rapid evolution of antipredator responses do pacific treefrog populations differ in their response...
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Rapid Evolution ofAntipredator Responses
Do Pacific Treefrog Populations Differ in Their Response to an Introduced
Predator?
David Paoletti
Advisor: Dr. Andrew Blaustein
Loss of Biodiversity
• Declining globally across all taxa
Amphibian Population Declines
Various Factors Contribute:• UV radiation• Disease• Habitat Loss• Pollution• Over-harvesting• Introduced Species
Oregon Spotted Frog
Introduced Species
Many plant and animal species have become successfully established in foreign environments.
Zebra Mussel
Himalayan Blackberry
Cane Toad
Introduced Species
Brook Trout(Salvelinus fontinalus)
Focal Species
Pacific Treefrog(Hyla regilla)
Antipredator Behaviors
Most amphibian larvae rely on waterborne chemical cues to detect a potential threat. Upon detection, an individual may respond in several ways:
• Camouflage• Refuge use• Decrease in activity
Allopatric vs.Sympatric Populations
ALLOPATRY
SYMPATRY
Frogs Fish
Frogs+Fish
Allopatric vs.Sympatric Populations
Previous studies have shown that a population may evolve to avoid a newly introduced predator.
• Kiesecker and Blaustein, 1997
I Thought I Smelled Something…
HYPOTHESIS:Allopatric treefrog populations will not
exhibit antipredator behaviors. Sympatric treefrog populations will
recognize trout as potential predators and thus change their behavior accordingly.
Collection
H. regilla egg masses were collected from natural populations in the Cascade Mountains.
One from a lake with brook trout (allopatric).One from a trout-free habitat (sympatric).
Susan’s Pond
Trout-free habitat
Three Creeks Lake
Last stockedin 1961
Experimental Design
Allopatric Population
Sympatric Population
Control Group(No chemical cue)
Control Group(No chemical cue)
Predator Chemical Cue
Predator Chemical Cue
Alternate Chemical Cue
Alternate Chemical Cue
Methods
• 15 minute acclimation period• Individuals spot-checked every ten minutes for two hours and any change in position was recorded
MethodsObservations were conducted in a
laboratory setting. Activity levels for each group were recorded and analyzed.
Predictions
Movement
ANOVA- P<0.001 cue effect P=0.016 pop. effect
*
•Predator cue significantly decreased movement
•Tadpoles from the allopatric population moved significantly less often
Distance
ANOVA- P<0.001 cue effect P=0.05 pop. effect
*
•Both populations decreased distance traveled in the presence of predator cues
•Tadpoles from the allopatric population traveled less distance
Predicted Results Actual Results
Conclusions
Sympatric AND allopatric populations reduce activity in the presence of a predator
Treefrog populations exhibit antipredator behaviors in the presence of a perceived threat, regardless of prior experience
Rapid Evolution?
No evidence…No evidence…•MetapopulationMetapopulation•Ancestral populations previously Ancestral populations previously exposed to predatorexposed to predator
Acknowledgements
Howard Hughes Medical Institute and Undergraduate Research, Innovation, Scholarship and Creativity (URISC)
Kevin Ahern and Andy Blaustein
Blaustein Lab:Dr. Tiffany GarciaBetsy Bancroft Anna JollesJohn Romansic Erin
Scheessele