Plant Assessment Form

Alternanthera philoxeroides

Synonyms: Bucholzia philoxeroides Mart., Telanthera philoxeroides (Mart.)

Common Names: alligatorweed

Evaluated on: 2/26/05

List committee review date: 08/07/2005

Re-evaluation date:

Evaluator(s)

Elizabeth Brusati, project manager
California Invasive Plant Council
1442A Walnut St. #462, Berkeley, CA 94709
510-843-3902
edbrusati@cal-ipc.org
Joseph DiTomaso
University of California-Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu

List commitee members

Joe DiTomaso
Alison Stanton
Joanna Clines
Cynthia Roye
Doug Johnson

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? High
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes A Other Published Material
Impact?
Four-part score ABAD Total Score
A
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels A. Severe Other Published Material
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Other Published Material
Invasiveness?
Total Points
14 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state D. Declining Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Other Published Material
2.5 ?Potential for human-caused dispersal B. Moderate Other Published Material
2.6 ? Potential for natural long-distance dispersal A. Frequent Reviewed Scientific Publication
2.7 ?Other regions invaded C. Already invaded Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Other Published Material
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

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? A Other Published Material
Identify ecosystem processes impacted:

Dense floating mats reduce light penetration (1). Serious infestations can create anoxic conditions (1, 2).


Sources of information:

1. DiTomaso, J., and E. Healy. in prep. Weeds of California and Other Western States
2. Phillips M.V. 1993. Alternanthera philoxeroides: A Review of the Literature. Florida Dept. Natural Resources, Bureau of Aquatic Plant Management.


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Other Published Material
Identify type of impact or alteration:

Crowds out native species (1).


Sources of information:

DiTomaso and Healy in prep.


Question 1.3 Impact on higher trophic levels? A Other Published Material
Identify type of impact or alteration:

Can create situations for breeding mosquitos (1, 2). Crowds out forage plants used by wintering waterfowl (2).


Sources of information:

1. DiTomaso and Healy in prep.
2. Phillips M.V. 1993. Alternanthera philoxeroides: A Review of the Literature. Florida Dept. Natural Resources, Bureau of Aquatic Plant Management.


Question 1.4 Impact on genetic integrity? D Other Published Material

None No native Alternanthera species.


Sources of information:

Hickman, J. C. (ed.) 1993. The Jepson Manual, Higher Plants of California. University of California Press. Berkeley, CA enter text here


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Other Published Material
Describe role of disturbance:

Grows best in eutrophic conditions (1). Is not adversely affected by habitat manipulation and may benefit from disturbances such as drawdown for waterfowl management. Increased turbidity appears to adversely affect it, however (2).


Sources of information:

1. DiTomaso and Healy in prep.
2. Phillips M.V. 1993. Alternanthera philoxeroides: A Review of the Literature. Florida Dept. Natural Resources, Bureau of Aquatic Plant Management.


Question 2.2 Local rate of spread with no management? A Other Published Material
Describe rate of spread:

Would certainly double in less than 10 years based on fast growth rate and past history.


Sources of information:

DiTomaso and Healy in prep.


Question 2.3 Recent trend in total area infested within state? D Observational
Describe trend:

CDFA eradication efforts have reduced the population to only a few patches.


Sources of information:

CDFA biologists, observational.


Question 2.4 Innate reproductive potential? B Other Published Material
Describe key reproductive characteristics:

Stems stolon-like, root at node. Reproduces vegetatively from stems and roots. Rapid growth rate. Seeds rarely develop (1). More than 1000 shoots per square meter may develop (2).


Sources of information:

1. DiTomaso and Healy in prep.
2. Julien, M. H. and J. E. Broadbent. 1980. The biology of Australian weeds. 3. Alternanthera philoxeroides (Mart.) Griseb. J Aust Inst Agric Sci 46(3): 150-155..


Question 2.5 Potential for human-caused dispersal? B Other Published Material
Identify dispersal mechanisms:

Mechanical removal without careful removal of all plant parts can facilitate spread (1). Was previously used in the aquarium trade but is no longer today (2). Stems could be dragged by boats.


Sources of information:

1. DiTomaso and Healy in prep.
2. Julien, M. H. and J. E. Broadbent. 1980. The biology of Australian weeds. 3. Alternanthera philoxeroides (Mart.) Griseb. J Aust Inst Agric Sci 46(3): 150-155.


Question 2.6 Potential for natural long-distance dispersal? A Reviewed Scientific Publication
Identify dispersal mechanisms:

Floating mats can break away and colonize new sites (1, 2).


Sources of information:

1. DiTomaso and Healy in prep
2. Julien, M. H. and J. E. Broadbent. 1980. The biology of Australian weeds. 3. Alternanthera philoxeroides (Mart.) Griseb. J Aust Inst Agric Sci 46(3): 150-155..


Question 2.7 Other regions invaded? C Reviewed Scientific Publication
Identify other regions:

Native to South America. In southeastern states, including Texas. Also Central America (1) and Australia (2).


Sources of information:

1. DiTomaso and Healy in prep.
2. Julien, M. H. and J. E. Broadbent. 1980. The biology of Australian weeds. 3. Alternanthera philoxeroides (Mart.) Griseb. J Aust Inst Agric Sci 46(3): 150-155.


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Other Published Material

Inhabits shallow water, wet soils, ditches, marshes, pond margins, slow-moving watercourses. Tolerates saline conditions to 10% salt by volume. Cannot survive prolonged freezing temperatures. San Joaquin Valley, Southwestern region, and possibly elsewhere to 200m. Requires a warm summer growing season. Tolerates cold winters but cannot survive prolonged freezing temperatures (1). Usually a water plant but can also be semiterrestrial or terrestrial near water (2).


Sources of information:

1. DiTomaso and Healy in prep.
2. Aurand D. 1982. Nuisance Aquatic Plants and Aquatic Plant Management Programs in the United States, Volume 2. Southeastern Region. US EPA/ The Mitre Corporation.


Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

Uncommon due to control efforts of CDFA.


Sources of information:

DiTomaso and Healy in prep


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 No
Seeds remain viable in soil for three or more years No
Viable seed produced with both self-pollination and cross-pollination No
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: 0
Total score: B?

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?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirsD, < 5%
Aquatic Systemsrivers, streams, canalsD, < 5%
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, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grassland
Great 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): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Great Valley
  • Northwest
  • Southwest