Ambrosia pumila

• Overview
• Interesting Facts
• Common Names
• Description
• Biology
• Taxonomy
• Similar Species
• More Info
• Further Reading
• Notes

Overview

Critically Endangered

Interesting Facts

Common Names

Description

Family Compositae

The largest family of flowering plants , the Compositae (Asteraceae), comprising about 1,100 genera and more than 20,000 species and characterized by many small flowers arranged in a head looking like a single flower and subtended by an involucre of bracts. A head may consist of both ray flowers and disk flowers, as in the sunflower, of disk flowers only, as in the burdock, or of ray flowers only, as in the dandelion.

Tribe Heliantheae

The Heliantheae are a tribe of closely related genera of the sunflower family that can be readily recognized due to the association of a receptacular bract or chaff scale with each disk floret in the head . The heads usually include bisexual , actinomorphic disk florets with tubular corollas that have 4 or 5 distal lobes and also peripheral zygomorphic female or sometimes sterile florets with strap-shaped corollas that have 3 or fewer distal teeth. However, the ray flowers are sometimes absent and the heads are then discoid , containing only bisexual florets with tubular corollas. The pappus is absent or more commonly ranges from scales to stiff bristles . -- Gerald Carr.

Genus Ambrosia

Annuals , perennials , or shrubs , 10-400+ cm (usually rhizomatous ). Stems erect , decumbent , or prostrate , branched. Leaves usually cauline; opposite ± throughout or opposite (proximal ) and alternate or mostly alternate; sessile or petiolate ; blades (or lobes ) deltate, elliptic , filiform , lanceolate, linear , obovate , ovate , or rhombic (and most intermediate shapes ), usually pinnately, sometimes palmately lobed , ultimate margins entire or toothed , faces hairy or glabrate , usually gland-dotted or stipitate-glandular . Heads discoid (unisexual , pistillate proximal to or intermixed with staminates , staminates usually in racemiform to spiciform arrays; rarely, single plants all or mostly staminate or pistillate). Pistillate heads: phyllaries 12-30(-80+) in 1-8+ series, outer (1-) 5-8 distinct or ± connate , herbaceous, the rest (sometimes interpreted as paleae) ± connate, usually with free tips forming tubercles , spines, or wings (the whole becoming a hard perigynium or "bur") ; florets 1(-5+), corollas 0. Staminate heads: involucres cup-shaped to saucer-shaped , 1.5-6+ mm diam.; phyllaries 5-16+ in ± 1 series, ± connate; receptacles ± flat or convex ; paleae spatulate to linear, membranous, sometimes villous , hirtellous, and/or gland-dotted or stipitate-glandular, sometimes none; florets 5-60+; corollas whitish or purplish, ± funnelform , lobes 5, erect or incurved ; staminal filaments connate, anthers distinct or weakly coherent. Cypselae (black) ± ovoid or fusiform , enclosed within globose to obovoid , pyramidal , pyriform , obconic, or fusiform, hard, smooth , tuberculate , spiny , or winged "burs"; pappi 0. x = 18.

Species 40+: tropical to subtropical and temperate New World, mostly North America, some established in Old World.[1]

Physical Description

Habitat

Disturbed sites, damp to wet, alkaline soils ; 100-200 m [2].

San Diego ambrosia occurs in open habitats in coarse substrates near drainages , and in upland areas on clay slopes or on the dry margins of vernal pools . This species occurs in a variety of associations that are dominated by sparse grasslands or marginal wetland habitats such as river terraces , pools, and alkali playas (Munz 1974; Rieser 1996). In Riverside County, San Diego ambrosia is associated with open, gently-sloped grasslands and is generally associated with alkaline soils. Both extant Riverside County localities are found in close proximity to silty, alkaline soils of the Willows series (Knecht 1971). Preliminary testing of agricultural suitability of soils within a San Diego ambrosia population in San Diego County revealed mostly sandy loam textured soils, that were moderately acidic (pH ranging from 4.48 to 5.77) and low in salinity (DUDEK 1999). Control soil samples adjacent to this population where no San Diego ambrosia were present were more acidic ranging in pH from 3.97 to 4.63. Boling (1988) reported San Diego ambrosia from slopes from 0-9% slope on sandy or clay loams. At Mission Trails regional park in San Diego, Ambrosia pumila patches occurred upon slope angles ranging from 0 to 18% with the vast majority of plants occurring at slope angles of less than 5% (DUDEK 1999).

San Diego ambrosia generally occurs at low elevations generally less than 1600 feet in the Riverside populations and less than 600 feet in San Diego County (CNDDB; UCR database ; Munz 1974; Hickman 1993). Commonly associated species include Nasella spp. , Avena spp., Bromus spp., Centaurea melitensis, Ambrosia psilostachya , Hemizonia fascisulata, Holocarpha virgata, Distichlis spicata, Eremocarpus setigerus, and several vernal pool species (Burrascano 1997; DUDEK 1999).

