Overview

Distribution

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Global Range: Layia discoidea occurs on serpentines in San Benito and Fresno counties. The known range covers about 72 sq miles.

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Physical Description

Morphology

Description

Plants 3–20 cm (self-incom-patible); glandular, not strongly scented. Stems not purple-streaked. Leaf blades oblanceolate or lanceolate to linear, 2–35 mm, margins (basal leaves) lobed. Involucres cylindric or narrowly obconic to campanulate, 4–7 × 2–6+ mm. Phyllaries 0 ("involucres" formed of "paleae"). Paleae in 1 series (interpreted as constituting the involucre). Ray florets 0. Disc florets 5–35+; corollas 2.5–4 mm; anthers yellow to brownish. Ray cypselae 0. Disc pappi of 8–15 whitish to tawny, lanceolate to subulate, ± equal (often apically or marginally notched) scales 0.5–1.5 mm, each ± plumose or villous, not adaxially woolly. 2n = 16.
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Type Information

Isotype for Layia discoidea D.D. Keck
Catalog Number: US 2365667
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Verified from the card file of type specimens
Preparation: Pressed specimen
Collector(s): I. L. Wiggins & R. S. Ferris
Year Collected: 1940
Locality: Aurora Mine., San Benito, California, United States, North America
  • Isotype: Keck, D. D. 1958. Aliso. 4: 107.
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Ecology

Habitat

Comments: Serpentine talus slopes and alluvial terraces within Chaparral, Foothill/Cismontane Woodland, and Yellow Pine Forest communities. 795 - 1585 m.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 6 - 20

Comments: 20 EO's are known, but 17 are historic in that they haven't been reported on for over 20 years.

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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N2 - Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G2 - Imperiled

Reasons: Endemic to California, Layia discoidea is known from San Benito and Fresno Counties. The plant covers a small area and is endemic to serpentine. No sites are permanently protected, though many occur on BLM lands. Unfortunately, they occur in an area very popular with off road enthusiasts, both motorcycles and larger vehicles. These recreationists tear up the landscape and destroy rare plant habitat. Better information on the current status of this plant is urgently needed.

Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.

Comments: Serpentine endemic from only 2 counties in California.

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Global Short Term Trend: Relatively stable to decline of 30%

Comments: Short term trend is estimated to be stable to slightly declining.

Global Long Term Trend: Relatively stable to decline of 50%

Comments: Long term trend is estimated to be slightly to moderately declining.

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Threats

Degree of Threat: High - medium

Comments: Several sites list ORV or motorcycle damage as threats.

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Management

Biological Research Needs: 1. Ecology
2. Genetics

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Wikipedia

Layia discoidea

Layia discoidea is a rare species of flowering plant in the daisy family known by the common name rayless tidytips, or rayless layia.

Distribution[edit]

Layia discoidea is a local serpentine endemic where it is known only from the Diablo Range in southern San Benito County and far western Fresno County. The known distribution of the species is the New Idria serpentine mass (BLM Clear Creek Management Area) and nearby Laguna Mountain, Hepsedam Peak, and Panther Peak serpentine masses. Layia discoidea is regarded as a strict serpentine endemic with only four populations known (as of 2012) to occur on shale and chert outcrop at the edge of the New Idria serpentine mass near Condon Peak, Sampson Peak, and Idria Reservoir. Typical habitat of the species is serpentine rock outcrop, serpentine talus, and serpentine stream terraces where it grows in full sun with little to no competition from other plant species. The shale and chert outcrop habitat that a few populations of Layia discoidea grows on has similar (analogous) physical and microclimate conditions as the serpentine habitat that the species is primarily found growing.

Description[edit]

This is an annual herb growing a small glandular stem to a maximum height of about 20 centimeters. The thin leaves are generally lance-shaped, but the larger leaves on the lower part of the stem are usually lobed. Unlike other Layia species, which are known for their prominent white or yellow ray florets, Layia discoidea has no ray florets or real phyllaries. The flower head is a cluster of many deep yellow disc florets with a base of bractlike scales. The fruit is an achene with a short scaly brown pappus.

Speciation[edit]

Genetic analysis performed on this species suggest that it evolved directly from Layia glandulosa in what may be an example of both allopatric speciation and peripatric speciation.[1] Layia discoidea looks quite different from the white-rayed Layia glandulosa, and it lives in a specialized habitat, but the two species are genetically very similar and produce robust, fertile hybrids when crossed.[2]

Known extant Layia glandulosa populations within the range of Layia discoidea typically have deep yellow ray florets.

Individuals of Layia discoidea occasionally display ray florets that are light yellow in color (see Calphotos). Individuals bearing ray florets have been observed in populations at the New Idria, Laguna Mountain, and Panther Peak serpentine masses. It is unclear if the ray florets are a result of hybridization with nearby Layia glandulosa, a genetic mutation, or simply induced by environmental conditions.

References[edit]

  1. ^ Baldwin, B. G. (2005). Origin of the serpentine-endemic herb Layia discoidea from the widespread L. glandulosa (Compositae). Evolution 59:11 2473-79.
  2. ^ Gottlieb, L. D., S. I. Warwick and V. S. Ford. (1985). Morphological and electrophoretic divergence between Layia discoidea and L. glandulosa. Systematic Botany 10:4 484-95.
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Notes

Comments

Layia discoidea occurs in the South Inner Coast Ranges (Fresno and San Benito counties). Artificial hybrids with L. glandulosa are highly fertile (J. Clausen 1951).
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