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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