Download 17 Invasion Ecology 2010

LECTURE 18 INVASION ECOLOGY
Relevant pages in text:
17-18; 195; 287-8; 340; 342; 346-7; 364-5; 402-3; 559-60; 561; 575-7
MAJOR CONCEPTS
1) Invasion occurs in three stages: arrival, establishment, spread
2) Arrival happens by deliberate and accidental introductions by humans
3) Establishment depends on a predictable suite of traits.
4) Spread occurs because of escape from natural enemies, being strong competitor,
or being preadapted to disturbed habitats.
5) Vulnerability of an ecosystem to invasion depends open niches, disturbed habitat,
low species diversity, or little history of predators and competitors (as on islands).
6) Control is sought by use of biological control species, minimizing disturbance,
or use of pesticides/herbicides.
7) Invasive species imperil endangered species and result in biotic homogenization.
I. Definitions
Introduced species: non-native or exotic species moved accidentally or deliberately to
new ecosystem
Invasive species: introduced species that spread after establishment
II. Invasive species threaten native,
Rank #2 in threatening endangered species (# 1 = habitat degradation/loss)
III. ARRIVAL
General mechanisms deliberately introduced
immigrants bring from native country; bring game animals for hunting, domestication
General mechanisms accidentally introduced
ship ballasts; unprocessed wood; fruit shipments; bypass natural barriers
IV. ESTABLISHMENT
A. Traits of introduced species that increase probability of successful establishment
non-specific diet and habitat needs, including microbes
self-fertilization
small body size
high reproductive potential
good competitor
social/gregarious
B. Looking for generalities to make the science predictive
V. SPREAD
A. Hypotheses that explain why an introduced species successfully spreads
escape from natural enemies (predators, parasites, pathogens)
increased competitive ability  outcompete native species
pre-adaptation to disturbed habitats
B. General mechanisms by which introduced species displace (eliminate) native species
act as predator, competitor, parasite, pathogen
modify habitat
promote spread of other invaders
C.Displace native species vs. replace native with invasive species argument
Biotic Homogenization - increasing similarity in species among areas
Habitat loss and modification couple with widespread introduction of a
few species leads to homogenization
VI. Vulnerability of ecosystems to invasion: hypotheses –
Biotic resistance to invasion via high species diversity
Disturbance with fewer species and more open niches allows invasion.
Human areas have many species that have been associated with humans for a long time
Species on islands have little evolutionary history with competitors/natural enemies.
VII. Ecological Costs of Invasion
Displace native species
Alter native species’ interactions
Modify habitat
Change ecosystem processes (e.g. nutrient cycles)
VII Ways to control invasive species
use pesticides/herbicides
biological control – introduce natural enemy from native range
but, if not species-specific to invasive species, may affect other species
minimize disturbance to landscape
VIII. Problem associated with pesticide use
kill more species than targeted invasive species
acts as selective agent for resistance to pesticide
pose health risk to humans
IX Prevention of problems arising from invasive species
Education
Research for generalities
Monitor for early detection
Use quarantine once found so does not spread
Increase regulations/inspections