COSEWIC Assessment and Status Report on the Pink Milkwort Polygala incarnata in Canada ENDANGERED 2009 COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows: COSEWIC. 2009. COSEWIC assessment and status report on the Pink Milkwort Polygala incarnata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 24 pp. (www.sararegistry.gc.ca/status/status_e.cfm). Previous report(s): COSEWIC. 2000. COSEWIC assessment and update status report on the pink milkwort Polygala incarnata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 12 pp. Brownell, V.R. 1998. Update COSEWIC status report on the pink milkwort Polygala incarnata in Canada, in COSEWIC assessment and update status report on the pink milkwort Polygala incarnata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-12 pp. Brownell, V.R. 1984. COSEWIC status report on the pink milkwort Polygala incarnata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 35 pp. Production note: COSEWIC acknowledges Jane M. Bowles and Clint R. Jacobs for writing the status report on the Pink Milkwort Polygala incarnata in Canada, prepared under contract with Environment Canada, overseen and edited by Erich Haber, Co-chair, COSEWIC Vascular Plants Specialist Subcommittee. For additional copies contact: COSEWIC Secretariat c/o Canadian Wildlife Service Environment Canada Ottawa, ON K1A 0H3 Tel.: 819-953-3215 Fax: 819-994-3684 E-mail: COSEWIC/[email protected] http://www.cosewic.gc.ca Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur la polygale incarnat (Polygala incarnata) au Canada. Cover illustration/photo: Pink Milkwort — ©Gary Allen. ©Her Majesty the Queen in Right of Canada, 2010. Catalogue CW69-14/192-2010E-PDF ISBN 978-1-100-15161-8 Recycled paper COSEWIC Assessment Summary Assessment Summary – November 2009 Common name Pink Milkwort Scientific name Polygala incarnata Status Endangered Reason for designation This annual herb is highly restricted geographically and is present in tallgrass prairie habitats in southwestern Ontario. There are likely four populations with a total of approximately 1800 plants, most of which are found in one population. Threats to all populations include encroachment by woody plants due to fire suppression and invasive species. Habitat conversion to agriculture, housing development, mowing, trampling, drainage and moisture alteration threaten three populations. Occurrence Ontario Status history Designated Endangered in April 1984. Status re-examined and confirmed Endangered in April 1998, May 2000, and November 2009. iii COSEWIC Executive Summary Pink Milkwort Polygala incarnata Species information Pink Milkwort (Polygala incarnata) is an annual herb of the milkwort family (Polygalaceae) with a single, smooth, greyish, slender, unbranched or sparingly branched stem and tiny narrow leaves. Mature plants are usually 20 - 40 cm tall. Rose purple, tubular flowers in a dense terminal head continue opening throughout the flowering season. The fruit is a green 2-celled capsule. The seeds are black, hairy, and about 2 mm long with a small two-lobed air-filled, sac-like appendage. Distribution Restricted to North America, Pink Milkwort occurs from Delaware to Florida in the east and from Wisconsin and Iowa, south to Texas in the west part of its range. It no longer occurs in Michigan and New York and has not been seen in New Jersey and Pennsylvania in over 20 years. In Canada, Pink Milkwort has been recorded only from Ontario, where it is known from Walpole Island First Nation (WIFN) and from the Ojibway Prairie Provincial Nature Reserve in Windsor. Historic literature reports are known from Leamington and from the Niagara Falls area. The extent of occurrence in Canada is 52 km2. This excludes unsuitable habitat between the populations at WIFN and the Windsor population. The index of area of occupancy is 8 km2 based on the number of 1 km square grid units occupied, and 20 km2 based on 2x2 km squares. Canadian populations occupy less than 1% of the total range of the species. Habitat In Canada, Pink Milkwort is found in open wet mesic to mesic prairies on sandy loam and sandy clay loam soils. It is almost always associated with Little Bluestem (Schizachyrium scoparium). Periodic fire is probably essential for maintaining open prairie conditions. A high water table in spring and summer drought may also contribute to maintaining an open prairie. iv Biology Pink Milkwort is an annual species that reproduces only sexually, by seeds that are produced in small numbers (two seeds per flower). Plants flower mainly from June to September or early October in Ontario. Flowers are bisexual and can be self-pollinated, although the rates of self-pollination and outcrossing are unknown. Population sizes and trends Because Pink Milkwort is an annual, numbers of individuals fluctuate from year to year. On WIFN there are an estimated 1800 plants documented at 3 populations but there may be four extant populations. The largest population is spread over 6 sites and contained about 1700 individuals in 2008. At a single population on Ojibway Prairie Provincial Nature Reserve, the number of plants counted year to year has fluctuated from 0 to 30 individuals. Population trends are difficult to assess because of the lack of detailed census and long term monitoring. Some populations have been extirpated in the last 20 years and the extent and quality of habitat is still declining. Limiting factors and threats The major limiting factor for this species in Canada is the extent of tallgrass prairie habitat where it occurs. Lack of fire that maintains prairie habitat is allowing woody species to invade Pink Milkwort habitat. At WIFN, major threats are loss of habitat by conversion to agriculture, housing and other land uses. Direct trampling, especially from ATV traffic, may also be a factor. Regular mowing has caused the loss of part of one sub-population at WIFN and likely killed plants at another population in 2008. Invasive species (e.g., Giant Reed, White Sweet Clover and Canada Thistle) threaten several Pink Milkwort sites and cause a decline in habitat quality. Pink Milkwort may also be affected by changes in moisture regime as a result of dredging and ditching operations and natural changes in lake levels. High water levels during the late 1980s may have reduced populations at some sites. At Ojibway Prairie Provincial Nature Reserve, Black Locust and other species are invading Pink Milkwort habitat and pose a serious threat. Special significance of the species The presence of the species in Ontario is of ecological significance because of the limited amount of suitable habitat and the extreme rarity or extirpation of the species in adjacent states. The only known medicinal use of the root is for respiratory ailments. v Existing protection In Canada, Pink Milkwort is listed as Endangered under Schedule 1 of the Species at Risk Act, which applies to populations on federal land, including WIFN. Similarly in Ontario, the species is listed as Endangered with the plant and its habitat protected under the Ontario Endangered Species Act, 2007. At WIFN, sites with the largest number of plants are partially protected through land ownership and conservation leasing arrangements by the Walpole Island Heritage Centre; other sites are on private land and have little protection. The Ojibway Prairie Provincial Nature Reserve is protected and managed by Ontario Parks as a Provincial Nature Reserve. vi 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 (2009) 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)* A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.