Invasive alien plants in the Pampas grasslands: a tri-national cooperation challenge

The challenge of managing biological invasions requires novel approaches and coordinated efforts, especially among countries linked by intense trade routes and sharing common biomes. This is the case in Southern South America, where Argentina, Brazil and Uruguay maintain intense commercial relationships, whilst sharing continuous portions of the Pampas grasslands. Transnational similarities in this case exceed ecological features, including a common colonization history and similar development trends. This study represents a tri-national cooperation effort to describe the alien plant flora invading the Pampas grasslands of Argentina, Brazil and Uruguay and analyses their characteristics in order to detect species and traits that are shared among the three countries and those that have not yet managed to invade the whole region. Furthermore, we highlight the opportunities and needs of a common approach across countries to deal with plant invasions. Information about alien plant species was retrieved from the IABIN Invasives Information Network (I3N) project databases of Argentina, Brazil and Uruguay, complemented with some national herbaria. Three hundred and fifty-six alien plant species were recorded growing in natural or semi-natural habitats of the Pampas. A total of 50 species were found in Pampas grasslands of the three countries. Argentina shared 48 and 36 species with Brazil and Uruguay, respectively, while the Brazilian and the Uruguayan Pampas shared only 20 species. Poaceae, Asteraceae and Fabaceae were the families with the highest number of invasive species, and herbs were the most common life form (75 %). Most invasive plants originated from Europe, Asia and Africa, and almost one-quarter of the species is associated with some human use, especially gardening. We discuss the opportunities and needs for international cooperation, as the prevention of introductions from one country to another through the use of risk analysis tools, definition of priority invasive species, as well as the detection, containment, eradication and control of common invasions. Furthermore, we suggest the establishment of coherent regional legislation and the inclusion of social issues and the public perception in the biological invasion quest.