ARMI conducts research on the ecology of invasives, their impacts on native species, and how invasive species can be reduced or eradicated. Habitat used by amphibians has been exposed to many types of invasives through deliberate or accidental introductions. For example, sport fish deliberately introduced to ponds and streams in the western US that were formerly fishless, have been associated with the loss of amphibians in those water bodies. In another example, the American bullfrog of the Eastern US was introduced into the Western US through a combination of introductions into ponds for bait, and escapes from frog farms. The American bullfrog has been a relentless predator of several species already in conservation trouble in the Western US.
What types of problems do invasive species cause?
Some species harm native species directly by preying on them or competing with them for resources, and some modify or destroy the habitat used by native species.
Where do invasive species come from?
Some come from deliberate introductions such as biological control, stocking for hunting, fishing, or spreading bait species. Some are accidental escapes from pet stores, farming/aquaculture facilities, and ornamental gardens. Some animals are released by pet owners or teaching labs. Some species hitchhike with materials otherwise deliberately moved such as garden plants, ballast water, boats and nets.
Terms Related to Invasive Species
Invasive species: Plant, animal or pathogen that is not native to an area, and "whose introduction does or is likely to cause economic or environmental harm or harm to human health." [US Executive Order 13112. 1999]
Injurious Wildlife (defined by Lacey Act) - Mammals, birds, amphibians, reptiles, fish, crustaceans, mollusks and their offspring or gametes that are injurious to the interests of human beings, agriculture, horticulture, forestry, wildlife or wildlife resources of the United States. Plants and organisms other than those listed above cannot be listed as injurious wildlife. http://www.fws.gov/fisheries/ans/pdf_files/InjuriousWildlifeFactSheet2007.pdf
Nonindigenous species: Any species or other viable biological material that enters an ecosystem beyond its historic range, including any such organism transferred from one country into another. (Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990) http://anstaskforce.gov/Documents/nanpca90.pdf
Aquatic nuisance species: A nonindigenous species that threatens the diversity or abundance of native species or the ecological stability of infested waters, or commercial, agricultural, aquacultural or recreational activities dependent on such waters. (Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990) http://anstaskforce.gov/Documents/nanpca90.pdf
ARMI Papers & Reports on Invasive Species
Mountains, situated in a global biodiversity hotspot, is an area of conservation concern due to climate change, urbanization, and the introduction of non-native species. We examined the effect that non-native crayfish (Procambarus clarkii) have on an existing native predator, dragonfly nymphs (Aeshna sp.) and their mosquito larvae (Anopheles sp.) prey. We used laboratory experiments to compare the predation efficiency of both predators, separately and together, and field data on counts of dragonfly nymphs and mosquito larvae sampled from 13 local streams. We predicted a lower predation efficiency of crayfish compared to native dragonfly nymphs as well as a reduced efficiency of dragonfly nymphs in the presence of crayfish. Dragonfly nymphs were an order of magnitude more efficient mosquito predators compared to crayfish and dragonfly
nymphs suffered reduced efficiency in the presence of crayfish. Analyses of field count data showed that populations of dragonfly nymphs and mosquito larvae were strongly correlated with crayfish presence in streams, such that sites with crayfish tended to have fewer dragonfly
nymphs and more mosquito larvae. Under natural conditions, it is likely that crayfish reduce the abundance of dragonfly nymphs and their predation efficiency, and thereby, directly and indirectly, lead to higher mosquito populations and a loss of ecosystem services related to disease vector control.