Download - Invasive Species in Nova Scotia
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Invasive Species in Nova Scotia
A Primer
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Native Species
Any animal or plant that was here when we got here
Brook Trout
Red Spruce
Black Duck
Canada GoldenrodBumblebee
Mussel
Red Squirrel
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Introduced Species(Non-Native, Exotic, Alien, Naturalized)
Any animal or plant that humans brought here
Rainbow Trout
Scots Pine
Ring-Necked Pheasant
Queen-Anne’s Lace Gypsy Moth Norway Rat
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Invasive Species
An introduced species that displaces native species
• Tend to establish large populations Eurasian Watermilfoil
Spiny-CheekCrayfish
• Out-compete native species for space or other resources
• Sometimes also consume native species (e.g., fish larvae)
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Pest Species
• An organism that does things we don’t like
• Becoming too numerous
• Competing with preferred species
• Causing or carrying disease
• Growing where we don’t want it
• Being ugly
• May be native or introduced
• May or may not be invasive
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How do introduced species get here?
Accidental introductions
Species transported incidentally by human
traffic and transport
Dandelion Zebra Mussel WoodlouseDutch Elm Disease
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How do introduced species get here?
Deliberate Introductions
Species brought here to provide food, sport,
beauty or other amenities
Wild Apple
Honey BeeEuropean Starling
Purple Loosestrife
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What kinds of species are introduced?
ALL KINDS
Smallmouth Bass
Green Crab
Codium fragile
Didymosphenia geminata
BurdockNorway Maple Asian Ladybird Beetle
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Why are invasive species a problem?
1. Reduce populations of native species
(sometimes to extinction)
2. Reduce natural diversity and compromise ecosystem function
3. Interfere with important commercial
enterprises (fishing, farming, forestry)
4. Reduce aesthetic appeal of invaded areas
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What makes a species invasive?
• No single feature unites all invasives• Tend to be tolerant of physical conditions• Tend to be fast-growing• Tend to reproduce quickly and abundantly• Tend to be competitive or aggressive• Tend to disperse easily• Tend to show phenotypic plasticity• Tend to tolerate or welcome disturbance
Natural Advantage Hypothesis
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What makes a species invasive?
• Invasive species may be controlled in native range by a predator or disease
• Predator or pathogen absent in new range• Predators may be grazing mammals, insects,
fungi, viruses• Specialist enemies most important• Generalist enemies create biotic resistance
Enemy Release Hypothesis
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Evidence for Enemy Release
Based on 473 plant species naturalized in the U.S.A.(Mitchell , C.E. and Power, A.G. 2003. Nature 421: 625-627)
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What makes a species invasive?
• Invasive species may fill an unused niche• Using different resources• Acquiring resources in a different way• A form of natural advantage• Most likely in species-poor communities• Supported by Island Biogeography Theory
Empty Niche Hypothesis
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What makes a species invasive?
• Disturbance removes competitors and predators (reduces biotic resistance)
• Fewer competitors means unused resources• Invasive species may exploit new niche• Widespread human disturbance creates
many invasion opportunities• Addition of resources (fertilizer, CO2) creates
even more invasion opportunities
Anthropogenic Disturbance Hypothesis
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What to do about invasive species?
1. Prevention• Keep the invasive organism out• If it does get in, prevent or slow
its spread
2. Eradication • Remove populations that are already established
JapaneseKnotweedGood luck with that
Common Reed
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