Invasion Ecology Flashcards
(41 cards)
Invasion Ecology
Not just invasive species
Whole new subject area studying the whole process of invasion
- Exponential increase in research and citations around early 1990’s
Invasion Process
Transport: Death/captivity or Successful Introduction
Establishment: Fail or Establish Successfully (Japanese Knotweed)
Spread: Remain Local (Holly/English Daisy) or spread
Impact: Low or High(Scotch broom and Daphne) (can depend on human perception such as blackberries are yummy!)
What is currently happening in the Comox Valley regarding Introduction?
Saltmarsh Cordgrass has been introduced from California and is replacing native Distichilis. Cordgrass is very aggressive.
Guam Invasion
Pre 1945: 25 species with 18 native and 7 introduced
1965: Addition of brown tree snake brought total species to 28 with 18 native and 10 introduced, major impacts on food web
1995: Introduction of brown tree snake sent food web to hell after the only predator was eliminated (preyed on each other), Total 12 species with 4 native and 8 introduced
What is the most major anthropogenic cause of invasion?
Shipping routes and abundant trade
Either purposeful or accidental
Many caused by Europe
Hub and Spoke Invasion Theory
A hub port is at the center (eg Vancouver) with primary invasion
- From there, nearby ports can be invaded (Nanaimo, Victoria)
- Other Sites for secondary invasion can occur on export routes from the hub port
When did invasions really start to exponentially accumulate in most places?
Later 1800’s as shipping significantly increased. Correlation.
4 main causes of adverse impact on native fish (ie salmon)
- What may surpass all of those traditional impacts?
- Habitat Alteration (largest impact)
- Harvest (over-harvest)
- Hatcheries (Reduce genetic diversity)
- Hydro-systems (small or large)
- Non-indigenous species may exceed or equal the previous impacts
What is the U.S. ESA?
Endangered Species Act
- A real Act that is enforced and has power in the courts
- Number of invasive species correlates to more native fish added to the ESA
How are non-indigenous fish introduced?
What are the main introduced species that affect aquatic habitat?
Often purposefully for sport fishing purposes (Yummy)
- Brook Trout
- Walleye
- American Shad
- Freshwater Bass
- Channel Catfish
Main problematic species that are not fish?
- NZ Mudsnail
- Siberian Freshwater Shrimp
- Eurasion water Milfoil (Transported by boaters)
- Purple Loosestrife (Shifts hydrology and plant composition, forming a monoculture)
Reconstruction of the 1500’s exploration by Sir Francis Drake
- Easily transported marine inverts
- B/c ship sat on bottom of bay at low tide (picking up sedentary bottom dwellers)
- Most of these bays now have similar species composition - So which are the native ones? Most have naturalized
Where are the majority of invasive species found and why?
Temperate regions because there are more people (and potentially more land mass)
- Temperate regions are less extreme and easier to survive (introductions drop off as you go north from temperate areas)
Transportation routes and impacts
Most import routes are unidirectional
- Pacific Asia & NA frequently exchange species
- Areas around ports and islands are hit hardest b/c of the shipping
Hawaiian impacts
- Six import routes, no exports (no Hawaiian endemics found elsewhere)
- Most Hawaiian terrestrial endemics have disappeared
Modeling Invasibility
E = I x S
E - # exotics present (proportion of non-native species established is the sites invasibility, E)
I - # species introductions
S - Survival rate (establishment) of introductions
Components of # introductions
I = Ia + Ii
Ia - Accidental release (bilge waters)
Ii - Intentional release
Components of Survival rate of introductions
S = SvShScSm S is establishment after accounting for: Sv - Competition Sh - Herbivory Sc - Chance events Sm - Maladaption
I vs. S on Van Isle
Sometimes the # of introductions is enough to support the Establishment even with significant mechanisms such as competition, disturbance, life history, and climate
Global patterns of Plant invasions
- Non-native and Native species richness are weakly positively correlated (regardless of whether it is a mainland or island)
- The plot is a list of species # and doesn’t account for abundance
- Abundance is more important than list
- There is a tipping point where natives become outcompeted (abundance issue)
Propagule
Set of non-native individuals released into a new environment
- Can be seeds or clones
What are the 3 components of propagule pressure?
- # of individuals released per event
- # of release events
- Health of individuals released
Propagule pressure: Health of individuals released
Ballast water Plankton
- Phytoplankton and zooplankton can survive for weeks on board a ship, but will die over time
Propagule pressure: # of individuals released per event
More released = higher likelihood of establishment
- Ex. The release of insect in NZ to control Broom, more intros = larger population establishment
