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Invasive species: the worst case?
Benthic fauna 97% by number exotic
99% by biomass exotic
Biological invasions (Lec16)
ImpactsWhich species invade?Which communities are invaded?
ReadingsInvasional meltdown hypothesis
Management - Biological Control (Lec17)
SOME DEFINITIONS
Indigenous/native species - a spp found within its native rangeNon-indigenous/introduced species - a spp introduced to areas beyond its native range by human activity
Established - a spp with a self-sustaining population outside its native range
Invasive species - a non-indigenous spp that spreads from the point of introduction and becomes abundantNon-invasive species - a non-indigenous spp that remains localised within its new environment
Introduced species are common
Pine trees in Africa
African dung beetles in Australia
Australian Possum in New Zealand
New Zealand snails in North America
What proportion of species in BC are introduced?
%VASCULAR PLANTS 21FRESHWATER FISH 15MAMMALS 8REPTILES 27AMPHIBIANS 10
How serious is the problem in BC?
Most major agricultural pestseg apple clearwing moth
50% of weedsBC lists 47 noxious weeds.eg yellow starthistle Japanese knotweed
Check outE Flora BC Invasive species Page
What are the impacts of invasions?
Economic + cows, potatoes, oysters
- zebra mussel, gypsy moth, purple loosestrife
Public health - malaria - cholera pandemic
- avian flu?
Biodiversity - impacts on SAR
25% endangered species
31% threatened species
16% special concern species COSEWIC
IMPACTS OF INTRODUCED SPECIES
1. PREDATION
Nile Perch - - introduced to Lake Victoria in 1980 - caused extinction of many endemic cichlid fish
Seehausen et al 1997 Cons Biol 11:890-904
IMPACTS OF INTRODUCED SPECIES
1. PREDATION
Red Fox - introduced in 1855- linked to declines of ground nesting birds, many small mammals, turtles
Removal and rock wallabies in WA
1. PREDATION - the rosy wolfsnail Euglandina
The introduced predator from se USAIntroduced to Hawaii, Society Islands, Mascarene Islands, Seychelles
WHY?Brought in to control African giant snailAchatina fulica
ConsequenceHawaii15/20 endemic Achatinella spp.Society Islands56/61 endemic partulids extinct
IMPACTS OF INTRODUCED SPECIES
2. COMPETITION
Zebra musselFirst found in Great Lakes in 1988Small - 2.5 cm longHigh densities - 15000/m2
Unionid mussels - 297 endemics
40-75% spp extirpated or of special concern
>60% cases due to zebra mussels
IMPACTS OF INTRODUCED SPECIES
2. COMPETITION - Himalayan balsam
Introduced to Europe 100 yrs agoNectar produced at very high rateBumblebees visit 4X
more frequently
IMPACTS OF INTRODUCED SPECIES
2. COMPETITION - Himalayan balsam
Competes with natives for services of pollinators
IMPACTS OF INTRODUCED SPECIES
3. GENETIC - california tiger salamander
Native decliningCongener used as baitReleasedGenetic study - 6 ponds - all had hybrids
- no “pure” individuals in 50%
IMPACTS OF INTRODUCED SPECIES
3. GENETIC - the introduced mallard threatens
Endemic Hawaiian Duck NZ Grey duck
Endemic florida mottled duck
IMPACTS OF INTRODUCED SPECIES
4. HABITAT ALTERATION -
Beaver1946 - 50 to Argentina2006 - 115,000
Dominant tree spp - all Nothofagus
Regeneration dependant on seedlings
Beaver limit regeneration, deforest riparian habitat
IMPACTS OF INTRODUCED SPECIES
5. HABITAT ALTERATION - Yellowstone NP
New Zealand snail1994 - introduced2006 - 20K-500K /m2
Impact - consumes 75% GNP of the system - is 97% of primary consumer biomass - produces 2.5X total animal waste in
control stream - increases nutrient cycling - on native spp. unknown
IMPACTS OF INTRODUCED SPECIES
CAN BE NEGLIGIBLE
Crested mynahIntroducedBecame common in sw BCNow extinct
European cranefly1960’s pest in Vancouver2006 - non-pest status
Species imported into new area
Survives transport and introduction
Fails in transport
Establishment
Fails to establish
Spread
Noninvasive
Invasive
INVASIONS - a sequence of unfortunate events
Filters apply at each stage
1. Biogeographic - physical barriers2. Physiological - match between species and
climate
3. Biotic - Interaction with native species
The tens rule of invasions Williamson and Fitter (1996)
1 in 10 species imported survive --> introduced1 in 10 species introduced ---------> established1 in 10 species established --------> invasive (ie pest)
KEY QUESTIONS
What features of the invading species predict establishment and expansion?
What characteristics of a community favour invasions?
Why do species have a large impact?
What features of the invading species predict establishment and expansion?
Your Predictions
What features of the invading species predict Establishment and invasion success (expansion)?
Mammalian introductions into Australia
40 spp 30 genera 14 families
What features of the invading species predict Establishment?
Mammalian introductions into Australia
Establishment - 23 of 40 spp became established Numbers of individuals releasedLocation - greater area of climatically suitable habitatSpecies - larger overseas range size
ExpansionNumber of introductionsLocation - greater area of climatically suitable habitatSpecies - body size (smaller)
- lifespan (shorter)- fecundity (higher)- diet (Carnivore>Omnivore or herbivore)
What characteristics of a community favour invasions?
Predictions
1. The habitat is hospitable
2. There is “niche space available”
so species-rich communities are less vulnerable
= the biotic resistance hypothesis Elton (1958)
and disturbed communities are more vulnerable
Q. Explain why?
Invasions in streamside tussock communities
Natural data Exp’tal data
Q. Does this support the biotic resistance hypothesis?
Plant invasions in S African reserves
Q. What does this suggest?
Which communities are most vulnerable?
Hospitable habitatsResource rich systems
- combining biotic resistance+disturbance
Fig 9.14
Why do species have a large impact?
High impact invaders Can be plants, animals or microbesAct as predators, herbivores, parasites/disease
But are oftenKeystone predatorsEcosystem engineersFilling an empty niche
CONCLUSIONS
Species invasions Are CommonBut impacts vary from negligible to severe
Establishment increases with numbers released
Invasiveness (pests/weeds)is hard to predict
Risk varies with species-richness, resource availability and disturbance
What can you do? See E Flora BC Invasives page
NEXT - management and biological control