Pigeon Wings

Clitoria fragrans

Description

Pigeon wings (Clitoria fragrans ) is a long-lived perennial herb, 6-20 in (15-50 cm) tall, with an erect habit. The thick horizontal root, which may grow to more than 6.5 ft (2 m) long, bears one to several purplish, glaucous, wiry, crooked stems. The somewhat leathery leaves consist of three leaflets. Leaflets of the upper leaves are obtuse at the tip and narrower than those of lower leaves.

Pigeon wings has two kinds of flowers—the colorful insect-pollinated chas-mogamous flowers and the self-pollinating cleistogamous flowers. Cross-fertilization of the cleistogamous flowers is prevented, since the flowers do not open. The chasmogamous flowers usually occur in pairs, each corolla consisting of one standard petal, 1.4-1.8 in (3.5-4.5 cm) long or 1.8-2 in (4.5-5 cm) long, and a small white keel. The common name of this species refers to the petals of the chasmogamous flowers, which resemble wings. Pigeon wings plants are easily recognizable due to the inverted position of these pale purple flowers. The flowers are inverted so that the anthers and stigma touch the backs of visiting insects; the only other legume genus with inverted flowers is Centrosema, with two species in central Florida. Chasmogamous flowers bloom from May to June. Cleistogamous flowers occur later in the summer through late September.

The seed pod (legume) is 2-3.1 in (5-8 cm) long and extends from the calyx. No information is available on the pollination vector, fertilization rate, seed production, or germination rates for this species. This species can be confused with C. mariana but can be easily distinguished by its purplish, glaucous stems, nontwining habit, narrow leaflets, smaller flowers, and long-stipitate fruits.

Habitat

Some confusion exists with respect to the vegetative complex inhabited by pigeon wings. Some research indicates that the species is found primarily within habitats intermediate with high pine and scrub; other surveys located the species from scrub, turkey oak barrens, and the edges of high pines. Still others surveys report pigeon wings from scrubby high pine, more typical of hickory-dominated scrub (the hickory phase of high pineland). This apparent disagreement indicates that more information is needed on the distribution of these plants. It also demonstrates the limits to developing and applying consistent terminology to describe a complex mosaic of vegetation.

There is also disagreement about the plant's preference for white sand soils versus yellow sand soils. As mentioned above, the species has been found in turkey oak barrens and scrub hickory, both of which occur on yellow sand soils. Pigeon wings is usually regarded as a species of white sand soils; in the Lake Wales Ridge, however, it has been observed on both white and yellow sands.

Though the species may exist in a continuum of scrub to high pine habitat, it appears that it is most prevalent in an intermediate vegetative complex commonly referred to as the turkey oak barrens. In this habitat, wiregrass may be locally patchy or scattered, longleaf pine scattered, while bluejack and turkey oak are usually prominent. Prunus geniculata, Warea carteri, Eriogonum longifolium var. gnaphalifolium, Polygala lewtonii, and Nolina brittoniana also appear to be more common in the turkey oak barrens than in other habitats.

Distribution

Pigeon wings is distributed in Florida along the Lake Wales Ridge primarily in the Highlands, Orange, and Polk Counties. It was also found at one site central Osceola County in 1964 and near Leesburg, Lake County, in 1910. It has not recently been reported from either historic locality.

Pigeon wings has probably never been abundant since intermediate high pines/scrub habitat is not a major vegetative complex associated with central Florida ridges. At specific sites where pigeon wing has been located, it has never been found in large numbers—typically 20-30 plants per site. The species is known from about 40 sites, 13 of which are protected public and private lands or lands being considered for acquisition and protection. The remainder of sites are on private lands and receive no protection. On private land, the species is threatened by habitat loss due to conversion for agricultural, residential, and commercial uses.

The total number of pigeon wings has been estimated to be less than 3,000 in Lake, Orange, Polk, and Highlands Counties. Most populations are found on the Lake Wales Ridge in Highlands and Polk Counties, where they are protected at Archbold Biological Station, Lake Wales Ridge State Forest and State Park, Saddle Blanket Lakes, Lake Apthorpe, Tiger Creek, and Bok Tower Gardens in the Ridge Pine Nature Preserve, and in the surrounding natural buffer areas of Bok Tower Gardens. The species can also be found at the U. S. Air Force's Avon Park Bombing Range, and at two areas undergoing active acquisition efforts. The species may also exist in suitable, unsurveyed habitat within and adjacent to its known range.

