Aquatic plant (North America)
Submerged, rather densely bushy, aquatic perennial that grows and multiplies fairly rapidly in diverse habitats and conditions and has spread rapidly and easily throughout the world. It alters habitat, competes with native species, and threatens biodiversity.
Photo: Kristian Peters,www.commons.wikimedia.org
Enormous herb that may reach 6 meters in height. It is most common on roadsides, along streams and rivers, and in vacant lots. If forms a dense canopy, outcompeting native riparian species and increasing soil erosion along the stream banks where it occurs.
Photo: Terry English, USDA APHIS PPQ, www.forestryimages.org
Small to medium-sized tree of the mostly tropical Quassia family. Very prolific seed producer that grows rapidly and can overrun native vegetation. It produces toxins that prevent the establishment of other plant species.
Photo: James H. Miller, USDA Forest Service, www.forestryimages.org
Freshwater clam that spreads when it is attached to boats or carried in ballast water, used as bait, sold through the aquarium trade, and carried with water currents. It outcompetes native clams for food and space, and it damages intake pipes used by power, water, and other industries.
Photo: Noel M. Burkhead, U.S. Geological Survey
Beautiful but dangerous tropical fish that has spread to new marine environments through the aquarium trade. It has the potential to displace commercially important species such as groupers and to reduce recruitment of juvenile fishes, which in turn disrupts marine ecosystem processes.
Photo: Forest & Kim Starr
Nocturnal predator that kills its prey by constriction. It is the largest and most water-dependent of the Python molurus, though it lives on land or on trees when juvenile. It threatens native species of amphibians, birds, lizards, snakes, bats and mammals.