Biology

Reproduction

Little published information is available concerning the reproductive processes of San Diego Ambrosia. Ambrosia pumila is a clonal, perennial herb in the family Asteraceae (Munz 1974; Payne 1993). Sexual reproduction and seed-set are not considered to be common in this taxon suggesting that propagation and dispersal by seed is limited. Propagation is primarily through extensions of rhizomes (underground stems) indicating that each population could be a single plant and restricted to the immediate appropriate habitat . Ambrosia pumila is sensitive to seasonal conditions and variation causing the amount of above ground mass to fluctuate from year to year. Flowers are generally present from June through September (Munz 1974). Ambrosia species are probably primarily wind pollinated but other vectors (e.g. crawling insects) are a possibility (Payne, pers. comm. 1998). Because pollen is contained in the downward facing male flower and is positioned above female flowers Ambrosia pumila is probably to a large extent self pollinating. Pollen studies are needed to determine if out crossing is necessary for viable seed production within Ambrosia pumila (Burrascano 1997; Johnson, et al. 1999). Perennial Ambrosia species generally produce less seeds than annual species instead investing reproductive resources in below ground root structures (Payne 1962). Several biotechnical reports from transplantation efforts offer support for the lack of or low seed reproduction in the species (Boling 1988; Marquez 1993; RECON 1993).

Preliminary analysis of seed viability have revealed little evidence of viable embryonic material (Ransom Seed Labs report in DUDEK1999). Although this study adds support to the low rate of sexual reproduction in San Diego ambrosia, a larger, multi-season sample needs to be collected to determine the viability of reproduction by seed.

Most technical studies and anecdotal accounts have reported preliminary success propagating San Diego Ambrosia from root material both in the nursery and in the field (Boling 1988; Marquez 1991-1993; RECON 1993; Bohn, pers. comm. 1998; Johnson, et al. 1999). Because San Diego ambrosia reproduces vegetatively and appears to be limited in its ability to sexually reproduce it probably is not a species capable of adapting to rapidly changing conditions. This may be a factor related to its limited distribution.

Low genetic diversity and low rates of sexual reproduction may be further diminished by propagation and transplantation. When small samples of root material are collected from insular populations and propagated and transplanted over larger areas, reproductive function problems may increase. Research concerning the genetic diversity and sexual reproduction of the plant is needed to answer basic questions about the biology and long term viability of this species.

Dispersal: Seed dispersal mechanisms for San Diego ambrosia are unknown. Because San Diego ambrosia is one of the few members of the Ambrosia genus that do not have armed involucral bracts it is less likely to disperse seeds by attaching to animals. Additionally, because the species has been reported to persist within horse corrals and is aromatic it may be unpalatable and unlikely dispersed by ungulate consumption . The species propensity to reproduce asexually suggests that the most common form of dispersal may be movement of rhizome-like structures either short distances by growth or longer distance by flood disturbance .

Duration: Perennial

Growth

Culture: Space 15-18" apart.

Sunlight: Sun Exposure: Full Sun .

Temperature: Cold Hardiness: 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b. (map)

Taxonomy

Synonyms

Franseria pumila Nutt. • Franseria pumila Nuttall • N. s. 7: 344. 1840 • Trans. Amer. Philos. Soc.

Notes

Name Status: Accepted Name .

Comment: Data Providers: CONABIO, Govaerts World Compositae Checklist A-G, IPNI, Tropicos. GCC LSID: urn :lsid:compositae.org:names:53C493D9-C004-4AFE-B4B1-ED0EEC159D26

Last scrutiny: 10-Aug-09

Similar Species

Genetics: Approximately forty-two species of the genus Ambrosia occur in the western hemisphere primarily in arid regions of the southwest United States and northern Mexico (Payne 1975). Twelve of these occur in California and all but three are expected to occur in the Western Riverside study area. San Diego ambrosia is closely related to A. confertiflora, another herbaceous species with finely dissected leaves and single-seeded fruit (Payne, et al. 1972). Species variability is common within species of the Ambrosia in part because of the presence of polyploid races and dysploidy (Payne 1976). Based on a sample of San Diego ambrosia collected in San Diego County (Santee, CA) the gametic (haploid) chromosome number is 72 (unpublished data from Payne, et al. 1964). With the base 18, San Diego ambrosia in its vegetative stage is an octoploid with 144 chromosomes. This may be a mechanism for regularizing a hybrid background, which may serve to reduce the plant’s adaptability by stabilization of the phenotype ( Payne, pers. comm. 1998).

Preliminary results from work by the Soil Ecology and Restoration Group (SERG) using electrophoretic gels suggests that two distant populations ( El Cajon, CA and the Sweetwater area in southern San Diego, CA) are genetically distinct and that genetic variation within each of these two populations is low (Johnson et al. 1999). Additional work concerning genetic variability of San Diego ambrosia is currently in progress from the SERG lab.

