1. Community Ecology of Invasions: Direct and Indirect Effects of Invasive Fish and Bullfrogs

2. Part 1: Background Information

3. How do multiple invaders influence native communities?

4. American Bullfrog (Lithobates catesbeianus = [Rana catesbeiana]) Western Mosquitofish (Gambusia affinis)

5. Through what mechanisms do invasive mosquitofish and bullfrogs influence native community members and one another? Approach: Mesocosm Experiment

6. Mesocosm Experiment Experimental Design 1.) Natives 2.) Natives + Bullfrogs 3.) Natives + Mosquitofish 4.) Natives + Bullfrogs + Mosquitofish

7. California Newt Western Toad Pacific Chorus Frog Native Community Daphnia sp. Ramshorn Snail

8. California Newt Western Toad Mesocosm Food Web Toads Treefrogs Newts Phytoplankton (suspended algae) Zooplankton Periphyton (attached algae) Snails

9. Part 2: Results and Interpretation

10. Mesocosm Results Amphibian Survival

11. Sublethal Fish Effects

12. Amphibian Mass

14. Zooplankton & Phytoplankton Responses

15. Snail Responses

16. Conclusions Effects of invaders on native amphibians were species-specific and varied with palatability and competitive ability of natives Mosquitofish suppressed zooplankton, with cascading effects on phytoplankton Invader effects were largely additive Invaders did not negatively effect one another in a short-term experiment