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Species Invasions
Photo of the Panama Canal from www.pancanal.com
Native & Non-Native Species
Native (indigenous) – an organism (or organisms) that came
to be found in a given place by natural causes
Non-native (exotic, introduced, non-indigenous) – an organism (organisms)
that came to be found in a given place
by anthropogenic causes
Wild Turkey
Native to N. Am. (e.g., LA)
Photos from Wikipedia
Common Pheasant
Native to Asia;
Introduced to N. Am. (e.g., LA)
Domestic Chicken
Wild progenitor = Red Junglefowl,
native to Asia;
Domesticated & introduced to
N. Am. (e.g., LA)
Native & Non-Native Species
Range expansion – natural process whereby a species
immigrates into a given place that was previously
unoccupied by that species
Cattle Egret
Original range = western Europe,
plains of Africa, tropical & subtropical Asia;
Flew across Atlantic to northeastern South America – 1877;
Arrived in FL – 1941;
First bred in FL – 1953;
First bred in Canada – 1962
Considered native to N. Am. (e.g., LA)
Photo from Wikipedia
Native & Non-Native Species
Re-introduction – anthropogenic placement of a
species into a given place that was previously
occupied by that species
American bison
subsp. Plains bison
Original range = plains, prairies &
savannas of N. Am. (incl. LA)
There may not be sufficient appropriate
habitat available in LA to re-introduce
American bison
Photo from Wikipedia
Invasive Species
Your textbook’s definition: Introduced species
More commonly used definition: An introduced species that
establishes, expands its range, and has an appreciable
impact on native organisms & ecosystems
We don’t normally
consider these
two introduced
species to be invasive
Common Pheasant
Native to Asia;
Introduced to N. Am. (e.g., LA)
Domestic Chicken
Wild progenitor = Red Junglefowl,
native to Asia;
Domesticated & introduced to
N. Am. (e.g., LA)
Invasive Species
Your textbook’s definition: Introduced species
More commonly used definition: An introduced species that
establishes, expands its range, and has an appreciable
impact on native organisms & ecosystems
But cats often become
devastatingly invasive
when feral
Pair-wise Species Interactions
Influence of species A
Influence of Species B
A
-
- (negative)
0 (neutral/null)
-
0
-
A
-
B
Competition
Amensalism
-
0
A
B
0
A
B
A
B
Antagonism
(Predation/Parasitism)
+
A
B
0
0
Amensalism
Neutralism
(No interaction)
Commensalism
-
0
+
0
+
B
+ (positive)
+
A
B
+
Antagonism
(Predation/Parasitism)
From Abrahamson (1989); Morin (1999), pg. 21
A
B
+
Commensalism
A
+
Mutualism
B
Invasive Species – Examples
Parasites (disease organisms & other microbes,
including infectious non-living particles) – e.g., HIV
~ 25 million human deaths since it was first recognized in 1981;
0.6% of humans infected (~40.5 million)
Native to western Africa
Introduced globally
Scanning electron micrograph of virus particles (green) and lymphocyte from Wikipedia
Invasive Species – Examples
Competitors – e.g., Eurasian zebra mussel
U.S. Coast Guard estimates economic losses and control
efforts cost ~ $5 billion annually in the U.S.
Outcompetes native mollusks
Native to Russia
Introduced to N. Am., etc.
Photographs of color morphs from Wikipedia
Invasive Species – Examples
Predators – e.g., brown tree snake on Guam
9 of the island’s 11 native forest-dwelling bird species
are now extirpated (extinct on Guam)
Native to southeast Asia
Introduced to Guam
Image from http://www.fort.usgs.gov/Resources/Education/BTS (see this Web page for more info.)
Introduced, Exotic & Invasive Species
…illustrate the physical interconnectedness of the planet
& “homogenize” the planet’s biota
Today we live in the…
“Anthropocene”
Paul Crutzen
“Homogocene”
“New Pangaea”
(temporal focus)
(spatial focus)
Gordon Orians
Harold Mooney
Photo of Crutzen from Wikipedia; Orians from The Nature Conservancy; Mooney from Stanford
Organisms with Large Impact
Foundation species – a species that “defines much
of the structure of a community” (Dayton 1971)
Photo of bamboo forest from Wikipedia
Organisms with Large Impact
Keystone predator – helps maintain diversity by reducing opportunities
for competitive exclusion (Paine 1966)
Keystone resource – helps maintain diversity by providing food to many
species, especially during lean times (Terborgh 1986)
Photo of Pisaster starfish from www.royalbcmuseum.bc.ca ; Photo of barbet feeding on figs from Wikipedia
Organisms with Large Impact
Ecosystem engineer – creates or significantly
modifies habitats (Jones et al. 1994, 1997)
Allogenic (physical modifications through their activities)
Autogenic (modifications through the presence of their biomass)
Photo of beaver from Wikipedia; Map of North American native range from www.icwdm.org;
Map of Tierra del Fuego (introduced range) from www.student.britannica.com
Impacts of Non-Native Species
Impact = Range x Abundance x per-capita Effect
I=RxAxE
(Parker et al. 1999)
Photo of beaver from Wikipedia; Map of North American native range from www.icwdm.org;
Map of Tierra del Fuego (introduced range) from www.student.britannica.com
Impacts of Non-Native Species
Direct & indirect effects
–
+
+
+
–
+
Mosquitoes
Photos from Wikipedia
Ecological & evolutionary effects
Consider the potential evolutionary
consequences of reduced daytime
predation on mosquito behavior,
e.g., increased daytime activity
Scale & Scope of Biological Invasions
North American plains and prairies = 11% of plant spp.
