Download Invasive species

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