Common hoptree (Ptelea trifoliata) COSEWIC assessment and status report: chapter 2

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COSEWIC Executive Summary

Species information

Common hoptree (Ptelea trifoliata) is a small tree in the rue family (Rutaceae). It has alternate trifoliate leaves which are aromatic; flowers occurs in early summer; they are borne in terminal clusters, cream coloured and with (4-) 5 petals. Fruit matures late in the season; it is dry, disk-shaped and bears 2-3 seeds.

Distribution

The typical subspecies occurs from the lower Great Lakes and eastern Pennsylvania to northern Florida and Texas. Other subspecies occur further south and west into Mexico.

Habitat

In Ontario it occurs almost entirely along or near the Lake Erie shoreline. It is often found in areas of natural disturbance where it forms part of the outer edge of shoreline vegetation.

Biology

Common hoptree is dioecious (male and female individuals) with insect pollinated flowers. The fruit is wind dispersed and seedlings establish in open or disturbed sites.

Population sizes and trends

Three populations on protected sites have 100 or more individuals each; careful documentation of one has shown a decline in reproductive individuals of 60% in 17 years. Three populations have been lost since the original report was prepared due mostly to human activity near their shoreline habitat. This makes a total of 4 known extirpated populations. Several other populations have shown declines, some are similar or larger than in 1982. Four new sites have been verified since 1982. Of those 17 sites with comparative counts, numbers of trees have declined from 391 to 221 (43% decline). It is estimated that there are an additional 300-450 trees at Point Pelee and other sites not precisely resurveyed in 2000-01, plus 350 counted at Pelee Island west shore and Middle Island but with no numbers to compare with 1982.

Limiting factors and threats

This species only rarely colonizes open inland habitats, being mostly limited to shoreline sites. Human activity along the Lake Erie shoreline appears to be the greatest threat. In addition, a twig-boring beetle has been observed causing significant damage to a few populations.

Special significance of the species

Common hoptree is a component of the stabilizing vegetation along sections of the Lake Erie shoreline. It is one of two native species on which the larvae of the rare Giant Swallowtail butterfly feeds. This species has had a long history of medicinal and economic usage, including by first nation people.

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.