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Title: The evolutionary history of an invasive species: alligator weed, Alternanthera philoxeroides

Author
item SOSA, ALEJANDRO - South American Biological Control Lab(SABCL)
item GREIZERSTEIN, EDUARDO - Universidad De Buenos Aires
item CARDO, MARIA VICTORIA - Universidad De Buenos Aires
item MARTA, TELESNICKI - Universidad De Buenos Aires
item MIC, JULIEN - Commonwealth Scientific And Industrial Research Organisation (CSIRO)

Submitted to: CAB International United Kingdom
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2008
Publication Date: 11/1/2008
Citation: Sosa, A., Greizerstein, E., Cardo, M., Marta, T., Mic, J. 2008. The evolutionary history of an invasive species: alligator weed, Alternanthera philoxeroides. In Proceedings of the XII International Symposium of Biological Control of Weeds. (Eds. Julien, Sforza, Bon, Evans, Hatcher, Hinz Rector). CAB International United Kingdom. pp.: 443-450

Interpretive Summary: Biological invasions are still a big and central issue in the developing weed management strategies , understanding the mechanisms why some species become invaders and then pests is key question. Alligator weed, is a plant native to South America and invaded several countries, Australia among them. To better understand its success as an invader, we assessed the morphologic and genetic variability of 12 Argentinean populations and genetic variability of seven Australian populations. We found differences in leaf shape and stem architecture in the Argentinean populations, reproduction (some population produce viable seed while others do not). We propose a hypothesis about the mechanism that drove alligator weed to form highly invasive hybrid populations with vegetative reproduction from non invasive ancestors. We consider the implications for plant-herbivore interactions and biological control of this weed.

Technical Abstract: The eco-evolutionary mechanisms of biological invasions are still not thoroughly understood. Alligator weed, Alternanthera philoxeroides (Martius) Gisebach (Amaranthaceae), is a plant native to South America and a weed in Australia and other countries. To better understand its success as an invader, we assessed the morphologic and cytogenetic variability of 12 Argentinean populations and the cytogenetic variability of seven Australian populations. We found differences in leaf shape (width to length ratio) and stem architecture in the Argentinean populations, reproduction (sexual with regular meiosis in two Argentinean populations to completely asexual with irregular meiosis and low pollen viability in all other populations), and polyploid degree (tetraploids with sexual reproduction and seed production to hexaploids with or without sexual reproduction). We propose a hypothesis about the mechanism that drove alligator weed to form highly invasive hybrid populations with vegetative reproduction from diploid ancestors. We consider the implications for plant-herbivore interactions and biological control of this weed.