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Colocasia esculenta

Synonyms: Arum esculentum; Caladium esculentum; Colocasia antiquorum

Common Names: taro root; wild taro; coco-yam; eddo; elephant-ear-plant

Evaluated on: 20-Dec-16

List committee review date: 25/01/2017

Re-evaluation date:

Evaluator(s)

Mona Robison/Science Program Manager
Cal-IPC
916-802-2004
rrobison@cal-ipc.org

List committee members

Elizabeth Brusati
Tim Hyland
Eric Wrubel
Irina Irvine
Holly Forbes

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate

Alert Status? Alert

Documentation? 3 out of 5

Score

Documentation

1.1

?Impact on abiotic ecosystem processes

B. Moderate

Reviewed Scientific Publication

Impact?
Four-part score BBUD Total Score
B

1.2

?Impact on plant community

B. Moderate

Reviewed Scientific Publication

1.3

?Impact on higher trophic levels

U. Unknown

No Information

1.4

?Impact on genetic integrity

D. None

Reviewed Scientific Publication

2.1

?Role of anthropogenic and natural disturbance in establishment

B. Moderate

Reviewed Scientific Publication

Invasiveness?
Total Points
17 Total Score A

2.2

?Local rate of spread with no management

B. Increases less rapidly

Observational

2.3

?Recent trend in total area infested within state

A. Increasing rapidly

Observational

2.4

?Innate reproductive potential
(see Worksheet A)

B. Moderate

Reviewed Scientific Publication

2.5

?Potential for human-caused dispersal

A. High

Other Published Material

2.6

? Potential for natural long-distance dispersal

A. Frequent

Other Published Material

2.7

?Other regions invaded

B. Invades 1 or 2 ecological types

Other Published Material

3.1

?Ecological amplitude/Range
(see Worksheet C)

D. Narrow

Other Published Material

Distribution?
Total Score D

3.2

?Distribution/Peak frequency
(see Worksheet C)

