the Aspen Parkland Ecoregion in a humid to sub-humid region; the Saskatchewan-Alberta sites are located within the more arid Mixed Grassland Ecoregion (Wolfe, 1997; Padbury and Acton, 1991).

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