Round-leaved greenbrier (Smilax rotundifolia) COSEWIC assessment and status report: chapter 11
Technical Summary - Great Lakes Plains population
Smilax rotundifolia
Round-leaved Greenbrier: Great Lakes Plains population – Smilax à feuilles rondes : Population des plaines des Grands Lacs
Range of Occurrence in Canada:
southern Ontario
Extent and Area Information
Extent of occurrence (EO) (km²) :
Approx. 2500 km², based on the assumption of two post-glaciation points of entry, and thus two polygons (one for the Niagara/Norfolk populations; one for the Essex populations, extended slightly to include potential reports from Chatham-Kent)
Specify trend in EO :
Approx. stable
Are there extreme fluctuations in EO?
No
Area of occupancy (AO) (km²)
<20 km² based on 13 populations and using a 1x1 km grid and 40 km² based on a 2x2 km grid
Specify trend in AO :
Approximately stable.
Are there extreme fluctuations in AO?
No
Number of known or inferred current locations :
13 extant (only eight recently verified)
Specify trend in # :
Seemingly increasing through new sites found in Niagara through greatly increased search efforts but these likely represent previously overlooked colonies
Are there extreme fluctuations in number of locations?
No. Most sites are of recent discovery (since 1985).
Specify trend in area, extent or quality of habitat :
Area, extent, and quality of habitat are all gradually declining, due to human activities.
Population Information
Generation time (average age of parents in the population) :
Difficult to assess: clonal – Average age of well-developed vines and clones could readily be several decades or older; age to reproduction could be only a few years.
Number of mature individuals
Probably between 1000 and 5000 crowns (largely influenced by a single population); there is much uncertainty as to how many individuals this total represents. Only three populations are currently identified as being mixed gender populations and these have < 100 crowns.
Difficult to assess; possibly <250 mature reproductive individuals but not all of the known populations have been surveyed to determine their ability to reproduce by seeds
Total population trend:
Difficult to assess: perhaps stable in terms of numbers of crowns and presumably population(s) with mixed gender plants
% decline over the last/next 10 years or 3 generations.
NA
Are there extreme fluctuations in number of mature individuals?
No
Is the total population severely fragmented?
Yes
Specify trend in number of populations:
Increased numbers simply reflect the increased search effort in recent years
Are there extreme fluctuations in number of populations?
No
List populations with number of mature individuals in each:
See Table 2.
Threats (actual or imminent threats to populations or habitats)
Habitat degradation/destruction: loss of existing potential habitat, urban spread and impacts on adjacent populations, housing development proposed at one site, degradation of site where deer enclosure was built and population biology constraints due to the extreme scarcity of populations with both male and female individuals.
Rescue Effect (immigration from an outside source)
Status of outside population(s)?
USA: Common; globally secure (G5); secure (S5) in all states except Illinois where it is S3? (questionably vulnerable to extirpation or extinction)
Is immigration known or possible?
Unknown, but possible.
Would immigrants be adapted to survive in Canada?
They would likely be suited to the more temperate areas, such as in the vicinity of known populations.
Is there sufficient habitat for immigrants in Canada?
Extremely scarce in Essex; reasonably good in Niagara.
Is rescue from outside populations likely?
Possible given the proximity of large US populations and dispersal by birds
Quantitative Analysis
[provide details on calculation, source(s) of data, models, etc] : None available.
Current Status
- COSEWIC: Threatened (2001, 2007)
- Ontario MNR: Threatened
Status and Reasons for Designation
Status: Threatened
Alpha-numeric code: Met criteria for Endangered, B1ab(iii)+2ab(iii), but designated Threatened, B1ab(iii)+2ab(iii), because plants are long-lived vines reproducing vigorously by vegetative growth.
Reason for Designation: The species is currently known from 13 highly fragmented populations in Ontario’s Carolinian Zone. Four populations have been found since the previous COSEWIC assessment due to more extensive surveys, and although no population was lost, habitat declines have occurred. Population size and trend are poorly known due to the clonal nature of the species. Many Ontario populations appear to have plants of only one sex and therefore cannot produce seed. The plants, however, are vigorous, long-lived and resistant to habitat changes.
Applicability of Criteria
- Criterion A: (Declining Total Population): No decline data.
- Criterion B: (Small Distribution, and Decline or Fluctuation): Meets Endangered B1ab(iii)+2ab(iii) with EO and AO below maximum limits for Endangered and the occurrence of 13 severely fragmented populations as reflected in part by the fact that perhaps half of these represent unisexual populations. There is continued risk from habitat degradation and loss due to the presence of most on private properties and in highly urbanized regions.
- Criterion C: (Small Total Population Size and Decline): NA. Because of the uncertainty as to the actual number of mature individuals present in this clonal species with unisexual plants, the criterion cannot be applied with any confidence
- Criterion D: (Very Small Population or Restricted Distribution): Meets Threatened D2 if the area of occupancy is based on a 1x1 km grid but exceeds 20 km² if a 2x2 km grid is used.
Criterion E: (Quantitative Analysis): None available.
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