Download 1091(Lec16Inv)

Invasive species: the worst case?
Benthic fauna 97% by number exotic
99% by biomass exotic
Biological invasions (Lec16)
Impacts
Which species invade?
Which communities are invaded?
Readings
Invasional meltdown hypothesis
Management - Biological Control (Lec17)
SOME DEFINITIONS
Indigenous/native species - a spp found within its native
range
Non-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 abundant
Non-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
FRESHWATER FISH
MAMMALS
REPTILES
AMPHIBIANS
%
21
15
8
27
10
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
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 USA
Introduced to
Hawaii, Society Islands, Mascarene Islands, Seychelles
Consequence
WHY?
Brought in to control
African giant snail
Achatina fulica
Hawaii
15/20 endemic Achatinella spp.
Society Islands
56/61 endemic partulids extinct
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
>60% cases due to zebra mussels
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
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 declining
Congener used as bait
Released
Genetic study - 6 ponds - all had hybrids
- no “pure” individuals in 50%
IMPACTS OF INTRODUCED SPECIES
3. GENETIC - the introduced mallard
threatens
Endemic florida
mottled duck
Endemic Hawaiian Duck
NZ Grey duck
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
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
IMPACTS OF INTRODUCED SPECIES
CAN BE NEGLIGIBLE
Crested mynah
Introduced
Became common in sw BC
Now extinct
European cranefly
1960’s pest in Vancouver
2006 - non-pest status
INVASIONS - a sequence of unfortunate events
Species imported into new area
Fails in transport
Survives transport and introduction
Fails to establish
S
p
r
e
a
d
Establishment
Noninvasive
Invasive
Filters apply at each stage
1. Biogeographic - physical barriers
2. 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 --> introduced
1 in 10 species introduced ---------> established
1 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 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 (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
Q. Does this
support the
biotic
resistance
hypothesis?
Exp’tal data
Plant invasions in S African reserves
Q. What does this suggest?
Which communities are most vulnerable?
Hospitable habitats
Resource rich systems
- combining biotic resistance+disturbance
Fig 9.14
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
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