White wood aster (Eurybia divaricata) COSEWIC assessment and status report: chapter 12
TECHNICAL SUMMARY
Eurybia divaricata (L.) Nesom | |
White wood aster Heart-leaved aster |
aster divariqué |
Occurrence in Canada: | Ontario and Quebec |
Extent and Area information | ||
· extent of occurrence (EO)(km²) | <1500 | |
· specify trend (decline, stable, increasing, unknown) | In Ontario, populations appear to be stable presently but have declined in the past. Infrequent data collection for populations in Quebec makes it hard to predict trends. | |
· are there extreme fluctuations in EO (> 1 order of magnitude)? | No | |
· area of occupancy (AO) (km²) | <50 | |
· specify trend (decline, stable, increasing, unknown) | Stable | |
· are there extreme fluctuations in AO (> 1 order magnitude)? | No | |
· number of extant locations | 25 | |
· specify trend in # locations (decline, stable, increasing, unknown) | Increase in reported number of locations in Ontario. Increase in reported number of locations in Quebec. |
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· 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 | Unknown | |
Population information | ||
· generation time (average age of parents in the population) (indicate years, months, days, etc.) | Unknown | |
· number of mature individuals (capable of reproduction) in the Canadian population (or, specify a range of plausible values) | 8000-9000 individuals in scattered populations | |
· total population trend: specify declining, stable, increasing or unknown trend in number of mature individuals | Stable | |
· 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)? | Yes | |
· list each population and the number of mature individuals in each | See Tables 1 & 2 | |
· specify trend in number of populations (decline, stable, increasing, unknown) | Increasing | |
· are there extreme fluctuations in number of populations (>1 order of magnitude)? | No |
Threats (actual or imminent threats to populations or habitats) | |
- Habitat destruction | |
- Invasive species | |
- Browsing by deer | |
- Weevil predation | |
- Trampling | |
· does species exist elsewhere (in Canada or outside)? | Yes |
· status of the outside population(s)? | Stable |
· is immigration known or possible? | Not known |
· would immigrants be adapted to survive here? | Possibly |
· is there sufficient habitat for immigrants here? | Possibly |
Quantitative Analysis |
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