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"When I see disjunct plant distributions on Calflora maps, I explore the data to determine if the populations are likely to be real or not." says BLM botanist Ryan O'Dell. "Multiple records of the species in the same disjunct area point to a true disjunct distribution. A single record on its own often suggests a problem with the record: incorrect identification, incorrect georeference coordinate, etc." 

Calflora aggregates data from thousands of sources: you can see all records for one species on one map without having to harvest the records from the original sources.

Deinandra lobbii, or Threeray tarweed, is an annual herb that is native to California and endemic (limited) to California. Why does it have these three disjunct populations?

Deinandra lobbi photo by Ken-ichi Ueda

Botanist Ryan O'Dell responded, "I believe that the disjunct distribution of Deinandra lobbii is due to humans disturbing its optimal niche. Most disjunct populations are related to the species' climate tolerance limits, habitat affinity (niche), and dispersal (vectors)."

"The niche of Deinandra lobbii includes gravelly clay soils of low rolling hills and the climate tolerance limit of Köppen climate classification CSA (temperate, dry summer, hot summer). The distributions of most plant species are an interplay of their environmental tolerance limits and ability (probability) to disperse to suitable habitats (niche)."

"Similar to long-distance dispersal events of weeds (e.g., Mediterranean species to California), Deinandra lobbii 'found' (by chance) an exact match of habitat and climate within its environmental tolerance limits. The most likely long distance dispersal vectors in this case are birds."

O'Dell is also examining several other Long Distance Disjuncts (LLD) species shown below.

Astragalus clevelandii

LDD from the serpentine perennial seep habitats of North Coast Ranges to the serpentine perennial seep habitats of South Coast Ranges at San Benito Mountain, San Benito County.

Photo by Paul Aigner.

Astragalus rattanii var. jepsonianus

LDD from the serpentine clay grassland habitats of North Coast Ranges to the serpentine clay grassland habitats of South Coast Ranges at San Benito Mountain, San Benito County.

Photo by Charles Russell.

Dicoria canescens

LDD from the Mojave Desert dunes habitats to the San Joaquin Desert dunes habitat on Monocline Ridge, western Fresno County

Photo by Don Davis.

Tetradymia stenolpeis

LDD from the Mojave Desert to San Joaquin Desert habitat in Griswold Hills, eastern San Benito County.

Photo by Steve Matson.

Trichostema rubisepalum

LDD from the serpentine seasonal seep habitats of Red Hills (Tuolumne County) in the Sierra foothills to the serpentine seasonal seep habitats of South Coast Ranges at San Benito Mountain, San Benito County, or vice versa.

Photo by Mike Russler.

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