Invasive species: the worst case?

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Invasive species the worst case?
Benthic fauna 97 by number exotic 99 by
biomass exotic
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Biological invasions (Lec16)

• Impacts
• Which species invade?
• Which communities are invaded?
• Readings
• Invasional meltdown hypothesis
• Management - Biological Control (Lec17)

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SOME DEFINITIONS Indigenous/native species - a
spp found within its native range Non-indigenous/i
ntroduced 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 abundant Non-invasive species - a
non-indigenous spp that remains localised within
its new environment
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Introduced species are common
Pine trees in Africa
African dung beetles in Australia
Australian Possum in New Zealand
New Zealand snails in North America
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What proportion of species in BC are introduced?
VASCULAR PLANTS 21FRESHWATER
FISH 15MAMMALS 8REPTILES 27 AMPHIBIANS 10
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How serious is the problem in BC?
Most major agricultural pests eg apple clearwing
moth 50 of weeds BC lists 47 noxious
weeds. eg yellow starthistle Japanese
knotweed Check out E Flora BC Invasive species
Page
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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
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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 11890-904
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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
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1. PREDATION - the rosy wolfsnail Euglandina
The introduced predator from se USA Introduced to
Hawaii, Society Islands, Mascarene Islands,
Seychelles
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IMPACTS OF INTRODUCED SPECIES
2. COMPETITION
Zebra mussel First found in Great Lakes in
1988 Small - 2.5 cm long High densities -
15000/m2
Unionid mussels - 297 endemics 40-75 spp
extirpated or of special concern gt60 cases due
to zebra mussels
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IMPACTS OF INTRODUCED SPECIES
2. COMPETITION - Himalayan balsam
Introduced to Europe 100 yrs ago Nectar
produced at very high rate Bumblebees visit 4X
more frequently
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IMPACTS OF INTRODUCED SPECIES
2. COMPETITION - Himalayan balsam
Competes with natives for services of pollinators
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IMPACTS OF INTRODUCED SPECIES
3. GENETIC - california tiger salamander
Native declining Congener used as
bait Released Genetic study - 6 ponds - all had
hybrids - no pure individuals in 50
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IMPACTS OF INTRODUCED SPECIES
3. GENETIC - the introduced mallard
threatens
Endemic florida mottled duck
Endemic Hawaiian Duck
NZ Grey duck
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IMPACTS OF INTRODUCED SPECIES
4. HABITAT ALTERATION -
Beaver 1946 - 50 to Argentina 2006 - 115,000
Dominant tree spp - all Nothofagus Regeneration
dependant on seedlings Beaver limit
regeneration, deforest riparian habitat
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IMPACTS OF INTRODUCED SPECIES
5. HABITAT ALTERATION - Yellowstone NP
New Zealand snail 1994 - introduced 2006 -
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
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IMPACTS OF INTRODUCED SPECIES
CAN BE NEGLIGIBLE
European cranefly 1960s pest in Vancouver 2006 -
non-pest status
Crested mynah Introduced Became common in sw
BC Now extinct
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INVASIONS - a sequence of unfortunate events
Species imported into new area
Fails in transport
Survives transport and introduction
Fails to establish
Establishment
Spread
Noninvasive
Invasive
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• Filters apply at each stage
• Biogeographic - physical barriers
• Physiological - match between species and
  climate
• Biotic - Interaction with native species

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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?
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What features of the invading species predict
establishment and expansion?
Your Predictions
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What features of the invading species predict
Establishment and invasion success (expansion)?
Mammalian introductions into Australia 40 spp 30
genera 14 families
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What features of the invading species predict
Establishment?
Mammalian introductions into Australia Establishm
ent - 23 of 40 spp became established
Numbers of individuals released Location -
greater area of climatically suitable
habitat Species - larger overseas range size
Expansion Number of introductions Location -
greater area of climatically suitable
habitat Species - body size (smaller) -
lifespan (shorter) - fecundity (higher) -
diet (CarnivoregtOmnivore or herbivore)
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What characteristics of a community favour
invasions?

• Predictions
• The habitat is hospitable
• 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?

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Invasions in streamside tussock communities
Natural data Exptal data
Q. Does this support the biotic resistance
hypothesis?
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Plant invasions in S African reserves
Q. What does this suggest?
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Which communities are most vulnerable?
Hospitable habitats Resource rich systems -
combining biotic resistancedisturbance
Fig 9.14
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Why do species have a large impact?
High impact invaders Can be plants, animals or
microbes Act as predators, herbivores,
parasites/disease
But are often Keystone predators Ecosystem
engineers Filling an empty niche
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CONCLUSIONS Species invasions Are Common But
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