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Why do we have to think about
invasive species
• A new species in the ecosystem should
higher the biodiversity.
• What is wrong on such hypothesis
Species invasion can be seen as predominantly post-Columbian events.
Magnitude of human driven species migration of the last 500 years
(deliberate and accidential)
rivals the changes wrought by continental glaciation cycles.
(Mack et al. 2000)
European trend in aquatic invasions: Seas
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European trend in plant invasions
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Sources on non-native plants in the UK
Garden Escape
Seed Contaminant
Feral Crop
Landscaping
Aquarium Escape
Medicinal Herb
Forestry
Other
Exotic species: a Scottish perspective
A total of 988 non-indigenous species occur in Scotland
Vascular plants
Molluscs
Birds
Insects
Fish
Mammals
Bryophytes
Amphibia
Over 80% are plants
http://dabrownstein.files.wordpress.com/2013/09/number_of_harmful_alien_species-1.jpg
Number of known harmful invasive marine species on a global view
http://dabrownstein.files.wordpress.com/2013/09/number_of_harmful_alien_species-1.jpg
Number of known harmful invasive marine species on a global view
Invasive: penetrate into a new region, what causes damages.
Invasive species is a species, which is introduced into a an
environment which is spatial different from its original
distribution.
Invasive: causing damages => invasive species are believed to
cause damages in the new ecosystem.
A species which immigrates into a new habitat is NOT by
definition an invasive species.
If the status of damage is uncertain: alien, exotic, neophytes,
nonindigenous....
A species which immigrates into a new habitat is NOT
by definition an invasive species.
Why species immigrate? Inidividuals of species immigrate.
Naturally:
By accident: wind blown, stream / ocean floated, orientation loss
Spatial population expanding by:
adaptation to wider range of environmental conditions
changes of environmental condition to favour species
out side former distribution range
Immigrating means also emigrating of individuals from former habitat
Driven by:
habitat loss:
changes in habitat size,
changes in population density
changes in environmental conditions
A species which immigrates into a new habitat is NOT
by definition an invasive species.
Why species immigrate? Inidividuals of species immigrate.
Human impacts:
By accident: transported along human made transportation ways:
trails and track by food, horses, etc.
streets and ways used by cars
highways
ship routs
Species ’tramp’ with transpoted goods and food: globalisation problem
since continental trading.
On purpose: introduction of exotic species
into botanical gardens, private gardens
pets, domestic and farm animals
food
A species which immigrates into a new habitat is NOT
by definition an invasive species.
Why species immigrate? Survival of Inidividuals of species.
Naturally:
By accident: wind blown, stream / ocean floated, orientation loss
Spatial population expanding by:
adaptation to wider range of environmental conditions
changes of environmental condition to favour species
out side former distribution range
Immigrating means also emigrating of individuals from former habitat
Driven by:
habitat loss:
changes in habitat size,
changes in population density
changes in environmental conditions
Possibility of species becoming invasive species
Number of contacts with new environment
times and number of individuals
Genetic diversity and mutation rate to adapts to new environment
Success in resource use to compete against native species
Succes in reproduction to outcompete native species in individual
numbers
The processes involved in
invasions
• Barriers
• What makes a species successful
• What makes a habitat or ecosystem
vulnerable
• Impacts
Impacts examples:
• Impacts on community structure – composition & diversity
• Impacts on higher trophic levels e.g consumers and decomposers
• Impacts on nutrient cycling e.g. Nitrogen fixers increase available nitrogen
• Impacts on Hydrology e.g. Changes in ET or runoff
• Impacts on fire regimes – changes in frequency or intensity
Direct damage on biotic environment:
Direct changes in the food web and food web hierarchy
Generalistic predator reduces populations size of certain species until
at least local extinction occurs
Raccoon dog and European singing bird & reptile population
Effects of invasive species to ecosystem
Nyctereutes procyonoides
(Gray, 1834)
native
introduced
Indirect damage on biotic environment:
Direct changes in the food web and food web hierarchy by
competetive effects
Same niche for resource use, but at least slightly higher reproduction
rate reduces succes of native species
American grey squirrel versus European red squirrel
Effects of invasive species to ecosystem
http://images.northrup.org/picture/xl/squirrel/north-
american-grey-squirrel084.jpg https://c1.staticflickr.com/7/6002/5921845600_1ba3
272f04_z.jpg
Direct changes in abiotic environment:
Indirect changes in the food web and food web hierarchy
Primary producer: more efficient use of one resource give ability to
reduce a second resource to change abiotic conditions from micro
scalic to mesoscalic extend.
