Purshia Explained

Purshia (bitterbrush or cliff-rose) is a small genus of 5–8 species of flowering plants in the family Rosaceae which are native to western North America.

Description

Purshia species form deciduous or evergreen shrubs, typically reaching NaNfrac=2NaNfrac=2 tall. The leaves are NaNcm (-2,147,483,648inches) long, deeply three- to five-lobed, with revolute margins. The flowers are 1–2 cm in diameter, with five white to pale yellow or pink petals and yellow stamens. The fruit is a cluster of dry, slender, leathery achenes which are 2–6 cm long. The roots have nodules that host nitrogen-fixing Frankia bacterium.^[1]

Taxonomy

Taxonomic history

The genus was originally placed in the subfamily Rosoideae.^[2] In the past, the evergreen species were treated separately in the genus Cowania; this genus is still accepted by some botanists.

Modern classification

The classification of Purshia within the family Rosaceae has been unclear.^{[3] [4]} It is now placed in the subfamily Dryadoideae.

Species

Purshia comprises the following species:^{[5] [6]}

• Purshia ericifolia (Torr. ex A.Gray) Henr. – Heath cliffrose (Texas)
• Purshia glandulosa Curran – Desert bitterbrush (Nevada, Utah, Arizona)
• Purshia mexicana (D.Don) Henr. – Mexican cliffrose (Mexico, Arizona)
• Purshia pinkavae Schaack – Pinkava's cliffrose (Arizona)
• Purshia plicata (D.Don) Henrard (syn. Cowania plicata) – Antelope bush (Nuevo León, Mexico).
• Purshia stansburyana (Torr.) Henr. – Stansbury cliffrose (Idaho south to California, Arizona and New Mexico)
• Purshia tridentata (Pursh) DC. – Antelope bitterbrush (British Columbia south to California and New Mexico)

Hybrids

The following hybrid has been described:^[5]

• Purshia × subintegra (Kearney) Henr. (P. pinkavae × P. stansburyana) – (Arizona)

Species names with uncertain taxonomic status

The status of the following species and hybrids is unresolved:^[5]

• Purshia ciliata Dennst.
• Purshia mollis  Lehm.
• Purshia plicata (D.Don) Henr.
• Purshia subintegra (Kearney) Henrickson

Distribution and habitat

The genus is native to western North America, where the species grow in dry climates from southeast British Columbia, Canada, south throughout the western United States to northern Mexico.

External links

• • Jepson Flora Project: Purshia — (click 'taxon' to see treatments of California native species)

Notes and References

1. Swensen . S.M. . Mullin . B.C. . 1997 . The impact of molecular systematics on hypotheses for the evolution of root nodule symbioses and implications for expanding symbioses to new host plant genera . Plant and Soil . 194 . 1–2 . 185–192 . 10.1023/A:1004240004063 .
2. Potter . D. . Eriksson . T. . Evans . R.C. . Oh . S. . Smedmark . J.E.E. . Morgan . D.R. . Kerr . M. . Robertson . K.R. . Arsenault . M. . Dickinson . T.A. . Campbell . C.S. . 2007 . Phylogeny and classification of Rosaceae . Plant Systematics and Evolution . 266 . 1–2 . 5–43 . 10.1007/s00606-007-0539-9. 2007PSyEv.266....5P .
3. Morgan . D.R. . Soltis . D.E. . Robertson . K.R. . 1994 . Systematic and evolutionary implications of rbcL sequence variation in Rosaceae . American Journal of Botany . 81 . 7 . 890–903 . 10.1002/j.1537-2197.1994.tb15570.x . 2445770.
4. Eriksson . T. . Hibbs . M.S. . Yoder . A.D. . Delwiche . C.F. . Donoghue . M.J. . 2003 . The phylogeny of Rosoideae (Rosaceae) based on sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA and the trnL/F region of chloroplast DNA . International Journal of Plant Sciences . 164 . 2 . 197–211 . 10.1086/346163.
5. Web site: The Plant List entry for Purshia . September 2013 . The Plant List, v.1.1 . . 15 December 2020.
6. Web site: Purshia DC. ex Poir. . Govaerts R . Plants of the World Online . Board of Trustees of the Royal Botanic Gardens, Kew . 15 December 2020.