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 Bullfrogs
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• Part 1 Background Information

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How do multiple invaders influence native
communities?
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Western Mosquitofish (Gambusia affinis)
American Bullfrog (Lithobates catesbeianus
Rana catesbeiana)
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• Through what mechanisms do invasive mosquitofish
  and bullfrogs influence native community members
  and one another?
• Approach Mesocosm Experiment

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Mesocosm Experiment

• Experimental Design
• 1.) Natives
• 2.) Natives Bullfrogs
• 3.) Natives Mosquitofish
• 4.) Natives Bullfrogs Mosquitofish

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Pacific Chorus Frog
Daphnia sp.
Native Community
California Newt
Ramshorn Snail
Western Toad
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Mesocosm Food Web
Newts
Snails
Treefrogs
Toads
Zooplankton
California Newt
Periphyton (attached algae)
Phytoplankton (suspended algae)
Western Toad
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• Part 2 Results and Interpretation

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Mesocosm Results
Amphibian Survival
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Sublethal Fish Effects
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Amphibian Mass
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(No Transcript)
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Zooplankton PhytoplanktonResponses
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Snail Responses
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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