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

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

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

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?