Invasive Species as a global threat to biodiversity
What prevents species from dispersing globally?
Geographic Barriers:
Oceans
Mountains
Deserts
Large Lakes
Barriers are in the eye of the beholder: what is a
barrier for one species is not a barrier to another
e.g. mountains may restrict plant distributions, but not birds
Limits to Dispersal
• Wallace identified 6 global biodiversity realms, each
different from the other.
•Neotropical, Nearctic,
Palearctic,
Ethiopian
Oriental
Australasian
Invasive Species: Species introduced to regions
outside of their historic native range;
Species are being transported across these
barriers at an increasing rate owing to human
movement and commerce (50,000 times greater
rate of spread than by natural dispersal in some
cases) major vectors are planes, ships and
humans
Invasive Species:
• What are they?
• Why should we care?
• ecological concerns
• human, plant and animal health
• economic concerns
What are invasive Species?
• Invasive Species
– implies exotic and a threat to native species
• Exotic Species
– from another part of the world
• Introduced Species
– implies introduction but not a threat
• Alien Species
– Implies introduction to a particular ecosystem
Classical Model of Invasion
Natural Colonization
Establishment requires dispersal across barriers, colonization in acceptable
number, and successful reproduction
Natural colonization and human-mediated
invasion
from Rahel (2002), Homogenization of freshwater faunas. Ann. Rev. Ecol. System.
What allows invaders to invade?
• Only some novel species will survive and
establish self-sustaining populations in the novel
habitat.
• A subset of these species may not only survive,
but become invasive, dominating the new
community and even causing the extinction of
natives.
• But, what allows a species to become invasive?
What allows invaders to invade?
Broad Environmental Tolerance
- posses life history traits that confer superior
colonizing ability or ability to acclimate to a wide
range of habitats.
Local Adaptation
- readily adapt to local selective pressures.
Sexton et al. 2002. Ecological Applications 12: 1652-1660.
Evolution of Increased Competitive
Ability Hypothesis (EICA)
• As applied to plants –
• Under identical growing conditions, species will
produce more biomass in an area where it has
been introduced vs. in its native range.
• Invasive species will exhibit lower herbivore
defense rates in introduced range than in native
range.
• A species is not as fit (in its native habitat) at the
time of introduction vs. when it becomes invasive.
Blossey and Notzold. 1995. Journal of Ecology 83(5):887-889.
Chinese Tallow Tree (Sapium sebiferum)
• Introduced to SE US in 1700s from China
• Soap from seed oils  ornamental
• Naturalized throughout much of South
• Alters access to light for other plants
• Leaves contain toxins that can kill other plants
• Creates monospecific stands
Chinese Tallow Tree: A Test of EICA hypothesis
• Collected seeds from native and introduced
ranges
• Seeds planted and raised for ~ 1 year in native
range
• Measured growth and herbivore leaf damage
• Compared native plants with individuals from
introduced range
Zou et al. 2006. Oecologia 150:272-281.
Chinese Tallow Tree (Sapium sebiferum)
Sapium has evolved reductions in defense allocation and
increased growth and reproduction in the absence of
herbivores in its introduced range.
Growth
• Shoot mass, root mass and total mass
higher in invasive range
• Leaves tended to be more damaged by
herbivores when grown in native range
Leaf Damage
Do invasives evolve?
Experimental design
• Collected seeds from source trees in
China(native range), Georgia, Texas
and Louisiana.
•
grown in field for 14 years and then
measured size, seed production, leaf
chemistry and defense chemicals.
18th century
early 20th
century
Siemann & Rogers. 2001. Ecology Letters 4:514-518.
Tallow Tree EICA Results
• Native genotypes were less vigorous than invasive
genotypes. Propagules from areas of recent invasion
produced largest genotypes.
• Foliage from native genotypes was of ~ higher quality
and had greater concentrations of defense compounds.
20th century
17th century
native
Siemann & Rogers. 2001. Ecology Letters 4:514-518.
Invasion model
Species frequency
• Plasticity and adaptive evolution can lead to
greater invasiveness
Introduced
Local
adaptation
Phenotypic
plasticity
Naturalized
Lag
Invasive
Sexton et al. 2002. Ecological Applications 12:1652-1660.
Why should we care?
Causes of Global Species Endangerment
All Species
Marine Species
Lawler et al. (2006), Frontiers in Ecology & the Environment
1.0
Drivers
of
Species
Change
Lakes
1.0
0.5
0.5
0.0
0.0
1.0
Arctic
1.0
0.5
0.5
0.0
0.0
1.0
Temperate
Forests
1.0
0.5
0.5
0.0
0.0
Streams
Boreal
Grassland
Invasive Species a major threat to some systems (Sala et al. Science 2000)
Impacts of Invasive Species and
Changes in Biodiversity
Chapin et al. 2000. Nature 405: 234-242.