Precipitation and run-off driven shallow lakes underly changes in
hydrologidal regime by invasion of riparian plant species with high net
primary production and resulting higher transpiration rate.
Results in lower reproduction rate of lake associated natice species.
Effects of invasive species to ecosystem
Ranunculus aquatilis L. Iris pseudacorus
Direct changes in abiotic environment:
Indirect changes in the food web and food web hierarchy
Primary producer: more efficient use of one resource give ability to
change environmental conditions like fire regime.
Effects of invasive species to ecosystem
Invasive species must be adapted to fire
already in its native distribution range
Brooks et al. 2004
Direct changes in abiotic environment:
Indirect changes in the food web and food web hierarchy
Secondary producer: more efficient use of one resource give ability to
change mechanically/chemically abiotic conditions from micro scalic
to mesicalic extend.
Physically damage in topography and stabilty of ground.
Effects of invasive species to ecosystem
muskrat (Ondatra zibethicus)
native introduced
Build nest while burrow into the bank with an
underwater entrance, can cause sometimes enormous
damage to riparian zones and reed beds
http://en.wikipedia.org/wiki/Muskrat
Direct changes in abiotic environment:
Indirect changes in the food web and food web hierarchy
Secondary producer: more efficient use of one resource give ability to
change mechanically/chemically abiotic conditions from micro scalic
to mesicalic extend.
Physically damage via changes in net radiation impact to soil by
different shade intensities of tree species.
Birch via beech
Effects of invasive species to ecosystem
http://ichef.bbci.co.uk/naturelibrary/images/ic/credit/640x395/e/en/engli
sh_lowlands_beech_forests/english_lowlands_beech_forests_1.jpg http://static.panoramio.com/photos/large/13011606.jpg
Direct changes in abiotic environment:
Indirect changes in the food web and food web hierarchy
Secondary producer: more efficient use of one resource give ability to
change mechanically/chemically abiotic conditions from micro scalic
to mesicalic extend.
Chemically changes/damage in environemt.
Cyano bacteria or algea bloom in linological environments (change
from aerobic to an-aerobic conditions)
Effects of invasive species to ecosystem
http://p5.focus.de/img/fotos/crop828278/1732716228-w1200-h627-o-q75-p5/Umwelt-Am-Strand-von-St-Michel-en-Greve-in-der-Bretagne-tuermen-sich-die-Algen.jpg
Indirect changes in abiotic environment:
Direct changes in the food web and food web hierarchy
See before
Effects of invasive species to ecosystem
Alien impacts: non-native flora
Campylopus introflexus
Reduces Calluna regeneration
Rhododendron ponticum
Reduces species richness
Picea sitchensis
Ecosystem change
Hyacinthoides hispanica
Hybridization with natives
Ambrosia trifida
Health risk
Oxalis pes caprae
Economic damage
Alien impacts: non-native fauna
Arthurdendyus triangulatus
Earthworm predator
Arion lusitanicus
Economic damage
Cervus nippon
Hybridization with natives Wildfowl predator
Sciurus carolinensis
Wildlife disease
Branta canadensis
Social and economic pest
Three steps to invasion
Species
introduced
Species
naturalised
Esta
blis
hm
ent
Species
spread &
invasion
Epidemiology of invasion
Multistage process
transport, migration, immigration from origin source to new
locals
overcome ’distance’ barriers survival of individuals
overcome physical and biotic stresses
establishment of population
overcome competetive stresses and environmental
unsuitabilities
naturalized in new environment
independent from new ’recruits’ arrival from source
population
adaptation to new environment
invading new environment
spread through new environment by population increase
and dispersal and have an measurable impact on the
ecosystem
Mack et al. 2000
Understanding pathways: entry routes
How many routes lead to species introductions?
