Invasive Species
Feral hogs trapped at St Marks NWR, FL. Photo by: W. Barichovich.
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
Resources
http://www.fws.gov/invasives/laws.html
http://www.invasivespeciesinfo.gov/laws/main.shtml
ARMI Products on Invasive Species
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USGS
Joint estimation of habitat dynamics and species interactions: disturbance reduces co-occurrence of non-native predators with an endangered toad.
Authors: Miller DAW, Brehme CS, Hines JE, Nichols JD, Fisher RN | Date: 2012-11-01 | Outlet: Journal of Animal Ecology 81:1288-1297
1. Ecologists have long been interested in the processes that determine patterns of species occurrence and co-occurrence. Short-comings of many existing empirical approaches for these questions include a reliance on patterns of occurrence at a single time point, failure to properly account for imperfect detection, and treating the environment as a static variable. <br />
2. We fit detection and non-detection data collected from repeat visits using a dynamic site occupancy model that simultaneously accounts for the temporal dynamics of a focal prey species, its predators, and its habitat. Our objective was to determine how disturbance and species interactions affect the co-occurrence probabilities of an endangered toad and recently introduced non-native predators in stream breeding habitats. To do this we determined support for alternative processes that could affect co-occurrence frequency in the system. <br />
3. Co-occurrence probabilities of toads with non-native predators in high-disturbance ephemeral streams and low-disturbance perennial streams were directly related to the differences disturbance regimes in each of the stream types. If predators were established at a site, they were rarely lost from the site except in cases when the site dried out. Once a dry site became suitable again, toads colonized them much more rapidly than predators, creating a period of predator-free space.<br />
4. We attribute the dynamics to a ‘storage effect’ where toads persisting outside of the stream environment during periods of drought rapidly colonized sites when they become suitable again. Our results demonstrate that, even in a highly connected stream network, temporal disturbance can structure frequencies with which breeding amphibians encounter non-native predators.<br />
5. Dynamic site occupancy models are a powerful tool for quantifying inter-species and species-habitat interactions. In contrast to previous methods that infer dynamic processes based on static patterns in occupancy, the approach we take allows the dynamic processes that determine species-species and species-habitat interactions to be directly estimated.
Brad M. Glorioso
Diet of the invasive Cuban Treefrog (Osteopilus septentrionalis) in pine rockland and mangrove habitats in South Florida
Authors: Glorioso BM, Waddle JH, Crockett ME, Rice KG, Percival HF | Date: 2012 | Outlet: Carribean Journal of Science 46 (2-3):346:355
Native to Cuba, the Bahamas and the Cayman Islands, the Cuban Treefrog (CTF) is an invasive<br />
species in Florida, with the ability to inflict serious ecological damage to invaded habitats. By examining the diet of the CTF, a known predator of native frogs, better predictions may be made on the impacts on native species and ecosystems. From 2002 – 2003, CTF diet was investigated in south Florida at four sites, two each within pine rockland and mangrove habitat. Within each habitat, one site exhibited a low density of CTFs and the other a high density of CTFs. CTFs were captured in PVC pipes attached to trees and stomach contents were examined after euthanasia. Beetles were the most numerous and widely consumed prey item among sites; roaches, orthopterans, spiders, ants, and caterpillars were also major dietary components. There were significant differences in the proportion of taxa consumed by CTFs between low and high density populations within each habitat, with the low density site in every instance having the higher proportion. Across habitats, ants comprised a significantly higher proportion of the diet in mangroves, whereas beetles, orthopterans, and snails comprised a significantly higher proportion of the diet in pine rocklands. Approximately 3.5% of all stomachs examined contained anuran remains. Though not significant, CTFs from low density sites consumed a higher proportion of frogs than those at high density sites. Corroborating previous research,the data show the CTF to be a generalist feeder, consuming a wide variety of invertebrate prey, with anurans playing only a minor role in the overall diet.
General methods for sensitivity analysis of equilibrium dynamics in patch occupancy models.
Author: Miller DAW | Date: 2012-05 | Outlet: Ecology 93:1204-1213
Sensitivity analysis is a useful tool for the study of ecological models that has many potential applications for patch occupancy modeling. I use the rich foundation of existing methods for Markov chain models to demonstrate new methods for sensitivity analysis of the equilibrium state dynamics of occupancy models. Estimates from three previous studies are used to illustrate the utility of the sensitivity calculations: a joint occupancy model for a prey species, its predators, and habitat used by both; occurrence dynamics from a well-known metapopulation study of three butterfly species (Hanski 1994); and golden eagle occupancy and reproductive dynamics (Martin et al. 2009a). I show how to deal efficiently with multistate models and how to calculate sensitivities involving derived state variables and lower level parameters. In addition, I extend methods to incorporate environmental variation by allowing for spatial and temporal variability in transition probabilities. The approach used here is concise and general and can fully account for environmental variability in transition parameters. The methods can be used to improve inferences in occupancy studies by quantifying the effects of underlying parameters, aiding prediction of future system states, and identifying priorities for sampling effort.
U.S. Department of the Interior |
U.S. Geological Survey
