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SUMMARY

Rating	Alert	Impact	Invasiveness	Distribution	Doc.
Moderate	N	B	B	A	3.23
Comments:
Rating 1 = High 2 = Moderate 3 = Limited 4 = Evaluated, not listed		Alert Y = Yes N = No	Scores A = Severe B = Moderate C = Limited D = None U = Unknown	Documentation 4 = Reviewed scientific publications 3 = Other published material 2 = Observational 1 = Anecdotal 0 = No information

Scores

1.1	1.2	1.3	1.4	2.1	2.2	2.3	2.4	2.5	2.6	2.7	3.1	3.2
B	B	C	D	B	A	A	B	B	B	C	A	A

IMPACT

1.1 Impact on abiotic ecosystem processes - B

Identify ecosystem processes impacted: The dense floating mats will restrict light penetration (1, 2, 3, 4) and can create anoxic conditions (1, 4). It can cause an increase in sedimentation (3). The thick mats will cause flooding by preventing proper drainage of water from ditches and small waterways (3, 4).

Sources of information: 1. DiTomaso, Joseph and Evelyn Healy. Weeds of California and Other Western States Vol. 1: Aizonaceae-Fabaceae. Regents of the University of California: 2007.

2. Pan et al. 2006. The influence of abiotic stess and phenotypic plasticity on the distribution of invasive Alternanthera philoxeroides along a riparian zone. Acta Oecologica: 30 (2006). Pg. 333-341.

3. Buckingham, G.R. US department of Agriculture, Agriculture Research Service, Invasive Plants Research Laboratory. Gainesville, Florida. (Accessed October 21, 2009) http://invasive.org/eastern/biocontrol/1Alligatorweed.html.

4. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

Documentation: Other Pub. Mat’l

1.2 Impact on plant community composition, structure, and interactions - B

Identify type of impact or alteration: It crowds out native species with dense floating mats (1). The canopy shades out seedlings (2). It is able to outcompete other species for light (3). Light restricting mats and anoxic conditions will interfere with the growth of submerged flora (4).

Sources of information: 1. DiTomaso, Joseph and Evelyn Healy. Weeds of California and Other Western States Vol. 1: Aizonaceae-Fabaceae. Regents of the University of California: 2007.

2. Pan et al. 2006. The influence of abiotic stess and phenotypic plasticity on the distribution of invasive Alternanthera philoxeroides along a riparian zone. Acta Oecologica: 30 (2006). Pg. 333-341.

3. NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [wed application]. Version 7.1. NatureServe, Arlington, VA. Available http://natureserve.org/explorer. (Accessed Oct 19, 2009).

http://natureserve.org/explorer/servlet/NatureServe?searchName=Alternanthera%20philoxeroides.

4. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

Documentation: Other Pub. Mat’l

1.3 Impact on higher trophic levels - C

Identify type of impact or alteration: It provides a breeding ground for mosquitoes (1, 2) and disease vectors (2).

Sources of information: 1. DiTomaso, Joseph and Evelyn Healy. Weeds of California and Other Western States Vol. 1: Aizonaceae-Fabaceae. Regents of the University of California: 2007.

2. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

Documentation: Other Pub. Mat’l

1.4 Impact on genetic integrity - D

Identify impacts: Alternanthera philoxeroides is not known to reproduce sexually/produce viable seeds under field conditions (1, 2). There are also no known native Alternanthera species.

Sources of information: 1. DiTomaso, Joseph and Evelyn Healy. Weeds of California and Other Western States Vol. 1: Aizonaceae-Fabaceae. Regents of the University of California: 2007.

2. Sainty, McCorkelle, and Julien. 1998. Control and spread of Alligatorweed Alternanthera philoxeroides (Mart.) Griseb., in Australia: lessons for other regions. Wetlands Ecology and Management (1998) 5:195-201.