Contaminants of agricultural & aquacultural produce
Contaminants of commercial grain supplies
Seed contaminants of nursery & cut flower trade
Organisms on timber
Seed contaminants of soil
Machinery, equipment, vehicles, aircraft
Contaminants of packing materials
Contaminants of mail and cargo
Ballast soil
Ballast water
Hull fouling
Tourists and their luggage
Other
Humans as dispersal vectors
Accidental:
globalisation in transport
The brown tree snake
(Boiga irregularis)
responsible for
devastating the majority
of the native bird
population in
http://en.wikipedia.org/wiki/Brown_tree_snake
Guam
http://en.wikipedia.org/wiki/Guam
http://ec.europa.eu/environment/marine/images/picture-descriptor2-
indigenous-species.png
Humans as dispersal vectors
Accidental:
globalisation in transport
Humans as dispersal vectors
Accidental:
ancient human migration
http://www.utexas.edu/features/2007/ancestry/graphics/ancestry5_medium.jpg
Humans as dispersal vectors
Accidental:
ancient human migration
http://www.utexas.edu/features/2007/ancestry/graphics/ancestry5_medium.jpg
Invasion of
live stock with
parsites and diseases,
human co-eolved
parsites and diseases
Humans as dispersal vectors
Accidental:
tourists
Alien Invaders Hitchhiking to
Antarctica
http://news.discovery.com/earth/plants/invasives-across-antarctica-
120305.htm
Poa annua Annual bluegrass
Humans as dispersal vectors
deliberate:
botanical garden escape
Impatiens parviflora (Small Balsam or Small-
flowered Touch-me-not)
http://de.wikipedia.org/wiki/Kleines_Springkraut
European vegetation development
since the last glacial maximum Huntley (1990)
Distribution of ”vegetation units” based on pollen data
Natural migration
Range shift by climate change in the past
Trachycarpus fortunei (Hook.) Wendl.
Palms a bioindicator of
warm and humid climates
Walther et al. 2007, Palms
tracking climate change, Global
Ecology & Biogeography
Natural migration
Range shift by climate change current
260
275
290
305
320
335
350
365
2000199019801970196019501940193019201910
year
# d
ay
s w
ith
ou
t fr
os
t
Trachycarpus fortunei (T.f.) widely planted in garden and parks
T. f. seeds freely in protected sites
Small palms in herb layer
T. f. palms in shrub layer
Reproducing T. f. palm population
Stages of invasion process
y = 0,0127x + 1,3932
R2 = 0,1374
-2
-1
0
1
2
3
4
5
1864
1874
1884
1894
1904
1914
1924
1934
1944
1954
1964
1974
1984
1994
2004
Year
Me
an
mo
nth
ly J
an
ua
ry t
em
pe
ratu
re
Local climate data vs invasion history in southern Switzerland.
Milder winters (days without frost)
50 years ago colonised protected sites, 20 years ago palm seedlings in
forest stands and persisted in face of competition leading to fully
functioning populations
Natural migration
Range shift by climate change in the future
Simulated present and potential future ranges
of Locustella naevia.
(a) Simulated distribution of Locustella naevia
(Grasshopper Warbler) in Europe for the
‘present’ (1961–90) climate. Blue symbols
represent grid squares simulated as suitable,
yellow symbols grid squares simulated as
unsuitable.
(b) Simulated potential distribution of
Locustella naevia in Europe for the HadCM3
B2 future climate scenario (2070–99).
Potential Impacts of Climatic Change on
European Breeding Birds
Brian Huntley et al. 2008
Epidemiology of invasion
Multistage process
transport, migration, immigration from origin source to new locals
overcome ’distance’ barriers
survival of individuals
overcome physical and biotic stresses
establishment of population
overcome competetive stresses and
environmental unsuitabilities naturalized in new environment
independent from new ’recruits’ arrival from source
population
adaptation to new environment
invading new environment
spread through new environment by population increase
and dispersal and have an measurable impact on the
ecosystem
Mack et al. 2000
What makes a species successful
The transformation process from an immigrant to
an invader
Lag phase: time span often uncertain:
European beech time lag up to 2000 years after LGM
African bees, time span for lag phase almost not recognisable
A species immigrating into a new area could always transform from
an immigrating into an invasive species.