D. Very low

Other Published Material

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include: - fire occurrence, frequency, and intensity; - geomorphological changes such as erosion and sedimentation rates; - hydrological regimes, including soil water table; - nutrient and mineral dynamics, including salinity, alkalinity, and pH; - light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open). Select the one letter below that best describes this species' most severe impact on an abiotic ecosystem process: A. Severe, possibly irreversible, alteration or disruption of an ecosystem process. B. Moderate alteration of an ecosystem process. C. Minor alteration of an ecosystem process. D. Negligible perceived impact on an ecosystem process. U. Unknown.	B Reviewed Scientific Publication
Identify ecosystem processes impacted: Vegetative growth leads to dense populations and its large leaves shade out native vegetation. Since light restriction is considered an abiotic impact, the question was answered as Moderate. Sources of information: Weber 2003
Question 1.2 Impact on plant community composition, structure, and interactions? Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include: - formation of stands dominated (>75% cover) by the species; - occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below; - significant reduction or extirpation of populations of one or more native species. Examples of impacts usually less than severe include: - reduction in propagule dispersal, seedling recruitment, or survivorship of native species; - creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer; - change in density or depth of a structural layer; - change in horizontal distribution patterns or fragmentation of a native community; - creation of a vector or intermediate host of pests or pathogens that infect native plant species. Select the one letter below that best describes this species' impact on community composition, structure and interactions: A. Severe alteration of plant community composition, structure, or interactions. B. Moderate alteration of plant community composition. C. Minor alteration of community composition. D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions. U. Unknown.	B Reviewed Scientific Publication
Identify type of impact or alteration: Forms dense growth along river and lake shores, displacing native shoreline vegetation. Vegetative growth leads to dense populations and its large leaves shade out native vegetation. Colocasia esculenta can tolerate a wide range of wet to dry sites. It easily invades wetland edges, swamps, backwater streams and riverine forests. Colocasia esculenta can form dense stands out-competing native plants. In south-eastern Queensland, it invades waterways and wetlands and replaces native aquatic plants. Extensive stands alter the vegetational structure and dynamics of riparian plant communities. Vegetative growth leads to dense populations and large leaves shade out native vegetation. Grows 1m to 2.5m tall. C. esculenta grows along the edge of the river and along The Meadows Slough mixed with other riparian vegetation, including the State-listed Rare California hibiscus (Hibiscus lasiocarpus var. occidentalis). This will make control of the C. esculenta difficult in some of the area as management of C. esculenta would conflict with the persistence of California hibiscus (Robison pers. comm.). Sources of information: Langeland and Burks 2008 Weber 2003 Invasive Plant Atlas 2016 Queensland Biosecurity 2016 Robison, R. Personal communication.
Question 1.3 Impact on higher trophic levels? Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species' net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types. Examples of severe impacts include: - extirpation or endangerment of an existing native species or population; - elimination or significant reduction in native species' nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors. Examples of impacts that are usually less than severe include: - minor reduction in nesting or foraging sites, cover, etc. for native animals; - minor reduction in habitat connectivity or migratory corridors; - interference with native pollinators; - injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species. Select the one letter below that best describes this species' impact on community composition and interactions: A. Severe alteration of higher trophic populations, communities, or interactions. B. Moderate alteration of higher trophic level populations, communities, or interactions. C. Minor alteration of higher trophic level populations, communities or interactions. D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions. E. Unknown.	U No Information
Identify type of impact or alteration: There is no information available on the impacts of C. esculenta on higher trophic levels in California or elsewhere. Sources of information:
Question 1.4 Impact on genetic integrity? Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include: - production of fertile or sterile hybrids that can outcompete the native species; - production of sterile hybrids that lower the reproductive output of the native species. Select the one letter below that best describes this species' impact on genetic integrity: A. Severe (high proportion of individuals). B. Moderate (medium proportion of individuals). C. Minor (low proportion of individuals). D. No known hybridization. U. Unknown.	D Reviewed Scientific Publication
No known hybridization occurs with native species. There are no native Colocasia species in California and few members of the Araceae in California with similar floral structure which it could hybridize with. Sources of information: Jepson eFlora 2016
Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance in establishment? Assess this species' dependence on disturbance: both human and natural: for establishment in wildlands. Examples of anthropogenic disturbances include: - grazing, browsing, and rooting by domestic livestock and feral animals; - altered fire regimes, including fire suppression; - cultivation; - silvicultural practices; - altered hydrology due to dams, diversions, irrigation, etc.; - roads and trails; - construction; - nutrient loading from fertilizers, runoff, etc. Examples of natural disturbance include: - wildfire; - floods; - landslides; - windthrow; - native animal activities such as burrowing, grazing, or browsing. Select the first letter in the sequence below that describes the ability of this species to invade wildlands: A. Severe invasive potential: this species can establish independent of any known natural or anthropogenic disturbance. B. Moderate invasive potential: this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances. C. Low invasive potential: this species requires anthropogenic disturbance to establish. D. No perceptible invasive potential: this species does not establish in wildlands (though it may persist from former cultivation). U. Unknown.	B Observational
Describe role of disturbance: C. esculenta is introduced through cultivation and after introduction can spread on its own along river banks and in wetlands. Flooding is also a means of establishment. Sources of information: Langeland and Burks 2008 Weber 2003 CABI 2017 Wagner 1999
Question 2.2 Local rate of spread with no management? Assess this species' rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented. Select the one letter below that best describes the rate of spread: A. Increases rapidly (doubling in <10 years) B. Increases, but less rapidly C. Stable D. Declining U. Unknown	B Observational
Describe rate of spread: Colocasia esculenta was first collected and verified as occurring naturally in California in 2014 (CCH 2014). The exact introduction date is unknown, but the species has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). There has been no known management in the introduction area since 2014 and the natural resources manager of Delta Meadows State Park reports that it has been observed to spread less than a mile upstream. Sources of information: Calflora 2016 CCH 2016 Molinar and Yang 2001 Moore and Lawrence 2003 Beard, D. Personal communication
