Source: California Invasive Plant Council


URL of this page: http://www.cal-ipc.org/site/paf/540
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Cal-IPC Plant Assessment Form

For use with "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands"
by the California Invasive Plant Council and the Southwest Vegetation Management Association

Table 1. Species and Evaluator Information

Species name
(Latin binomial):
The official Latin binomial name for this species. Specify only one name here. Additional species names may go into the Synonyms field.

Colocasia esculenta

Synonyms:
Additional Latin binomial names for this species. Separate multiple names with a ; character. Please avoid narrative descriptions, and list only the binomial names.
Arum esculentum; Caladium esculentum; Colocasia antiquorum
Common names:
Common names for this species. Separate multiple names with a ; character.
taro root; wild taro; coco-yam; eddo; elephant-ear-plant
Evaluation date:
The date(s) when this species PAF was filled out, modified, or reviewed. This is free-form text, so it may include multiple dates or other notes.
December 20, 2016
Evaluator #1 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
Committee review date: January 25, 2017
List date: June 2, 2017
Re-evaluation date(s):
General comments
on this assessment:
Enter any additional notes about this assessment, such as factors affecting the reliability or completeness of the answers, likely affects of impacts, or research which is not specific to California but is still relevant in the evaluation of this species.

Table 2. Criteria, Section, and Overall Scores

Overall Score

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistribution
AA BAnyHighNo Alert
AC DAnyModerateAlert
BA BA BModerateNo Alert
BA BC DModerateAlert
BC DAnyLimitedNo Alert
CAA BModerateNo Alert
CAC DLimitedNo Alert
CBAModerateNo Alert
CBB DLimitedNo Alert
CCAnyLimitedNo Alert
DAnyAnyNot ListedNo Alert

Moderate

Alert Status

Plant scoring matrix
Based on letter scores from Sections 1 through 3 below

ImpactInvasivenessDistributionAlert
AA or BC or DAlert
BA or BC or DAlert

Alert

Documentation

The total documentation score is the average
of Documentation scores given in Table 2.

Reviewed Scientific Publication4 points
Other Published Material3 points
Observational2 points
Anecdotal1 points
Unknown or No Information0 points

3 out of 5

Score Documentation
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. Moderate Reviewed Scientific Publication
Impact
Section 1 Scoring Matrix
Q 1.1Q 1.2Q 1.3Q 1.4Score
AAAnyAnyA
ABA,BAnyA
ABC,D,UAnyB
AC,D,UAnyAnyB
BAAAnyA
BABAA
BAB,CB-D,UB
BAC,D,UAA
BAC,D,UB-D,UB
BBAAA
BC,D,UAAB
BB-DAB-D,UB
BB-DB-D,UAnyB
BD,UC,D,UA-BB
BD,UC,D,UC,D,UC
C-D,UAAAnyA
CBAAnyB
CA,BB-D,UAnyB
CC,D,UAnyAnyC
DA,BBAnyB
DA,BC,D,UAnyC
DCAnyAnyC
DD,UAnyAnyD
UAB,CAnyB
UB,CA,BAnyB
UB,CC,D,UAnyC
UUAnyAnyU


Four-part score
BBUD

Total Score
B
1.2 Impact on plant community
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. Moderate Reviewed Scientific Publication
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.
E. Unknown No Information
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. None Reviewed Scientific Publication
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. Moderate Reviewed Scientific Publication
Invasiveness
Section 2 Scoring Matrix
Total pointsScore
17-21A
11-16B
5-10C
0-4D
More than two U’sU


Total Points
17

Total Score
A
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. Increases less rapidly Observational
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. Increasing rapidly Observational
2.4 Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
B. Moderate Reviewed Scientific Publication
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. High Other Published Material
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. Frequent Other Published Material
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. Invades 1 or 2 ecological types Other Published Material
3.1 Ecological amplitude/Range
(see Worksheet C)
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. Narrow Other Published Material
Distribution
Section 3 Scoring Matrix
Q 3.1Q 3.2Score
AA, BA
AC,D,UB
BAA
BB,CB
BDC
CA,BB
CC,DC
DAB
DB,CC
DDD
A,BUC
C,DUD
UUU


Total Score
D
3.2 Distribution/Peak frequency
(see Worksheet C)
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
D. Very low Other Published Material

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".
Short citations may be used in this table. List full citations at end of this table.

Section 1: Impact

Reviewed Scientific Publication B 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.
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

Reviewed Scientific Publication B 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.
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.

No Information U 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.
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:

Reviewed Scientific Publication D 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.
Identify impacts:
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

Reviewed Scientific Publication B 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.
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

Observational B 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
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

Observational A 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
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.

Reviewed Scientific Publication B Question 2.4 Innate reproductive potential
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
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

Other Published Material A 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.
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

Other Published Material A 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.
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

Other Published Material B 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.
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

Other Published Material D 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.
Describe ecological amplitude, identifying date of source information and approximate date of introduction to the state, if known:
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

Other Published Material D 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.
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.

