Willowleaf aster (Symphyotrichum praealtum) COSEWIC status assessment and status report chapter 7

Population Sizes and Trends

About 12 extant populations are known. The species is clonal and actual numbers of individuals are difficult to determine, but clone sizes range from one shoot to over 100 shoots. Three populations are known only from reports in the 1960s. At least one population has definitely been extirpated but possibly as many as five in total. With the likely loss of the Pt. Edward locality at Sarnia (site 3 below), the extent of occurrence has declined. No population trend information is available. Indications from local biologists is that the species is locally common within the remnant prairies in Windsor as well as being found in disturbed habitats such as abandoned fields (pers. comm. Paul Pratt, Naturalist, Windsor Department of Parks and Recreation, July 2002). The species is also similar to white panicle aster (S. lanceolatum) and might be confused with that species (pers. comm. Mike Oldham, Ontario NHIC, Peterborough, July 2002).

Plants have been collected or observed at the locations documented in Table 1 based on herbarium records. [In some instances it is difficult to definitively correlate localities indicated on specimen labels with those documented by the authors during their fieldwork surveys.

Extirpated populations or of unknown status:

  1. Essex Co.: Windsor, Titcombe field; lat/long: 42°18’N / 83°01’W; 11 Oct. 1971, W. Botham 1372A (CAN 498454) - extirpated
  2. Municipality of Chatham-Kent: Harwich Twp., Rondeau Provincial Park. 1956, W.J. Cody s.n. (DAO).
  3. Lambton Co.: Pt. Edward (Sarnia). 24 Sep. 1958, L.O. Gaiser 1848PE (OAC).
  4. Lambton Co.: Squirrel Island. 10 Sep. 1916, N. Tripp s.n. (OAC).
  5. Middlesex Co.: Cairngorm. 8 Oct. 1960, Y.S. Shaw s.n. (UWO 23765).

Potential Sites for Investigation:

  • Tall-grass prairies in Windsor and Sarnia areas and Walpole Island First Nation.

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