CPC Plant Profile: Slender-horned Spineflower
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Plant Profile

Slender-horned Spineflower (Dodecahema leptoceras)

The center plant in the photo is D. leptoceras. Photo Credit: Dylan Hannon
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Polygonaceae
  • State: CA
  • Nature Serve ID: 150862
  • Date Inducted in National Collection: 02/09/1992

Slender-horned spineflower is a federally-endangered, small, spreading annual in the buckwheat family (Polygonaceae), with stems reaching 3-15 cm across. The size of spineflowers varies, however, depending on annual available moisture (Ferguson et al. 1996). This annual has a basal rosette of leaves, from which rise dense flowering stalks. Slender-horned spineflower is distinguished from other spineflowers by the presence of 6 terminal awns and 6 hooked basal awns on each involucre. The involucre in this species is a group of bracts that have been fused together to enclose approximately 3 white to pink flowers within each involucre, blooming April through June (Hickman 1993; Munz 1974).

Participating Institutions
Updates
  • 09/09/2020
  • Genetic Research

An investigation was made into the population biology of the slender-horned spineflower at 4 sites to determine population demographics, breeding systems, and genetic variation (Ferguson et al. 1996).

  • 09/09/2020
  • Reproductive Research

An investigation was made into the population biology of the slender-horned spineflower at 4 sites to determine population demographics, breeding systems, and genetic variation (Ferguson et al. 1996).

  • 09/09/2020
  • Genetic Research

An assessment of seed bank buffering of genetic change in slender-horned spineflower at 4 locations was conducted by Ferguson and Ellstrand, University of California Riverside (1999).

  • 09/09/2020
  • Demographic Research

A number of studies on slender-horned spineflower have been conducted with funding provided by U.S. Fish and Wildlife Service Section 6 money: An assessment of seed bank buffering of genetic change in slender-horned spineflower at 4 locations was conducted by Ferguson and Ellstrand, University of California Riverside (1999). Mycorrhizal associations within slender-horned spineflower habitat were studied in 8 locations. Typically, annuals within the buckwheat family do not form mycorrhizae. However, slender-horned spineflower was found to form associations, although not likely mutualistic, with arbuscular-mycorrhizal fungi. These associations were determined not to be a limiting factor in suitable but unoccupied habitat (Young et al. 2000) Various analyses have been conducted to characterize the habitat of slender-horned spineflower, from an ecological and geomorphic analysis. An attempt was made to characterize soils, vegetation cover, associated species, and ages of alluvial sediments that support populations of slender-horned spineflower (Allen 1996; Wood and Wells 1996). In addition, an investigation was made into the population biology of the slender-horned spineflower at 4 sites to determine population demographics, breeding systems, and genetic variation (Ferguson et al. 1996).

  • 09/09/2020
  • Propagation Research

Previous efforts at growing slender-horned spineflower from germinated seeds have failed. More research is needed in establishing successful germination protocols and growing conditions for slender-horned spineflower if future management plans are to include the establishment of new sites (Ferguson et al. 1996).

Nature Serve Biotics
  • 05/02/2017

There are thirty five occurrences known with only 19 still extant. The habitat where this species occurs, alluvial terrace, is highly threatened by development, agriculture, off-road vehicle use, non native plants and other threats. The long term trend for this species is one of significant decline due to the alteration and degradation of its habitat, alluvial terrace. Further, short term decline is also quite steep.

Valerie Soza
  • 01/01/2010

Many historical occurrences of this species have been lost to urbanization and stream channelization. Current threats include development, sand and gravel mining, flood control, hydrological alteration, proposed reservoir construction, off-road vehicle

Valerie Soza
  • 01/01/2010

There have been 37 reported occurrences of slender-horned spineflower in southern California, 23 are existing occurrences and 14 have been or are presumed extirpated. These occurrences are located in 8 general areas: Bee Canyon, Big Tujunga Wash, Lytle Creek/Cajon Canyon, Santa Ana River wash, Bautista Creek, San Jacinto River, Temescal Canyon, and Vail Lake/Dripping Springs area (CNDDB 2000).