References

List full citations for all references used in the PAF (short citations such as DiTomaso and Healy 2007 may be used in table above). Websites should include the name of the organization and the date accessed. Personal communications should include the affiliation of the person providing the observation. Enter each reference on a separate line.
Allen, C. 2017. Personal communication with Cara Allen, Environmental Scientist with California State Parks, Gold Fields District. Phone conversation 2/1/17. Beard, D. 2016. Personal communication with Denali Beard, Environmental Scientist with California State Parks, Gold Fields District. Email, December 2016. CABI Datasheet. 2016. Colocasia esculenta. http://www.cabi.org/isc/datasheet/17221. Accessed November 23, 2016. Calflora. 2016. Species information for Colocasia esculenta. http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=13042. Accessed December 18, 2016. Consortium of California Herbaria (CCH). 2014. Specimen reference for Colocasia esculenta. http://ucjeps.berkeley.edu/cgi-bin/new_detail.pl?CDA40536&YF=0. Accessed December 18, 2016. Chair, H., R. E. Traore, M. F. Duval, R. Rivallan, A. Mukherjee, L. M. Aboagye, J. Van Rensburg, et al. 2016. Genetic Diversification and Dispersal of Taro (Colocasia Esculenta (L.) Schott). PLoS One 11 (6): e0157712. doi:10.1371/journal.pone.0157712. Invasive Plant Atlas. Colocasia esculenta. http://www.invasiveplantatlas.org/subject.html?sub=5369. Accessed November 23, 2016. Jepson eFlora treatment. Araceae Family. http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?key=53. Accessed December 20, 2016. Langeland, K.A., and K. Craddock Burks. 2008. Identification and Biology of Non-Native Plants in Florida’s Natural Areas. IFAS Publication. SP257, http://www.fleppc.org/ID_book/invasive1.pdf. Accessed November 23, 2016. p. 20-21. Molinar, R. and M. Yang. 2001. Guide to Asian specialty vegetables in the Central Valley, CA. ucanr.edu/sites/Small_Farms_and_Specialty_Crop/files/88378.pdf. Accessed December 18, 2016. Moore, L. M. and J. H. Lawrence. 2003. USDA NRCS Taro Colocasia esculenta Plant Guide. http://plants.usda.gov/plantguide/pdf/cs_coes.pdf. Accessed November 23, 2016. Onwueme, I. 1999. Taro cultivation in Asia and the Pacific. Bangkok, Thailand: Food and Agriculture Organization of the United Nations. Regional Office for Asia and the Pacific, 15 pp. [FAO Report.] http://www.fao.org/docrep/005/AC450E/ac450e00.HTM. Accessed December 20, 2016. Queensland Biosecurity. 2016. http://keyserver.lucidcentral.org/weeds/data/media/Html/colocasia_esculenta.htm Accessed December 20, 2016. Robison, R. 2014. Taro Root (Colocasia esculenta) Reported Naturalizing in California. Poster presented at the Cal-IPC Annual Symposium, Chico, CA. http://www.cal-ipc.org/symposia/archive/2014_presentations.php. Accessed December 16, 2016. Vanderhoff, R. 2017. Personal communication from Ron Vanderhoff, Roger’s Gardens Nursery. Email received 2/2/17. Wagner, W.L., Herbst, D.R., Sohmer, S.H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Honolulu, Hawai'i, USA: Bishop Museum Press, 1919 pp. Weber, E. 2003. Invasive plant species of the world: A reference guide to environmental weeds. CABI Publishing, Zurich, Switzerland.

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes, 1 points
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, 1 points
Fragments easily and fragments can become established elsewhere Yes, 2 points
Resprouts readily when cut, grazed, or burned Yes, 1 points
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).
Note any related traits:
Information on seed production from Onwueme (1999). Flowering and seed set in taro are relatively rare under natural conditions. Most plants complete their field life without flowering at all, and some cultivars have never been known to flower. For many years, this characteristic was a great hindrance to taro improvement through cross pollination. However, the problem was solved when it was discovered that gibberellic acid (GA) could promote flowing in taro (Wilson, 1979). Essentially, plants are grown from corms or cormels to the 3-5 leaf stage in the field, and then treated with 15,000 ppm GA, a process known as “pro-gibbing” (Alvarez & Hahn, 1986). Alternatively, the plants could be multiplied in a seedbed, and pro-gibbed at the 1-2 leaf stage with 1,000 ppm GA. A third method involves leaving taro in the field at the end of the growing season and then pro-gibbing the first leaves that emerge at the onset of the next rainy season. Whichever method is used, pro-gibbed plants produce normal flowers 2-4 months after treatment. Today, researchers are able routinely to induce flowering of both taro and tannia by the application of GA. Controlled pollination can then be carried out on the flowers that are produced. The resulting seeds, thousands per spadix, are first germinated in nutrient media in petri dishes. The plantlets are later transplanted to humid chambers in the greenhouse. When the seedlings have reached a height of 15-20cm, they can be transplanted to the field. The large genotypic and phenotypic variability resulting from this process affords the plant breeder ample scope for selection.
Return to Table 2

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 Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal 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, coastal prairie
Meadows, and other Herbvalley and foothill grassland
CommunitiesGreat Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swampD. < 5%
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth)   D
Distribution (highest score)   D
Return to Table 2

Addendum J - Jepson Regions Infested
 
Click here for a map of Jepson regions

Infested Jepson Regions:
Check the boxes to indicate the Jepson floristic provinces in which this species is found.














Addendum L - External Links & Resources

Calflora Plant Profile:
The Calflora Plant Profile for this species.
http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=13042
CalWeedMapper:
Load CalWeedMapper with this species already selected.