The U.S. Fish and Wildlife Service (Service) recently published a proposed rule (pdf) to list the Kentucky glade cress (Leavenworthia exigua var. laciniata) as threatened under the Endangered Species Act (ESA). The Service also proposed (pdf) designating critical habitat for the species.

The Service previously identified the Kentucky glade cress as a candidate species on November 9, 2009. However, it was designated as a Listing Priority Number (LPN) 3. LPNs are assigned based on the immediacy of the threat to the species, as well as taxonomic status. As an LPN 3, Kentucky glade cress was identified as a candidate species for which the Service had on file sufficient information on biological vulnerability and threats to support preparation of a listing proposal, but for which development of a listing regulation was precluded by other higher priority listing activities.

Kentucky glade cress is an annual member of the mustard family, known only to occur in Jefferson and Bullit counties in Kentucky. The species is a wildflower that grows to four inches and has small white to lilac blooms. Kentucky glade cress prefers environments with shallow soils with flat-bedded limestone, known as cedar or limestone glades.

The Service determined that Kentucky glade cress is threatened by the loss and degradation of habitats supporting the species due to development, roads, utilities, conversions to lawns, horseback riding, off-road vehicle use, and changes in grazing practices and forest encroachment. Additionally, other factors, including narrow range, low genetic diversity, and small population size, also warrant listing Kentucky glade cress as threatened.

In conjunction with the proposed rule to list the Kentucky glade cress as threatened under the ESA, the Service proposed designating 2,053 acres of critical habitat for the species. The designated habitat consists of six units, with 18 subunits, representing 18 of the 61 extant occurrences of Kentucky glade cress. Each unit contains all of the physical or biological features essential to the conservation of the species.