Round-leaved greenbrier (Smilax rotundifolia) COSEWIC assessment and status report: chapter 8

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Limiting Factors and Threats

In Ontario, the main threats to this species are habitat destruction and modification and the small number of known populations, the majority of which are confined to small woodlots where they exist as fragmented populations, especially considering that only a few are sexually reproductive.

Specific examples of impacts are reflected in the following examples. In the western portion of its Ontario range in Essex County, half of the woodlot at site 4, containing only male plants, has been converted to a fenced deer enclosure resulting in excessive pressure from browsing. In the eastern portion of its range in the Niagara Peninsula, site 7, one of the few mixed sex colonies in Ontario that was seen to be producing fruit in 2006, is found in a remnant woodlot on private land adjacent to a major suburb where it is potentially at risk from human impacts. In the same region, site 13 is in a remnant woodlot on private land that is scheduled for the development of an 83-unit housing development. A smaller narrow woodlot, formerly present to the south of the main site and representing potential habitat, is no longer present. Site 12, in Woodlawn Park, City of Welland, was historically at least twice its current size; it was divided for roadway construction and residential development.

Considering the relatively extensive surveys in 2006 and 2007 by the Niagara Peninsula Conservation Authority, few new populations/clones are likely to be found in this region. This is highly likely also for Essex County where woodlots are few, extremely small, and fragmented. As a consequence of the species’ rarity in Ontario, where it occurs at only 13 small sites, 10 of which are on private land, the species is at risk from further habitat loss and degradation to an already fragmented and small overall population. This is further exacerbated by the fact that likely less than one half of the 13 colonies have both male and female plants and are therefore sexually reproductive. Of the 13 colonies, only 3 are known to have both male and female plants and 6 only have plants of the same gender, with the balance being undetermined. Although the colonies reproduce primarily vegetatively (no seedlings reported by Ambrose in the 1994 status report but no data are currently available on this subject), genetic variability and hence adaptability would appear to be compromised for the Ontario populations/colonies.

In Nova Scotia, threats to the populations are limited. Cottage and residential development along lakeshores have the potential to negatively impact this species (M.F. Elderkin, pers. comm. 2006).