Invasive Species

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Invasive Species

• Ecol 6080 Fall 2009

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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.
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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)
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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
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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.
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European Teasel
An introduced non-native, non-invasive
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Teasel flowers in a spiral
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Teasel dry seed head
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Teasel seeds Note elaiosome on seed Ant
dispersed !
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Fire Antsscourge of the South!!
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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

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Workers highly polymorphic and exhibit mass
recruitment
queen
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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.
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Fire ants have hydrophobic cuticle allowing them
to float during floods.
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Polygyne colonies
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Fire ants eat the eggs of endangered Florida
snails
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Fire ants kill the nestlings of ground and shrub
nesting birds.
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Fire ants have invaded the dark blue and can
invade the light blue areas of Australia
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S. (Diplorhoptrum) spp. thief ant predator on
queens
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Phorid flies attack and decapitate ants. Possible
biological control for fire ants???
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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
  cant 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 cant be ignored

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Guam and spread of Boiga and the loss of forest
bird species
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What is a common characteristic of the species
that persisted after the invasion of the Brown
tree snake???
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ZAP !!!
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Electrical outages caused by brown tree snake on
Guam
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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?
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Euphydryas editha ovipositing on native Collinsia
parviflora vs. introduced Plantago lanceolata
Evolutionary shift??
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Bumblebee pollination of native Stachys palustris
Impatiens
Stachys
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Disease as an agent to control invasive species
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Impact of invasive depends on environmental
context

• An example with comb jellys

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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

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Benoethe predator
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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 couldnt
tolerate lower salinity
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Chinese tallow trees

• Benjamin Franklins curse
• Charitably called
• The Popcorn Tree
• Sapium sebiferum

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Chinese tallow Forms dense coastal
thickets Toxic leaves..no insects for migratory
birds Flowers attract many pollinators
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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)

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Unintended consequences

• Knapweed X seed weevil X field mice X
• native grass seeds

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Knapweed controlled by introduced weevil
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Knapweed infestation
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Normal seed
Gall seed
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Gall fly ovipositing
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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.
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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
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• When considering a response to an invasive
  species, a manager should ask.
• Is the process of control destructive to other
  species?
• Is the probability of success high?
• Will this be a continuing effort?
• How significant are the negative effects of the
  invasive species?