Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Amaranthus dubius
(spleen amaranth)

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Datasheet

Amaranthus dubius (spleen amaranth)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Amaranthus dubius
  • Preferred Common Name
  • spleen amaranth
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • A. dubius is an annual herb native to South America, Mexico and the West Indies. This species has been widely introduced as a green vegetable for human consumption and as a medicinal herb. It has escaped from c...

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Pictures

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PictureTitleCaptionCopyright
Amaranthus dubius (spleen amaranth); uprooted plant, showing stem, leaves and inflorescences. Puu o Kali, Maui, Hawaii, USA. May 2004.
TitleGeneral view
CaptionAmaranthus dubius (spleen amaranth); uprooted plant, showing stem, leaves and inflorescences. Puu o Kali, Maui, Hawaii, USA. May 2004.
Copyright©Forest Starr & Kim Starr - CC BY 4.0
Amaranthus dubius (spleen amaranth); uprooted plant, showing stem, leaves and inflorescences. Puu o Kali, Maui, Hawaii, USA. May 2004.
General viewAmaranthus dubius (spleen amaranth); uprooted plant, showing stem, leaves and inflorescences. Puu o Kali, Maui, Hawaii, USA. May 2004.©Forest Starr & Kim Starr - CC BY 4.0

Identity

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Preferred Scientific Name

  • Amaranthus dubius Mart. Ex Thell

Preferred Common Name

  • spleen amaranth

Other Scientific Names

  • Amaranthus tristis Willd.

International Common Names

  • English: pigweed amaranth
  • Spanish: bledo de Jamaica; bledo de puerco; pira
  • French: amarante; brede de Malabar

Local Common Names

  • Bahamas: southern pigweed
  • Cuba: bledo
  • Dominican Republic: bledo blanco; zepina; zepino
  • Haiti: epinard; epinard marron
  • India: chauli; cheera; koyagura; kuppai keerai; thotakura
  • Jamaica: Spanish calalu
  • Lesser Antilles: epinard dupays; zépinna
  • Mexico: zac-tec
  • Portugal: caruro
  • Puerto Rico: blero; blero blanco
  • Suriname: klaroen
  • Sweden: mchicha
  • Venezuela: amaranto; pira; yerbacaracas

EPPO code

  • AMADU (Amaranthus dubius)

Summary of Invasiveness

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A. dubius is an annual herb native to South America, Mexico and the West Indies. This species has been widely introduced as a green vegetable for human consumption and as a medicinal herb. It has escaped from cultivation and now it is considered casual or naturalized mainly in tropical and subtropical regions of Africa, Asia, Australia and the Pacific. A. dubius also grows as a weed of annual crops, plantations, village gardens, disturbed sites and secondary vegetation (Waterhouse and Mitchell, 1998; USDA-ARS, 2015). A. dubius is recorded as invasive on Cousine Island, Seychelles, where it occupies plateau and high woodland areas (Dunlop et al., 2005). It is also listed as invasive in Cuba and on several islands in the Pacific Ocean (Oviedo Prieto et al., 2012; PIER, 2014). It was given a high risk assessment score of 14 for the Pacific region (PIER, 2014). In Africa A. dubius is locally naturalized.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Caryophyllales
  •                         Family: Amaranthaceae
  •                             Genus: Amaranthus
  •                                 Species: Amaranthus dubius

Notes on Taxonomy and Nomenclature

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The name Amaranthus dubius was first published by Martius (1814) without diagnosis and description, so it has to be considered invalid (McNeill et al., 2012). Thellung (1912) validly published the name.

Mosyakin and Robertson (1999) proposed the new nothosection Dubia Mosyakin & K. R. Robertson (subgenus Amaranthus section Amaranthus) to house A. dubius, which is a morphologically deviant allopolyploid taxon very closely related to both A. spinosus L. (Sect. Centrusa Griseb.) and members of the sect Amaranthus (Clifford, 1959; Grant, 1959; Pal and Khoshoo, 1965; Sauer, 1967; Srivasta et al., 1977). A. dubius most probably originated as a result of ancient hybridization between A. spinosus and either A. hybridus or A. quitensis (Mosyakin and Robertson, 2004). 