Hawaii = 35% of plant spp.
Successful invaders in San Francisco Bay = 1 marine sp.
every 14 wk (1961 to 1995)
Rate of introduction of crustracean zooplankton into Great Lakes region
~50,000 times background natural immigration rate
San Francisco Bay & Great Lakes illustrate that the
rates are (much) higher than natural rates
Refs.: White et al. (2000); Pimentel et al. (2000); Cohen & Carlton (1998); Hebert & Cristescu (2002)
How are species introduced?
Intentional – agriculture, hunting, fishing, ornamental, etc.
Unintentional – transport (airplanes, ships, cars, shoes, etc.),
escaped pets, etc.
Photo of cornfield from www.ugogrill.com; Photo of the Panama Canal from www.pancanal.com
Successful Invasions
Under the right conditions any community can be invaded and
any organism can be a successful invader somewhere
Potential invaders begin as rare populations, faced with the same
disadvantages of any small population (e.g., demographic
stochasticity, Allee effects, inbreeding, etc.)
Photo of kudzu (Pueraria lobata) in Georgia from Wikipedia
Successful Invasions
Passing Through Filters
Regional species pool
Past
Present
A B C D E F G H I
A B C D E F G H I
Anthropogenic
introductions
Biogeographic filter
F G H I
Physiological filter
Biotic filter
Local assemblage
A B C
A B C
See Fig. 9.9, pg. 307 of Groom et al., Principles of Conservation Biology, 3rd ed.
H I
Successful Invasions
Escape / Release from Enemies
molluscs
crustaceans
amphibians & reptiles
fish
birds
mammals
Standardized S of parasites
in introduced range
Parasite species richness (S, shown below) and parasite
prevalence (% infected hosts) showed similar patterns
1.0
0.5
0
0
Redrawn from Torchin et al. (2003) Nature
1.0
0.5
Standardized S of parasites
in native range
Successful Invasions
Making Predictions (it’s a multi-variate problem)
Traits of organisms
(Not surprisingly one of the best “traits” for predicting
invasiveness is whether the species
is invasive elsewhere)
Characteristics (biological and physical) of focal site
E.g., Elton’s (1958) biotic resistance hypothesis
(species-rich communities are more resistant to invasion)
Photo of marine toad (Bufo marinus) from Wikipedia
Successful Invasions
Many hypotheses…
Mechanisms of invasion success (some based on traits of organisms,
some based on characteristics of the environment):
Enemy release
Biotic resistance
Evolution of increased competitive ability (EICA)
Darwinian pre-adaptation (e.g., extended leaf phenology)
Novel weapons (e.g., allelochemicals)
Horticultural selection
Resource availability
Etc.
Synergistic Effects: Invasional Meltdown
“a process by which a group of nonindigenous species facilitate one another’s
invasion in various ways, increasing the likelihood of survival and/or of
ecological impact, and possibly the magnitude of impact”
Daniel Simberloff
(rec’d. Ph.D. 1969;
E. O. Wilson’s student who
experimentally investigated the
Theory of Island Biogeography on
mangrove islands in Florida)
Definition from Simberloff & Von Holle (1999); photo from www.conservationbytes.com
Synergistic Effects: Invasional Meltdown
E.g., yellow crazy ants on Christmas Island, Australia
Native red crabs drive ecosystem processes
Exotic yellow crazy ants kill red crabs
Crazy ants also associate with introduced scale insects to exacerbate damage
Photos from http://www.environment.gov.au
Synergistic Effects: Invasional Meltdown
E.g., yellow crazy ants on Christmas Island, Australia
(a) Uninvaded site
(b) Invaded site, 1-2 yr after
ant invasion
Figure from O’Dowd, Green & Lake (2003)
Control of Introduced & Invasive Species
Physical control
Chemical control – E.g., chlorine
bags over Caulerpa in CA
Biological control – Presents the paradox of adding species
(“diluting” natural biodiversity) to control or remove other species
Invasion prevention – use the Precautionary Principle
Photo of Caulerpa from www.outernode.pir.sa.gov.au
Legislation
National Invasive Species Council’s
National Invasive Species Management Plan
Established by a Clinton Executive Order, 1999;
Coordinates all U.S. federal activity
and legislation on introduced species;
Updated every 2 yr
National Invasive Species
Information Center
Looking ahead towards our climate change lecture…
News report from National Public Radio
“Belief in Climate Change Hinges on Worldview,” aired Feb. 23, 2010
Suggests that education alone may not
be sufficient to change persons’ opinions
(e.g., on subjects relevant to Conservation Biology)
Does that sound like something Aldo Leopold would say?