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?

Not picky eaters Good dispersers Rapid reproduction Fast growth  Able to change form to tolerate varying conditions Clockwise from top: Lampreys spreading through the Great Lakes; Cane toad eating a snake; hundreds of cane toadlets emerging from a pond; English ivy growing on a building; garlic mustard flowering. Center: Two images of Japanese knotweed growing large and dense in a wet habitat, and remaining short in a dry habitat. 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: Originally from Europe, tansy ragwort is an invasive weed in North America. When tansy ragwort came to North America, it escaped its natural predator, the cinnabar moth, and was able to spread much more rapidly. Tansy ragwort is also known for spreading in disturbed areas, such as construction sites, or along roads.

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: Originally from Europe, tansy ragwort is an invasive weed in North America. When tansy ragwort came to North America, it escaped its natural predator, the cinnabar moth, and was able to spread much more rapidly. The cinnabar moth has since been introduced to North America as a successful biocontrol, because its caterpillars specialize on eating tansy ragwort flowers and leaves.

Barriers Construction of physical or non-physical barriers (e.g. electric barriers) that block the spread of invasive species Electrical barriers have been used to keep Asian carp from entering Lake Michigan, however, these barriers have the potential to disrupt migratory pathways of other species.

Physical removal Manually removing the invasive species from the area (hunting, pulling up plants, trapping, etc…) Community garlic mustard pulls are a common springtime event in Michigan (Center)

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 N I C N = native I = invasive C = control The moth is used to control invasive prickly pear cactus in Australia, but the moth is invasive in North America, and damages the North American prickly pear populations. N I 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. Parasitic wasps have been used to control gypsy moth caterpillars (pictured) and may also be useful for controlling Cactoblastis caterpillars.

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#