Documentation: Rev’d Sci. Pub’n

IMPACT: B B C D = B

INVASIVENESS

2.1 Role of anthropogenic and natural disturbance in establishment - B

Describe role of disturbance: It grows best under eutrophic conditions (1). It can spread if not all plant parts are removed during mechanical separation (1). Plant fragments can spread during storms and high water levels (2) as well as with water current (3). Cattle and horses may facilitate spread of fragments in their hooves or from their mouths while grazing (3).

Sources of information: 1. DiTomaso, Joseph and Evelyn Healy. Weeds of California and Other Western States Vol. 1: Aizonaceae-Fabaceae. Regents of the University of California: 2007.

2. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

3. Oosterhout, Elissa. Weeds of National Significance: Alligatorweed Control Manual. NSW Department of Primary Industries: 2007.

Documentation: Other Pub. Mat’l

2.2 Local rate of spread with no management - A

Describe rate of spread: Alternanthera philoxeroides exhibits a doubling time of 41-50 days under normal growing conditions (1, 2) between fifteen and twenty degrees Celsius (3). Primary growth is vegetative as no reproduction via seeds has been noted in the United States (1).

Sources of information: 1. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

2. Julien, M. H. and M. W. Griffiths (eds.). 1998. Biological Control of Weeds: A World Catalogue of Agents and Their Target Weeds, 4th ed. CAB International, Wallingford, United Kingdom.

3. Julien M.H., Bourne, A.S. and V.H.K. Low. 1992. Growth of the weed Alternanthera philoxeroides (Martius) Grisebach, (alligator weed) in aquatic and terrestrial habitats in Australia. Journal of Aquatic Botany (1992) 7: 102-108.

Documentation: Other Pub. Mat’l

2.3 Recent trend in total area infested within state - A

Describe trend: The coverage of Alternanthera philoxeroides has remained stable due to the effectiveness of control measures across the state since 1964 (1). Population control has been most heavily affected by the release of the Alligator Weed Flea Beatle, Agasicles hygrophila, since 1964 (2). To this day, the Texas Department of Wildlife maintains the release of the Flea Beatle across the state. Chemical control measures using 2,4-D and Glycophosphate are also used to control local outbreaks on the Texas River (3, 4). It should be noted that very little documentation exists regarding cover class, vegetation surveys or reliable data regarding population and spread of Alternanthera philoxeroides in Texas.

Sources of information: 1. Buckingham, G. R. 1996. Biological control of alligatorweed, Alternanthera philoxeroides, the world’s first aquatic weed success story. Castanea 61: 231-243.

2. Maddox, D. M., L. A. Andres, R. D. Hennessey, R. D. Blackburn, and N. R. Spencer. 1971. Insects to control alligatorweed: an invader of aquatic ecosystems in the United States. Bioscience 21: 985-991.

3. Allen, S.L., G.R. Hepp, and J.H. Miller. 2007. Use of herbicides to control alligatorweed and restore native plants in managed marshes. Wetlands 27(3):739-748.

4. Sainty, G., G. McCorkelle, and M. Julien. 1998. Control and spread of alligator weed Alternanthera philoxeroides (Mart.) Griseb., in Australia: Lessons for other regions. Wetlands Ecology and Management (1998) 5:195-201.

Documentation: Rev’d Sci. Pub’n

2.4 Innate reproductive potential - B

Describe key reproductive characteristics: Alternanthera philoxeroides is known to reproduce only through vegetative means and disperse by fragmentation (1, 2). Fragments with at least one node can produce a new plant (1). Aquatic forms have hollow, floating stems that break off easily and form new colonies (1). It spreads horizontally by stolons and rhizomes (2).

Sources of information: 1. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

2. Sainty, McCorkelle, and Julien. 1998. Control and spread of Alligatorweed Alternanthera philoxeroides (Mart.) Griseb., in Australia: lessons for other regions. Wetlands Ecology and Management (1998) 5:195-201.

