Ogden's Pondweed (Potamogeton ogdenii) COSEWIC assessment and status report: chapter 11
Technical Summary
Potamogeton ogdenii
Ogden’s pondweed – potamot de Ogden
Range of Occurrence in Canada:
Ontario
Extent and Area Information
Extent of occurrence (EO) (km²)
Based on a polygon including the three known specimens. For the purposes of this calculation, central Hastings County was arbitrarily used as the site of the 1873 collection. Although old, its vague locality precludes it being considered extirpated : ca. 1000 km²
Specify trend in EO :
unknown
Are there extreme fluctuations in EO?
unlikely
Area of occupancy (AO) (km²)
On the basis that the Davis Lock and Murphys Point sites are extant. actual area <1 km² (<2 ha) but based on a grid system of 2 km² certainly < 20 km²
Specify trend in AO :
(loss of beaver pond population at Black Creek). decline due to the loss of one recent location
Are there extreme fluctuations in AO?
unknown
Number of known or inferred current locations :
(historic Hastings Co population unknown but possibly still extant; possibly present in Murphys Point Prov. Park near former Black Creek population, and possibly still extant at Davis Lock) . 0-3
Specify trend in # :
(loss of Black Creek population) decline
Are there extreme fluctuations in number of locations?
no
Specify trend in area, extent or quality of habitat :
(loss of area at Black Creek and likely loss of quality due to spread of aquatic invasive plants). decline
Population Information
Generation time (average age of parents in the population):
(most plants reproduce vegetatively and overwinter as specialized winter buds). Unknown but potentially several years from seed to flowering
Number of mature individuals :
unknown
Total population trend:
decline (loss of Black Creek population)
% decline over the last/next 10 years or 3 generations.
unknown
Are there extreme fluctuations in number of mature individuals?
unknown
Is the total population severely fragmented?
(Two recent localities are within the same drainage and dispersal is by water and possibly waterfowl). no
Specify trend in number of populations :
decline
Are there extreme fluctuations in number of populations?
no
List populations with number of mature individuals in each :
none verified but potentially up to 3 sites with plants extant
Threats (actual or imminent threats to populations or habitats)
- Loss of most of aquatic habitat observed at one site;
- threats to other site(s) mainly potential due to spread of aquatic invasive plants
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA : ranks in adjacent states are: New York (S1)
Is immigration known or possible?
unlikely
Would immigrants be adapted to survive in Canada?
yes
Is there sufficient habitat for immigrants in Canada?
yes
Is rescue from outside populations likely?
no
Quantitative Analysis
none available
Current Status
COSEWIC: Endangered (2007)
Status and Reasons for Designation
Status: Endangered
Alpha-numeric code: B1ab(ii,iii,iv)+2ab(ii,iii,iv)
Reasons for Designation: This species is an aquatic plant that is globally at risk with low population numbers and only 11 extant sites known worldwide. In Canada, it is known from only 3 sites in southeastern Ontario where it was last collected in 1987. Recent fieldwork has documented the loss of habitat and probable extirpation of one population but failed to relocate the others – one of these is a historic site in a relatively undisturbed region with no specific locality information. The presence of aquatic invasive plants in areas around presumed extant populations suggests a further decline in overall area and quality of habitat for native pondweeds. However the species, which is easily confused in the field with other similar narrow-leaved pondweeds, may still be present in Canada in suitable habitats in the vicinity of previously known sites.
Applicability of Criteria
Criterion A: (Declining Total Population): Not met. Insufficient information.
Criterion B: (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab(ii,iii,iv)+2ab(ii,iii,iv) due to the small extent of occurrence and area of occupancy, presence at fewer than 5 sites and continued decline in area of occupancy due to the loss of the Black Creek population and presumed decline in area of potential habitat in and around Big Rideau Lake due to the spread of invasive aquatic species. Although the presence of the two other populations could not be confirmed, one or more populations may still be extant as suitable habitat appears to be present.
Criterion C: (Small Total Population Size and Decline): Not met. Insufficient information since population size is unknown.
Criterion D: (Very Small Population or Restricted Distribution): Likely meets Threatened, D2, based on the presence of fewer than 5 sites within an area of occupancy < 20 km² and the presence of an aggressively invasive aquatic plant in waters adjacent to the Davis Lock site.
Criterion E: (Quantitative Analysis): Not met. No analysis available.
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