Astragalus bibullatus
| Pyne's ground plum | ||||||||||||||||||
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| Astragalus bibullatus Barneby and E.L. Bridges | ||||||||||||||||||
Astragalus bibullatus (Pyne's ground plum) is an endangered species that is endemic to the cedar glades of the central basin of Tennessee. It is found in only about five populations located within a few kilometers of each other in Rutherford County, Tennessee.
The common name refers to Milo Pyne, who discovered the species in the 1980's, and the odd-looking smooth, purplish fruits that ripen on the ground in June and look superficially like plums. However, the species is a legume and is unrelated to the plum. The foliage of A. bibullatus looks similar to the more widespread cedar glade endemic, A. tennessensis. However, the flowers of A. bibullatus are pinkish purple in contrast to the white flowers of A. tennessensis. The fruits are also quite different. A. tennessensis fruits are greenish, hairy, and are more elongated as is more typical for legumes.
Threats
Because of the small number of populations, A. bibullatus is threatened by habitat destruction. One population is now protected in the Flat Rock Cedar Glade and Barrens State Natural Area. Because there is very little genetic differentiation among populations [1], further loss of genetic variabliliy is not a threat.
References
Barneby, R.D. and E.L. Bridges. 1987. A new species of Astragalus (Fabaceae) from Tennessee's Central Basin. Brittonia 39:358-363.
Morris, A. B., R. S. Baucom, and M. B. Cruzan. 2002. Stratified anyalysis 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.