1. Hamilton, McGlathery, Miller, Walsh, Lovett, Fraterrigo
Invasive species (IS)
Hamilton, McGlathery, Miller, Walsh, Lovett, Fraterrigo
Zebra mussels, macroalgae on mud flats, Sargassum displacing kelp, bryozoans, spiny water fleas, forest pests, Japanese stilt grass

2. LTER opportunities for IS study
Long-term monitoring
May span pre- and-post invasion
May reveal interannual variation in IS abundance
We may be able to relate IS abundance to impacts – linear or not?
We make concurrent measurements of ecosystem processes (e.g., primary production, metabolism, nutrients etc.)

3. LTER opportunities
Ability to anticipate invasions (or range expansions)
Could predict impacts based on our understanding
Could organize monitoring in advance
Same IS may affect multiple sites, and may do so differentially
Our diversity is a strength: Terrestrial/freshwater/marine; disciplinary; etc.

4. IS leadership position filled!
Still no pay
Improved prospects for success
Guaranteed high status among LTER group

5. Data mining vs. strategic planning for future research?
Alternative approach is to think about future research to fill gaps in our understanding
How could LTER better organize to study invasions as they occur?
Early detection and projection
Before/after comparisons with replicated sites
Compare invaded and uninvaded sites
IS exclusion plots
Metrics of ecosystem functions and services

6. Scientific frontiers Strayer (2012) outlined knowledge gaps
Temporal dynamics: Abundance often peaks early then drops over time since introduction
Another group is already focused on temporal dynamics – we need to find out what they are doing
Effects on ecosystem functions: This could be our niche
Some IS seem to be functionally redundant with natives while others change ecosystem functions, sometimes dramaticall

7. range * abundance * per capita effect
Hypotheses
Parker et al. 1999: Impact of IS is a function of
range * abundance * per capita effect
The abundance term is often greatest at lower trophic positions
Producers and primary consumers vs. predators
Becomes impactful when IS becomes dominant
The per capita effect is often greater at higher trophic positions
Can be impactful even if not dominant or abundant
May need to reach a certain threshold

8. Hypotheses
Per capita effects of IS are disproportionately large when they:
alter resources (e.g., water and nutrient cycles)
E.g., Tamarisk ET, N-fixing shrubs in Hawai’i
have unique trophic roles
Predators on islands
alter or create habitat structure
Zebra mussel reefs, Gracilaria macroalgae on formerly bare mud flats
influence keystone species
Forest pests that eliminate dominant trees

9. Step 1: Survey sites Do you have time series data on IS abundance?
Before and after invasion?
We will check with Latzka survey
Have you made comparisons with and without IS?
Invaded/uninvaded or IS removals
How do/will they produce impacts?
Ecosystem processes
Community structure: Species composition, habitat
Negative impacts on native species of similar functional groups
Are there cases where the impacts seem smaller than expected?
What new IS invasions are anticipated?
Can you suggest other sites/investigators who could contribute this kind of information?