Description

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Annual herb, 10-100(-200) cm tall, glabrous or sparsely pubescent in distal parts. Stems erect, green, branched, 0.3-1 m. Leaves: petiole of proximal leaves equalling or longer than blade, becoming shorter distally; blade rhombic-ovate or ovate to elliptic, (1.5-)3-12(-20) by (0.6-)2-8(-10) cm, base broadly cuneate, margins entire, apex slightly acuminate to obtuse and faintly emarginate, mucronate; stipules absent. Inflorescences terminal panicles and axillary spikes; panicles erect or often drooping, green, dense, branched, leafless at least distally. Bracts lanceolate, shorter than 2 mm (usually 1.0-1.5 mm), shorter than tepals, apex spinescent, midrib prominent, glabrous, usually white-yellow. Pistillate flowers: tepals 5, oblong-spathulate to oblong, not clawed, 1.5-2(-2.5) mm, apex acute, often very shortly mucronate, yellowish; style branches strongly spreading, shorter than body of fruit; stigmas 3. Staminate flowers usually clustered at tips of inflorescence branches, sometimes gathered in proximal glomerules (as in A. spinosus); tepals 5, equal or subequal; stamens 5, about 2 mm long. Utricles ovoid or subglobose, 1.5-2 mm, slightly shorter than tepals, smooth to irregularly wrinkled, dehiscence regularly circumscissile. Seeds dark reddish brown to black, subglobose or lenticular, 0.8-1 mm diameter, shiny, smooth.

Cultivated types of A. dubius are larger, more erect and more succulent than weedy types (Grubben, 2004). A. dubius is morphologically similar to A. hybridus and A. powellii. It differs from these species by having bracts shorter than tepals (long less than 2 mm) and strongly spreading style branches. In A. hybridus and A. powellii the bracts are longer than or equal to the tepals (2-7 mm long) and the style branches are erect or slightly reflexed. Grubben (2004) noted that ‘it is almost impossible to make a distinction between A. dubius and A. spinosus based on morphological characters’ other than by the axillary spines in A. spinosus. Sogbohossou and Achigan-Dako (2014) distinguished two main groups of A. dubius accessions: (1) the dwarf types morphologically close to A. spinosus, which are early flowering, with low plant height (up to 1.2 m), small leaves and many branches and (2) the giant types which are late flowering, tall (up to 2 m), with broad leaves and few branches.

 

Distribution

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A. dubius is native to South America, Mexico and the West Indies, and naturalized or invasive in the USA (Florida and Hawaii Islands), central and southwestern Africa, Asia (India, Indonesia, Nepal, and Taiwan) and Oceania (Australia and many Pacific islands). In Europe, it occurs locally in France and Germany. It is cultivated in many countries, especially in Africa, but it can be difficult to know whether its presence in a country is only as a cultivated plant or as a naturalised plant.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

BangladeshPresentIntroducedGBIF, 2014
ChinaPresentPresent based on regional distribution.
-GuangdongPresentWang et al., 2015Along bank of Hanjiang River, Chaozhou
Christmas Island (Indian Ocean)PresentIntroduced Invasive PIER, 2014
East TimorPresentIntroducedGBIF, 2014
IndiaPresentIntroduced Not invasive Townsend, 1980
IndonesiaPresentPresent based on regional distribution.
-Irian JayaPresentIntroduced Invasive PIER, 2014
-JavaPresentIntroduced Not invasive USDA-ARS, 2013
-Nusa TenggaraPresentIntroduced Not invasive Palmer, 2009Only in Timor
LaosPresentIntroducedGBIF, 2014
MaldivesPresentIntroducedGBIF, 2014
NepalPresentIntroduced Not invasive Sukhorukov, 2011Central Nepal (Myadgi)
OmanPresentIntroducedGBIF, 2014
PhilippinesPresentIntroduced Invasive GBIF, 2014; PIER, 2014
Sri LankaPresentIntroducedGBIF, 2014
TaiwanPresentIntroducedChen and Wu, 2007Biyun Village, Kuangtung st.. Naturalized
ThailandPresentIntroducedGBIF, 2014
VietnamPresentIntroducedGBIF, 2014
YemenPresentIntroduced Not invasive Brown and Mies, 2012Socotra