Members of the genus Ambrosia

ZipcodeZoo has pages for 36 species, subspecies, varieties, forms, and cultivars in this genus:

A. acanthicarpa (Annual Bursage) · A. ambrosioides (Ambrosia Bursage) · A. artemisifolia (Common Ragweed) · A. artemisiifolia (Annual Bur-Sage Ambrosia Artemisiifolia) · A. artemisiifolia L. var. artemisiifolia L. (Ragweed) · A. artemisiifolia L. var. paniculata (Michx.) Blank. (Annual Ragweed) · A. artemisiifolia var. artemisiifolia (Common Ragweed) · A. artemisiifolia var. elatior (Annual Ragweed) · A. artemisiifolia var. paniculata (Annual Ragweed) · A. bidentata (Lance-Leaf Ragweed) · A. canescens (Hairy Ragweed) · A. chamissonis (Beach-Bur) · A. cheiranthifolia (Rio Grande Ragweed) · A. chenopodiifolia (San Diego Ambrosia) · A. confertiflora (Ragweed) · A. cordifolia (Heartleaf Bursage) · A. deltoidea (Rabbit Bush) · A. dumosa (Burro Bush) · A. elatior var. elatior (Ragweed) · A. eriocentra (Hollyleaf Bursage) · A. grayi (Bur Ragweed) · A. helenae (Helen Ragweed) · A. hispida (Coastal Ragweed) · A. ilicifolia (Holly-Leaf Bursage) · A. intergradiens (Intergrading Ragweed) · A. linearis (Linear-Leaf Bursage) · A. peruviana (Peruvian Ragweed) · A. psilostachya (Cuman Ragweed) · A. pumila (Dwarf Burr Ragweed) · A. tenuifolia (Field Ragweed) · A. tomentosa (Bur Sage Ragweed) · A. trifida (Blood Ragweed) · A. trifida var. texana (Texan Great Ragweed) · A. trifida var. trifida (Great Ragweed) · A. × helenae (Helen Ragweed) · A. × intergradiens (Intergrading Ragweed)

More Info

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Further Reading

• 1997 IUCN red list of threatened plants Cambridge: IUCN, World Conservation Union, 1998 url p. 146.
• Britton, N. L. (ed.). North American flora. [New York]New York Botanical Garden. url p. 20.
• Compositae of southern California / by Harvey Monroe Hall. Berkeley, [Calif.]: The University Press, 1907. url p. 119.
• Flora of southern and Lower California: a check-list of the flowering plants and ferns / by Charles Russell Orcutt. San Diego, Calif.: [s.n.], 1885. url p. 6.
• Occasional papers - San Diego Society of Natural History. 1949 San Diego, The Society. url p. 145, p. 145.
• Proceedings of the Biological Society of Washington. Washington, Biological Society of Washington url p. 120, p. 120.
• Smithsonian miscellaneous collections. 31 1888 Washington: Smithsonian Institution, 1862-1968. url p. 250.
• Synoptical flora of North America. New York, American Book Company, 1878-1895/97 [v.2, pt. 1, 1878] url p. 250.
• Synoptical flora of North America: the Gamopetalæ, being a second edition of vol. I, part II, and vol. II, part I, collected. London, Iverson, Blakeman, Taylor, and Company;1886. url .
• Transactions of the San Diego Society of Natural History. 12 1959 [San Diego]: The Society, 1905-1989. url p. 382, p. 482.
• Ambrosia (Compositae). J. Arnold Arbor. 45: 401430.
• Payne, W. W. 1964. A re-evaluation of the genus
• Peterson, K. M. and W. W. Payne. 1973. The genus Hymenoclea (Compositae: Ambrosieae). Brittonia 25: 243256.
• Strother, J. L. and B. G. Baldwin. 2002. Hymenocleas are ambrosias (Compositae). Madroño 49: 143144.

Notes

Contributors

• Brands, S.J. (comp.) 1989-present. The Taxonomicon. Universal Taxonomic Services, Zwaag, The Netherlands. Accessed January 10, 2012.

Data Sources

Accessed through GBIF Data Portal February 16, 2008:

• USDA PLANTS, USDA PLANTS Database

Identifiers

• Biodiversity Heritage Library NamebankID: 2657940
• Catalogue of Life Accepted Name Code: Ast-25404
• Global Biodiversity Information Facility Taxonkey: 13749025
• Globally Unique Identifier: urn:lsid:ipni.org:names:176124-1
• GRIN Nomen Number: 444529
• Integrated Taxonomic Information System (ITIS) Taxonomic Serial Number (TSN): 36517
• International Plant Names Index (IPNI) ID: 176124-1
• Natural Heritage Network Species Identifier: PDAST0C0M0
• U.S. Fish and Wildlife Service Species Identifier: Q01H
• U.S.D.A. Plant Symbol: AMPU4
• Zipcode Zoo Species Identifier: 20791

Footnotes

1. John L. Strother "Ambrosia". in Flora of North America Vol. 21 Page 3, 9, 10, 25. Oxford University Press. Online at EFloras.org. [back]
2. "Ambrosia pumila". in Flora of North America Vol. 21 Page 12, 18. Oxford University Press. Online at EFloras.org. [back]

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