Скачать 0.74 Mb.
Status and Distribution
Mead=s milkweed was federally listed as a threatened species on September 1, 1988 (53 FR: 33992-33995). The species formerly occurred in the eastern tallgrass prairie region of the central United States in Illinois, Indiana, Iowa, Kansas, Missouri, and Wisconsin but is now considered extirpated in Indiana and Wisconsin (USFWS 2003) and is threatened with extirpation in Iowa (Watson 1998). The species currently exists in approximately 171 extant populations (USFWS 2003) across 34 counties (Figure 1) in Illinois, Iowa, Missouri, and Kansas (Tecic et al. 1998). The majority of the remaining populations (75%) are now restricted to primarily Ahigh quality@ tall grass prairies and prairie hay meadows in the Osage Plains Physiographic Region in Kansas and Missouri, and on igneous glades in Iron and Reynolds counties, Missouri (Bowles et al. 1998, Tecic et al. 1998). The remaining populations occur in the Shawnee Hills of Illinois, the Southern Iowa Drift Plain in Iowa, the Glaciated Plains, Ozark Border, Ozark Springfield Plateau, and the Ozark-St. Francois Mountains of Missouri, and the Glaciated Physiographic Region of Kansas (USFWS 2003).
Rankings of these populations are provided in Table 18 and are based on habitat quality as well as population size and vigor. Rankings range from A to D with “A” being populations in high quality habitats, greater than 200 or more ramets and which exhibit sufficient recruitment to sustain the population. A rank of “D” are populations in poor quality habitats and less than 25 ramets or less than 100 ramets that have not produced/released viable seeds over a period of five years.
In Iowa, the species historically occurred on small, isolated prairie remnants that contain low to very low numbers of individual plants (Watson 1998). Watson (1998) surveyed six historic sites in 1998 and located the species at only the Woodside Prairie site. Although he found seven flowering plants that produced two mature pods, he concluded that “Asclepias meadii must at present be considered near the brink of extinction in Iowa” (Watson 1998). Later, Watson located the species at the Powell Prairie site (USFWS 2003).
In Illinois, only four extant native populations occur on four small glades in the Shawnee Hills physiographic region, Saline County (Schwegman 1987, Tecic et al. 1998). These occurrences are all within two miles of each other along a sandstone escarpment. Historically, the species is known to have occurred in Cook, Ford, Fulton, Hancock, Henderson, LaSalle, Menard, Peoria, and Saline counties (USFWS 2003). However, according to Bowles et al. (2001) the species likely occurred throughout much of Illinois, but disappeared before being discovered. In 2001, the last remaining population of Mead’s milkweed occurring in Ford County, consisting of one individual, was destroyed after a change in land ownership (Bowles et al. 2001 and Elizabeth Shimp, USFS, pers. comm. 2005).
According to Horner (2001) most populations of Mead’s milkweed in Missouri occur on private lands and nearly half are in Benton and Tettis counties (USFWS 2003). A record from 1898 at Buzzard Mountain, Iron County, was apparently relocated, but recent searches have not located individuals. A new population was found in 2001 in Adair County, where the species was thought to be extirpated (USFWS 2003). In recent surveys of 35 prairie sites, only five sites had populations of Mead’s milkweed (USFWS 2005).
In Kansas there are approximately 101 known occurrences in 13 counties (USFWS 2003). The plant is not known to be extirpated from any county where it historically occurred, although several populations have been destroyed. Most of the Kansas populations were discovered after 1950, although one population is known from a pre-1900’s record (Freeman 1988). A single report of the species from Harvey County, Kansas can not be verified and is probably inaccurate (USFWS 2003). Mead’s milkweed sites in Kansas are predominantly managed as hay meadows (USFWS 2003).
Table 18. Natural Heritage ranking and number of extant natural Mead’s milkweed populations by physiographic region and state. Ranking is based on population size and habitat integrity. A= >200 ramets, B=>100 ramets, C=>25 ramets, D=<25 ramets. (From U.S. Fish and Wildlife Service 2003). The Mead’s milkweed population on the SNF is in the Shawnee Hills physiographic region.
A summary of Table 18, shows that out of 171 populations of Mead’s milkweed across the range of the species, only 15 are in good to high quality habitat, with good or better viability. Most extant populations persist in poor quality habitat and/or have low viability.
Figure 1. Current and historic distribution of Mead’s milkweed by county.
|Appendix hm references used in habitat models for Southwest Regional Gap Analysis Project||Appendix Bibliography (list of all articles cited and what chapter cited in)|
|Appendix 8: Curricula Vitae for Part-Time Faculty Appendix 1||Draft appendix a appendix a documents to for accreditation|
|Appendix a1||Appendix L|
|Appendix 1 – References||Supplementary Appendix|
|Bibliography: All References, Including Sources and Literature Cited||Appendix User Bibliography|