Stylocline, commonly known as neststraw, is a small genus of annual flowering plants in the family Asteraceae (tribe Gnaphalieae), named and described by Thomas Nuttall in 1840. The genus encompasses roughly seven to ten species of diminutive desert herbs found exclusively in the arid and semi-arid landscapes of the southwestern United States and northern Mexico.
Plants in this genus are characteristically small, typically low-growing annuals notable for their woolly, hairy, or spiderweb-like (arachnose) textures — adaptations well suited to dry, open, often disturbed habitats such as sandy flats, gravelly washes, and desert scrub. Thin stems terminate in compact heads bearing both disc flowers and tubular pistillate flowers. The fruits are smooth, shiny achenes encapsulated within the persistent disc heads. A distinctive challenge of the genus is that several species are morphologically very similar, with distinguishing characters sometimes too minute to resolve without magnification.
Well-known members include Stylocline micropoides (woolly neststraw), the most broadly distributed species, ranging across California, Arizona, Nevada, Utah, New Mexico, Texas, and into Sonora and Baja California; Stylocline gnaphaloides (mountain neststraw) of California and Arizona; Stylocline intertexta (Morefield's neststraw) of the Great Basin and Mojave regions; and Stylocline masonii (Mason's neststraw), restricted to a handful of California counties. The generic boundaries of Stylocline have shifted over time, with several former members now placed in related genera such as Micropus, Cymbolaena, Hesperevax, and Ancistrocarphus.
Distribution
Stylocline is native to the southwestern United States and northern Mexico. Individual species are distributed across California, Arizona, Nevada, Utah, New Mexico, and Texas, extending into the Mexican states of Sonora and Baja California. Most species occupy arid or semi-arid habitats such as sandy desert flats, gravelly washes, and open scrubland.
Taxonomy Notes
The genus was established by Thomas Nuttall in 1840 (published in Transactions of the American Philosophical Society, ser. 2, 7: 338). Stylocline belongs to the tribe Gnaphalieae within Asteraceae (order Asterales). Generic limits have been revised over time: several species formerly placed in Stylocline — including S. amphibola, S. griffithii, and S. filaginea — have been reclassified into related genera (Micropus, Cymbolaena, Ancistrocarphus, and Hesperevax).