Africa

BeninPresentIntroduced Not invasive Grubben, 2004
Burkina FasoPresentIntroducedGBIF, 2014
BurundiPresentIntroduced Not invasive Grubben, 2004
CameroonPresentIntroduced Not invasive Grubben, 2004
ComorosPresentIntroducedGBIF, 2014
Congo Democratic RepublicPresentIntroduced Not invasive Grubben, 2004
Equatorial GuineaPresentIntroducedGBIF, 2014
EritreaPresentIntroduced Not invasive Grubben, 2004
EthiopiaPresentIntroduced Not invasive Grubben, 2004
GhanaPresentIntroduced Not invasive Grubben, 2004
KenyaPresentIntroduced Not invasive Grubben, 2004
MadagascarPresentIntroduced Not invasive Grubben, 2004
MalawiPresentIntroduced Not invasive Grubben, 2004
MauritiusPresentIntroducedMcIntyre, 1991; PIER, 2014
MayottePresentIntroducedGBIF, 2014
MozambiquePresentIntroduced Not invasive Grubben, 2004
NigerPresentIntroducedGBIF, 2014
NigeriaPresentIntroduced Not invasive Grubben, 2004
RwandaPresentIntroduced Not invasive Grubben, 2004
Saint HelenaPresentIntroducedGBIF, 2014
Sao Tome and PrincipePresentIntroducedGBIF, 2014
SenegalPresentIntroducedGBIF, 2014
SeychellesPresentIntroduced Invasive Hill et al., 2002; Dunlop et al., 2005Cousine Islands
Sierra LeonePresentIntroduced Not invasive Grubben, 2004
SomaliaPresentIntroduced Not invasive Grubben, 2004
South AfricaPresentIntroducedPROTA, 2014
SudanPresentIntroducedPROTA, 2014
TanzaniaPresentIntroduced Not invasive Grubben, 2004
UgandaPresentIntroduced Not invasive Grubben, 2004
ZambiaPresentIntroduced Not invasive Grubben, 2004
ZimbabwePresentIntroduced Not invasive Grubben, 2004

North America

MexicoPresentNative Not invasive Sánchez-del Pino et al., 2013Campeche, Chapas, Quintana Roo, Tabasco
Saint Pierre and MiquelonPresentNative Not invasive USDA-ARS, 2013
USAPresentPresent based on regional distribution.
-FloridaPresentIntroduced Not invasive Mosyakin and Robertson, 2003
-HawaiiPresentIntroducedUSDA-ARS, 2013; PIER, 2014
-MassachusettsPresentIntroducedUSDA-NRCS, 2015Weed