Documentation: Other Pub. Mat’l

2.5 Potential for human-caused dispersal - B

Identify dispersal mechanisms: Fragments are able to be moved y earthmoving machinery (1), watercrafts (1,3), slashing and mowing (1), gravel/turf extraction (1,3) and control activities involving improper disposal, incomplete removal of plants (1,3), or root fragmentation (2).

Sources of information: 1. Oosterhout, Elissa. Weeds of National Significance: Alligatorweed Control Manual. NSW Department of Primary Industries: 2007.

2. Xin, Jia et al. 2009. Allometric growth, disturbance regime, and dilemmas of controlling invasive plants: a model analysis. Biological Invasions (2009) 11: 743-752.

3. Sainty, McCorkelle, and Julien. 1998. Control and spread of Alligatorweed Alternanthera philoxeroides (Mart.) Griseb., in Australia: lessons for other regions. Wetlands Ecology and Management (1998) 5:195-201.

Documentation: Rev’d Sci. Pub’n

2.6 Potential for natural long-distance dispersal - B

Identify dispersal mechanisms: Natural spread aquatically is by the movement of fragments by water flow or floods. Terrestrial spread is through competition and eventual domination of other vegetation. (1, 2).

Sources of information: 1. Oosterhout, Elissa. Weeds of National Significance: Alligatorweed Control Manual. NSW Department of Primary Industries: 2007.

2. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

Documentation: Other Pub. Mat’l

2.7 Other regions invaded - C

Identify other regions: Native to South America. Invasive weed in 30 countries, including the US, China, Australia, Thailand, Indonesia, Japan and India (1, 2).

Sources of information: 1. Oosterhout, Elissa. Weeds of National Significance: Alligatorweed Control Manual. NSW Department of Primary Industries: 2007.

2. Julian, Skarratt, and Maywald. 1995. Potential Geographic Distribution of Alligatorweed and its Biological Control by Agasicles hygrophila. Journal of Aquatic Plant Management (1993)33: 55-60.

Documentation: Rev’d Sci. Pub’n

INVASIVENESS: B A A B B B C = B

DISTRIBUTION

3.1 Ecological amplitude - A

Describe ecological amplitude, identifying date of source information and approximate date of introduction to the state, if known: Alternanthera philoxeroides is known to grow rapidly in both terrestrial and aquatic habitats. It requires a moist habitat. It is most troublesome on warm regions, as it limited by frost, but can be found in a variety of microclines (1). It can tolerate salt water at 10% sea strength in still water and 30% in flowing water (1, 2). As aquatic, it is able to root near water’s edge and form a floating mat out onto the water’s surface (2).

Sources of information: of information: 1. Holm et al. World Weeds: Natural Histories and Distribution. John Wiley, New York: 1997.

2. Sainty, McCorkelle, and Julien. 1998. Control and spread of Alligatorweed Alternanthera philoxeroides (Mart.) Griseb., in Australia: lessons for other regions. Wetlands Ecology and Management (1998) 5:195-201.

Invaders of Texas Citizen Science Observations (Accessed 7 November 2011: http://texasinvasives.org/observations/search.php?satellite=&sn=ALPH&cn=

USDA PLANTS Database (Accessed 7 November 2011: http://plants.usda.gov/java/county?state_name=Texas&statefips=48&symbol= ALPH)

Documentation: Other Pub. Mat’l

3.2 Distribution/Peak frequency - A

Identify type of impact or alteration: Colonization has occurred along southeast and central TX (1, 2). It is known to occupy Hunt, Collin, Orange, Jefferson, Chambers, Galveston, Brazoria, Harris, Walker, Madison, Brazos, Williamson, Travis and Freestone counties (2). Of these, it is found to be in East Texas Pineywoods, Gulf Coast Prairies and Marshes, Post Oak Savannah, Blackland Prairie, and Cross Timbers and Prairies (2).