Question 2.3 Recent trend in total area infested within state? Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them. Select the one letter below that best describes the current trend: A. Increasing rapidly (doubling in total range statewide in <10 years) B. Increasing, but less rapidly C. Stable D. Declining U. Unknown	A Observational
Describe trend: Colocasia esculenta was first collected and verified as occurring naturally in California in 2014 (CCH 2014). The exact introduction date is unknown, but the species has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). There has been no known management in the introduction area since 2014 and the natural resources managers of Delta Meadows State Park reports that it has been observed to spread less than a mile upstream, and the population is expanding enough to be considered doubling in 10 years (Beard, D. and Allen, C. personal communications). After the first detection at Delta Meadows, populations were reported in San Joaquin, Solano and Orange counties, so it is assumed that the plant will be spreading and found elsewhere over time. Sources of information: Calflora 2016 CCH 2016 Molinar and Yang 2001 Moore and Lawrence 2003 Allen, C. Personal communication. Beard, D. Personal communication.
Question 2.4 Innate reproductive potential? Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.	B Reviewed Scientific Publication
Describe key reproductive characteristics: Like most other root and tuber crops, taro is vegetatively propagated, although seed production is possible. Natural breeding and population spread have been reported for wild taro. Cultivars are propagated through the use of corms, cormels (also known as suckers), while vegetative propagation occurs through stolons in the wild. According to Weber (2003), naturalized plants rarely produce seeds and only in hot, tropical climates. Sources of information: Chair 2016 Weber 2003
Question 2.5 Potential for human-caused dispersal? Assess whether this species is currently spread: or has high potential to be spread: by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include: - commercial sales for use in agriculture, ornamental horticulture, or aquariums; - use as forage, erosion control, or revegetation; - presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.; - spread along transportation corridors such as highways, railroads, trails, or canals; - transport on boats or boat trailers. Select the one letter below that best describes human-caused dispersal and spread: A. High: there are numerous opportunities for dispersal to new areas. B. Moderate: human dispersal occurs, but not at a high level. C. Low: human dispersal is infrequent or inefficient. D. Does not occur. U. Unknown.	A Other Published Material
Identify dispersal mechanisms: Dispersed primarily by purposeful or accidental movement of vegetative fragments. Only a portion of corm crown and petiole are needed to establish a new plant. C. esculenta has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). Sources of information: Langeland and Burks 2008 Molinar and Yang 2001 Moore and Lawrence 2003
Question 2.6 Potential for natural long-distance dispersal? We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms: - the species' fruit or seed is commonly consumed by birds or other animals that travel long distances; - the species' fruits or seeds are sticky or burred and cling to feathers or hair of animals; - the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water; - the species has light propagules that promote long-distance wind dispersal; - The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed). Select the one letter below that best describes natural long-distance dispersal and spread: A. Frequent long-distance dispersal by animals or abiotic mechanisms. B. Occasional long-distance dispersal by animals or abiotic mechanisms. C. Rare dispersal more than 1 km by animals or abiotic mechanisms. D. No dispersal of more than 1 km by animals or abiotic mechanisms. U. Unknown.	A Other Published Material
Identify dispersal mechanisms: Rhizome fragments are carried by streams. Grows mostly next to rivers so there is high potential for long-distance dispersal. Floods can dislodge bud-laden rhizomes from the banks. Growth seems to be best in the silty soils lining the river-banks. Sources of information: Langeland and Burks 2008 Weber 2003
Question 2.7 Other regions invaded? Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state. Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range. A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively). B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state. C. Invades elsewhere but only in ecological types that it has already invaded in the state. D. Not known as an escape anywhere else. U. Unknown.	B Other Published Material
Identify other regions: C. esculenta is native to Australia, India, and southeastern Asia. It is naturalized in Florida, New Zealand, West Indies, southern Europe, and the Canary Islands, mainly in tropical climates. It can be found growing mainly in moist forests and wet areas in riparian habitats, riverbanks, along streams, marshes, and canals. It can also be found in secondary forests, roadsides, and disturbed areas near to abandoned crop fields. It has invaded some of these habitat types in California, but is not yet found in woodlands or riparian habitats away from the immediate water's edge, and has not yet spread widely. Sources of information: Langeland and Burks 2008 Calflora 2016 Wagner et al. 1999
Section 3: Distribution
Question 3.1 Ecological amplitude/Range? Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades. A. Widespread: the species invades at least three major types or at least six minor types. B. Moderate: the species invades two major types or five minor types. C. Limited: the species invades only one major type and two to four minor types. D. Narrow: the species invades only one minor type. U. Unknown.	D Other Published Material
Colocasia esculenta was first collected and verified as occurring naturally in California in 2014 (CCH 2014). The exact introduction date is unknown, but the species has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). A specimen was collected from Delta Meadows State Park in 2014, located near Isleton in Sacramento County. Plants were growing along the edge of the river and in The Meadows Slough mixed with other riparian vegetation, including the State-listed Rare California hibiscus (Hibiscus lasiocarpus var. occidentalis). Further mapping in the area identified it as occurring in 7 patches in the Park as well as upstream and downstream from the Park boundary in two places (Robison 2014). Other reports were submitted to Calflora for locations in Solano, San Joaquin and Orange counties (Calflora 2016). The locations in Solano and San Joaquin counties are on river edges, the Orange County habitat is unknown, but appears to be a wetland edge from the aerial photograph. Sources of information: CCH 2014 Calflora 2016 Molinar and Yang 2001 Moore and Lawrence 2003 Robison 2014
Question 3.2 Distribution/Peak frequency? To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.	D Other Published Material
Describe distribution: Occurs along river and slough edges in the Sacramento and San Joaquin delta. In Orange County it is growing along the shaded, moist edge of a small drainage, probably fed by urban runoff, but in a native plant community. Probably best described as a light riparian area (Vanderhoff, R. pers. comm.). Sources of information: CCH 2014 Calflora 2016 Robison 2014 Vanderhoff, R. Personal communication.

