Transcript Invasion
Invasion Ecology
Marjorie Becus
Invasive species are troublesome.
• Currently 97 invasive plants in E. North America3
• 10,000 person hours in Smoky Mountain National Park1
• In the US, costs of ~ $137 billion per year2
1 http://www.invasive.org/eastern/
2 Webster
et al. (2006). Journal of Forestry 104: 366-374.
3 Pimental et al. (2000). BioScience 50: 53-65.
Invasive species are troublesome.
They…
• reduce native species diversity, richness, etc.
• alter the way ecosystems work.
http://www.fs.fed.us/invasivespecies/
http://tncinvasives.ucdavis.edu/
The invasion process involves
three general phases…
Regional Invasive Species Pool
Proliferation
{
Dispersal
#1
Proliferation
Colonization
#2
#3
habitat space
Nascent Foci
Invasion & Other Processes:
- Invasion causes ecosystem alteration- but it can also be a
consequence of other (alteration) processes.
Invasional Meltdown
Colonization
Invasion Ecology: General Questions
- How are species able to dominate the
habitats they invade?
- What impacts do invasive species have on
species diversity and ecosystem processes?
- What determines the invasibility of habitats?
Theories explaining why/how species become invasive
Natural enemies escape
(Predator escape)
Exotics are released from natural enemies
that control their population.
Evolution of invasiveness (EICA)
Exotics go through rapid genetic change
due to new environments.
Empty (vacant) niche
Exotics use resources that are left
available by absent natives
Novel Weapons
Exotics bring novel ways of biochemical
interactions to recipient communities.
Invasion Ecology: General Questions
- How are species able to dominate the
habitats they invade?
- What impacts do invasive species have on
species diversity and ecosystem processes?
- What determines the invasibility of habitats?
Bush honeysuckle (Lonicera maackii)
Range
http://web.utk.edu/~vrudis/nnis/f2105.jpg
Bush honeysuckle (Lonicera maackii), does bad things to good plants...
• reduces diversity of native plants
• reduces fecundity of native herbs
• reduces growth of native seedlings
• inhibits germination of native seeds
• Etc
Invasive species impacts (insects)
Highly polyphagous
http://www.fs.fed.us/ne/morgan
town/4557/gmoth/atlas/quar1a.
gif
Invasive species impacts (insects)
Specialist
http://www.emeraldashborer.info/
buprestid
Invasive species impacts (fungi)
At the end of the 1800s:
- American chestnut was
found throughout much of the
Eastern Deciduous Forest.
- Chestnut was among the
largest of eastern trees.
- And formed pure stands.
(> 80 % Basal Area in some stands)
Range of American chestnut
From: Paillet and Rutter (1989)
- In 1904, chestnuts in the New
York area began exhibiting a
previously unknown canker.
Photos from The Canadian Chestnut Council:
- This disease, caused by the fungal
pathogen Cryphonectria parasitica, spread
throughout the native range of the
American chestnut.
- By 1960, chestnut had been rendered
functionally extinct as a canopy tree
throughout its native range.
Invasion Ecology: General Questions
- What are the features that enable species to
become invasive?
- What impacts do invasive species have on
species diversity and ecosystem processes?
- What determines the invasibility of habitats?
Regional Invasive Species Pool
Landscape matrix
Presence of edge
Land-use history
Various
modifications
Site characteristics
Dispersal in space
Dispersal in time
Colonization and
proliferation potential
Site Specific Invasion Intensity
habitat space
Site modification by
invasive species
Invasion Ecology