Central America and Caribbean

AnguillaPresentNativeSmithsonian Institution, 2012
Antigua and BarbudaPresentNativeSmithsonian Institution, 2012
ArubaPresentNativeGBIF, 2014
BahamasPresentNativeCorrell and Correll, 1982
BarbadosPresentNativeSmithsonian Institution, 2012
BelizePresentNativeGBIF, 2014
British Virgin IslandsPresentNativeAcevedo-Rodríguez, 1996; Smithsonian Institution, 2012
Cayman IslandsPresentNativeSmithsonian Institution, 2012
CubaPresentIntroduced Invasive León and Alain, 1957; Oviedo Prieto et al., 2012
DominicaPresentNativeSmithsonian Institution, 2012
Dominican RepublicPresentNativeSmithsonian Institution, 2012
GrenadaPresentNativeSmithsonian Institution, 2012
GuadeloupePresentNativeSmithsonian Institution, 2012Maria Galante
HaitiPresentNativeSmithsonian Institution, 2012
HondurasPresentNativePancho et al., 1979
JamaicaPresentNativeAdams, 1972; Smithsonian Institution, 2012
MartiniquePresentNativeSmithsonian Institution, 2012
Netherlands AntillesPresentNativeGBIF, 2014
NicaraguaPresentNativePancho et al., 1979
PanamaPresentNativeGBIF, 2014
Puerto RicoPresentNativeLiogier and Martorell, 1982; Liogier, 1990; USDA-ARS, 2013
SabaPresentNativeSmithsonian Institution, 2012
Saint Kitts and NevisPresentNativeSmithsonian Institution, 2012
Saint LuciaPresentNativeSmithsonian Institution, 2012
Saint Vincent and the GrenadinesPresentNativeSmithsonian Institution, 2012
Turks and Caicos IslandsPresentNativeMosyakin and Robertson, 2003
United States Virgin IslandsPresentNativeSmithsonian Institution, 2012

South America

ArgentinaPresentNativeZuloaga et al., 2008; GBIF, 2014
BoliviaPresentNativeGBIF, 2014
BrazilPresentNativeUSDA-ARS, 2013
ColombiaPresentNativeUSDA-ARS, 2013; USDA-ARS, 2013
EcuadorPresentNativeEliasson, 1987; Guézou et al., 2010
-Galapagos IslandsPresentIntroduced Invasive Charles Darwin Foundation, 2008
French GuianaPresentNativeUSDA-ARS, 2013
GuyanaPresentNativeUSDA-ARS, 2013
PeruPresentNativeUSDA-ARS, 2013
SurinamePresentNativeUSDA-ARS, 2013
VenezuelaPresentNativePinto and Velásuez, 2010; GBIF, 2014Mainly in the north

Europe

FrancePresentIntroducedGBIF, 2014
GermanyPresentIntroducedGBIF, 2014
NetherlandsPresent
SpainPresentIntroducedGBIF, 2014

Oceania

AustraliaPresentPresent based on regional distribution.
-Australian Northern TerritoryPresentIntroduced Not invasive Palmer, 2009Nhulunby
-QueenslandPresentIntroduced Not invasive Palmer, 2009Cooktown
Cook IslandsPresentIntroducedGBIF, 2014
FijiPresentIntroduced Not invasive USDA-ARS, 2013; PIER, 2014
French PolynesiaPresentIntroduced Invasive PIER, 2014Tahiti, Tupai and Toau islands
Johnston IslandPresentIntroduced Invasive PIER, 2014
KiribatiPresentIntroduced Invasive PIER, 2014Kanton, Abemama and Tarawa islands
Marshall IslandsPresentIntroduced Invasive PIER, 2014Ralik Chain
Micronesia, Federated states ofPresentIntroduced Invasive PIER, 2014Kosrae, Ulithi, Yap Islands
NauruPresentIntroduced Invasive PIER, 2014
New CaledoniaPresentIntroduced Invasive GBIF, 2014; PIER, 2014New Caledonia and Ile Grande Terre islands
Northern Mariana IslandsPresentIntroduced Invasive PIER, 2014Alamagan Island
PalauPresentIntroduced Invasive GBIF, 2014; PIER, 2014Babeldaob, Koror and Malakal islands
Papua New GuineaPresentIntroduced Not invasive Palmer, 2009; PIER, 2014
Solomon IslandsPresentIntroducedGBIF, 2014
Wake IslandPresentIntroduced Invasive PIER, 2014

History of Introduction and Spread

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A. dubius has been intentionally introduced and grown as a green vegetable for human consumption in tropical and subtropical regions of the world, but there is also a high probability that it has been introduced unintentionally as a contaminant due to the small size of its seeds (PROTA, 2014; USDA-ARS, 2015). It has been suggested that Amaranthus species were dispersed along trade routes between America, Europe and Asia. In the case of Cuba, where this species is invasive, it appears in herbarium collections made as early as 1900 in Havana, Pinar del Rio, and Cienfuegos (US National Herbarium collections).  

