Astragalus brauntonii

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Braunton's milkvetch
Astragalus brauntonii 189814020.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Fabaceae
Subfamily: Faboideae
Genus: Astragalus
Species:
A. brauntonii
Binomial name
Astragalus brauntonii
Parish, 1903

Astragalus brauntonii is a rare species of milkvetch known by the common name Braunton's milkvetch. It is a short-lived perennial shrub with lilac flowers that is typically found on carbonate soils in fire-prone areas. It is a opportunistic pioneer species that usually appears in the aftermath of wildfires and other disturbances. It is known from fewer than 20 extant occurrences in the hills and mountains surrounding the Los Angeles Basin in Southern California, [1] as well as an isolated population in northern Baja California.

Contents

Altered fire cycles, urban development, and habitat fragmentation all pose threats to the survival of the species. It is a federally listed endangered species in the United States.

Description

Braunton's milkvetch is a large perennial herb which grows from a woody caudex and reaches up to 1.5 m (4.9 ft) tall. The thick hollow stems are coated in coarse white hairs. Leaves are up to 16 cm (6.3 in) long and are made up of many pairs of oval-shaped leaflike leaflets.

The inflorescence is a dense spike of up to 60 bright lilac flowers. Each pealike flower is about a centimeter long with a reflexed hood. The flowers wither and turn brown but remain on the plant instead of dropping off. The plant is pollinated by native Megachile bees and native bumble bees (i.e. Bombus sp.).

The fruit is a small bent legume pod.

Taxonomy

Astragalus brauntonii was described by Samuel Bonsall Parish in the Bulletin of the Southern California Academy of Sciences in 1903. It was first discovered by Herman Edward Hasse in 1899, who collected it in "sterile clay soil" in the Santa Monica Mountains. A later 1902 collection by Hasse served as the type specimen. Parish named the species in honor of Ernest Braunton, an English-American botanist who worked in the Los Angeles area. [2]

A new variety endemic to Baja California was described in 2022. It was discovered in the vicinity of Tijuana during a cross-border BioBlitz by Mexican and American naturalists. [3] The variety is named lativexillum in reference to the much wider banner petal compared to var. brauntonii. It is further distinguished by its shorter peduncles and reduced number of flowers per raceme. [4]

There are two described varieties of Astragalus brauntonii:

var. lativexillum in Baja California, growing in disturbed soil along a dirt road 20241127 astragalus brauntonii lativexillum.jpg
var. lativexillum in Baja California, growing in disturbed soil along a dirt road

Distribution and habitat

Astragalus brauntonii is a plant of the coastal prairie grasslands, coastal sage scrub, and chaparral plant communities of the region. It is often found growing in disturbed areas, especially in carbonate soils areas. [5] The 16 known remaining populations in California are found in the southwestern Transverse Ranges (eastern Santa Monica Mountains, east end Simi Hills, south base San Gabriel Mountains), northern Peninsular Ranges (northwest side Santa Ana Mountains) — within Los Angeles, Orange, and Ventura Counties. [6]

A disjunct population (var. lativexillum) occurs in the coastal hills between Tijuana and Rosarito in extreme northwest Baja California. It occurs almost 240 km to the south of the southernmost populations of var. brauntonii. It grows sympatric with Astragalus tijuanensis . [4]

Fire ecology

Sign designating a protected area for Braunton's milk-vetch Sign designating area for Endangered Braunton's milk-vetch (16984801360).jpg
Sign designating a protected area for Braunton's milk-vetch

Astragalus brauntonii is an opportunistic species that relies on disturbance to reproduce, which primarily comes in the form of natural wildfire. Unlike other fire-adapted perennials in the chaparral, it does not resprout from a vegetative underground part, but rather relies on a long-lived dormant seedbank, a trait also seen in another rare perennial legume, Thermopsis macrophylla . [7]

The beanlike seeds require scarification from fire or mechanical disturbance to break down their tough seed coats before they can germinate. The seeds persist for years in the soil until fire or disturbance allows them to sprout, with populations of the plant springing up in an area that has been recently swept by wildfire. [5]

A significant threat to the species is the alteration of natural fire regimes. Natural fire frequencies in Southern California historically occurred in intervals of 50-100 years, compared to the current substantially higher frequency of 15 years or less, despite modern fire suppression. Wildlands in proximity to urban areas suffer from more frequent fires and ignition sources, leading to the conversion of native woody perennial vegetation into landscapes of invasive non-native annual grasses and forbs. The non-native grasslands further the alteration of the fire cycle with their easy ignition and flashier fuels. [8] [9]

Shortened fire cycles create diminished seedbanks as a result of mature plants dying before they can set large numbers of seed. Subsequently, the non-native annuals outcompete the species, reduce critical habitat, and lead to more alteration of the fire cycle. [8] [9]

Related Research Articles

<i>Astragalus</i> (plant) Genus of legumes

Astragalus is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to temperate regions of the Northern Hemisphere. Common names include milkvetch, locoweed and goat's-thorn. Some pale-flowered vetches are similar in appearance, but they are more vine-like than Astragalus.

