Layia discoidea
Encyclopedia
Layia discoidea is a rare species of flowering plant in the daisy family
known by the common name rayless tidytips, or rayless layia.
in southern San Benito County
and far western Fresno County
. The known distribution of the species is the New Idira 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 one population known to occur on a shale outcrop at the edge of the New Idria serpentine mass near Condon Peak. Typical habitat of the species is serpentine rock outcrop, serpentine scree, and serpentine stream terraces where it grows in full sun with little to no competition from other plant species.
. 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
.
A few specimens of Layia discoidea containing ray florets were discovered on Laguna Mountain in 2010 (see Calflora photos). The ray florets were light yellow color in contrast to the deep yellow disc florets. It is unclear if expression of aberrant ray florets in these specimens was due to genetic mutation or induced by environmental conditions.
in what may be an example of both allopatric speciation
and peripatric speciation
. 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.
Known extant Layia glandulosa populations within the range of Layia discoidea typically have deep yellow ray florets.
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common name rayless tidytips, or rayless layia.
Distribution
Layia discoidea is a local serpentine endemic where it is known only from the Diablo RangeDiablo Range
The Diablo Range is a mountain range in the California Coast Ranges subdivision of the Pacific Coast Ranges. It is located in the eastern San Francisco Bay area south to the Salinas Valley area of northern California, the United States.-Geography:...
in southern San Benito County
San Benito County, California
San Benito County is a county located in the Coast Range Mountains of the U.S. state of California, south of San Jose. As of 2010 the population was 55,269. The county seat is Hollister, which includes nearly two-thirds of the county's population. El Camino Real passes through the county and...
and far western Fresno County
Fresno County, California
Fresno County is a county located in the Central Valley of the U.S. state of California, south of Stockton and north of Bakersfield. As of the 2010 census, it is the tenth most populous county in California with a population of 930,450, and the sixth largest in size with an area of . The county...
. The known distribution of the species is the New Idira 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 one population known to occur on a shale outcrop at the edge of the New Idria serpentine mass near Condon Peak. Typical habitat of the species is serpentine rock outcrop, serpentine scree, and serpentine stream terraces where it grows in full sun with little to no competition from other plant species.
Description
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 phyllariesBract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
. The flower head
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
is a cluster of many deep yellow disc florets with a base of bractlike scales. The fruit is an achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
with a short scaly brown pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
.
A few specimens of Layia discoidea containing ray florets were discovered on Laguna Mountain in 2010 (see Calflora photos). The ray florets were light yellow color in contrast to the deep yellow disc florets. It is unclear if expression of aberrant ray florets in these specimens was due to genetic mutation or induced by environmental conditions.
Speciation
Genetic analysis performed on this species suggest that it evolved directly from Layia glandulosaLayia glandulosa
Layia glandulosa is a species of flowering plant in the daisy family known by the common names whitedaisy tidytips and white layia. It is native to western North America from British Columbia to Baja California to Utah, where it is common in a number of habitat types.-Description:This is an annual...
in what may be an example of both allopatric speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
and peripatric speciation
Peripatric speciation
Peripatric and peripatry are terms from biogeography, referring to organisms whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur – for example a wide river or a mountain range. Such organisms are usually closely related Peripatric and...
. 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.
Known extant Layia glandulosa populations within the range of Layia discoidea typically have deep yellow ray florets.