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less	Yes
Dense infestations produce >1,000 viable seed per square meter	No
Populations of this species produce seeds every year.	No
Seed production sustained over 3 or more months within a population annually	Unknown
Seeds remain viable in soil for three or more years	Unknown
Viable seed produced with both self-pollination and cross-pollination	Unknown
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes	Yes
Fragments easily and fragments can become established elsewhere	Yes
Resprouts readily when cut, grazed, or burned	Yes
Total points:	5
Total unknowns:	3
Total score:	B? Scoring Criteria for Worksheet A A. High reproductive potential (6 or more points). B. Moderate reproductive potential (4-5 points). C. Low reproductive potential (3 points or less and less than 3 Unknowns). U. Unknown (3 or fewer points and 3 or more Unknowns).

Related traits:

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)

Major Ecological Types	Minor Ecological Types	Code? A means >50% of type occurrences are invaded; B means 20% to 50%; C means 5% to 20%; D means present but <5%; U means unknown (unable to estimate percentage of occurrences invaded)
Marine Systems	marine systems
Freshwater and Estuarine	lakes, ponds, reservoirs
Aquatic Systems	rivers, streams, canals
Aquatic Systems	estuaries
Dunes	coastal
	desert
	interior
Scrub and Chaparral	coastal bluff scrub
	coastal scrub
	Sonoran desert scrub
	Mojavean desert scrub (incl. Joshua tree woodland)
	Great Basin scrub
	chenopod scrub
	montane dwarf scrub
	Upper Sonoran subshrub scrub
	chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communities	coastal prairie
	valley and foothill grassland
	Great Basin grassland
	vernal pool
	meadow and seep
	alkali playa
	pebble plain
Bog and Marsh	bog and fen
Bog and Marsh	marsh and swamp	D, < 5%
Riparian and Bottomland habitat	riparian forest
	riparian woodland
	riparian scrub (incl.desert washes)
Woodland	cismontane woodland
	piñon and juniper woodland
	Sonoran thorn woodland
Forest	broadleaved upland forest
	North Coast coniferous forest
	closed cone coniferous forest
	lower montane coniferous forest
	upper montane coniferous forest
	subalpine coniferous forest
Alpine Habitats	alpine boulder and rock field
Alpine Habitats	alpine dwarf scrub
	Amplitude (breadth):	D
	Distribution (highest score):	D

Infested Jepson Regions

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Great Valley
Southwest

California Invasive Plant Council

Protecting California’s environment and economy from invasive plants

Plant Assessment Form

More Colocasia esculenta resources

Colocasia esculenta

Evaluator(s)

List committee members

General Comments

Table 2. Criteria, Section, and Overall Scores

Table 3. Documentation

Worksheet A - Innate reproductive potential

Related traits:

Worksheet C - California Ecological Types

Infested Jepson Regions