Astragalus michauxii
| Astragalus michauxii | |
|---|---|
 | |
| Astragalus michauxii in flower | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Embryophytes |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Fabales |
| Family: | Fabaceae |
| Subfamily: | Faboideae |
| Genus: | Astragalus |
| Species: | A. michauxii |
| Binomial name | |
| Astragalus michauxii (Kuntze) F.J.Herm. | |
Astragalus michauxii,commonly known as sandhill milkvetch or Michaux's milkvetch, is a species of flowering plant in the family Fabaceae. It is endemic to the southeastern United States, where it occurs in the Atlantic Coastal Plain from southern North Carolina through South Carolina to Georgia.[2][3]
Description
Astragalus michauxii is a perennial herb with erect stems and compound leaves bearing 21–31 coriaceous to somewhat fleshy leaflets. The fruit is a straight to slightly curved legume measuring 2–3 cm long and 4–6 mm in diameter.[2]
Taxonomy
The species belongs to Astragalus section Michauxiani.[2] It was originally described as Tragacantha michauxii by Otto Kuntze in 1891 and later transferred to Astragalus by F.J. Hermann in 1948.[2][3]
It is morphologically distinct within the genus; Rupert Barneby described it as “greatly isolated from any member of the genus morphologically similar”.[2]
- Astragalus apilosus E.Sheld.
- Astragalus glaber Michx. (nom. illeg.)
- Tium apilosum (E.Sheld.) Small
- Tium michauxii (Kuntze) Rydb.
- Tragacantha michauxii Kuntze
Distribution and habitat
Astragalus michauxii is restricted to the southeastern Coastal Plain of the United States and is considered a regional endemic.[2][1] It occurs primarily in longleaf pine sandhill ecosystems, including xeric to dry-mesic sandhills and scrub oak woodlands on nutrient-poor sandy soils.[2][1] These habitats are fire-dependent and historically maintained by frequent natural fires.[1] Reports of the species from Alabama and Florida are considered erroneous.[2]
Ecology
Astragalus michauxii is a heliophilous species associated with open, fire-maintained habitats. It flowers from late April through June, with fruits developing through summer and often persisting into fall.[2] Reproduction is primarily outcrossing and dependent on insect pollinators. However, fruit set is often low and natural recruitment is extremely limited, with seedlings rarely observed in wild populations.[4][5] The species occurs in association with other fire-adapted Coastal Plain plants and is characteristic of intact longleaf pine ecosystems.[1]
Germination and propagation
Seeds of Astragalus michauxii exhibit physical dormancy, which can be effectively broken through mechanical scarification.[6] Germination rates exceeding 90% have been achieved following scarification, and direct sowing methods have yielded high seedling survival under controlled conditions.[6] These findings indicate that low recruitment in natural populations is likely due to environmental limitations rather than seed viability.[6]
Conservation
Astragalus michauxii is ranked as globally vulnerable (G3) due to its restricted range, small population sizes, and habitat fragmentation according to NatureServe.[1] The species is estimated to occur at 21–80 sites, with total global abundance of approximately 1,000–2,500 individuals.[1] Populations are typically small and widely scattered, often consisting of only a few individuals per site.[1]
Genetic studies have identified evidence of a historical population bottleneck, although most genetic variation occurs within populations.[4]
The primary threat to the species is habitat loss due to fire suppression, which allows woody vegetation to encroach into open sandhill habitats.[1] Additional threats include land conversion, fragmentation, trampling, pine straw harvesting, and poorly timed management activities such as burning or mowing during the reproductive period.[1]
Effective conservation depends on active habitat management, particularly prescribed burning on a 3–5 year cycle to maintain open conditions.[1]
References
- 1 2 3 4 5 6 7 8 9 10 11 "Astragalus michauxii". NatureServe Explorer. NatureServe. Retrieved 26 March 2026.
- 1 2 3 4 5 6 7 8 9 10 "Astragalus michauxii". Flora of the Southeastern United States. North Carolina Botanical Garden. Retrieved 26 March 2026.
- 1 2 3 "Astragalus michauxii (Kuntze) F.J.Herm". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 26 March 2026.
- 1 2 Wall, W.A. (2013). "Evidence of population bottleneck in Astragalus michauxii". Journal source: —.
- ↑ Population biology and reproductive ecology of Astragalus michauxii (Thesis). ProQuest. Retrieved 26 March 2026.
- 1 2 3 Kunz, M.; Randall, J.L.; Gray, J.B.; Wall, W.A.; Hohmann, M.G. (2016). "Germination and propagation of Astragalus michauxii, a rare southeastern US endemic legume". Native Plants Journal. 17 (1): 47–52. doi:10.3368/npj.17.1.47.