Sources of information: 1. USDA Plants Database. US Department of Agriculture, Natural Resource Conservation Service. (Accessed October 14, 2009) http://plants.usda.gov/java/nameSearch?keywordquery=alligatorweed&mode=comname&submit.x=22&submit.y=5

2. Turner, Billie Lee et al. Texas Atlas of Vascular Plants, Vol 1: Dicots. Botanical Research Institute of Texas. 2003.

Invaders of Texas Citizen Science Observations (Accessed 7 November 2011: http://texasinvasives.org/observations/search.php?satellite=&sn=ALPH&cn=

USDA PLANTS Database (Accessed 7 November 2011: http://plants.usda.gov/java/county?state_name=Texas&statefips=48&symbol= ALPH)

Documentation: Other Pub. Mat’l

IMPACT: A A = A

TEXAS ECOREGIONS

Source: Level III and IV Ecoregions of Texas. Griffith, G.E., Bryce, S.A., Omernik, J.M., Comstock, J.A., Rogers, A.C., Harrison, B., Hatch, S.L., and Bezanson, D., 2004, Ecoregions of Texas, U.S. Environmental Protection Agency, Corvallis, OR.

Score: 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.

Code	Level III	Level IV	Score
ER01	Arizona/New Mexico Mountains	Chihuahuan Desert Slopes
		Montane Woodlands
ER02	Chihuahuan Deserts	Chihuahuan Basins and Playas
		Chihuahuan Desert Grasslands
		Low Mountains and Bajadas
		Chihuahuan Montane Woodlands
		Stockton Plateau
ER03	High Plains	Rolling Sand Plains
		Canadian/Cimarron High Plains
		Llano Estacado
		Shinnery Sands
		Arid Llano Estacado
ER04	Southwestern Tablelands	Canadian/Cimarron Breaks
		Flat Tablelands and Valleys
		Caprock Canyons, Badlands, and Breaks
		Semiarid Canadian Breaks
ER05	Central Great Plains	Red Prairie
		Broken Red Plains
		Limestone Plains
ER06	Cross Timbers	Eastern Crosstimbers
		Western Crosstimbers
		Grand Prairie	A
		Limestone Cut Plain
		Carbonate Cross Timbers
ER07	Edwards Plateau	Edwards Plateau Woodland
		Llano Uplift
		Balcones Canyonlands
		Semiarid Edwards Plateau
ER08	Southern Texas Plains	Northern Nueces Alluvial Plains
		Semiarid Edwards Bajadas
		Texas-Tamaulipan Thornscrub
		Rio Grande Floodplain and Terraces
ER09	Texas Blackland Prairies	Northern Blackland Prairies	A
		Southern Blackland/Fayette Prairie
		Floodplains and Low Terraces
ER10	East Central Texas Plains	Northern Post Oak Savanna
		Southern Post Oak Savanna
		San Antonio Prairie
		Northern Prairie Outliers
		Bastrop Lost Pines
		Floodplains and Low Terraces
ER11	Western Gulf Coastal Plain	Northern Humid Gulf Coastal Prairies	B
		Southern Subhumid Gulf Coastal Prairies
		Floodplains and Low Terraces	C
		Coastal Sand Plain
		Lower Rio Grande Valley
		Lower Rio Grande Alluvial Floodplain
		Texas-Louisiana Coastal Marshes
		Mid-Coast Barrier Islands and Coastal Marshes
		Laguna Madre Barrier Islands and Coastal Marshes
ER12	South Central Plains	Tertiary Uplands	A
		Floodplains and Low Terraces
		Pleistocene Fluvial Terraces
		Southern Tertiary Uplands
		Flatwoods
		Red River Bottomland

EVALUATORS

Evaluation Date: 2009-10-29

Evaluator 1
Kimberly Mighel and Charles Mansfield
University of North Texas

kimberlymighell@yahoo.com, chad.mansfield@gmail.com


Evaluator 2
Bishnu Twanabasu and Chase Cade
University of North Texas

twanabasu@hotmail.com

REVIEW

Reviewers:
Review Date: 0000-00-00
Comments:

REFERENCES