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What are invasive species? Can you think of any examples? Invasive species • Non-native, introduced species (plants or animals) that has a negative impact on the habitats it invades. What traits do you think would help a species become a successful invader? Good dispersers Not picky eaters Able to change form to tolerate varying conditions Close association with humans Rapid reproduction The environment itself can also play a role in invasion • The amount of available unused resources • Disturbed habitats (fire, human use) • Absence of predators or herbivores that can eat the invasive Human disturbance: Herbivore present: Herbivore absent: How bad can it be? • Outcompete native species for limited resources (space, food, etc.) • May directly reduce population size of natives by predation or herbivory • If the invasive species is toxic it may kill off native predators or herbivores that try to eat it • May change function of ecosystems (fire regimes, nutrient cycling) What can we do to control or remove invasive species? • There have been numerous different methods used to control invasive species. Chemical control • Herbicides and pesticides are used to kill off invasives. Occasionally these chemicals are species specific (e.g. lampricides). Reproductive interference • Some methods try to disrupt the reproductive cycle by releasing sterilized males into the population. • Use of synthetic pheromones can also interfere with reproduction Biological control • Releasing predators or herbivores to eat the invasive species • Releasing a pathogen into the invasive species population Herbivore present: Herbivore absent: Barriers • Construction of physical or nonphysical barriers (e.g. electric barriers) that block the spread of invasive species Physical removal • Manually removing the invasive species from the area (hunting, pulling up plants, trapping, etc…) Example: Cane toad • • • • Introduced to Australia, quickly became invasive Eats just about anything Very high reproductive rate Toxic Cane toad control • Most attempts at control have focused on physical removal • Future efforts are looking at using an alarm pheromone, lung parasite, and a natural predator to control the toad Example: Cactoblastis moth • Caterpillars feed on prickly pear cactus Cactoblastis moth N I N I N C N = native I = invasive C = control Cactoblastis moth • Cactoblastis is a biocontrol in Australia, but it needs to be “biocontrolled” in North America, where it is invasive. • Some research is exploring the possibility of introducing a parasitic wasp from South America that lays eggs in the Cactoblastis caterpillars. • The wasp larvae eat the caterpillar from the inside out. Example: Zebra mussels • Since they were first sighted in Lake Erie in 1986, zebra mussels have spread to 30 states. • http://nationalatlas.gov/dynamic/dyn_zm.html#