''Stylocline citroleum'' is a rare species of flowering plant in the family

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

known by the common name oil neststraw.

Description

This inconspicuous annual herb produces a grayish, trailing, forking stem no more than long. The grayish, woolly, pointed leaves are up to long. The

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

bears spherical

flower heads A pseudanthium (; : pseudanthia) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, composite flowers ...

just a few millimeters long with tiny, rough-haired

phyllaries In botanical terminology, a phyllary, also known an involucral bract or tegule, is a single bract of the involucre of a composite flower. The involucre is the grouping of bracts together. Phyllaries are reduced leaf-like structures that form one o ...

and scaly, woolly florets. It is hard to tell apart from other ''Stylocline'' because its defining characteristics are microscopic.

Distribution

It is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Kern County, California Kern County is a county (United States), county located in the U.S. state of California. As of the 2020 United States census, 2020 census, the population was 909,235. Its county seat is Bakersfield, California, Bakersfield. Kern County compris ...

, where it is known from about 46 occurrences on and around the

Elk Hills Oil Field The Elk Hills Oil Field (formerly the Naval Petroleum Reserve No. 1) is a large oil field in western Kern County, in the Elk Hills of the San Joaquin Valley, California in the United States, about west of Bakersfield. Discovered in 1911, and ...

. The occurrences are patchy and variable in size, and some sources consider them to be part of a single widely spread

metapopulation A metapopulation consists of a group of spatially separated populations of the same species which interact at some level. The term metapopulation was coined by Richard Levins in 1969 to describe a model of population dynamics of insect pests in a ...

.The Nature Conservancy
/ref> The species has been collected from coastal

San Diego County San Diego County (), officially the County of San Diego, is a county in the southwest corner of the U.S. state of California, north to its border with Mexico. As of the 2020 census, the population was 3,298,634; it is the second-most populous ...

, but any occurrences there are probably now

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

.Flora of North America
/ref> The plant has been known for over one hundred years, and the

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

was collected in 1935, but it was not described to science as a distinct species until 1992.San Joaquin Valley Endangered Species Recovery Program
CSU Stanislaus.Morefield, J. D. (1992). Three new species of ''Stylocline'' (Asteraceae:Inuleae) from California and the Mojave Desert. ''Madroño'' 39:114-130. ''Stylocline citroleum'' grows in the valley saltbush scrub ecosystem in the sandy flats and clay soils of the

San Joaquin Valley The San Joaquin Valley ( ; Spanish language in California, Spanish: ''Valle de San Joaquín'') is the southern half of California's Central Valley (California), Central Valley. Famed as a major breadbasket, the San Joaquin Valley is an importa ...

in areas developed into

oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the prese ...

s, the inspiration for the

common Common may refer to: As an Irish surname, it is anglicised from Irish Gaelic surname Ó Comáin. Places * Common, a townland in County Tyrone, Northern Ireland * Boston Common, a central public park in Boston, Massachusetts * Cambridge Com ...

and

scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

s of the species. The plant probably evolved as a

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two diff ...

of mountain neststraw (''Stylocline gnaphaloides'') and California filago ('' Filago californica''), and it is almost always found growing alongside one or both of its parent species.

References

External links

Jepson Manual Treatment - ''Stylocline citroleum''
{{Taxonbar, from=Q7629671 citroleum Endemic flora of California Natural history of the Central Valley (California) Natural history of Kern County, California Plants described in 1992