Autumn Buttercup

Ranunculus acriformis var. aestivalis

Description

The autumn buttercup, Ranunculus acriformis var. aestivalis, is a herbaceous perennial that grows 12-24 in (30-60 cm) tall. Most of the leaves are clustered at the base and are deeply palmately divided. Both leaves and stems are hairy. Plants bear six to 10, five-petaled yellow flowers, about 0.5 in (1.3 cm) in diameter. Each flower has five reflexed, yellow-green sepals, which fall off soon after the flower opens. The height of plants at flowering is affected when they are grazed by herbivores. Heavily grazed plants have flowered when only three in (7.6 cm) tall.

Flowering and seed production is completed between late July and early September. Seedlings with several leaves also have been noted at this time. Seeds are generally dispersed in close proximity to the parent plant, but could be transported by animals and water. Insects and/or wind are the likely mechanisms for pollination.

The species has been the subject of considerable taxonomic controversy. Some botanists have disagreed with the initial description of autumn buttercup as a variety of R. acriformis, and considered it a species in its own right, R. aestivalis. Others have argued that the species is a variety of R. acris, which is native to Europe and Asia. The current scientific consensus is that the species is aligned with R. occidentalis of the Pacific Northwest, and that its closest relative is R. acriformis var. montanensis. The species is important for understanding the development of the buttercup genus and its relationships in Asia and North America.

Habitat

The plant is found on a series of small peaty hummocks on a low knoll, less than 0.01 acres (0.004 hectares) in size. The knoll, which is surrounded by a marsh, may be the result of a raised peat bog, uplifted by the water from the surrounding spring.

Distribution

Autumn buttercup was first collected in 1894 from the upper Sevier River Valley in western Garfield County, Utah, at a location documented as "Orton's Ranch." The plant was not described at the time, but specimens eventually made their way to a university collection.

In the late 1940s, a botanist, working with the university collection, noted the uniqueness of the specimens and set out to relocate the living plant. He found a grandson of Orton, who led him to a swampy stretch of the Sevier River where he discovered about 15 or 20 small clumps of autumn buttercup.

The plant was then essentially lost for more than 30 years. Attempts to relocate the population failed and it was presumed extinct. The original population has indeed been lost, but in 1982 a new population was discovered in a wetland above the Sevier River, about 1 mi (1.6 km) north of the original population site. The population at this new site consisted of 407 mature plants and 64 seedlings

Since its rediscovery in 1982, the sole population of autumn buttercup has declined by more than 90%, to about 20 plants. Yearly counts observed the signs of heavy grazing by livestock and small herbivores. In 1988 there were nine mature plants and 13 seedlings remaining at the site. The Nature Conservancy bought a tract of land that included this population in 1989. Livestock grazing was halted. In 1990, the buttercup was located at two new nearby sites, bringing the total known population to around 200 plants; 42 were flowering plants.

Threats

Livestock grazing and trampling by cattle, sheep, and horses were the most significant threats to the survival of this species. In December 1988, The Nature Conservancy purchased the property containing the sole remaining population, thus removing the grazing and trampling threat (though small, non-domesticated animals still graze on the land); still, given the low number of plants now existing, extinction of the autumn buttercup remains a real possibility.

Trampling and grazing may still pose a threat at potential reintroduction sites and to currently unknown populations. Another possible threat is water development for irrigation, which could impact the wetland leading to desiccation in the flowers, since the change in hydrology could affect the species. Other potential sources of disturbance include agricultural development on potential or unknown sites; extended periods of drought; and unusual weather patterns such as several consecutive years of extremely cold winters.

Conservation and Recovery

In order to prevent the almost certain extinction of the species, the remaining plants have been covered with wire cages. Seedlings were moved to the Arboretum at Flagstaff, Arizona, for greenhouse cultivation under the auspices of the Center for Plant Conservation.

The 1991 Recovery Plan for the Autumn Buttercup outlines a number of goals and recommended efforts to restore the plant's population. The plan calls for increasing the current population to a self-sustaining population of 1,000 plants on 10 acres (4 hectares) at the known site; establishing at least two artificial populations at suitable, recognized botanical gardens; establishing viable self-sustaining populations in at least five additional sites on land managed to protect the species; and, ultimately, establishing an overall self-sustaining population of at least 20,000 plants.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
P.O. Box 25486
Denver Federal Center
Denver, Colorado 80225
http://www.r6.fws.gov/

References

U.S. Fish and Wildlife Service. 1991. "Autumn buttercup (Ranunculus acriformis A. Gray var. aestivalis L. Benson) Recovery Plan." U.S. Fish Wildlife Service, Denver.

Welsh, S. L. 1986 "New Taxa and Combinations in the Utah Flora." Great Basin Naturalist 46: 254-260.

Welsh, S. L., and L. M. Chatterley. 1985. "Utah's Rare Plants Revisited." Great Basin Naturalist 45:173-236.