Description
Atriplex is a genus with complex taxonomy (200 spp. worldwide) and species concepts varying greatly from author to author (Kartesz 1994; Taschereau 1972). Atriplex prostrata was until recently identified in North America as a variety of A. patula (Bassett and Munro 1987; Taschereau 1972), and most Chesapeake Bay literature refers to it as simply 'A. patula'. However, these species differ in chromosome number (Taschereau 1972). Most or almost all 'Atriplex patula' in the intertidal Chesapeake appears to be A. prostrata (e.g. Brown and Brown 1984, 'our variety is var. hastata'). The name A. laciniata (the name of a more northern species) is used in older literature (Aiken 1837; Gray 1848; Torrey 1821; Pursh 1814; Gronovius 1739; Reveal 1983).
Potentially Misidentified Species - Atriplex patula (as A. patula var. japonica) has been reported from ore piles in Baltimore Harbor (Reed 1964); as var. bractaea it has been reported from the shores of Chesapeake Bay (Fernald 1950). However, all of the specific intertidal records we have found are for 'A. patula var. hastata', actually A. prostrata. Atriplex patula is also thought to be introduced to North America (Bassett and Munro 1987). A. pentandra (=A. arenaria) is native and found mostly above tidelines on beaches and marshes (Brown and Brown 1984). The other Atriplex species listed are known from dry ballast or ore piles in Baltimore (Reed 1964; Shreve et al. 1910). A. rosea and A. nitans are Eurasian; Atriplex elegans var. thornberi comes from the southwest U.S. (Bassett and Munro 1987; Natural Resources Conservation Service 2002; Reed 1964).
Taxonomy
| Kingdom | Phylum | Class | Order | Family | Genus |
|---|---|---|---|---|---|
| Plantae | Magnoliophyta | Magnoliopsida | Caryophyllales | Chenopodiaceae | Atriplex |
Synonyms
Invasion History
Chesapeake Bay Status
| First Record | Population | Range | Introduction | Residency | Source Region | Native Region | Vectors |
|---|---|---|---|---|---|---|---|
| 1877 | Established | Stable | Introduced | Regular Resident | Europe | Eurasia | Shipping(Dry Ballast) |
History of Spread
Atriplex prostrata (Halberd-Leaved Orach) is native to Eurasia and is frequently considered to be probably (Bassett and Munro 1987; Gleason 1963; Gleason and Cronquist 1991; Grime 1988; Hulten 1958) or 'at least in part' introduced to North America (Bassett et al. 1983; Taschereau 1972), based in part on its abundant occurrence in dry ballast piles (Brown 1879; Burk 1876) and its weedy characteristics (Bassett and Munro 1987). It probably invaded very early and was well established on the coast by the 1800's. Atriplex prostrata is definitely introduced to New Zealand and South America (Bassett and Munro 1987).
A. prostrata seeds first appear somewhat later than 240 yrs ago in marsh sediments in the Hackensack (NJ) marshes, but this may also reflect environmental changes at this site (Carmichael 1980). The early history of A. prostrata in North America is obscured by taxonomic problems. As indicated by Gray (1848), some pre-1848 records of 'A. laciniata' may refer to A. prostrata (regarded by Gray as a variety of A. patula), but specimens of 'A. laciniata' collected by John Clayton from VA are the native A. pentandra (=A. arenaria) ( Natural History Museum, London 2000). Other A. laciniata records, 'New York to Virginia; near the sea-coast; on the banks of rivers' (Pursh 1814; Torrey 1823), could refer to A. arenaria, A. patula, or A. prostrata. Gray's (1848) range for 'A. patula' ('Salt marshes and brackish river banks; New Jersey and northward') probably refers to A. prostrata. A. prostrata was collected near Montreal in 1821 (Bassett and Munro 1987). By the early 20th century, the range was given as: 'P.E.I. (Prince Edward Island) to NJ; westward along Great Lakes' (Robinson and Fernald 1908). This plant is now distributed across the US and Canada from Nova Scotia and the Gaspe Peninsula south at least to SC, west to TN, and throughmost of the prairie and southwestern states especially in saline areas. It is widespread on the West Coast from Mexico northward, but is rare in coastal British Columbia (Bassett and Munro 1987; Natural Resources Conservation Service 2001).
