Threadleaf Brodiaea

Brodiaea filifolia, known by the common name threadleaf brodiaea, is a rare species of flowering plant in the cluster-lily genus. It is endemic to southern California, mostly in the region around the junction of Orange, Riverside, and San Diego Counties, but it is also found in open areas containing or associated with patches of coastal-sage scrub found in San Bernardino County. The range of this species extends from the foothills of the San Gabriel Mountains at Glendora in Los Angeles County, east to Arrowhead Hot Springs in the western foothills of the San Bernardino Mountains in San Bernardino County, and south through eastern Orange and western Riverside counties to the City of San Diego.
Thread-leaved brodiaea is a member of the brodiaea family (Themidaceae) and is a perennial bulbiferous herb. The bulb is a resident of scattered remaining vernal pool, alkali playa and grassland habitats. It is a federally listed threatened species and it is listed as an endangered species on the state level.
The genus Brodiaea was named after the Scottish botanist J. J. Brodie. The species name filifolia literally means thread-leaved.
Brodiaea filifolia is a perennial, producing a flower cluster 20 to 30 centimeters tall which bears bright purple, blue to red-purple flowers. Each flower has six spreading petals/sepals/tepals 1 to 1.5 centimeters long with a center containing three stamens and narrow or small staminodes, which are flat sterile stamens lying against the petals/sepals/tepals. It produces several linear leaves from an underground corm. Its flowers are at the terminus of a leafless stalk.
This plant occurs in grassland areas, often in floodplains, and it is a member of the local vernal pool flora and grassland habitats. It requires heavy clay soils. This type of habitat is becoming very rare as it is being cleared for development, especially as residential areas expand.
Thread-leaved brodiaea is a California endangered plant species, which means that killing or possession of plants collected from the wild is prohibited by the California Endangered Species Act. This species is also listed as threatened under the federal Endangered Species Act. At the time of federal listing in 1998, the U.S. Fish and Wildlife Service identified loss of habitat from urbanization and agricultural conversion as the most significant threat to thread-leaved brodiaea. Since that time, urbanization has remained the most significant threat to the species because populations occur in close proximity to heavily urbanized areas. Other threats to thread-leaved brodiaea include alteration of hydrology and impacts from livestock grazing, unauthorized off-highway vehicle activity, discing and mowing for fire suppression, and competition from nonnative plants. The dumping of livestock manure and sewage dumping has also been identified as a threat to a few localized populations in Riverside County.
The plant is also at risk for reduced genetic variability. It often reproduces vegetatively by producing new corms, a method of cloning which does not produce individuals with new combinations of genes. When the plant does reproduce sexually, it requires unrelated individuals which have different genes; it cannot fertilize itself, nor can it successfully reproduce with closely related individuals. Small population sizes that have low genetic diversity and wide distances between populations make it less likely the plant will successfully undergo sexual reproduction. The plant sometimes hybridizes with Brodiaea orcuttii.
There have been 103 remaining occurrences of this species quantified in widely spaced locations between the San Gabriel Mountains and west-central San Diego County, according to the California Natural Diversity Database. Several occurrences have been discovered since the plant joined the endangered species list, including locations on Camp Pendleton, and a few have been extirpated.
Although urbanization remains the most prominent threat to thread-leaved brodiaea, several populations of this species have been protected by regional planning efforts. Long-term conservation of thread-leaved brodiaea is dependent upon continued protection of additional existing occurrences and minimization of habitat loss caused by development. According to the California Department of Fish and Wildlife, “Sites with large or geographically distinct populations of this species should be acquired and protected, and nonnative plants should be controlled and managed on sites that have been set aside for conservation. Research on thread-leaved brodiaea should be conducted that focuses on pollinators and their impact on the number of new plants that are developed, soil characteristics that facilitate establishment and propagation, and germination.”

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