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

Part 1: Background Information

How do multiple invaders influence native communities?

American Bullfrog (Lithobates catesbeianus= [Rana catesbeiana])

Western Mosquitofish (Gambusia affinis)

Through what mechanisms do invasive mosquitofish and bullfrogs influence native

community members and one another?Approach: Mesocosm Experiment

Mesocosm Experiment

Experimental Design1.) Natives2.) Natives + Bullfrogs3.) Natives + Mosquitofish4.) Natives + Bullfrogs + Mosquitofish

California Newt

Western Toad Pacific Chorus Frog

Native CommunityDaphnia sp.

Ramshorn Snail

California Newt

Western Toad

Mesocosm Food Web

ToadsTreefrogs

Newts

Phytoplankton(suspended algae)

Zooplankton

Periphyton(attached algae)

Snails

Part 2: Results and Interpretation

Mesocosm ResultsAmphibian Survival

Sublethal Fish Effects

Amphibian Mass

Zooplankton & PhytoplanktonResponses

Snail Responses

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