1. Testing adaptive hypotheses: a case study
Appl;y what you;ve learned so far in class
Thought exercise: go basically a lot like an exam questio.
Purpose of today is to have some discussion, ask questions, do some critiacal thinking and proactice applying the concepts you learned on Tuesday
Going to go through a scenario... Similar to what you might see on an exam, should also help you figure out if you understand what’s going on or not in class so far.

2. Trinidad
Venezuela
John Endler
Poecilia reticulata
...the wild guppy

3. Poecilia reticulata
Lives in gravel-bottomed forest streams: headwaters to lowlands

4. Poecilia reticulata
Lives in gravel-bottomed forest streams: headwaters to lowlands
Great variation in coloration from population to population, even within the same stream

5. Poecilia reticulata
Lives in gravel-bottomed forest streams: headwaters to lowlands
Great variation in coloration from population to population, even within the same stream
Lots of natural predators; generally more and the most ferocious are at lower elevations (downstream)

6. Poecilia reticulata
Lives in gravel-bottomed forest streams: headwaters to lowlands
Great variation in coloration from population to population, even within the same stream
Up to 7 natural predators; generally more and the most ferocious are at lower elevations (downstream)
Brightest guppy populations tend to live upstream: populations downstream are duller in color

7. Lives in gravel-bottomed forest streams: headwaters to lowlands
Poecilia reticulata
Lives in gravel-bottomed forest streams: headwaters to lowlands
Great variation in coloration from population to population, even within the same stream
Up to 7 natural predators; generally more and the most ferocious are at lower elevations (downstream)
Brightest guppy populations tend to live upstream: populations downstream are duller in color
Females are dull gray (and blend in with the stream bed) in all populations
Females (always look like this)

8. Forming an adaptive hypothesis about wild guppies
What are the necessary conditions for evolution by natural selection?
1. variation
2. heritability: offspring resemble parents
3. survival and reproduction are not random: consistent relationship between phenotype and fitness

9. Forming an adaptive hypothesis about wild guppies
What are the necessary conditions for evolution by natural selection?
1. variation
2. heritability: offspring resemble parents
3. SELECTION: consistent relationship between phenotype and survival and reproduction
What is an adaptation?
The phenotypic variant that results in the highest fitness in a given environment

10. You can: Move and remove guppies and predators from streams
Maintain and breed guppies in a laboratory
Cross guppies from different populations
Determine paternity/maternity of individual guppies
Genetically engineer and clone guppies
Spend years of your life on this project (i.e. allow many, many guppy generations to pass
Anything else (within reason)

11. Endler’s experiments:
The phenotype of each population is adapted, and is the result of the local balance of sexual and predator selection
If the balance of sexual and predator selection is changed, the phenotype should evolve in response
Environment-dependent

12. Endler’s experiments:
Greenhouse pool experiment
Set up guppy populations in pools in a greenhouse
Foundation population highly variable
Sexual selection constant (always)
Vary predation pressure
Vary environment
Track phenotypes through time: number, size, location, color variation of spots

13. Endler’s results:
“innocuous” predator
Ponds with no predators (K) showed a steady increase in the # of spots
control
“voracious” predator
Little change in spot # (compared to the control) after addition of the innocuous predator (R)
Pools that received a voracious predator treatment (C) showed a marked decrease in the # of spots
Foundation population
Treatments applied

14. Summary of greenhouse experiment:
Phenotypes evolved in response to changes in the balance of sexual and predation selection

15. Endler’s experiments: 2. Field transplant in Trinidad
Each population has an adapted phenotype, reflecting the local balance of sexual and predation selection.
If evolution was “replayed”, the same adapted phenotype would evolve.

16. Endler’s experiments: 2. Field transplant in Trinidad
Each population has an adapted phenotype, reflecting the local balance of sexual and predation selection.
Trinidad stream: 3 sites... 1 2 3
2 km
Guppies, innocuous predator and dangerous predator present
No guppies: innocuous predator present
Both guppies and innocuous predator present
Transplanted 200 guppies from site 3 to site 1, measured phenotypes 10 months later.
Population 1 should evolve the same phenotypes as population 2 (site 1 = site 2).

17. Endler’s field experiment: results
In site 1 (x)....
Spot size, number and color diversity increased
Color pattern converged on that of fish in site 2 (r)
c = site 3 (source pop), x = site 1 (transplant site), r = site 2

18. Endler’s work: Conclusions
Demonstration of natural selection in action
Evolutionary hypotheses are experimentally testable