Slender-horned Spineflower (Dodecahema leptoceras)
Slender-horned spineflower is a California endangered plant species, which means that killing or possessing the plant is prohibited by the California Endangered Species Act (CESA). It is also listed as endangered under the federal Endangered Species Act. Slender-horned spineflower is a small annual plant in the buckwheat family with distinctive basal leaves and small clusters of flowers. It is found in areas prone to drought, and plants usually occur in isolated patches of large floodplain habitats categorized as alluvial scrub. Onset of germination is likely related to rainfall, and occurred by late February at several study sites in 1995 and 1996. Flowers generally bloom from April to May.
Slender-horned spineflower is endemic to southwestern California, and occurs in Los Angeles, San Bernardino, and Riverside Counties. At the time of this webpage posting, the California Natural Diversity Database listed 22 occurrences presumed to still exist. However, the records for many of these occurrences have not been updated for several years, so the status of these populations is unknown. According to the 2010 U.S. Fish and Wildlife Five Year Review, slender-horned spineflower population trends are difficult to estimate because it is an annual plant, and germination and reproduction rates are highly dependent upon rainfall and other environmental factors that vary from year to year. Therefore, the number of occurrences is likely a better estimate of overall abundance of the plants than individual population counts.
Slender-horned spineflower is currently threatened by direct and indirect habitat destruction from urbanization, agricultural development and highway development. It is also threatened by sand and gravel mining, altered hydrology, off-highway vehicle activities, nonnative plants and climate change. In order to ensure the continued existence of slender-horned spineflower, current and historical occurrences should continue to be monitored range-wide. Cooperation with landowners is needed to protect occurrences on privately-owned land. The extent to which altered hydrology threatens the species should be assessed, and a range-wide conservation plan should be prepared and implemented.
CDFW has participated in the following slender-horned spineflower studies and papers through participation in the Cooperative Endangered Species Conservation Fund or other mechanisms:
- Assessment of Seed Bank Buffering of Genetic Change in Dodecahema leptoceras (Slender-horned Spineflower)
- Characterizing the Habitat of Slender-horned Spineflower (Dodecahema leptoceras)
- Final Report: Characterizing the Habitat of Slender-Horned Spineflower (Dodecahema leptoceras): Geomorphic Analysis
- Slender-horned Spineflower (Dodecahema leptoceras) Microhabitat Characterization of Mycorrhizal Associations
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