Negative Impacts of Invasive Species
Ecosystem Level Impacts
• Disturbance Regimes
• Hydrology: Alterations of Water Regimes
• Geomorphological processes (erosion, sedimentation)
• Soil chemistry
Community or Population Level Impacts
• Habitat structure
• Community composition
• Resource competition
• Population reductions, eliminations
• Genetic Impacts
Alteration of disturbance regimes
1) cogon grass (Imperata cylindrica): increases vulnerability
of vegetation to fire, which it itself is invulnerable to since it
regenerates quickly from belowground rhizomes (roots);
result is that the plant completely takes over the region.
Alteration of disturbance regimes
Hydrology: alteration of water regimes
salt cedar (Tamarisk): absorbs large quantities of water
along riverbanks in arid regions, and excretes salt into soils;
forms monocultures.
Gaskin and Shaal. 2002. PNAS 99(17): 11256-11259.
Soil chemistry
Zou et al. 2006. Oecologia 150: 272-281.
Community or Population Level Impacts
Community Composition and Structure
a) Predation
b) Competition
c) Parasitism
d) Disease
Homogenization of Flora and Fauna
Introduced species
X
extirpated species
Rahel (2002), Homogenization of freshwater faunas. Ann. Rev. Ecol. System.
Homogenization of Flora and Fauna
•
more species change due to introduction of
nonindigenous fishes than to loss of native fishes
•
this pattern may not be general - may vary from system
to system
E. Taylor, Canadian Journal of Fisheries and Aquatic Sciences (2004)
Predation
Lake Victoria, Africa
• introduced Nile perch drove hundreds of cichlid fishes extinct
• current problem with introduced water hyacinth (plant) from S. America
largest lake in
Africa
Nile perch
hyacinth: spread from 300 to
700Ha coverage in 2007
cichlid fish
Predation
Island of Guam
• brown tree snake (Boiga irregularis) introduced accidentally
•Species moved across the island, preying on and eliminating
native birds, which evolved in the absence of predators and lacked
the ability to fly
Predation
Competition
Zebra mussels (Dreissena) eliminated
native unionid mussels from Lake St. Clair
Zebra mussels swept from S to N in L. St.
Clair, wiping out native mussels as they
dispersed across the lake.
Nalepa (1994) Can. Jour. Fish. Aquatic. Sci.
Parasitism
South Pacific snail Partula turigida driven extinct
following infection with microsporidian parasite called
Steinhausia
This followed population decline caused by human exploitation of the shells
and predation by introduced biological control agents (another snail)
Cunningham and Daszak (1998) Conservation Biology
Human, Plant and Animal
Diseases
• Cholera spread (e.g. Peru from India)
• West Nile Virus (spread by birds and mosquitoes)
• Dutch Elm disease (fungus arrived with beetles
from Europe)
• Chronic Wasting Disease (affects cattle in Alberta)
• Infectious Salmon Anemia (came to farmed
salmon in N.B. from Europe)
• SARS and HIV in humans
Disease
Dogwood anthracnose: wilt and death caused by Discula destructiva
Dutch elm disease (beetle transmitted fungus Ophiostoma ulmi, that kills
American elm)
Economic Impacts
Along with irreplaceable
losses to biodiversity Billions per year from
• Lost agricultural
productivity
• Lost forest productivity
• Lost recreational
opportunity
Pimental et al. 2005. Ecological Economics 52:273-288.
Notable invasive species in Essex County
Phragmites
European starling
house sparrow
zebra mussel
sea lamprey
purple loosestrife
emerald ash borer
Invasive Species in the Great Lakes
175
150
125
100
75
50
25
2010
1990
1970
1950
1930
1910
1890
1870
1850
0
1830
Cumulative number of invasions
200
Ricciardi (2006), Canadian Journal of Fisheries and Aquatic Sciences
Number of Species
Invasion History in Great Lakes
45
40
35
30
25
20
15
10
5
0
Fish
Algae
Plants
Invertebrates
Early dominance by plants, currently most new invaders are invertebrate animals
Holeck et al. (2004), Bioscience
Invasion Vectors post-1959 (Seaway opens)
ships
9
(wind, waterfowl)
13
Ships are implicated in 75% of NIS invasions since 1959
Holeck et al. (2004), Bioscience
Our Lakes are Vulnerable
Asian Carp Are Poised to Enter the Great Lakes
1) Bighead Carp
- 3 found in Lake Erie in 2000
- sold live in Asian food markets in Toronto
2) Silver Carp
restrictions on sale of live fishes in Ontario since 2005
Ballast Water in Ships
• Ships loaded with cargo
called are stable and do
not need ballast water
• Ships without cargo
carry ballast water to
increase stability
• Probably the single
biggest source of
invasive species
globally (when
combined with hull
fouling species)
Opening of the St.