<i>Adenostoma fasciculatum</i> Species of flowering plant

Adenostoma fasciculatum, commonly known as chamise or greasewood, is a flowering plant native to California and Baja California. This shrub is one of the most widespread plants of the California chaparral ecoregion. Chamise produces a specialized lignotuber underground and at the base of the stem, known as a burl, that allow it to resprout after fire has off burned its stems. It is noted for its greasy, resinous foliage, and its status as one of California's most iconic chaparral shrubs.

<i>Penstemon haydenii</i> Species of flowering plant

Penstemon haydenii, the blowout penstemon or blowout beardtongue, is a species of flowering plant in the genus Penstemon and the family Plantaginaceae. The warm-season perennial is native to nine counties in the Nebraska Sand Hills and a single location in Carbon County, Wyoming. The plant has a milky blue color with a waxy cuticle, pale purple leaves, and an alternating leaf pattern with one central stalk. The flowers, while in the inflorescence stage, originate from the bases of the leaves of the plant. Blowout penstemon flowers from May until early June and drops its seeds from late August into September.

<i>Astragalus pycnostachyus <span style="font-style:normal;">var.</span> lanosissimus</i> Variety of legume

Astragalus pycnostachyus var. lanosissimus, the Ventura marsh milk-vetch, is a short-lived, herbaceous perennial in the pea family Fabaceae,

<i>Astragalus lentiginosus</i> Species of flowering plant in the milkvetch genus

Astragalus lentiginosus Astragalus lentiginosus is a species of legume native to western North America where it grows in a range of habitats. Common names include spotted locoweed and freckled milkvetch. There are a great number of wild varieties. The flower and the fruit of an individual plant are generally needed to identify the specific variety.

<i>Astragalus trichopodus</i> Species of legume

Astragalus trichopodus is a species of legume known by the common name Santa Barbara milk vetch. It is native to southern California and Baja California, where it grows in several types of open habitat, including in the Transverse Ranges and Mojave Desert.

<i>Astragalus agnicidus</i> Species of legume

Astragalus agnicidus is a rare species of milkvetch known by the common name Humboldt County milkvetch. It is endemic to northern California, where it is known only from two populations in Humboldt County and one in Mendocino County.

<i>Astragalus cimae</i> Species of legume

Astragalus cimae is a species of milkvetch known by the common name Cima milkvetch. It is native to the Mojave Desert and its sky island woodlands of eastern California western Nevada, especially on calcareous soils, including the Cima Dome area in the Mojave National Preserve.

<i>Astragalus coccineus</i> Species of plant

Astragalus coccineus is a species of milkvetch known by the common name scarlet locoweed or scarlet milkvetch. It is native to the deserts, scrub, and chaparral of the Southwestern United States in Arizona, California, and Nevada, and in northwestern Mexico.

<i>Astragalus didymocarpus</i> Species of legume

Astragalus didymocarpus is a species of milkvetch known by the common names Dwarf white milkvetch and Two-seeded milkvetch. It is native to the southwestern United States and northern Mexico, where it can be found in many types of habitat.

<i>Astragalus douglasii</i> Species of plant

Astragalus douglasii is a species of milkvetch known by the common name Douglas's milkvetch. It is native to California and Baja California, where it can be found in many types of desert, valley, chaparral and woodlands, and montane habitats, usually below 8,000 feet (2,400 m) elevation.

<i>Astragalus kentrophyta</i> Species of flowering plant in the milkvetch genus

Astragalus kentrophyta is a species of milkvetch known by the common name spiny milkvetch. It is native to western North America from central to west Canada, to California, to New Mexico. It grows in rocky mountainous areas, such as the Sierra Nevada, and on plateaus.

