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Slide 2:So, what is an invasive species?
Monk Parakeet colony near Chicago, Illinois"Exotic," "alien," "introduced," non-indigenous," and "non-native" are all synonyms for plant or animal species that are intentionally or unintentionally introduced into an area outside of their natural range. Brown Tree Snake introduced to Guam, but they are native to New Guinea Can you find Guam and New Guinea on a map of the world? New Guinea Factors Determining the Success of an Exotic Species 1. Suitability of Habitat and Ecological Niche English Sparrow 2. Adequacy of the “introduction unit” a. Health b. Behavior- including social aspects c. Simple numbers 3. Degree of escape from diseases, parasites and predators 4. Degree of escape from competitors Mechanisms of Introduction 1. Intentional European Rabbits in Australia Rabbit Impacts on Native Wildlife 1. Direct competition for food 2. Selective grazing changes ecosystem composition 3. Evicted various species from their burrows- e.g. bilby, hare-wallaby 4. A colony of rabbits will support a high number of predators (e.g. feral cats and introduced foxes) which will shift to other, more easily obtained, native prey 5. Native wildlife killed by poisons and traps set for rabbits 6. Shooters, culling rabbits, also culled native species for the pelt trade. 7. Bounties paid for wombats, why? 8. Harm to vegetation during drought- digging of roots and ringing Red Fox introduced to control rabbits, but decimated native fauna, also ….. Present distribution of Rusty Crayfish range intentionally expanded by anglers Rusty crayfish (Orconectes rusticus) are native to streams in the Ohio, Kentucky and Tennessee region. Spread by anglers who use them as bait, rusty crayfish are prolific and can severely reduce lake and stream vegetation, depriving native fish and their prey of cover and food. They also reduce native crayfish populations Methods of Introduction 2. Inadvertent Cattle Egret- native to Africa, first crossed to South America then into the United States in the 1940’s 3. Natural Invaders Determinants of Impact 1. Ecological distinctiveness- highly successful invaders are usually different in structure, physiology or behavior from native forms Keystone Exotics Kudzu, a keystone exotic species infestation in Georgia. Keystone species are those, that if lost, would precipitate an extinction cascade or vortex Determinants for Impact 2. Potential for competitive exclusion Zebra Musses attached to the shell of a native mussel in the Ohio River
Slide 17: One of the more drastic impacts of zebra mussels are their influence in causing the near extinction of native American unionid clams in Lake St. Clair Also found to be the case for the western basin of Lake Erie Zebra mussels will attach and build colonies on native species of clams, hindering movement and overall fitness
Zebra mussels attached to a native clam found within the Great Lakes region
Slide 18:Interesting Zebra Mussel attachments
Sometimes they even attach to one another Zebra mussels tend to colonize on just about anything, including native clams, boats, plants, and slow moving animals Zebra mussels have also been known to attach to trash that can be found in water bodies Zebra mussels attached to a crayfish (top) and a snapping turtle (bottom) Terrible waste of a good beer can
Slide 19: Since zebra mussels attach to water intakes, surrounding areas could go for days without any water Companies that use water to power their plants can have trouble keeping them up and running A number of plants in the Great Lakes regions are having trouble keeping the zebra mussels out of their water intake pipes
Zebra mussels encrusted inside water pipes3. Potential for disease transmission Fungi accidently introduced on Chinese Chestnut trees imported to the United States, the map documents the timing of the spread 4. Potential for genetic swamping Rainbow trout introduced for anglers, readily hybridizes with native species such as cutthroat trout. Dealing with Detrimental Exotics 1. Prevention of entry 2. Control of spread 3. Creation of pristine areas 4. Local eradication 5. Protection of individuals 6. General population reduction