False-rue anemone COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Information about meta-populations in Ontario is summarized in Table 1. This information is based on field visits made by Austen during May and June 1989 and fieldwork conducted by J. Bowles in the summers of 1986, 1988, and 1989.  Estimates of numbers of plants per sub-population are presented for localities visited in May 1989 by Austen.  These estimates were based on stem counts for smaller populations and on the amount of area covered by colonies for larger populations.  Updated information is based on field surveys done by M. Thompson in May 2003 and June 2004 (six days). 

Numbers represent total number of stems found at the site, both vegetative and flowering.  It is difficult to determine the number of clones represented in some of the sub-populations without damaging the plants.  The use of the term "subpopulations" indicates separate groupings of plants (or separate clones) that are part of a larger meta-population with each of the subpopulations generally being less than 1 km apart (NHIC, 2002).

Summary of extant populations

At one time, Enemion biternatum was found within 8 areas of southwestern Ontario.  The 1990 status report (Austen, 1990) documented 4 areas for Ontario.  Six populations in Ontario were extant as of the year 2003.  These sites are Medway Creek, Kettle Creek north of Port Stanley, Ausable River, Parkhill, Thames River, and Kettle Creek.  Three of these populations (Medway Creek, Kettle Creek north of Port Stanley, and Ausable River) consist of 2 to 10 subpopulations.

The Medway Creek population in Middlesex County represents an important segment of the Canadian population due to the large numbers of plants.  Arisaema dracontium and Lithospermum latifolium, both rare plants in Ontario, are also found in the area.  The 10 subpopulations within this population are in a public use area, which is unlikely to be developed because it is a floodplain zone managed by the Upper Thames River Conservation Authority (Austen, 1990).

Table 1. Ontario population summary for Enemion biternatum
EOID Sub-population # Location 1897, L. Boughner pre 1986, D. Britton 1988 1989, J. Bowles 1989, M. Austen 1993, M.J. Oldham 1994, J. Bowles 2002, D. Bradley 2003 2004, M.J. Thompson
2 2a Medway Creek       1 colony, 200 plants       Not found
2 2b Medway Creek     4 colonies         Not found
2 2c Medway Creek       <500 plants       Not found
2 2d Medway Creek     ?         Not found
2 2e Medway Creek     1 colony, 2500 plants         Not found
2 2f Medway Creek       3 colonies, 12 500 plants       Not searched
2 2g Medway Creek       4 colonies, 1750 plants       Not found
2 2h Medway Creek       15 000-20 000 plants       35 000 plants
2 2i Medway Creek       1 colony, 500 000-700 000 plants       500 000-700 000 plants
2 2j Medway Creek       1 colony, 50-75 plants       Not found
1 1a Kettle Creek, North of Port Stanley       30 colonies, 12 500 plants       10 000 plants
1 1b Kettle Creek, North of Port Stanley       25 colonies, 10 000 plants       10 000 plants
1 1c Kettle Creek, North of Port Stanley       8 colonies       Not found
1 1d Kettle Creek, North of Port Stanley       10 colonies, 800 plants       Not found
1 1e Kettle Creek, North of Port Stanley       100s of thousands of plants       100 000 plants
1 1f Kettle Creek, North of Port Stanley       9 colonies, 12 000 plants       10 000 plants
1 1g Kettle Creek, North of Port Stanley       6 colonies, 3500 plants       3000 plants
1 1h Kettle Creek, North of Port Stanley       2 colonies, 3500-5000 plants       3000 plants
4 4a Ausable River       14 colonies, 2500-3000 plants       Not found
4 4b Ausable River         20-30 colonies, 50-100 plants per colony     1000 plants
5 5 Thames River           ?   Pas de permission
3 3 Parkhill             11 colonies, 400 plants Not surveyed
6   Middlemarch Forest   ?           Extirpated
7   Lynn Valley ?             Extirpated
17 17 Kettle Creek         ?     Not found

Note: EOID indicates the Element Occurrence ID number associated with information stored for each occurrence at the Ontario Natural Heritage Information Centre, Peterborough. The question marks indicate that only occurrence was noted and no population data were provided.

Similarly, the population located along Kettle Creek and its tributaries (Elgin Co.) is also particularly significant since the scattered subpopulations, often with thousands of plants each, are found associated with other rare taxa such as Mertensia virginica.  Some subpopulations here are often bordered by farmers’ fields or steep wooded slopes on one side and Kettle Creek or one of its tributaries on the other.  This area is under the ownership of one family. The population found along the Ausable River (Lambton County), was the only one found in the county by Austen (1989). 

Population 3, located at Parkhill Conservation Area, was thought to be extirpated and was last collected in 1893.  This population has since been rediscovered (Bradley, 2002).

Population 5, located along the Thames River is likely extant (M. Oldham, pers. com).  There has been no data collected on this population to date. The record is based on a sighting by Jane Bowles in 1994 (NHIC, 2002).

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