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28 Cards in this Set
- Front
- Back
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Biotic Exchange
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The spread of invasive alien spp and disease organsims has increased because of increased trade and travel.
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Biotic homogenization
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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.
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Invaders
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There are few places in the world that dont have exotic spp
Not all exotic spp will be invasive |
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Successful Invader
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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 |
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Invasion prone communities
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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 |
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Invasive spp on Islands
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* 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 |
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New Zealand
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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 |
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Possoms in NZ
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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 |
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Pest Invasions in Australia
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• 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 |
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The Overall Impact
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• In total: over 90 animals and nearly 1000 plants have been introduced
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Introduced Species
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Dog
Horse Goat Hare Cat Trout Starling Ship rat Fox Mouse Pig Rabbit Pigeon Deer Camel Buffalo 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! |
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Reasons
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Inadvertantly, (geckos, mice, rats)
Deliberate Agriculture cattle, sheep, goats, chickens Transport horses, camels, donkets Sport trout, foxes, rabbits, ducks Ornaments finches, sparrows, starlings Pest Control cane toad, cattle egret, mosquito fish, foxes (to control rabbits) Alclimitise to new envmt Europeans arrived- evertthing unfamiliar |
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Effects
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Land degredation
-native plants can withstand high grazing. hard hoofed animals trample Competition - between introduced grazers and native herbivores Predation - Australian wildlife naive to introduced predators and their hunting strategies |
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Case study 1: rabbits
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• 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 |
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Reasons for sucess
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Climate and soil are ideal
Huge repro potential Pasture that has been modified for and b sheep and cattle grazing--> great for them |
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IMPACTS
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Significantly and irrevocably altered the landscape
Significant overgrasing of many regions of OZ Rabbits eat everything, even bark=tree death |
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Consequences
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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 |
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“Bunnies” & Bilbies
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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. |
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Control measures
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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 Immonocontraception |
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The cane toad
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• 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 |
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Reasons for Success
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• 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 moves! |
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WHY
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* control sugar cane beetles- FAILED
- Cane toads dont eat cane beetles, they live up in cane, toad is on the ground |
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Impacts and consequences
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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 |
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Control Measures
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No effective meathod
Rely on public awareness and response- collecting and killing Problems- misidentificaiton Bio control?? |
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FOXES
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• 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. |
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Reasons for Success
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Highly efficient predator
(native spp naive to predation) Omniverous: can survive harsh conditions No competition except with dingos RAPID spread |
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Impacts and consequences
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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 |
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Control
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Hunting
Poisioning, 1080 |