Valerie Soza
  • 01/01/2010

A number of studies on slender-horned spineflower have been conducted with funding provided by U.S. Fish and Wildlife Service Section 6 money: An assessment of seed bank buffering of genetic change in slender-horned spineflower at 4 locations was conducted by Ferguson and Ellstrand, University of California Riverside (1999). Mycorrhizal associations within slender-horned spineflower habitat were studied in 8 locations. Typically, annuals within the buckwheat family do not form mycorrhizae. However, slender-horned spineflower was found to form associations, although not likely mutualistic, with arbuscular-mycorrhizal fungi. These associations were determined not to be a limiting factor in suitable but unoccupied habitat (Young et al. 2000) Various analyses have been conducted to characterize the habitat of slender-horned spineflower, from an ecological and geomorphic analysis. An attempt was made to characterize soils, vegetation cover, associated species, and ages of alluvial sediments that support populations of slender-horned spineflower (Allen 1996; Wood and Wells 1996). In addition, an investigation was made into the population biology of the slender-horned spineflower at 4 sites to determine population demographics, breeding systems, and genetic variation (Ferguson et al. 1996).

Valerie Soza
  • 01/01/2010

Most of the known occurrences of slender-horned spineflower are located on private property threatened by development, only several occurrences are located on federal lands (national forest system lands) and managed as sensitive.

Valerie Soza
  • 01/01/2010

Management recommendations for slender-horned spineflower have prescribed the preservation of older, stable alluvial and/or stream surfaces in washes for protection of this plant species (Wood and Wells 1996) and for the potential establishment of new populations.

Valerie Soza
  • 01/01/2010

Previous efforts at growing slender-horned spineflower from germinated seeds have failed. More research is needed in establishing successful germination protocols and growing conditions for slender-horned spineflower if future management plans are to include the establishment of new sites (Ferguson et al. 1996).

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Photos
Nomenclature
Taxon Dodecahema leptoceras
Authority (A Gray ex Benth.) Reveal & Hardham
Family Polygonaceae
CPC Number 12921
ITIS 195646
USDA DOLE
Common Names slender-horned spineflower | slenderhorn spineflower
Associated Scientific Names Dodecahema leptoceras | Centrostegia leptoceras | Chorizanthe leptoceras | Eriogonella leptoceras
Distribution This species is distributed in drainage systems of adjacent foothills to the Transverse and Peninsular Ranges of southern California from Los Angeles, Riverside, and San Bernardino counties (Young et
State Rank
State State Rank
California S1
Habitat

Slender-horned spineflower is known from alluvial fans, floodplains, stream terraces, washes and associated benches, from 700-2500 feet (210-760 m) in elevation. It grows in riverbed alluvium high in silt and low in nutrients and organic matter; in silt-filled, shallow depressions on relatively flat surfaces surrounded by scattered, river-rounded, cobble-sized rocks (Allen 1996; Wood and Wells 1996). These sediments are on stable surfaces, usually older than 100 years (Wood and Wells 1996). The slender-horned spineflower is generally found in open areas among alluvial fan scrub, often associated with other spineflower species, and in low density of exotic grasses and other introduced weedy species.

Ecological Relationships

Slender-horned spineflower germinates late February to early March in response to winter rains. Abundant germination is known to occur following successive years of little or no seed production, suggesting that seeds remain viable in the soil for a number of years (Ferguson and Ellstrand 1999). With respect to the reproductive biology of slender-horned spineflower, it has been demonstrated that this species has a higher level of genetic diversity, mostly within populations, than is typical for annual or endemic plant species. In addition, this large amount of genetic variation is typical of species with a predominantly outcrossed mating system. During studies, mostly ants and flying insects were observed visiting flowers of slender-horned spineflower (Ferguson et al. 1996)

Pollinators
Common Name Name in Text Association Type Source InteractionID
Other
Self pollinated Confirmed Pollinator Link
Thread-waisted wasps Plenoculus davisii Suspected Pollinator Floral Link
Ants Floral Visitor Link
Flying Insects Floral Visitor Link
Thread-waisted wasps Plenoculus davisii Confirmed Pollinator Link

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