Risk of Introduction

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Potential risks mainly relate to the spread of A. dubius in the African and Asian countries, where this species is grown for food. It could also propagate and spread in Europe, possible by human activity and bird migrations.

Habitat

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The main habitats in which A. dubius occurs are: tropical forest, humid lowland waste areas, vegetable gardens and roadsides (Mosyakin and Robertson, 2003; Palmer, 2009; Sukhorukov, 2011; Sanchez-del Piño et al., 2013). On Cousine Island, Seychelles, where A. dubius is recorded as invasive, Dunlop et al. (2005) reported it growing in plateau and high woodland areas. It is also recorded growing in disturbed sites in Hawaii, in secondary vegetation, and as a weed in clearings, gardens, waste places and plantations (PIER, 2014). It can grow from near sea level up to 1300 m altitude in Papua New Guinea (PIER, 2014).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial ‑ Natural / Semi-naturalLowlands Present, no further details Natural
Lowlands Present, no further details Productive/non-natural
Terrestrial – ManagedCultivated / agricultural land Present, no further details Harmful (pest or invasive)
Cultivated / agricultural land Present, no further details Natural
Cultivated / agricultural land Present, no further details Productive/non-natural
Managed grasslands (grazing systems) Present, no further details Harmful (pest or invasive)
Managed grasslands (grazing systems) Present, no further details Natural
Disturbed areas Secondary/tolerated habitat Harmful (pest or invasive)
Disturbed areas Secondary/tolerated habitat Natural
Rail / roadsides Secondary/tolerated habitat Harmful (pest or invasive)
Rail / roadsides Secondary/tolerated habitat Natural
Urban / peri-urban areas Secondary/tolerated habitat Natural
Natural forests Principal habitat Natural
Natural grasslands Secondary/tolerated habitat Harmful (pest or invasive)
Natural grasslands Secondary/tolerated habitat Natural
Riverbanks Present, no further details Harmful (pest or invasive)
Riverbanks Present, no further details Natural

Biology and Ecology

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Genetics

A. dubius is the only known tetraploid Amaranthus taxon with 2n = 64. It possibly originated as a result of ancient hybridization between A. spinosus L. and either A. hybridus or A. quitensis (Grant, 1959; Pal and Khoshoo, 1965; Sauer, 1967), though doubts were expressed and discussed in Grubben (2004). Mosyakin and Robertson (1996) proposed a new taxon (Amaranthus nothosection Dubia Mosyakin & K. R. Robertson) to accommodate this particular species. However, plants identified as A. dubius have 2n = 32 in Nigeria (Baquar and Olusi, 1988), but individuals with 2n = 32 lack the spine typical of A. spinosus (Grubben, 2004).

Reproductive Biology

A. dubius is usually an annual herb (therophyte) with a short life-cycle. Each plant produces a high number of seeds. The emergence of the seedling takes place 3-5 days after sowing. Flowering starts after 4-8 weeks, showing a weak quantitative short-day reaction. The plant produces new shoots when older branches are already blooming. Pollination is by wind, but self-pollinating plants do occur. Vegetative development is fast.

Physiology and Phenology

A. dubius has the C4 photosynthesis pathway. It shows a high photosynthetic rate at high temperatures and light intensity, and lower CO2 compensation than C3 species. Flowering time is from May to September (summer to autumn in the tropics and various seasons in the subtropics). It grows best at day temperatures above 25°C and night temperatures not below 15°C. Its preferred soils are fertile, well-drained and with a loose structure (Grubben, 2004)

Associations

No detailed studies about the vegetation communities associated with A. dubius have been published. A. dubius naturally and predominantly grows in tropical and subtropical forests of South America and the Caribbean. In Taiwan, it is associated with weeds: Amaranthus spinosus, Bidens pilosa var. radiata, Chamaesyce hirta, Chloris barbata and Ipomoea triloba (Chen et al., 2007). Further phytosociological studies are needed.

