community ecology of invasions: direct and indirect effects of invasive fish and bullfrogs
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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
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