Invasive Species - ramseylab.org Invasion lecture... · • African land snail ... Hanta Virus Deer...
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Transcript of Invasive Species - ramseylab.org Invasion lecture... · • African land snail ... Hanta Virus Deer...
• Native to Australia, Papua New Guinea, Solomon Islands
• Brought to Guam (WWII, accidental cargo)
• Has devastated native lizards, birds (8 of 12 ground dwellers now extinct)
Brown tree snake
Other impacts• Power interruptions
• Consumption of poultry, pets
• Attacks on infantsand the disabled...
• Non-native (alien)
• Self-perpetuating
• Expanding populations (or historically expanding)
• Exerts ecological impacts
• Initial introduction due to human activity
Definition of "invasive species"
TimeframeUsually defined post-European settlement
ScaleCan be jump dispersal or range expansion
Non-Native?
Ecological consequences of invasion
• Outcompete native species
• No. 2 cause of species endangerment
• Change community structure
• Alter ecosystem processes
Asian Bark fungus; Chestnut blight1 in 4 trees were chestnut prior to 1900sAdult trees now virtually extinct
Species endangerment
Fire regime (Melaleuca in Everglades)
Change ecosystem processes
Nutrient cycles (Scotch broom in western U.S.)
• Disturbance and land-use history
• Cultivation and dispersal dynamics
• Escape of natural enemies, lack of resistance
Environmental factors mediating invasion
• “Pre-adaptation” to environments
• Bottlenecks and genetic diversity
• Rapid adaptation in introduced range
Genetic factors mediating invasion
• Fast growth, rapid maturity
• High dispersal ability
• Generalist ecology
• Single parent reproduction
• Association with humans/disturbance
• Invasive elsewhere
Characteristics of invasives
• Food
• Fiber
• Erosion control
• “Recreational”
• Accidental
Why are non-native species introduced?
Can invasions be controlled?Lets review the causes of invasion...
• Introduced taxa better competitors
• "Preadaption" to disturbed habitats
• Filling empty ecological niches
• Escaping from enemies
Can invasions be controlled?Lets review the causes of invasion...
• Introduced taxa better competitors
• "Preadaption" to disturbed habitats
• Filling empty ecological niches
• Escaping from enemies
There is a long history of bio-control efforts for invasive species...
Bio-control: introduction of enemies(predators) of pests (native or introduced)
• Rabbits in Australia
• Cacti in Australia
• St. John’s Wort in North America
Bio-control successes
Knapweed Gall Fly Gall Fly Larvae
Deer MouseDeer MouseHanta Virus
Populations have tripled Mice eat 1000+ larvae/night
Fly lays eggs in flowerhead Larvae eat seeds
Increased reservoir of virus
Major invader of rangelands
Unintended consequences of biocontrol