|Listed||March 26, 1997|
|Description||Prostrate, annual, herbaceous plant.|
|Threats||Conversion of habitat to agriculture or urbanization, flooding, competition with non-native plants.|
Hoover's spurge ('Akoko), Chamaesyce hooveri, a member of the spurge family (Euphorbiaceae), is a prostrate, glabrous annual herb. The leaves are gray-green, asymmetric at the base, rounded to kidney-shaped, and have small, narrow white teeth around the margins. The small flowers occur singly in the leaf axils. C. ocellata can occur in the same range with C. hooveri but is readily distinguished by its spreading rather than prostrate habit, yellowish-green color, and entire leaf margins. C. serpyllifolia is similar to C. hooveri ; both species have a gray-green color and may be prostrate, but C. serpyllifolia has less rounded leaves, while the marginal teeth are shorter and are usually limited to the leaf apex. Neither C. ocellata nor C. serpyllifolia have been documented growing together with C. hooveri in the same vernal pool.
This plant was first collected in Tulare County in 1937 and described three years later as Euphorbia hooveri. This species was placed in the genus Chamaesyce in 1985 based on the presence of a sheath around the vascular bundle, its sympodial (lateral branching) growth habit, and its photosynthetic pathway.
Hoover's spurge occurs in vernal pools.
Hoover's spurge is found in vernal pools on remnant alluvial fans and related depositional stream terraces along a stretch of 240 mi (386 km) on the eastern margin of the Central Valley. Four populations of C. hooveri are extirpated or possibly extirpated in Butte, Tehama, and Tulare Counties. Of the 25 extant populations, 10 populations are known from Glenn, Merced, Stanislaus, and Tulare Counties. Three populations occur at the northern end of Butte County and the remainder are located in Tehama County. Five of the 12 Tehama County populations occur on the Nature Conservancy's Vina Plains Preserve. All populations are on privately owned lands, except for the four populations in Glenn County found on the Sacramento National Wildlife Refuge.
About one-third of the 25 remaining populations of Hoover's spurge are threatened by agricultural land conversion, competition with non-native weeds, and a flood control project.
Conversion of land to agricultural use within the last 20 years is known to have eliminated one population of Hoover's spurge in Tulare County. Agricultural land conversion now threatens two populations of this taxon in Stanislaus County and three populations in Tulare County.
One population of Hoover's spurge in Stanislaus County is threatened by increases in agricultural irrigation runoff and by grazing.
Five populations of Hoover's spurge in Tehama County are threatened by one or more native or non-native plant species.
Conservation and Recovery
Four populations of the Hoover's spurge in Glenn County occur in the Sacramento National Wildlife Refuge. Actions to protect these habitats should be incorporated into the management plan for the wildlife refuge. Most populations of Hoover's spurge are on privately owned land, making them vulnerable to conversion to agricultural or urbanized land-uses, or to degradation by disturbances or water pollution. To avoid further depletions of the rare plant, the largest populations on private land should be protected. This could be done by acquiring the land and designating ecological reserves, or by negotiating conservation easements with the private landowners. It will be essential that the protected populations not be subjected to degrading changes in hydrology or water chemistry from activities occurring outside of the reserve boundaries. All private landowners with habitat of the Hoover's spurge should be made aware of the presence of the plant, and of the need to conserve its habitat. Its populations should be monitored, and research undertaken into its biology, habitat needs, and management practices to enhance its populations.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
U. S. Fish and Wildlife Service
Sacramento Field Office
2800 Cottage Way, Room W-2610
Sacramento, California 95825-1846
U.S. Fish and Wildlife Service. 26 March 1997. "Endangered and Threatened Wildlife and Plants: Determination of Endangered Status for Three Plants and Threatened Status for Five Plants From Vernal Pools in the Central Valley of California." Federal Register 62 (58):14338-14352.