Chapter 12: Predation, Risk Assessment and Management of

Species InvasionsBy Nicole Cardona and Ruth Singer

Explanation vs. Prediction

Explanation: Statements about what has already occurred

Prediction:Statements about the likelihood that events will occur

Is it more important to generate predictions or explanations? Should we place more emphasis on what we think will occur, or should we concentrate on the past to help us predict the

future?

Risk Assessment: Government Protocols

WRA (Weed Risk Assessment)• evaluate risk of importing plant species through 49 questions answered with yes or no• questions based on “weedy” attributes from 3 areas• biogeography- distribution, climate, domestication, and previous establishment success• undesirable attributes- toxicity, unpalatable, and ability to establish within native plant communities• biology/ecology- attributes that would allow a plant to reproduce, spread, and persist

Risk Assessment: Quantitative Tools

• Rejmanek & Richardson (1996)- pine species in N. Hemisphere• 12 with known instances of invasion, 12 non-invaders• used DFA- Discriminant Function Analysis to determine which 10 life history characteristics had the biggest influence on the categorization • 3 most important characteristics:• mean seed mass• minimum juvenile period• interval between large seed crops

Does it surprise you that these are the 3 most important characteristics? Why do you think height was not as

important?

Risk Assessment: Quantitative Tools

• Ricciardi & Rasmussen (1998)- aquatic invaders, Great Lakes• 3 step “low-cost screening profile”1) Identify potential donor regions 2) Select potential invader with biological criteria3) Narrow down list using prior invasion success

The authors said that Ricciardi & Rasmussen’s method involved using list traits that had been previously put

together to narrow down the potential invaders. Do you think using previous lists takes away from the

effectiveness of the program?

Risk Assessment: Stage-specific approaches

• Marchetti et al. (2004)-• Documented presence/absence of every non-native fish inhabiting each watershed across CA• Found 8 species-level characteristics for all fishes, determined which characteristics were important to each stage of invasion• Species establishment- all 8 equally important• Spread- physiological tolerance and prop pressure• Intergration/impact- prior invasion success & prop pressure

Does it surprise you that prior invasion success was only important at the integration/impact stage? Why do you think propagule

pressure remained important for the last 2 stages?

Is this data conclusive? Why do you think there is so much variation in the

data for some of the categories and not others?

Ecological niche modeling

Peterson and Vieglais (2001)• utilized complex informatics algorithm to quantify a species’ ecological niche based on its native range• used the niche’s biophysical properties (elevation, rainfall, temperature) to project that model onto other, possibly suitable landscapes• lots of time needed to gather data and make models, lack of native species occurrence data

What do you think about the success of this model?

How can you explain the discrepancy between the

predicted location and where the Himalayan

bushclover was actually found in the US?

Prevention of Accidental Introduction

•Ballast Water Exchange (BWE)• Mid-ocean exchange of ballast water• Based on the idea that coastal aquatics could not survive if release in the middle of the ocean, vice versa• Turns out ballast organism diversity increases after BWE

• Alternative treatments to ballast water• intensive filtration, thermal treatment, biocide treatment, ultraviolet light control, nitrogen gas

Prevention of Purposeful Introductions

• top-down regulation will not work as well• need to educate people in the provider industries

Removal and Management• Early detection• best to look at previous performances after introduction in previous places • ideally have a cross-agency database to help with this

•Eradication• manual removal, trapping, chemicals •concept of brute force

•Control • Herbicides, manual removal, grazing regimes• Bio-control

What are the ethical boundaries when it comes to eradication?

In the process of early detection, it is often researchers who are discovering non-native in a new area.

Is it the scientist’s responsibility to alert the proper authorities? Or is publishing a paper with their findings

all they have to do?

How do you balance the cost against the benefits of sufficient control/eradication? Is there a point in

management when its just too expensive?

With the current economy, it is likely that less money will be available for invasive species control and prevention. Do you think this economy will increase the number of

invasive species?

Guilty until proven innocent?or

Innocent until proven guilty?