Lawrence Seaway 1959
with water from the 7
Seas of the world
...little did they know
what they were doing
Welland Canal opened in 1959, allowing large
ships into Lakes Ontario, Erie, Huron, Michigan
Nonindigenous animals established in the Great
Lakes drainage since the mid-1980s
Common name
Year
of
Discovery
Ruffe
1986
Zebra mussel
1988
Quagga mussel
1989
Rudd
1989
Round goby
1990
Tubenose goby
1990
New Zealand mudsnail
1991
Echinogammarus amphipod 1994
Sphaeromyxa sevastopoli protist 1994
Scolex pleuronectis cestode 1994
Ichthyocotylurus pileatus trematode1994
Blueback herring
1995
Heteropsyllus nr. nunni
1996
Acineta nitocrae ciliate
1997
Cercopagis waterflea
1998
Daphnia lumholtzi
1999
Schizopera borutzkyi
1999
Nitocra incerta copepod
1999
3 testate rhizopod spp.
2003
Gammarus tigrinus
2003
Endemic
region
Mode of
transfer
Probable
donor
region
Ponto-Caspian Ballast water Danube River
Ponto-Caspian Ballast water Baltic Sea
Ponto-Caspian Ballast water Black Sea
Eurasia
Bait release
-Ponto-Caspian Ballast water Black Sea
Ponto-Caspian Ballast water Black Sea
New Zealand
Ballast water Baltic Sea
Ponto-Caspian Ballast water Baltic Sea
Black Sea
Ballast water Black Sea
Black Sea
Ballast water Black Sea
Black Sea
Ballast water Black Sea
Atlantic, N.A.
Canal
Atlantic N.A.
Atlantic N.A.
?
Atlantic N.A.
Eurasia
Ballast water Black Sea
Ponto-Caspian Ballast water Baltic Sea
Africa
Fish?
Ohio Reservoirs
Ponto-Caspian Ballast water Danube River
Ponto-Caspian Ballast water Black Sea
Ponto-Caspian Ballast water Eurasia
Atlantic, N.A.
Ballast water Atlantic N.A.
Invaders use ‘Corridors’ to the Great Lakes
Baltic and North Sea ports are major sources of ships for the Great Lakes;
most of our invaders began in the northern Black Sea region
How can we determine where invasive
species originated?
1. Track the vector: look at import: export
records
2. Look at pathways that airlines & ships utilize
3. Assess at genetic composition of the
populations in introduced areas and source
areas
Eurasian distribution of the fishhook flea
• Native to Aral and Caspian Lakes, Azoz and Black
Seas
• Introduced to several rivers and Baltic Sea
• Discovered in Lake Ontario in 1998
fishhook flea, Cercopagis pengoi
MacIsaac et al. (1999), Can. J. Fisheries and Aquatic Sciences
Cercopagis distribution
1998
1999
2001
2002
MacIsaac et al. (1999), Can. J. Fisheries and Aquatic Sciences
Cercopagis invasion genetics
mitochondrial ND5 gene
Hebert & Cristescu (2002), Can. J. Fisheries and Aquatic Sciences
Animal and protist NIS ‘hotspots’ in the Great Lakes
Ships discharge mainly into Lake Superior, yet most invasions are focused in
the Huron-Erie corridor
Grigorovich et al. (2003), Canadian Journal of Fisheries and Aquatic Sciences
Spiny waterflea invasion history in Ontario
Year
MacIsaac et al. (2004), Ecological Applications
Distribution of spiny waterfleas in Canada (2005)
Ontario
Minnesota
Michigan
+ 13 new reported invasions in 2006
Ohio
N. Yan, pers. comm.
Crustacean Richness (spp.sample
-1
)
Invasion causes a decline in zooplankton
diversity in Harp Lake, Ontario
spiny waterflea
invades
12
11
10
Pre-invasion mean
9
8
Post-invasion mean
7
80
~ 20% loss
in species
richness
85
90
95
Year
Dr. Norman Yan, York Univ.
Waterflea infestations are a major nuisance for
commercial fishermen on Lake Erie
Overland transport mechanisms
Bythotrephes:
• Fishing/Downrigger lines
• Bait buckets
• Live well water
• Bilge water
• Macrophytes attached to boat
What can be done?
Grigorovich et al. (2003), Canadian Journal of Fisheries and Aquatic Sciences