Transcript Invasive Species - University of Georgia

Invasive Species
Ecol 6080 Fall 2009
Conservation concern is with species that are greatly
expanding their range while reducing the populations of other
species or degrading the ecosystem. They may be native
species expanding their range or population (white-tailed deer).
Most commonly they are non-native species that are colonizing
a new disjunct range ( English Sparrow, fire ants, cogongrass,
etc.)…and this is our primary focus.
We will refer to these species as native invasives or non-native
invasives. Note that this classification differs from your
textbook.
Generally, the use of the term “alien species” is no longer used
because it carries too much political baggage.
The vast majority of species that arrive in a new habitat do not
become established. (Rule of 10)
Of those that do become established, most are not
considered invasive in our sense of the term (teasel)
Only a small fraction of species that arrive in a new habitat
become invasives. But, they can cause major environmental
problems (fire ants, cogon grass, tallow trees, hydrilla, etc)
Some problems caused by invasives
• competitive exclusion (cogongrass)
• disrupting pollination syndromes
(chinese tallow)
• lowers (increases) nutrient cycling
• changes ecological function (zebra
mussel)
• severe predation rates (mongoose)
• increase disease (pathogens are
invasive species)
Etc etc etc
Are invasives always “bad”?
What if they are N-fixers and enrich low nutrient
soils? Lespedeza enriches piedmont soils
What if they provide resources for other species?
Chinese tallow supports pollinators.
What if they “jump start” restoration?
Guava in tropical pastures
Important to be specific about the ecological effects
Of invasive species.
European Teasel
An introduced non-native, non-invasive
Teasel flowers in a spiral
Teasel dry seed head
Teasel seeds Note: elaiosome on seed
Ant dispersed !
Fire Ants…scourge of the South!!
Red Imported Fire Ant
Solenopsis invicta from seasonally flooded
areas in southern Brazil and Paraguay
Affects native ants, seed dispersal, wildlife,
Soil mixing and structure
Major natural biological control is S.
(Diplorhoptrum) spp.
Shift from single queen to multiple queen
colonies
Workers highly polymorphic and exhibit mass
recruitment
queen
Fire ant mounds have
radiating tunnels for
foraging and water. They
are adapted to
disturbances such as
floods. Now, many
mounds may have
hundreds of fertile queens.
Fire ants have hydrophobic cuticle allowing them to float
during floods.
Polygyne colonies
Fire ants eat the eggs of endangered
Florida snails
Fire ants kill the nestlings of ground and
shrub nesting birds.
Fire ants have invaded the dark blue and
can invade the light blue areas of Australia
S. (Diplorhoptrum) spp. “thief ant” predator on queens
Phorid flies attack
and decapitate
ants. Possible
biological control
for fire ants???
Fire ants: some general lessons
for invasive species
•
Evolution is important and small genetic
changes can have big ecological effects
• Chemical controls can have unforseen consequences
• Biological control has to be integrated and can’t be
recalled
• Source areas can subsidize populations in sink areas
• Large population and high dispersal rates mean that
novel habitats are frequently “sampled”
• Politics and human behavior can’t be ignored
Guam and spread of Boiga and the loss of
forest bird species
What is a common
characteristic of the species
that persisted after the
invasion of the Brown tree
snake???
ZAP !!!
Electrical outages caused by
brown tree snake on Guam
The Brown Tree Snake has become
increasingly diurnal.
Peak activity occurs during day and night
time hours of minimal electrical demand.
An evolutionary shift? Possible because
native birds have no experience with snakes
and so snakes are efficient predators day
and night. Will this change?
Collinsia parviflora vs. introduced
Plantago lanceolata
Evolutionary shift??
Bumblebee pollination of native Stachys palustris
Stachys
Impatiens
Disease as an agent to control invasive species
Impact of invasive depends
on environmental context
An example with comb jellys
Meniopsis
• A comb jelly (Ctenophore) native to
Atlantic of North America
• Arrived in Black Sea in ballast water
• Later arrival in brackish Caspian Sea
• Decimated zooplankton
• Predator Ctenophore Benoe
arrives in Black and then Caspian Sea
Benoe…the predator
Meniopsis: Lessons
Learned
• Meniopsis disrupted ecosystem processes
from bottom up
• Fishing collapsed in Black Sea
• Arrival of predator Benoe controlled
Meniopsis and fishing returned in Black
Sea
• Benoe did not control Meniopsis in
Caspian Sea because couldn’t tolerate
lower salinity
Chinese tallow trees
Benjamin Franklin’s curse
Charitably called
The Popcorn Tree
Sapium sebiferum
Chinese tallow
Forms dense coastal
thickets
Toxic leaves..no
insects for migratory
birds
Flowers attract many
pollinators
Wild boars and feral pigs
• Most common in southeast and
Pacific coastal mountains of U.S.
• Major mortality on acorns and
small plants
• Facilitate invasion of toxic or
spiny invasive plants (inedible)
Unintended consequences
• Knapweed X seed weevil X field mice X
native grass seeds
Knapweed controlled by introduced
weevil
Knapweed infestation
Gall seed
Normal seed
Gall fly ovipositing
Deer mice eat up 5000 galls/night. Mouse
population grows. Seeds of native grasses are
depleted. Free of competition, knapweed
increases more rapidly. Large populations of
field mice positive for sin nobre hantavirus.
Invasives: general themes
• Initial population growth slow due to:
Poor local adaptation (selection and gene recombination)
Inbreeding depression
Mating structure (Allee Efect)
Stochastic extinction of small populations
• Success due to:
Invading with low loads of predators (?), competitors (?),
pathogens
Generalized habitat/nutritional requirements
Colonization of natural areas subsidized by large populations in
disturbed habitats
Initial establishment in habitats with a recent history of biodiversity
losses
When considering a response to an
invasive species, a manager
should ask….
1. Is the process of control destructive
to other species?
2. Is the probability of success high?
3. Will this be a continuing effort?
4. How significant are the negative
effects of the invasive species?