Willowleaf aster (Symphyotrichum praealtum) COSEWIC status assessment and status report chapter 12
Technical Summary
Symphyotrichum praealtum
Willowleaf Aster – Aster très élevé
Range of Occurrence in Canada:
Ontario
Extent and Area information
extent of occurrence (EO) (km²)
<1000
specify trend (decline, stable, increasing, unknown) :
decline
are there extreme fluctuations in EO (> 1 order of magnitude)?
no
area of occupancy (AO) (km²) :
perhaps only about 20
specify trend (decline, stable, increasing, unknown) :
decline in typical habitat
are there extreme fluctuations in AO (> 1 order magnitude)?
no
number of extant locations :
about 12 primarily within 2 areas (Windsor and Walpole Is.)
specify trend in # locations (decline, stable, increasing, unknown) :
decline
are there extreme fluctuations in # locations (>1 order of magnitude)?
no
habitat trend: specify declining, stable, increasing or unknown trend in area, extent or quality of habitat :
decline
Population information
generation time (average age of parents in the population) (indicate years, months, days, etc.) :
perhaps 2-3 years
number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values) :
perhaps several thousand stems in total estimated based on inferences from 7 sites with clones of various sizes seen in 1997)
total population trend: specify declining, stable, increasing or unknown trend in number of mature individuals :
unknown
if decline, % decline over the last/next 10 years or 3 generations, whichever is greater (or specify if for shorter time period)
are there extreme fluctuations in number of mature individuals (> 1 order of magnitude)?
no
is the total population severely fragmented (most individuals found within small and relatively isolated (geographically or otherwise) populations between which there is little exchange, i.e., < 1 successful migrant / year)?
likely fragmented due to presence in remnant prairie sites and meadows in a region with little of the original habitats remaining
list each population and the number of mature individuals in each :
no precise data are available but locally common in the Windsor area
specify trend in number of populations (decline, stable, increasing, unknown) :
at least 1 and possibly 5 historic sites lost and likely many local populations/sub-populations lost within the Windsor and Walpole Is. areas.
are there extreme fluctuations in number of populations (>1 order of magnitude)?
no
Threats (actual or imminent threats to populations or habitats)
- some plants found as roadside clones subject to human activities;
- reduced seed production in some clones due to the need for out-crossing;
- potential development of some sites planned
Rescue Effect (immigration from an outside source)
Low
does species exist elsewhere (in Canada or outside)?
USA
status of the outside population(s)?
adjoining states: MI S3; PA S3; OH SR; NY SR
is immigration known or possible?
unlikely due to fragmented habitat
would immigrants be adapted to survive here?
probably
is there sufficient habitat for immigrants here?
not much prairie but various types of open habitat are present
Quantitative Analysis
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