Guests and gatecrashers in a New World’s banquet: Old World plant species introduced from the Mediterranean Basin enriched the flora of grasslands and croplands in the Pampas of Argentina

Abstract

Exchange of domesticated plants between Europe and the Americas has been a paramount episode of World History, which transformed agriculture and food habits at both sides of the Atlantic Ocean. However, many plant species have been inadvertently introduced mostly as contaminants of crop seeds, causing important changes in the flora. Here, we present a brief description of the floristic enrichment of the Pampa grasslands of Argentina due to the naturalisation of plant species from the Mediterranean Basin. Since the European colonisation in the 16th century, Old World plant species have been continuously introduced, intentionally or not, in the Pampas, especially during the expansion of agriculture in the late 19th century. Four botanical families comprised the highest numbers of species (Asteraceae, Poaceae, Fabaceae, and Brassicaceae), which have been recognised for having the largest contribution to the total number of alien species in local floras. Some families were only present in the Pampas by Mediterranean species occurring as weeds in croplands. The flora of the Pampas was also enriched with life-forms that were poorly represented in the pristine grasslands, such as species from Fabaceae and short-lived species vegetating during the cool season. Finally, seed trade from South America to Europa provided a vector for the dispersion of Neotropical and Pampean species naturalised in Mediterranean ecosystems. While the long term impact of alien naturalization in the evolutionary history of life-forms in the Pampas and the Mediterranean basin is difficult to elucidate, some naturalised Mediterranean plants are involved in providing ecosystem services in the intensively managed croplands in the Pampas or are seen as a threat to native flora.