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