Climate

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ClimateStatusDescriptionRemark
A - Tropical/Megathermal climate Preferred Average temp. of coolest month > 18°C, > 1500mm precipitation annually
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
C - Temperate/Mesothermal climate Tolerated Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C
Cs - Warm temperate climate with dry summer Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
28 23

Air Temperature

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Parameter Lower limit Upper limit
Mean annual temperature (ºC) -3 18
Mean maximum temperature of hottest month (ºC) 10 35
Mean minimum temperature of coldest month (ºC) 2 15

Rainfall

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ParameterLower limitUpper limitDescription
Dry season duration34number of consecutive months with <40 mm rainfall
Mean annual rainfall4003300mm; lower/upper limits

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Choanephora cucurbitarum Pathogen All Stages not specific PROTA, 2014
Helicoverpa armigera Herbivore Adults
Hypolixus truncatulus Herbivore All Stages not specific PROTA, 2014
Rotylenchulus reniformis Parasite Adults not specific Grubben, 2004 Africa continent
Spodoptera litura Herbivore Adults not specific
Spoladea recurvalis Herbivore Adults not specific PROTA, 2014
Xanthomonas campestris Parasite Adults not specific Grubben, 2004 Africa continent Bananas

Notes on Natural Enemies

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Taken from PROTA (2014):

In general, A. dubius is susceptible to the main pests and diseases of A. cruentus, but it is less susceptible to stemrot caused by the fungus Choanephora cucurbitarum, the main disease of A. cruentus, and to damping-off caused by Pythium. No virus diseases have been reported. Insects are a serious problem for amaranth growers. Hymenia recurvalis [Spoladea recurvalis], Spodoptera litura, Heliothis armigera and sometimes grasshoppers are the most harmful pests. The larvae of the stem borer Lixus truncatulus [Hypolixus truncatulus] may cause much damage. A. dubius is a host plant for the bacterium Xanthomonas campestris affecting tomato and for the nematode Rotylenchulus reniformis affecting banana.

Means of Movement and Dispersal

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A. dubius spreads by seeds. This species is a prolific seed producer (Waterhouse and Mitchell, 1998). Seeds are dispersed by wind, water, birds and as a contaminant in pasture and crop seeds and attached in agricultural machinery. 

Natural Dispersal

Self-pollinated; wind.

Vector Transmission (Biotic)

Carried by animals.

Accidental Introduction

Associated with trade and transport.

Intentional introduction

As a vegetable plant.

 

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
Leaves Yes Pest or symptoms usually visible to the naked eye
Stems (above ground)/Shoots/Trunks/Branches Yes Pest or symptoms usually visible to the naked eye
Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Roots
Seedlings/Micropropagated plants
True seeds (inc. grain)
Wood

Impact Summary

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CategoryImpact
Economic/livelihood Positive and negative
Environment (generally) Negative
Human health Positive and negative

Economic Impact

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There are no known economic impacts of A. dubius. However, especially in tropical Africa it is widely naturalized and cultivated and could compete with other cultivated plants, causing a reduction in agricultural income (see for example Costea et al., 2001a; Iamonico, 2010). In Australia, it grows as a weed of annual crops and plantations and as an environmental weed (Waterhouse and Mitchell, 1998). 

Environmental Impact

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A. dubius could cause a loss of biodiversity, especially decreasing floristic richness, in communities where it is naturalized and where it is becoming invasive, such as in Cuba (Oviedo Prieto et al., 2012), Taiwan (Chen et al., 2007), Australia (Palmer, 2009) and Pacific islands (PIER, 2014).

