A literature review for the exotic invasive Alternanthera philoxeroides (alligatorweed)

Authors: PAN, XIAO-YUN - FUDAN UNIVERSITY; GENG, YU-PENG - FUDAN UNIVERSITY; SOSA, ALEJANDRO - USDA - ARS - SABCL; ZHANG, WEN-JU - FUDAN UNIVERSITY; LI BO CHEN, JIA-KUAN - FUDAN UNIVERSITY

Submitted to: Acta Phytotaxonomica Sinica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2007
Publication Date: 10/15/2007
Citation: Pan, X., Geng, Y., Sosa, A., Zhang, W., Li Bo Chen, J. 2007. A literature review for the exotic invasive Alternanthera philoxeroides (alligatorweed). Acta Phytotaxonomica Sinica 45 (6): 1 (2007).

Interpretive Summary: In this review, we present a detailed account of alligator weed, including description, intraspecific variation from native to introduced regions, its life history strategy, invasive mechanisms, and management strategy. This plant is an herbaceous amphibious weed native to southern South America, distributed from Buenos Aires Province in Argentina (39° southern latitude) to Southern Brazil. Two distinct morphological forms of alligator weed exist in Argentina: A. philoxeroides f. philoxeroides in the southern range and A. philoxeroides f. angustifolia in the northern range. Both forms set fruits and produce viable seeds. Alligator weed is considered as a serious weed throughout tropical and warm temperate regions, including the USA, China, India, South-East Asia, Australia and New Zealand. It is thought to have been brought to China during the 1930s, and later widely cultivated and spread in southern China as fodder during 1950s. The present distribution of alligatorweed in China is cause for considerable concern, earning it a place among the top 16 exotic invasive species of National Significance. Alligator weed is found on stationary and slow moving water bodies, creeks, channels, riverbanks and associated areas that are occasionally flooded. It can also be found in terrestrial situations as a pasture weed and increasingly within urban environments. Alligator weed does not produce viable seed in China and reproduces vegetatively from propagule fragments (stems, rhizome or root tubes), which can be spread by water movement, boats, machinery and vehicles and in hay. Movement between river catchments is most commonly due to human activities. We need better understanding of the biology and ecology of alligator weed to assess the impact of control methods in any theoretical framework. Hence we suggest that metapopulation theory is a good tool to improve management efficiency from watershed and regional perspective.

Technical Abstract: In this review, we present a detailed account of Alternanthera philoxeroides(alligatorweed), including A. philoxeroides description, intraspecific variation from native to introduced regions, its life history strategy, invasive mechanisms, and management strategy. Alternanthera philoxeroides is a herbaceous amphibious weed of Amaranthaceae, native to southern South America, distributed from Buenos Aires Province (39° southern latitude) to Southern Brazil. It was first described by Martius in 1826, and consists of several taxa in both its native and adventive ranges. Current knowledge indicates that two forms of alligator weed exist in Argentina: A. philoxeroides f. philoxeroides in the southern range and A. philoxeroides f. angustifolia in the northern range. In Argentina, both forms set fruits and produce viable seeds. Alternanthera philoxeroides is now found as a serious weed throughout tropical and warm temperate regions, including the USA, China, India, South-East Asia, Australia and New Zealand. It is thought to have been brought to China during the 1930s, and later widely cultivated and spread in southern China as fodder during 1950s. The present distribution of alligatorweed in China is cause for considerable concern, earning it a place among the top 16 exotic invasive species of National Significance. Alligatorweed is found on stationary and slow moving water bodies, creeks, channels, riverbanks and associated areas that are occasionally flooded. It can also be found in terrestrial situations as a pasture weed and increasingly within urban environments. Alligatorweed does not produce viable seed in China and reproduces vegetatively from propagule fragments (stems, rhizome or root tubes), which can be spread by water movement, boats, machinery and vehicles and in hay. Movement between river catchments is most commonly due to human activities. Alligatorweed forms a floating mass which spreads out over the water. Its growth disrupts the ecology of banks and shallows and crowds out other plant species, restricts water flow, increases sedimentation, aggravates flooding, limits access and use by man and provides a favorable breeding area for disease vectors. We need better understanding of the biology and ecology of alligatorweed to assess the impact of control methods in any theoretical framework. According to the knowledge of the life history strategy of alligatorweed, we suggest that metapopulation theory is a good tool to improve management efficiency from watershed and regional perspective.