Gold-edged gem (Schinia avemensis) COSEWIC assessment and status report: chapter 11

Technical Summary

Schinia avemensis

Gold-edged Gem – Héliotin d'Aweme

Range of Occurrence in Canada:

Prairie Ecological Area, southwestern Manitoba to southeastern Alberta (MB, SK and AB)

Extent and Area Information

Extent of occurrence (EO)(km²)
70,500 km². Area of polygon as per COSEWIC 2003 (including all extant sites in Canada)
Specify trend in EO
significant past declines; stable over short term
Are there extreme fluctuations in EO?
probably not
Area of occupancy (AO) (km²)
approx. 1.5 km² total at 4 extant sites (max. potential AO =~ 6 km²). Conservative estimate of occupied habitat as per 2004-5 observations
Specify trend in AO
decline or stable
Are there extreme fluctuations in AO?
none known
Number of known or inferred current locations
2 populations at 5 sites
Specify trend in #
probably stable
Are there extreme fluctuations in number of locations?
none known
Specify trend in area, extent or quality of habitat
severe long-term historic decline; slow decline or stable at present.

Population Information

Generation time (average age of parents in the population)
1 year, longer diapause over more than 1 year is possible
Number of mature individuals
unknown; estimate in the range of 700-6,000
Total population trend:
slow decline or stable
 % decline over the last/next 10 years or 3 generations.
unknown; probably stable
Are there extreme fluctuations in number of mature individuals?
probably, but no data to measure
Is the total population severely fragmented?
yes
Specify trend in number of populations
probably stable
Are there extreme fluctuations in number of populations?
none known
List populations with number of mature individuals in each:
  • Spirit Dunes, MB – 500-5,000 est.
  • Burstall SK (unknown)
  • Bindloss & Pakowki AB 200-1,000 est.

Threats (actual or imminent threats to populations or habitats)

Stabilization of active sand dune habitat by native and introduced vegetation due to largely natural processes, probably accelerated since settlement due to suppression of wildfires.

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA: Probably stable
Is immigration known or possible?No
Would immigrants be adapted to survive in Canada?
Possibly but unlikely
Is there sufficient habitat for immigrants in Canada?
Yes
Is rescue from outside populations likely?
No

Quantitative Analysis

Current Status

COSEWIC: Endangered (2006)

Status and Reasons for Designation

Status: Endangered

Alpha-numeric code: B2ab(iii)

Reasons for Designation: This moth is a habitat specialist that needs dunes or blow-outs with populations of its sole larval host plant. It is known from only two small populations in Canada and two in the United States. Large-scale decline in active dune habitat over the past 100 years has likely resulted in a corresponding reduction in the moth. Only very small, scattered, isolated patches of suitable habitat, totalling approximately 6 km², remain. They are threatened by habitat loss in the form of stabilization of active dunes by both native and introduced vegetation and by overgrazing of their larval host plant, which severely impacts small, isolated populations of the moth. The closest population of the moth in the United States is about 1,200 km to the south in Colorado, so immigration of individuals into the Canadian population is not possible.

Applicability of Criteria

  • Criterion A: (Declining Total Population): Not applicable, no decline data
  • Criterion B: (Small Distribution, and Decline or Fluctuation): Although the extent of occurrence is large, the area of occupancy is smaller than 500 km² (known AO is approximately 1.5 km²; max potential AO is approximately 6 km²) – B2 the total population is severely fragmented with the species known to occur as 2 populations spread over 5 sites – (a) the area and quality of suitable habitat are continuing to decline – (b)(iii) but there is no evidence for extreme fluctuations
  • Criterion C: (Small Total Population Size and Decline): not applicable, no decline data and insufficient information on population structure
  • Criterion D: (Very Small Population or Restricted Distribution):  Meets Threatened under D2. The total population occurs at a restricted number of locations (2 populations at 5 sites) and the area of occupancy is very small and restricted (max of approximately 6 km²) such that the species appears to be prone to the effects of human activities and stochastic events.
  • Criterion E: (Quantitative Analysis): not applicable, no data.

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