Thread-leaved sundew (Drosera filiformis) COSEWIC assessment and status report: chapter 2

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Species information

Thread-leaved sundew is a small, rare carnivorous wildflower that only grows in bogs. It produces up to 15 purplish flowers with yellow centers on the elongate, leafless flowering stalk that often forms a broad crook at its tip. It is an herbaceous perennial that grows long, erect, thread-like leaves each summer from a whitish tuber. Numerous reddish-purple, sticky, hair-like glands cover the leaves and trap small arthropods (insects and spiders). Enzymes in the droplets digest the trapped victims that serve as an additional source of nutrients.

Distribution

The Canadian range of thread-leaved sundew is restricted to only five bogs in a small area of extreme southwestern Nova Scotia. It also occurs in the eastern United States, ranging from a few populations in coastal New England to more abundant ones on the Gulf Coast of Florida and Louisiana.

Habitat

In Nova Scotia, thread-leaved sundew only occurs in raised (or plateau) bogs. These are infertile, acidic, domes, open wetlands dominated by peat mosses, heath shrubs, and short sedges and grasses.

Biology

Thread-leaved sundew is a perennial, low-growing, herbaceous plant. It is capable of photosynthesis. However, it is also a “carnivore” that captures small invertebrates on its sticky leaves, digests them, and absorbs some of the nutrients.

Population sizes and trends

The total population of the thread-leaved Sundew amounts to tens of thousands of plants, but it only occurs in five known populations.

Limiting factors and threats

One of the largest populations of the thread-leaved sundew is threatened by a proposal to develop a peat mine, which would destroy or degrade its habitat. The other four known populations are also potentially threatened by proposals to develop peat mines or cranberry farms.

Special significance of the species

Like other carnivorous plants, thread-leaved sundew holds a fascination for many people. Other species of sundews have had minor use in herbal medicine, but such use is not known for thread-leaved sundew.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines the national status of wild species, subspecies, varieties, and nationally significant populations that are considered to be at risk in Canada. Designations are made on all native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fish, lepidopterans, molluscs, vascular plants, lichens, and mosses.

COSEWIC Membership

COSEWIC comprises representatives from each provincial and territorial government wildlife agency, four federal agencies (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership), three nonjurisdictional members and the co-chairs of the species specialist groups. The committee meets to consider status reports on candidate species.

Definitions

Species

Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.

Extinct (X)

A species that no longer exists.

Extirpated (XT)

A species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A species facing imminent extirpation or extinction.

Threatened (T)

A species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)^Footnotea

A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Not at Risk (NAR)^Footnoteb

A species that has been evaluated and found to be not at risk.

Data Deficient (DD)^Footnotec

A species for which there is insufficient scientific information to support status designation.

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.