<i>Astragalus nuttallii</i> Species of legume

Astragalus nuttallii is a species of milkvetch known by the common name Nuttall's milkvetch. It is native to California and Baja California, where it grows in the sandy soils of coastal habitat. This is a perennial herb forming thick, tangled clumps of hairy to hairless stems up to a meter in length. The abundant leaves are up to 17 centimeters in length and made up of many oval-shaped leaflets. The inflorescence is a large, dense body of up to 125 flowers, each around 1 to 1.5 centimeters long. The flowers are dull cream-colored and sometimes purple-tinted. The fruit is an inflated legume pod up to 6 centimeters long which dries to a papery texture and contains many seeds in its single chamber. One variety of this species, the ocean bluff milkvetch is endemic to the Central Coast of California.

<i>Astragalus purshii</i> Species of legume

Astragalus purshii is a species of milkvetch known by the common names woollypod milkvetch and Pursh's milkvetch.

<i>Astragalus pycnostachyus</i> Species of aquatic plant

Astragalus pycnostachyus is a species of milkvetch known by the common name marsh milkvetch. It is endemic to the coastline of California, where it grows in wet saline habitat such as marshes.

<i>Pentachaeta lyonii</i> Species of flowering plant

Pentachaeta lyonii, the Lyon's pentachaeta or Lyon's pygmydaisy, is an annual plant in the family Asteraceae. It is endemic to southern California, where it is now known only from a few areas on the heavily developed coastline of Los Angeles and Ventura counties. It is a federally listed endangered species.

<i>Astragalus microcymbus</i> Species of legume

Astragalus microcymbus is a species of flowering plant in the legume family known by the common name skiff milkvetch. It is endemic to Colorado in the United States, where it is known from Gunnison County and the edge of Saguache County. It was discovered in 1945 by Rupert Barneby, a British botanist. Currently, skiff milkvetch is experiencing population declines and is listed as a Tier 1 species in the Rare Plant Addendum to the Colorado State Wildlife Action Plan.

<i>Astragalus ripleyi</i> Species of legume

Astragalus ripleyi is a species of flowering plant in the legume family known by the common name Ripley's milkvetch. It is native to southern Colorado and northern New Mexico in the United States.

<span class="mw-page-title-main">Flora of the Colorado Desert</span>

Flora of the Colorado Desert, located in Southern California. The Colorado Desert is a sub-region in the Sonoran Desert ecoregion of southwestern North America. It is also known as the Low Desert, in contrast to the higher elevation Mojave Desert or High Desert, to its north.

<i>Arctostaphylos glandulosa <span style="font-style:normal;">subsp.</span> crassifolia</i> Subspecies of flowering plant

Arctostaphylos glandulosa subsp. crassifolia is a rare perennial shrub, a subspecies of manzanita within the heather family commonly known as the Del Mar manzanita. It is narrowly endemic to the sandstone coastal terraces of San Diego County and northwestern Baja California. It is a burl-forming evergreen shrub typically found growing in a rambling habit on poor soils and hardpan. From December to February, white to pink urn-shaped flowers decorate its foliage, giving way to small fruits. It is listed as endangered and is threatened by land development, invasive species and modifications to the natural fire regime.

References

  1. ↑ Topanga Watershed Report Archived 2008-07-25 at the Wayback Machine accessed 7/4/2010
  2. ↑ Parish, S. B. (1903). "Two New Plants from Southern California". Bulletin of the Southern California Academy of Sciences. 2 (2): 26 – via Biodiversity Heritage Library.
  3. ↑ Watson, Julie (2024-05-19). "Botanists are scouring the US-Mexico border to document a forgotten ecosystem split by a giant wall". AP News. Retrieved 2025-01-16.
  4. 1 2 Estrada Castillón, Eduardo; Rebman, JON P.; González, Carlos; Villarreal Quintanilla, José Ángel (2022). "Astragalus tijuanensis and Astragalus brauntonii var. lativexillum, a new species and a new variety in the genus Astragalus (Fabaceae) from extreme northwestern Baja California, Mexico". Phytotaxa. 577: 1–13. doi:10.11646/phytotaxa.577.1.1.
  5. 1 2 Center for Plant Conservation Profile Archived August 23, 2009, at the Wayback Machine
  6. ↑ USDA counties distribution map [ permanent dead link ] . accessed 1.8.2013
  7. ↑ Fotheringham, C.J.; Keeley, Jon E. (1 April 1998). Ecology and Distribution of Braunton's milkvetch (Astragalus brauntonii) and Lyon's pentachaeta (Pentachaeta lyonii).
  8. 1 2 Astragalus brauntonii (Braunton’s milk-vetch) 5-Year Review: Evaluation and Summary. Ventura, California: U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office. August 2023.
  9. 1 2 Braunton’s milk-vetch (Astragalus brauntonii) 5-Year Review: Summary and Evaluation. Ventura, California: U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office. January 2009.
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