Threats

Along with other Central Florida scrub plants, pigeon wings has experienced major habitat loss to agriculture and residential development. Only 28,420 acres (11,500 hectares) of the original 436,880 acres (176,800 hectares) of xeric upland vegetation remain on the Lake Wales Ridge. The Lake Wales Ridge continues to experience population growth and expansion of citrus groves, resulting in further destruction of scrub habitat. Other threats to pigeon wings include off-road vehicle use, trashing, and trampling. Pigeon wings is especially at risk because it is found in small, fragmented populations.

Conservation and Recovery

Florida scrub has historically experienced variable fire frequencies and patchy high-intensity fires. Scrub plant communities are therefore fire-adapted, and recover relatively quickly. The fire ecology of the turkey oak barrens varies slightly from surrounding scrub and high pine. The irregular pattern of hills, valleys, and wetlands affects the frequency and magnitude of fires in this habitat. Periods of relatively frequent fires favor high pine species while periods of infrequent fire favor scrub species. The result of this changing fire regime is a plant complex in which neither scrub nor high pine vegetation dominate.

Studies at Archbold Biological Station have documented positive postfire responses in flowering and vegetative growth of pigeon wing. Decreased flowering within one year after burning suggests fire suppression and canopy closure adversely affect this plant, resulting in reduced vegetative vigor and reproduction. Nevertheless, the plant has been observed flowering in a location that had not been burned in 30 years, indicating that pigeon wings will persist for many years under suboptimal conditions. Even though plants may persist with infrequent fire, fire management appears to be essential to the long-term survival of this species. Pigeon wings' dependence on fire is particularly evident when considering the quick and profuse blooming in response to fire. Adequate management is still needed at many of the protected sites.

Several ongoing habitat acquisition efforts are intended to benefit pigeon wing, along with other threatened and endangered plant species in central Florida. Florida's Conservation and Recreation Lands program and the Nature Conservancy are acquiring scrub land for preservation, and the U. S. Fish and Wildlife Service (FWS) plans to expand Lake Wales Ridge National Wildlife Refuge. Populations of pigeon wing will also benefit as the FWS undertakes protection of other federally listed plants and the endangered Florida scrub jay, an inhabitant of the scrub vegetation on Lake Wales Ridge. Critical habitat has not been designated for pigeon wings, since such designation could increase the risk of collection and/or extermination.

The number and distribution of pigeon wings have been greatly reduced. It is clear that additional losses of habitat and individuals will occur as more than half of the known remaining sites are on private lands and are afforded no protection. Though protected sites represent a small fraction of the historic distribution of many endemic scrub plants, a number of pigeon wings sites are, or soon will be, protected by public and private purchase and conservation efforts. Although more than half of the remaining sites where this species occurs are still afforded no protection, current conservation efforts may be sufficient to ensure long-term survival of this plant. On those protected sites described above, land management efforts are targeting restoration and maintenance of scrub and high pine vegetative complexes. Management of other public scrub habitats will likely favor most endemic scrub plants, including pigeon wings.

Management of scrub habitat on the U. S. Air Force's Avon Park Bombing Range appears to be successful as many scrub endemics are responding well to management prescriptions there. Monitoring of turkey oak barrens' response to fires regimes and other management tools used in scrub and high pine habitats will help determine which techniques most effectively maintain the turkey oak barrens vegetative complex.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

U. S. Fish and Wildlife Service
Jacksonville Ecological Services Field Office
6620 Southpoint Dr. South, Suite 310
Jacksonville, Florida 32216-0958
Telephone: (904) 232-2580
Fax: (904) 232-2404
http://www.fws.gov/r4jafl/

Reference

U. S. Fish and Wildlife Service. 27 April 1993. "Determination of Endangered or Threatened Status for Seven Central Florida Plants." Federal Register 58 (79): 25746-25755.