Social Impact

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Although no studies on social impacts have been carried out, the abundant flowers, pollen production and small pollen size in the genus Amaranthus mean it could have an impact as an allergenic species (see for example Costea et al., 2001a; 2001b; Costea and Tardif, 2003; Iamonico, 2010).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Highly mobile locally
  • Benefits from human association (i.e. it is a human commensal)
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
Impact outcomes
  • Ecosystem change/ habitat alteration
  • Host damage
  • Increases vulnerability to invasions
  • Monoculture formation
  • Negatively impacts cultural/traditional practices
  • Reduced native biodiversity
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Herbivory/grazing/browsing
  • Hybridization
  • Interaction with other invasive species
  • Parasitism (incl. parasitoid)
  • Rapid growth
  • Rooting
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Difficult to identify/detect in the field

Uses

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Economic Value

A. dubius is a subsistence vegetable and a collected pot herb, seldom found in markets, but in Kenya and recently in Benin it is grown on a commercial scale and sold in city markets. No statistical data on production are available.

Social Benefit

A. dubius is mainly used as a leaf vegetable, both in Africa (Grubben, 2004) and in Asia (George et al., 1989). In Kenya it is cooked with other leaf vegetables such as Solanum spp., Cleome gynandra and Launaea cornuta. In Benin it is usually cooked alone. In general, amaranth leaves are recommended as food with medicinal properties for young children, lactating mothers and for patients with fever, haemorrhage, anaemia, constipation or kidney complaints. In Tanzania the whole plant is used as a medicine against stomach ache. In Uganda A. dubius is used in the preparation of potash. Taiwanian aborigines (from the Hualien area) use leaves and stems of this species as a kind of pot herb (Chen et al., 2007).

Similarities to Other Species/Conditions

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A. dubius is morphologically similar to A. hybridus and A. powellii. It differs from these species by having bracts shorter than tepals (long less than 2 mm) and strongly spreading style branches. In A. hybridus and A. powellii the bracts are longer than or equal to the tepals (2-7 mm long) and the style branches are erect or slightly reflexed. PROTA (2014) noted that ‘it is almost impossible to make a distinction between A. dubius and A. spinosus based on morphological characters’ other than by the axillary spines in A. spinosus.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Chemical control

A. dubius is not known to differ from other Amaranthus species in its susceptibility to herbicides. It is probable that, like A. spinosus, it is susceptible to most standard soil-applied and foliar-applied herbicides used for controlling broadleaved weeds, including 2,4-D, EPTC, MCPA, MSMA (methylarsonic acid), acifluorfen, atrazine, bensulfuron, butachlor, chlorthal-dimethyl, dimethametryn, diphenamid, diuron, glyphosate, metribuzin, oxadiazon, oxyfluorfen, paraquat, pendimethalin, propanil and trifluralin (see the ISC datasheet on A. spinosus: http://www.cabi.org/isc/datasheet/4653; CABI, 2014).

Gaps in Knowledge/Research Needs

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Nomenclature and Taxonomy

Historical and typification study; biometric intra- and interpopulation analyses on specimens collected from both native areas (central and southern America) and exotic ones (especially Africa); molecular studies at population level (both intrapopulational, especially for American native populations, and interpopulational, especially in comparison between American native populations and xenophyte populations in Africa, Asia and Australia), and comparative studies between the section Dubia Mosyakin & K. R. Robertson, the section Centrusa Griseb. and some related taxa (A. cruentus L., A. hybridus L., and A. quitensis Kunth) of the section Amaranthus (all of which are included in the subgenus Amaranthus).

Plant Sociology

Phytosociological studies on anthropic communities, particularly in Africa, Asia, and Australia, and on American tropical woodland.

Geographical Distribution

A detailed study on the chorology of A. dubius, including: native range (Central and Southern America plus the Caribbean), adventive territories and distribution pattern in areas in which it is cultivated.

Invasiveness

Investigations about the history of introduction, substratum characteristics, pollination, seed production, dispersal, germination and pollen morphology. Case studies on invasive behaviour.

References

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Acevedo-Rodríguez P, 1996. Flora of St. John, U.S. Virgin Islands. Memoirs of the New York Botanical Garden, 78:1-581.

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01/12/15 Updated by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

07/12/13: Datasheet by:

Duilio Iamonico, University of Rome Sapienza, Italy

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