Assessed by COSSARO as Threatened
February 2011
Final

Part 1 COSSARO Candidate Species at Risk Evaluation Form

February 2011
Pitcher’s Thistle (Cirsium pitcheri)

Current designations:

GRANKG3
NRANK Canada – N2
COSEWIC – Special concern (November 2010)
SARA – Endangered (Schedule 1)
General Status Canada – At risk (2005)
ESA 2007 – Endangered (Schedule 3)
SRANKS2
General Status Ontario – At risk (2005)

Distribution and status outside Ontario:

This species is a Great Lakes endemic that occurs only on sand dunes along the shorelines of Lakes Huron, Superior and Michigan. In addition to Ontario it occurs in Michigan, Wisconsin, Indiana and Illinois (COSEWIC 2010).

Eligibility criteria

Native status

Yes. The species occurs only along the Great Lakes in Ontario and several adjacent US states (COSEWIC 2010).

Taxonomic distinctness

Yes. There are no taxonomic controversies surround this species, which has been consistently classified as Cirsium pitcheri.

Designatable units

COSEWIC (2010) considered all Ontario populations as one designatable unit. Gauthier et al. (2010) determined that there is some genetic distinctness of the Pukaskwa (Lake Superior) population most likely attributable to geographic isolation and genetic drift. The southern Lake Huron populations were not included in the study.

Priority-setting criteria

Recent arrival

No. The species has long been known to occur in Ontario (COSEWIC 2010).

Non-resident

No.

Primary criteria (rarity and declines)

  1. Global rank
    TH. The global status rank of Pitcher’s Thistle as vulnerable (G3).
  2. Global decline
    Not in any category. No indication that Pitcher’s Thistle has decreased significantly in global range.
  3. Northeastern North America ranks
    EN. Pitcher’s Thistle is ranked S1, S2, or SX in 80% of the 4 northeastern North American jurisdictions where it occurs (Table 1).
  4. Northeastern North America decline
    Not in any category. No indication that Pitcher’s Thistle has decreased significantly in northeastern North America which is the same as the global range.
  5. Ontario occurrences
    SC. There are 30 element occurrences, all of which are extant (COSEWIC 2010). COSEWIC reports a total population estimate of over 50,000 individuals in Ontario.
  6. Ontario decline
    Not in any category. The number of known populations in Ontario has increased from 10 to 30 since 2000 (COSEWIC 2010). Twenty-five occurrences in the vicinity of Manitoulin Island are estimated to have a total population of 50,000 plants. The discovery of several new populations in recent years has significantly increased the known population size (COSEWIC 2010). Of the 30 occurrences, 15 are increasing, seven are fluctuating, three are stable and five are significantly declining.
  7. Ontario’s conservation responsibility
    TH. The Ontario occurrences are believed to comprise 15% of the global population and 25% of the global geographic range of the species (Jalava 2008).

Secondary criteria (threats and vulnerability)

  1. Population sustainability
    Not in any category. Half of the Ontario occurrences show signs of increasing and many of these populations are quite large therefore these populations appear to be sustainable.
  2. Lack of regulatory protection for exploited wild populations
    Not in any category. No known harvest in Ontario.
  3. Direct threats
    Not in any category. Threats to Pitcher’s Thistle include succession (dune stabilization and shading by shrubs), invasive plants, trampling by beach users, beach vegetation management, All terrain vehicles (ATVs) and browsing by deer. Shoreline erosion and sand blowouts threaten some populations (COSEWIC 2010). Currently these threats are not severe enough to cause decline at 25% of Ontario sites.
  4. Specialized life history or habitat-use characteristics
    TH. Pitcher’s Thistle inhabits active sand dunes along Great Lake shorelines, including several provincially rare community types. It is susceptible to stabilization of dunes through natural succession or climate change (COSEWIC 2010). Pitcher’s Thistle is a monocarpic perennial requiring 3 to 11 years to flower, after which it dies. The prolonged non-flowering period make it vulnerable to environmental changes.

COSSARO criteria met (primary/secondary)

Endangered – [1/0]
Threatened – [2/1]
Special concern – [1/0]

Recommended status: Threatened.

Summary

Pitcher’s Thistle (Cirsium pitcheri) is Threatened in Ontario. This perennial plant lives as a basal rosette for 3 to 11 years and then dies after flowering once. It is a Great Lakes endemic found on shoreline sand dunes on Lakes Huron and Superior in Ontario. It inhabits a provincially rare habitat (Great Lakes coastal dunes) and its life history is specialized in terms of habitat. Many new populations have been discovered in the vicinity of Manitoulin Island in the past 10 years, substantially increasing the population estimate for the province. Many of these populations show signs of increase. The populations outside of Manitoulin are smaller and not faring as well. The reasons for the listing include the vulnerability of populations on shores in Lake Huron and Lake Superior, the specialized life history, and Ontario’s conservation responsibility.

Information sources

COSEWIC. 2010. COSEWIC Status Report on Pitcher’s Thistle Cirsium pitcheri in Canada. 2-Month Interim Report, September 2010

Jalava, J.V. 2008. Recovery strategy for Pitcher’s Thistle (Cirsium pitcheri) – Lake Huron Dune Grasslands in Canada. Species at Risk Act Recovery Strategy Series. Parks Canada Agency, Ottawa. Xi + 38 pp. + appendices.

Appendix 1 Northeastern North America rank, status and decline

CTNot present
DENot present
ILS1
INS2
IANot present
KYNot present
LBNot present
MANot present
MBNot present
MDNot present
MENot present
MIS3
MNNot present
NBNot present
NFNot present
NHNot present
NJNot present
NSNot present
NYNot present
OHNot present
ONS2
PANot present
PENot present
QCNot present
RINot present
VANot present
VTNot present
WIS2
WVNot present

Occurs as a native species in 5 of 29 northeastern jurisdictions SRANK or equivalent information available for 5 of 5 jurisdictions = 100% S1, S2, SH, or SX in 4 of 5 = 80%

Part 2 Ontario evaluation using COSEWIC criteria

Regional (Ontario) COSEWIC criteria assessment

Criterion A – Decline in total number of mature individuals

N/A. 15 of 30 Populations appear to be increasing and only 5 are showing decline. Ontario population estimate is significantly higher than it was in 2000.

Criterion B – Small distribution range and decline or fluctuation

N/A. EO, if linear shoreline habitat is used, and IAO are both within limits but populations are not severely fragmented and the applicability of number of locations is in doubt; some decline in quality of habitat is on-going but no extreme fluctuations are evident

Criterion C – Small and declining number of mature individuals

N/A. No continuing decline demonstrated.

Criterion D – Very small or restricted total population

N/A. Population size is too large and IAO exceeds limits.

Criterion E – Quantitative analysis

N/A; none conducted

Rescue effect

No. Possibly because there are many populations in Michigan however considered unlikely because populations are more than 100 km which is reported as dispersal limit

COSEWIC Status: Special Concern