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28 Cards in this Set

  • Front
  • Back
Biotic Exchange
The spread of invasive alien spp and disease organsims has increased because of increased trade and travel.
Biotic homogenization
Spp assembleafes become increasingly dominated by a small numver of widespread spp. represents further losses in biodiverstiy that are often missed when only consering canges in absolute numbers of spp.
There are few places in the world that dont have exotic spp
Not all exotic spp will be invasive
Successful Invader
High repro rate
Pioneer spp
Short generation time
Long lived
High disperal rates
Single parent, vegetative or colonial repro
High genetic variablility
Phenotypically plastic, can adapt to new envmt easily
Broad native range and diet
Habitat generalist
Human commensal
Invasion prone communities
Similar climate to invaders habitat
Earlt successional community
Low diversity of native spp
Absence of predators or grazers of invading spp
Absence of ecologically similar spp
Native spp that are nive to grazing or predation pressure
Already disturbed by human actiivtes
Invasive spp on Islands
* island biota- high endemic spp
-lack top level predators and large herbivores
-flora and fauna have evolved without pressures from grazers and predators
* More prone to invations
* Island plants vulnerable to grazing
* island spp are naive ot hunting strategies of intorduces predators
New Zealand
No native mammals. Few top predators
Many spp of birds and reptiles are endimic to NZ and have evolved w/o predators
Introduces rats, ferrets, stoats, weasels, cats, disasterous
Australian federal quid pro quo in the form of possoms and macropods
Possoms in NZ
Developed stratagies to protect them from overgrazing --> NZ
ENTIRE forests have been stripped bare from possoms, and have destroyed possom grazing.
Now no possoms in NZ
Pest Invasions in Australia
• Australia is another example of a country with a high number of endemic species and specialised ecosystems.
• As a direct consequence of land clearing and introduced species following European occupation, Australia has one of the highest rates of species decline and extinction in the world.
5th in the world for # of extinctions
90% of birds declined in #
1 in 7 frogs are endangered
23% of mammal extinctions happened in OZ
Nearly 50% of OZ marsupials are extinct, endangered or threatened
Habitat distruction/competition/direct predation by intoduced plants and animals
The Overall Impact
• In total: over 90 animals and nearly 1000 plants have been introduced
Introduced Species
Ship rat
House gecko
Mosquito fish
Mallard duck
Cane toad
sheep and cattle that we don’t regard as feral animals but certainly
have a huge continuing impact on the Australian environment!
Inadvertantly, (geckos, mice, rats)
cattle, sheep, goats, chickens
horses, camels, donkets
trout, foxes, rabbits, ducks
finches, sparrows, starlings
Pest Control
cane toad, cattle egret, mosquito fish, foxes (to control rabbits)
Alclimitise to new envmt
Europeans arrived- evertthing unfamiliar
Land degredation
-native plants can withstand high grazing. hard hoofed animals trample
- between introduced grazers and native herbivores
- Australian wildlife naive to introduced predators and their hunting strategies
Case study 1: rabbits
• Origin: Mediterranean Europe
• When introduced: early 1800s
• Where: eastern Australia
• Why: food, skin and fur trade
• Current range: spread rapidly to most parts of Australia, excluding tropical north
Reasons for sucess
Climate and soil are ideal
Huge repro potential
Pasture that has been modified for and b sheep and cattle grazing--> great for them
Significantly and irrevocably altered the landscape
Significant overgrasing of many regions of OZ
Rabbits eat everything, even bark=tree death
Rabbits can eat entire habitats that are inportant for shlter and breeding of native animals
Severe grazing prementantly alters floristic composition of region
Burowing and grazing --> erosion
Compete with native animals for shelter and food
“Bunnies” & Bilbies
The decline of the bilby (left) from much of its former range is partly attributed to competition for burrows with rabbits.
Bilbies were originally widely distributed & relatively abundantacross much of the Southern half of the continent. They are now restricted to a few tiny pockets of their
former range.
Control measures
Hunting and shooting
Rabbit proof fence
Poisions and gasses
Warren ripping- destroy burrows with poision (not easy to make burrows)
Myxomatosis- virus in 1950s
Calicivirus- viral disease
The cane toad
• Origin: South America
• When introduced: 1930’s
• Where: North Queensland
• Why: control of sugarcane beetle
• Current range: much of QLD, tropical
regions of NT, Northern NSW
–Spreading at 27km/yr
–Have reached Darwin & still heading West
–Northern NSW & still heading South
Reasons for Success
• Very hardy, tough skin unlike frogs –
they can survive in dry environments
• Long lived: 15 –20 years
• High fecundity: 30,000 eggs / yr
• Poisonous glands: very few animals eat them. (Some animals have learned to e.g. crows, Hydromysor been selected to avoid e.g. Black Snake)
• Omnivorous: they eat anything that
* control sugar cane beetles- FAILED
- Cane toads dont eat cane beetles, they live up in cane, toad is on the ground
Impacts and consequences
No natural pred in OZ.
Highly toxic, when they try to eat it they die. Uninhibited by any predator (cuz they would die).
Declines in native vertebrates
Out compete native frogs with #'s. and skinks and small mammals and cause poisioning
Control Measures
No effective meathod
Rely on public awareness and response- collecting and killing
Problems- misidentificaiton
Bio control??
• Origin: Europe
• When introduced: 1860’s
• Where: Victoria
• Why: sport, skins, rabbit control
• Current range: right across Australia
excluding tropical regions. It spreads North into desert areas in good seasons.
Reasons for Success
Highly efficient predator
(native spp naive to predation)
Omniverous: can survive harsh conditions
No competition except with dingos
RAPID spread
Impacts and consequences
Most distructive in OZ
Fox goes north w/ land clearing
Caused local extinction and range reduction- ground nesting birds and small mammals
Can only survive in the north
WORSE yet to COME!
released into Tasmania
many that are extinct in mainland only in Tasmania
Poisioning, 1080