Alternanthera philoxeroides, commonly referred to as alligator weed, is a native species to the temperate regions of South America, which includes Argentina, Brazil, Paraguay and Uruguay. Argentina alone hosts around 27 species that fall within the range of the genus Alternanthera. and is characterized by whitish, papery flowers along its short stalks, irregular, or sprawling hollow stems, and simple and opposite leaf pattern sprouting from its nodes. It produces horizontal stems, otherwise known as stolons, that can sprout up to in length and thanks to its hollow stems, floats easily. This results in large clusters of stem amassing and create dense mats along the surface. Presence of a peduncle is a key trait that distinguishes this species from the sessile inflorescences of Alternanthera sessilis.

Impacts on vegetation

The presence of this invasive species disrupts the natural flow of water due to the dense mats created by its clusters of stems. These dense mats can affect the natural flow of water that is used in irrigation systems and as well as affect the quality of the water by increasing the sedimentation present in the water. In addition, the dense mats present a challenge for the native wildlife by acting as a barrier between them and natural water sources.

Impacts on society

Dense mats formed by this species influence the natural flow of water, which can impede various recreational activities, such as boating and fishing. This is a commensal relationship between mosquitoes and A. philoxeroides because mosquitoes receive a breeding ground and the plant gains nothing nor loses anything. The increased population of mosquitoes can bring an increased risk of mosquito-borne diseases in humans.<!-- -->

Human dispersal

In effort to eradicate the species by manual means, such as mulching or pulling them out, if not removed efficiently, small stem fragments can be displaced to new areas. Amynothrips andersoni, the alligator weed thrips, and Vogtia malloi, the alligator weed stem borer, have also been released in the United States. These species result in immediate wilting and limit A. philoxeroides reproduction by colonizing its stems.[116th Congress (2019–2020)] on January 23, 2019.

See also

  • Ludwigia grandiflora

References

  • The evolutionary history of an invasive species: alligator weed, Alternanthera philoxeroides, XII International Symposium on Biological Control of Weeds
  • Pest Plant Risk Assessment: Alligatorweed, Biosecurity Queensland, Department of Employment, Economic Development and Innovation
  • Species Profile - Alligatorweed (Alternanthera philoxeroides), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Alligatorweed.
  • Alternanthera philoxeroides (Mart.) Griseb. Medicinal Plant Images Database (School of Chinese Medicine, Hong Kong Baptist University)