False-rue anemone COSEWIC assessment and status report: chapter 11

Technical Summary

Enemion biternatum

False Rue-anemone – isopyre à  feuilles biternées

Range of Occurrence in Canada:

Ontario

Extent and Area Information

Extent of occurrence (EO) (km²)
about 1000 km² excluding extirpated site #7; or <3500 km² including site #7. Extent of occurrence was calculated with a GIS by enclosing all known populations within a polygon and calculating the area as well as after eliminating the extirpated site #7 (E.Haber)
Specify trend in EO
Stable
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
<20 km². Area of occupancy was calculated by taking the linear distance from Lake Erie shore to populations in region of Lake Huron (ca 80 km) x maximum corridor width of riparian habitat (.25 km) = 20km². This is an overestimate of available riparian habitat surrounding the 6 populations which are actually discontinuous and fragmented within their riparian habitats (E. Haber).
Specify trend in AO
Decline in quality of habitat based on impacts noted
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations
6 populations
Specify trend in #
Stable ?
Are there extreme fluctuations in number of locations?
No
Specify trend in area, extent or quality of habitat
Habitat quality decline due to exotic plants in floodplain habitats

Population Information

Generation time (average age of parents in the population)
Unknown (likely several years to flowering of a new individual or new shoot of a clone)
Number of mature individuals
1 million stems in scattered sub-populations (species is clonal)
Total population trend:
Stable
% decline over the last/next 10 years or 3 generations.
No data
Are there extreme fluctuations in number of mature individuals?
No
Is the total population severely fragmented?
Yes, between watersheds but likely not within watersheds
Specify trend in number of populations
Stable
Are there extreme fluctuations in number of populations?
No
List populations with number of mature individuals in each:
See Table 1

Threats (actual or imminent threats to populations or habitats)

  • Habitat destruction
  • invasive plants
  • trampling

Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA : Stable
Is immigration known or possible?
Unknown
Would immigrants be adapted to survive in Canada?
Possibly
Is there sufficient habitat for immigrants in Canada?
Possibly
Is rescue from outside populations likely?
Unlikely due to lack of specialized means of dispersal

Quantitative Analysis

N/A

Current Status

COSEWIC: Threatened (May 2005)

Status and Reasons for Designation

Status:  Threatened

Alpha-numeric code:  Met criteria for Endangered, B1ab(iii)+2ab(iii), but designated Threatened because the populations appear stable and not at imminent risk of extirpation. Criteria met for Threatened: B1ab(iii)+2ab(iii); D2.

Reasons for Designation: A delicate, spring-flowering, perennial herb restricted to a few fragmented riverside forest sites in southwestern Ontario where its populations are at risk from habitat loss and decline in quality due to a variety of activities including recreational trail use, and expansion of exotic invasive plants.

Applicability of Criteria

  • Criterion A (Declining Total Population): Insufficient information
  • Criterion B (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab(iii)+2ab(iii) based on extent of occurrence and area of occupancy well below critical maximum levels and the populations are severely fragmented due to the fragmented nature of the wooded areas in southwestern Ontario. A continued decline in quality of habitat can be inferred based on the proximity of trails and expanding populations of exotic invasive plants. Populations of this perennial, clonal, species are not known to fluctuate. Since the populations seem to be relatively stable and not at imminent risk of extirpation but decline in habitat quality is on-going, the species is best regarded as threatened.
  • Criterion C (Small Total Population Size and Decline): Not met. The estimate given of perhaps 1 million stems does not take into account that the plants produce tubers and that they likely form clonal patches. Nevertheless, there are more than the maximum limit of 10,000 plants under this criterion.
  • Criterion D (Very Small Population or Restricted Distribution): Meets Threatened D2 based on an area of occupancy that is likely much less than 20 km² and a variety of direct threats are known.
  • Criterion E (Quantitative Analysis): No analysis is available.

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