The invasive legacy of forage grass introductions into Florida.
Exotic African warm-season forage grasses were first introduced into the Americas in the 16th century, and have become invasive in many areas. In Florida, 16 exotic grasses are considered invasive, with the majority originating in Africa and introduced as forages. The high propensity of Africa warm-season grasses to become invasive may be related to the same characteristics that are associated with their value as forages, including adaptability to a wide range of abiotic conditions, rapid establishment, persistence in the environment with minimal husbandry, high productivity under grazing pressure, and adaptation to disturbance. The majority of African warm-season grasses in Florida reproduce vegetatively, a trait known to be associated with invasiveness, and many have been widely planted leading to high propagule pressure and opportunities to invade a variety of niches. In spite of a long history of introduction and promotion in Florida, few African forage grasses are in use today, while many have become invasive. The benefit/cost ratio appears to be tilted in the direction of environmental and economic costs, with minimal benefits. We support newly enacted restrictions on the importation of potentially invasive plants into the USA, and suggest the establishment of a more comprehensive and transparent system for tracking past and future introductions.