Chapter 6: Establishment Success: The Influence of Biotic Interactions Jessica Oh and Ruth Singer

3 Difficulties in Exploring Biotic Interactions 1) Difficulty in observing establishment Mathematical models Observation Controlled experiments Question: What are the pros and cons of the three different methods? Should they be used in combination with each other?

2) Defining establishment versus spread 3) Defining resistance 3 Difficulties in Exploring Biotic Interactions Question: The definition of resistance varies throughout the literature from any negative influence on establishment to repelling non-natives completely. Where does your definition of resistance fall within this range?

Competition Example for resistance: Example for facilitation:

Predation Example for resistance: Example for facilitation:

Mutualism Example for resistance or facilitation (depending on the presence/absence of its obligate or facultative mutualist):

Questions: A great debate in invasion ecology exists about the relationship between native and non-native species richness. Do you agree with the book’s definition of species richness as sheer number of species in an area? How would you define species richness? (ie. functional groups) What are the most important components of species richness for biotic resistance?

Questions: The Eltonian “Diversity-Invasibility hypothesis” states that places with many diverse native species are more likely to repel non-natives. While data from small- scale experiments (ex. Smith & Knapp 2001) have agreed with Elton’s hypothesis, the opposite trend has been seen in experiments with larger scale observational studies and mathematical models. What are some of the factors that might be contributing to these contradicting findings?

Questions: Of the three categories of biotic interactions (competition, predation, and mutualism), which one do you think is the most important in either resisting or facilitating non-native establishment?

Questions: On Isla Victoria in Argentina, Simberloff et al found that introduced deer reduced the presence of the non-native pine species in areas where native competition was minimal. From an ethical/management perspective, how do we take a stand against non-native species when that same species prevent the establishment of another, potentially harmful, non-native species?

Questions: Ted Case (1990) found that a native species had an advantage over a non-native species by simply being there first. Why do you think the “priority effect” takes place? If there was a disturbance that created an opening for a non-native to establish, do you think the priority effect would still cause the native species to re-establish?