''Astragalus bibullatus'', the limestone glade milkvetch or Pyne's ground plum, is an

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

of flowering plant that is endemic to the cedar glades of the central basin of Tennessee in the United States. It is found in only eight populations located within a few kilometers of each other in

Rutherford County, Tennessee Rutherford County is a county located in the U.S. state of Tennessee. It is located in Middle Tennessee. As of the 2021 census, the population was 352,182, making it the fifth-most populous county in Tennessee. A study conducted by the Univers ...

Taxonomy and similar species

''Astragalus bibullatus'' was first described in 1987 by Rupert Charles Barneby and Edwin L. Bridges.Barneby, R. D. and E. L. Bridges (1987). A new species of ''Astragalus'' (Fabaceae) from Tennessee's Central Basin. '' Brittonia'' 39:358-363. The common name refers to Milo Pyne, who discovered the species in the 1980s, and the odd-looking smooth, reddish fruits that ripen on the ground and look superficially like plums ('' Prunus''). However, the species is a

legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock f ...

and is unrelated to plums, which are in the rose family. The foliage of ''Astragalus bibullatus'' looks similar to the more widespread cedar glade endemic, '' A. tennesseensis'' (Tennessee milkvetch). However, the stem, leaves, and fruits of ''A. tennesseensis'' are all fuzzy, while they are smooth in ''A. bibullatus''. Also, the flowers of ''A. bibullatus'' are pinkish purple in contrast to the yellow-white flowers of ''A. tennesseensis''. The fruits are also quite different. ''A. tennesseensis'' fruits are greenish, hairy, and are more elongated (similar to an elf shoe) as is more typical for legumes. The flowers of ''A. bibullatus'' bloom in April and May, while the fruit ripens in May or June.

Threats

Because of the small number of populations, ''A. bibullatus'' is threatened by habitat destruction.Morris, A. B., R. S. Baucom, and M. B. Cruzan. 2002. Stratified analysis of the soil seed bank in the cedar glade endemic ''Astragalus bibullatus'': evidence for historical changes in genetic structure. '' American Journal of Botany'' 89: 29-36. Eight populations are now protected including the Flat Rock Cedar Glade and Barrens State Natural Area and Manus Road Cedar Glade. Because there is very little genetic differentiation among populations, further loss of genetic variability is not a threat.

References

External links

''Astragalus bibullatus'' images at bioimages.vanderbilt.edu
{{Taxonbar, from=Q2705194 bibullatus Flora of Tennessee Rutherford County, Tennessee Plants described in 1987