Every immigrating species is a risk for the ecosystem!
Population size
time
The transformation process from an immigrant to
an invader
Lag phase: hypotheses of its occurring
1) Limits on detecting of small population’s growth
2) Limitation in number and arragements of sub-population occurring as
one meta population.
3) Natural selection among rare/newly created genotypes in new
environments (bottleneck hypothesis for immigrating species)
4) Vagaries / stochastic occurrences of environmental dynamics (small
population rather affected by environmental dynamics than
established populations
If certain population size is reached, threshold for population
size to be defined as established, species could transform into
an invasive species, log phase occurs.
Dlugosch & Parker 2008: genetic bottleneck in invasive species
Literature
study of 80
species
Proportional changes in allelic richness by the year since introduction is known
Epidemiology of invasion
Multistage process
transport, migration, immigration from origin source to new locals
overcome ’distance’ barriers
survival of individuals
overcome physical and biotic stresses
establishment of population
overcome competetive stresses and
environmental unsuitabilities
naturalized in new environment
independent from new ’recruits’ arrival from
source population
adaptation to new environment invading new environment
spread through new environment by population increase
and dispersal and have an measurable impact on the
ecosystem
Mack et al. 2000
What makes a species successful
The transformation process from an immigrant to
an invader
Log phase:
- Species is adapted to biotic and a-biotic environment
- Species developed high competetive strategies among native species
- Species developed higher reproduction rate than competing native species
Bradley et al.2006: Invasive grass reduces
aboveground carbon stocks in shrublands of
Western US. GCB 12, 1815-1822
Ecosystem conversion has changed parts of the western US from a carbon sink to a
source. The increasing importance of invasive species in driving land cover changes
may substantially change future estimates of US terrestrial carbon storage
Non-native annual
grass (cheatgrass)
promoted by
disturbance e.g. fires
and competition
Widespread neophyte plants in Europe
Phytolacca americana
http://www.europe-aliens.org
Carpobrotus edulis Conyza canadensis
Canadian fleabane Hottentot fig
American pokeweed
Epidemiology of invasion
Multistage process
transport, migration, immigration from origin source to new locals
overcome ’distance’ barriers
survival of individuals
overcome physical and biotic stresses
establishment of population
overcome competetive stresses and
environmental unsuitabilities
naturalized in new environment
independent from new ’recruits’ arrival from
source population
adaptation to new environment
invading new environment
spread through new environment by
population increase and dispersal and have an
measurable impact on the ecosystem Mack et al. 2000
What makes the environment vulnerable
Invasive plant
Introduced in Europe in late 19th century as an ornamental
Displaces local vegetation, roots disturb foundations and flood defences,
Reproduces clonaly via rhizomes, majority of plants are female
In the UK, all plants belong to the same clone which also occurs in Europe
http://upload.wikimedia.org/wikipedia/commons/2/23/Riesenknoeterich.jpg http://www.europe-aliens.org/images/factsheetMaps/9_faljap.jpg
Fallopia japonica: Japanese knotweed,
Scale of impacts on species richness
100 50 0
20
10
0
% abundance of Fallopia
nu
mb
er
of
sp
ec
ies
0
20
40
60
80
100
0 100 200 300 400 500
Number of native species
Num
be
r o
f e
xo
tic s
pe
cie
s
Species-Area Relationships S
pecie
s r
ichness (
x+
1)
Island area (km2)
1
10
100
1000
10000
0.001 0.01 0.1 1 10 100 1000 10000
Native
Alien
Source of aliens in Mediterranean islands
0
5
10
15
