Overview

Distribution

National Distribution

Mexico

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Global Range: The range in CA is only about 40 sq mi, since this plant just barely gets into the United States. However, it ranges quite far south in Baja.

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Physical Description

Morphology

Description

Shrubs, 30–80+ cm. Stems erect. Leaves mostly alternate; petioles 5–20 mm; blades ovate to rounded-deltate, 20–35(–50) × 18–30(–45) mm, bases broadly cuneate to ± truncate, margins toothed, abaxial faces ± densely tomentulose (between veins), adaxial faces sparsely tomentulose, glabrescent. Pistillate heads clustered, proximal to staminates; florets 2(–3). Staminate heads: peduncles 0–3 mm; involucres ± cup-shaped, 3–5 mm diam., tomentulose; florets 12–20+. Burs: bodies obconic to fusiform, 4–6 mm, tomentulose (little, if at all, stipitate-glandular), spines 15–20+, scattered or on distal 1/2, ± subulate (the proximal basally flattened), 2–3 mm, tips usually uncinate, sometimes straight. 2n = 72.
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Diagnostic Description

Synonym

Franseria chenopodiifolia Bentham, Bot. Voy. Sulphur, 26. 1844
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Type Information

Holotype for Franseria lancifolia Rydb.
Catalog Number: US 313846
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): A. W. Anthony
Year Collected: 1897
Locality: Cedros Island, Baja California Norte, Mexico, North America
  • Holotype: Rydberg, P. A. 1922. N. Amer. Fl. 33: 36.
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Ecology

Population Biology

Number of Occurrences

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

Estimated Number of Occurrences: 21 - 300

Comments: 10 extant in California as of 2005. Unknown number of occurrences in Baja, Mexico. Distribution in Baja extends pretty far south so there are likey large numbers of occurrences there.

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Conservation

Conservation Status

National NatureServe Conservation Status

Mexico

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: N2 - Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Ambrosia chenopodiifolia is known from southern California, where there are only about 10 sites, south into Baja, Mexico where there are probably numerous sites. The number of plants is only known for California where there are 1400 (as of 2005), but there are likely to be many thousands south of the border. The threats are fairly severe in CA; Baja threats are unknown.

Environmental Specificity: Broad. Generalist or community with all key requirements common.

Comments: Pretty broad, occurring in coastal scrub from southern CA south far into Baja, Mexico.

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Global Short Term Trend: Unknown

Global Long Term Trend: Unknown

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Threats

Degree of Threat: High

Comments: Threats recorded for CA occurrences include border patrol activities, trampling, vehicle trampling, development, gravel mining, dumping, and invasive plants. In Baja, threats may be slightly less since the plant ranges over a wider area, but locally probably includes development and other threats.

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Wikipedia

Ambrosia chenopodiifolia

Ambrosia chenopodiifolia is a species of ragweed known by the common names San Diego bursage and San Diego bur ragweed.[1] It is native to Baja California, and southern California as far north as San Diego County, where it is a member of the coastal sage scrub plant community.

Description[edit]

Ambrosia chenopodiifolia is a thickly branching shrub exceeding 3 meters in maximum height. The leaves are ovals up to 3 centimeters long and coated in white hairs. They are sometimes lobed.

Like other ragweeds it is monoecious, with each inflorescence bearing heads of pistillate (female) flowers below a cluster of staminate (male) flowers. The inflorescence is spiny, especially when in fruit. The fruit is a spherical, woolly bur about half a centimeter long covered in hooked spines.

See also[edit]

References[edit]

  1. ^ Ambrosia chenopodiifolia. NatureServe. 2012.
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