Calycadenia fremontii A. Gray

Last Addition: February 27, 2007

Each "thumbnail" image below is linked to a larger photograph.

For much of its taxonomic history Calycadenia fremontii was known only from the type collection by Fremont in 1846, and a second collection in 1937 "10 miles NW of Chico" by R. F. Hoover.  Fremont was exploring the Central Valley of California but no further locality data was provided for this collection.   Intensive field work in conjunction with a study of chromosome evolution in Calycadenia begun in 1970 led to discovery of a Sierra foothill population of C. ciliosa that shared many features with the poorly known C. fremontii. but failed to relocate the distinctive Central  Valley taxon.  Finally, in 1978, a group of botanists was led by the owner of Wurlitzer Ranch (10 miles NW of Chico) to what likely was the same population of C. fremontii known to Hoover.  Subsequent extensive field exploration and study of Calycadenia ciliosa has revealed additional populations that completely bridge the morphological gap between C. ciliosa and C. fremontii.  The two species have been merged and the combined entity bears the earliest name, C. fremontii, bestowed by Asa Gray in 1859.  Additional biosystematic studies identified and allowed mapping of 5 chromosome races of the former taxon know as C. ciliosa.  These have been given the names Ciliosa, Corning, Dry Creek, Lewiston, and Pillsbury.  These races are distinguished on the basis of chromosome structural differences related to fixation of a number of different reciprocal chromosome translocations and apparently at least one pericentric inversion.   Races Elegans and Healdsburg, formerly treated under C. pauciflora are now also considered to belong to C. fremontii (see Jepson Manual, 1993).  Still more chromosome races or this species are known but are not yet fully characterized.   Populations of C. fremontii occur at elevations of about 100 - 1400 m.  At several locations two or more chromosome races are sympatric and such mixed populations generate substantial numbers of translocation heterozygotes.  The chromosome number is n = 6; nucleolar organizing supernumerary chromosomes are known to occur in at least one population of Race Dry Creek.  Two or more chromosome races of C. fremontii are known to produce natural interspecific hybrids with C. pauciflora.   Additional interspecific hybrids between C. fremontii and C. multiglandulosa, C. oppositifolia, and C. pauciflora have been produced experimentally.


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The diminutive, white-flowered form of C. fremontii from the Central Valley locality 10 miles NW of Chico is here tentatively designated as Race Fremontii.  Note the paucity of glands, with usually only a terminal one on the peduncular bracts.
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Unlike Race Fremontii, the populations of C. fremontii that were formerly known as C. Ciliosa characteristically have an abundance of glands associated with the flowering heads.
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Also unlike Race Fremontii, many forms of C. fremontii such as Race Ciliosa shown here, are yellow-flowered and comprise robust, upright individuals.  The anthers in the genus Calycadenia are usually dark purple to black but note the light-colored anthers in a rare mutant of Race Ciliosa illustrated in the third photo.   Race Ciliosa apparently has only yellow-flowered individuals and is rather restricted in distribution, occurring in west central Lake County.
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Race Dry Creek is the most widespread and morphologically variable of the chromosome races of C. fremontii.  It includes both white- and yellow-flowered forms, some with basal red spots on the rays.  The stature of the plants also varies considerably.  The race extends from central Josephine County, OR to south central Tehama County, CA.
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Race Corning is also widespread, comprising yellow-flowered populations from south central Siskiyou County to northern Butte County.
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Race Lewiston is more restricted in distribution, comprising plants with white to cream-colored flowers in a narrow zone of populations extending from central Trinity County to southern Shasta County.
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Race Pillsbury is also restricted in distribution, occurring in northwestern Lake County and adjacent Mendocino County.  It normally has yellow-flowered heads but note the unique white-flowered mutant with 4-lobed rays in the third photo which appeared among progeny of fruits collected in Lake County.
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Race Elegans (formerly treated under C. pauciflora).  1 - Habitat in Napa County; 2 - Greenhouse-grown progeny of fruit from Napa County; 3 - Close view of flowering head, this race and Healdsburg (below) have smaller heads than other races of C. fremontii; 4 - Syrphid flies are frequent visitors to Calycadenia flowers; 5 - Flowering head from a unique pink-flowered population in Lake County.
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Race Healdsburg (formerly treated under C. pauciflora).  1 - Habitat in Sonoma County, 2 - Greenhouse-grown progeny of fruit from Sonoma County (much more diffusely branched and spreading than plants in the field), 3 - Close view of flowering, note cuneate base of middle lobe of ray flowers typical of this race.  The habit of Race Healdsburg is similar to that of Race Fremontii.

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