20
25
30
35
Region
Nu
mb
er
of
Sp
ecie
s
Balearics
Crete
Diversity and ecological equivalence
Aliens functionally different from natives
Agavaceae Simaroubaceae Nelumbonaceae
Cactaceae Phytolaccaceae Mimosaceae
0
20
40
60
80
Thero
phytes
Geo
phytes Hemi
crypto
phytes
Chamae
phytes
Phanero
phytes Succulent
European
Non-European
Nu
mb
er
of
sp
ecie
s
Growth-form (Raunkiaer)
Ant supercolony = super alien colonist
Introduced in Europe in 1920s on imported plants
Spread throughout much of western Mediterranean
Displaces local arthropod fauna, protects pest insects and destroys fruits
Largest supercolony ever recorded, stretches 6000km
Advantages of supercolony: high worker densities, interspecific dominance
100km
Argentine ant (Linepithema humile)
Zebra mussel crossing Europe
First mass invasion of a Ponto-Caspian species
Moved through canal and river networks on barges and boats
Can survive out of water for >2 weeks so spread by boats on trailers
Transforms eutrophic freshwaters via filter feeding resulting in loss of fish
Blocks drains of power and waste systems of power plants
Zebra mussel (Dreissena polymorpha)
Rhododendron ponticum
Glen Etive, Argyll
Rhododendron
introduced 1910
Subsequent
extensive spread
in moorland
along waterways
Re
lati
ve
Bio
div
ers
ity C
ha
ng
e
0.2
Tropical
0
0.4
0.6
0.8
1 Savanna
0
0.2
0.4
0.6
0.8
1
S Temp
0
0.2
0.4
0.6
0.8
1 Grassland
0
0.2
0.4
0.6
0.8
1
N Temp
0
0.2
0.4
0.6
0.8
1 Boreal
0
0.2
0.4
0.6
0.8
1
Alpine
0
0.2
0.4
0.6
0.8
1 Desert
0
0.2
0.4
0.6
0.8
1
Mediterranean
0
0.2
0.4
0.6
0.8
1 Arctic
0
0.2
0.6
0.8
1
0.4
0
0.2
0.4
0.6
0.8
1 Lakes
0
0.2
0.4
0.6
0.8
1 Streams
Barriers - Introductions
• Major geographical (intercontinental) >100km
(human involvement) – Introduction
• Introduced taxa may survive as casuals – can
reproduce but fail to maintain populations over
long periods.
• Casuals rely on repeated introductions
• Environmental barriers (abiotic or biotic) at site of
introduction
Barriers - Naturalization
• Naturalization occurs when
– Environmental barriers do not prevent
individuals surviving
– Barriers to reproduction are overcome
– Naturalised after Barriers A, B, C overcome
– Populations large enough so that the probability
of extinction due to chance events is low
Barriers – Invasion (1)
• Invasion – spread away from sites of
introduction
• Overcomes barriers to dispersal (D) and
barriers in the abiotic and biotic in the area
(E)
• Invade disturbed semi-natural habitats
Barriers – Invasion (2)
• – Invasion into mature undisturbed communities (F)
• Can be aided by for example mutualism – symbionts or mutualistic partners
– Generalistic pollinators
– Generalistic fruit eating species
– Generalistic mycorrhizas
– Nitrogen fixers
What makes a species successful ?
• Weedy e.g.
– ability to reproduce sexually and asexually
– Rapid growth from seedling to maturity
– Adaptation to environmental stress
– Tolerant of environmental heterogenity
What makes a species successful ?
• Plant growth form and habitat
characteristics
– Plant height
– Life form
– Competitiveness
• Broad ecological amplitude
(light/humidity)
What makes a community or ecosystem
invasible or not ?
• Abiotic conditions (e.g. light, temperature)
• Biotic conditions (e.g herbivory)
• Soil resources e.g. nitrogen availability
• Ecosystem stability?
http://blogs.oregonstate.edu/wise/2014/03/13/lionfishs-roaring-impacts-atlantic-ocean-fish-populations/
Lion fish (Pterois volitans) in Atlantic Ocean. Native to Indo-Pacific Ocean,
first found in Atlantic in 1980′s
Probably released by exotic fish aquarium owners off the coast of Florida;
carried northeast to North Carolina and Bermuda by gulf stream current as eggs
or larvae.
Food: anything smaller than them self: fish, shrimp, crabs and octopus.
no natural predator, Start hunt lionfish for food: biomass removal
Interactions Relationship between invader and invaded ecosystem