Round-leaved greenbrier (Smilax rotundifolia) COSEWIC assessment and status report: chapter 2

Executive Summary

Round-leaved Greenbrier
Smilax rotundifolia
Great Lakes Plains population
Atlantic population

Species information

Round-leaved greenbrier (Smilax rotundifolia) is a woody climbing vine that can reach a length of over four metres. Main stems are rounded and bear stout flattened prickles; its branchlets are sometimes four-angled. Leaves are alternate and simple, 5-10 cm long, with an ovate blade and a heart-shaped base. Plants are unisexual, with the small green male and female flowers clustered in rounded umbels whose stems arise from the leaf angles. Each female umbel produces a few blue-black, mostly two-seeded berries.

Distribution

The species is found across much of eastern North America from southwestern Nova Scotia to northern Florida, eastern Texas and north to eastern Michigan and southwestern Ontario. In Canada, it occurs near the north shore of Lake Erie in southern Ontario and in southwestern Nova Scotia. The 13 extant populations in Ontario cover an Extent of Occurrence of about 2500 km² and an Area of Occupancy of 13 km² if a 1x1 km grid is applied and 40 km² if a 2x2 km grid is used. The >50 Nova Scotia populations have an Extent of Occurrence of <5000 km² and an Area of Occupancy >> 50 km².

Habitat

In Ontario round-leaved greenbrier prefers open moist to wet woodlands, often growing on sandy soils. In Nova Scotia it commonly occurs along lakeshores. In other jurisdictions it is very variable in its habitat use.

Biology

This woody vine is dioecious, having its unisexual flowers on separate male and female plants. It forms clusters of shoots from a single crown and spreads vegetatively by its rhizomes and stolons. Only populations of mixed sexes produce fruits. Seeds seem to require a cold period before germination occurs. It is possible that for seedling establishment, open areas are required in the woodland canopy. Because of vegetative reproduction, the clones produced can become widely spread over time and individual clones can have a long life span.

Population sizes and trends

There are 14 confirmed sites of this species in Ontario, one of which is known to be extirpated. Six of the 13 potentially extant sites were confirmed in 2006 and one in 2007; one other was confirmed in 2005. The remaining five sites were not surveyed in 2006 but were assumed to be extant because the habitat was still present (landowners were either unavailable or they denied field workers access to their properties). Of the 13 sites, four have been discovered since the initial COSEWIC status assessment. There are between approximately 1000 and 5000 extant crowns (each representing a multi-stemmed “individual” that may or may not be physically separated from other such individuals). More than 50 occurrences are known from Nova Scotia where the total population is considered stable and consists of between 3,000 and 10,000 individuals.

Limiting factors and threats

Although round-leaved greenbrier reproduces asexually and is relatively long-lived, it is limited in Ontario because few sites are occupied by plants of both sexes. This limited capability for seed production potentially reduces the amount of natural variability and therefore the adaptability of the Ontario populations. Urban expansion and the reduction of available habitat in the Niagara area of Ontario also threaten the sites in this portion of the species' range. Threats to the Nova Scotia populations appear to be limited or absent in most cases.

Special significance of the species

No significant Aboriginal Traditional Knowledge on current uses for round-leaved greenbrier is known.  In areas where it is a common component of woodlands, it is an extremely important wildlife food.

Existing protection or other status designations

In Ontario, one population is in a city park, and portions of another are on Long Point Region Conservation Authority property. The others are on private land, without specific protection. No specific data have been compiled on this species in Nova Scotia since the species is considered secure in the province, but it is known to occur in some protected areas such as Kejimkujik National Park and Tobeac Wilderness Area.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2007)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)
A wildlife species that no longer exists.

Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A wildlife species facing imminent extirpation or extinction.

Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)Footnotea
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)Footnoteb
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)Footnotec
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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