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U.S. Forest Service

Some Fuzzy Little Cinquefoils Get Sorted Out

Potentilla rimicola Cliff cinquefoil (Potentilla rimicola) is rare in the San Jacinto Mountains of southern California, but somewhat more common in Baja California, Mexico Photo by: Jordan Zylstra, U.S. Forest Service.

Potentilla rhyolitica Potentilla rhyolitica has two varieties. The Huachuca cinquefoil (var. rhyolitica) grows in the Huachuca and Santa Rita Mountains. The Chiricahua cinquefoil (var. chiricahuaensis) grows in the Chiricahua Mountains. Drawing adapted from Ertter, 2007.

Potentilla demotica Hualapai cinquefoil (Potentilla demotica) grows in the Hualapai Mountains. This mountain range is in west-central Arizona and not part of the Sky Islands, but it still has the Sky Island characteristic of being an isolated mountain range. Drawing adapted from Ertter, 2007.

The cinquefoils (genus Potentilla) are a large group of plants in the rose family that are often hard to identify. It is usually easy to decide that a plant is a cinquefoil, but often quite another matter to figure out which cinquefoil the plant actually is. The section Subviscosae in the genus has nine species and varieties in the southwestern United States and they are just as hard to identify as the other cinquefoils. Dr. Barbara Ertter has been studying these plants for years and has begun to get them sorted out.

As Dr. Ertter explains, what makes these plants intriguing is the extent to which they exemplify evolutionary radiation in an island setting, with the “islands” in this case being scattered mountain ranges isolated by arid lowlands. The center of radiation for the plants, at least in the United States, is the isolated mountains extending north from Mexico’s Sierra Madre Occidentale, called the Southwestern Sky Island Ecosystem. As a result, different unique and endemic members of the group occur on the Pinaleno, Santa Catalina/Rincon, Huachuca/Santa Rita, and Chiricahua ranges in southeastern Arizona.

To have the variation in this group make sense, Dr. Ertter had to realign some old names and propose new names for groups of plants that deserved formal recognition. She named Potentilla rhyolitica with two varieties, rhyolitica and chiricahuensis. Variety rhyolitica grows in Huachuca and Santa Rita mountains while variety chiricahuensis grows in the Chiricahua Mountains. These plants were formerly called Potentilla albiflora that grows in the Pinaleno Mountains. She also named Potentilla demotica that grows on a single peak in the Hualapai Mountains. These mountains in west-central Arizona are not part of the Sky Islands proper, but are similarly isolated. These plants appear to be most closely related to Potentilla rimicola from southern California and Baja California, Mexico.

Further Reading

  • Ertter, Barbara. 2007. Lectotypification of new taxa in Potentilla Sect. Subviscosae (Rosaceae) in Arizona. Journal of the Botanical Research Institute of Texas 1(1)47-57.