In Chesapeake Bay, Pursh (1814, collected in VA in 1806) found 'A. laciniata', probably on the VA western shore, as did Aikin (1837) on 'river banks', Baltimore (Aikin 1837). The first clear record of A. prostrata is an 1877 collection 'in vicinis Washington DC' (US National Herbarium collection). A. prostrata was listed for Washington by the Potomac-Side Naturalists Club (1876) and Ward (1881); and for Baltimore by Sollers (1888). It was 'common in streets and waste places' in Alexandria (Hitchcock and Standley 1919). Now A. prostrata is common in brackish marshes and shorelines (Shreve et al. 1910), and widespread on meso-euhaline shores of Bay and tributaries from Baltimore southwards (Harvill et al. 1992; Sipple 1978).
History References - Aikin 1837; Bassett et al. 1983; Bassett and Munro 1987; Brereton 1830; Brown 1879; Burk 1877; Carmichael 1980; ; Gleason 1963; Gleason and Cronquist 1991; Grime 1988; Harvill et al. 1992; Hitchcock and Standley 1919; Natural History Museum, London 2000; Pursh 1814; Robinson and Fernald 1908; Shreve et al. 1910; Sipple 1978; Sollers 1888; Torrey 1823; Ward 1881; Natural Resources Conservation Service 2001
Invasion Comments
Ecology
Environmental Tolerances
| For Survival | For Reproduction | |||
|---|---|---|---|---|
| Minimum | Maximum | Minimum | Maximum | |
| Temperature (ºC) | ||||
| Salinity (‰) | 0.0 | 32.0 | 0.0 | 10.0 |
| Oxygen | ||||
| pH | 4.0000000000 | 9.0000000000 | ||
| Salinity Range | meso-poly |
Age and Growth
| Male | Female | |
|---|---|---|
| Minimum Adult Size (mm) | ||
| Typical Adult Size (mm) | 500.0 | 500.0 |
| Maximum Adult Size (mm) | 1000.0 | 1000.0 |
| Maximum Longevity (yrs) | ||
| Typical Longevity (yrs | 0.8 | 0.8 |
Reproduction
| Start | Peak | End | |
|---|---|---|---|
| Reproductive Season | |||
| Typical Number of Young Per Reproductive Event |
|||
| Sexuality Mode(s) | |||
| Mode(s) of Asexual Reproduction |
|||
| Fertilization Type(s) | |||
| More than One Reproduction Event per Year |
|||
| Reproductive Startegy | |||
| Egg/Seed Form |
Impacts
Economic Impacts in Chesapeake Bay
Atriplex prostrata (Halberd-Leaved Orach does not have important reported impacts in the Chesapeake Bay region. It is apparently a good wildlife food (Bassett and Munro 1987).
Economic Impacts Outside of Chesapeake Bay
Atriplex prostrata (Halberd-Leaved Orach is an occasional weed inland, and a host for Psilopa leucostema, an insect pest of sugar beets in northwest U.S. It is grazed by sheep, and its leaves are sometimes cooked as a potherb. the seeds are edible and nutritious, can be used in breads and muffins. This plant could be developed as a potential crop for saline soils (Bassett and Munro 1987).
Ecological Impacts on Chesapeake Native Species
Impacts of Atriplex prostrata (Halberd-Leaved Orach) on native species are unknown because of the early date of the presumed introduction. Possible impacts include:
Competition- A prostrata is a pioneer colonizer of disturbed areas (Bassett and Munro 1987; Grime et al. 1988). Competition is possible, especially with other annuals.
FoodPrey- A prostrata 's seeds are nutritious and are eaten by rodents and waterfowl (Bassett and Munro 1987).
Habitat Change - A prostrata may provide cover for birds and mammals, but its effects would be limited to summer and fall because of its annual life history and fall dieback. It may play a role in stabilizing mud and sand, permitting colonization by other plants (Bassett and Munro 1987; Grime et al. 1988).
References - Bassett and Munro 1987; Grime et al. 1988
Ecological Impacts on Other Chesapeake Non-Native Species
Atriplex prostrata (Halberd-Leaved Orach) is a possible competitor with other introduced or cryptogenic annuals of similar habitats: e.g., Suaeda maritima; Cakile maritima; Spergularia marina.
References
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