Question

6) a. As you learned in class, guppies in Trinidad exist naturally in river segments with large predators and above large waterfalls in river segments that lack large predators. Guppies can live for around 2 years in captivity and typically take approximately 2 months to become reproductively mature. For each of the following statements, determine if it is most likely TRUE or FALSE. (20 pts)

Trade-offs between traits like lifespan and number of offspring constrain the ability of natural selection to always favor longer lifespans.      T     F

Imagine a genetic variant that causes a benefit early in life (first 4 months of life) but causes a life-threatening disease once an individual reaches 1 year old. This variant would be favored more strongly in the low predation environments than in the high predation environments.      T     F

When Dr. Reznick transferred guppies from high predation locations to low predation locations, he found a decrease in reproductive allocation and an increase in the age at maturity in the population over time.      T     F

Because natural selection should always favor higher reproductive output, guppy populations will always evolve to produce more and more offspring over time.      T     F

Dr. Reznick's results were not consistent with the predictions from life history theory.     T     F

b. Another trait that differs between high and low predation guppies is escape ability. Guppies from high predation locations have evolved faster escape responses than guppies from low predation locations. For each of the following statements, determine if it is most likely TRUE or FALSE.

The evolution of faster escape responses by guppies is unlikely to cause a change in natural selection acting on predators.      T     F

The evolution of faster escape responses by guppies is likely to cause selection favoring faster capturing ability in predators.      T     F

The geographic mosaic theory of coevolution would predict that there is variation across the landscape in Trinidad in how strongly the reciprocal selection is acting on predators and on guppies.      T     F

If dispersal by guppies up and down the barrier waterfalls increased, you would expect the escape responses in the high and low predation populations to become more similar because of increased gene flow.     T     F

The longer that guppies co-occur with predators, guppies should continue to evolve faster and faster escape responses at the same rate.     T     F   

Answer 1

Trade-offs between traits like lifespan and number of offspring constrain the ability of natural selection to always favor longer lifespans.      T

Imagine a genetic variant that causes a benefit early in life (first 4 months of life) but causes a life-threatening disease once an individual reaches 1 year old. This variant would be favored more strongly in the low predation environments than in the high predation environments.      T

When Dr. Reznick transferred guppies from high predation locations to low predation locations, he found a decrease in reproductive allocation and an increase in the age at maturity in the population over time.      T

Because natural selection should always favor higher reproductive output, guppy populations will always evolve to produce more and more offspring over time.      T

Dr. Reznick's results were not consistent with the predictions from life history theory. F

b. Another trait that differs between high and low predation guppies is escape ability. Guppies from high predation locations have evolved faster escape responses than guppies from low predation locations. For each of the following statements, determine if it is most likely TRUE or FALSE.

The evolution of faster escape responses by guppies is unlikely to cause a change in natural selection acting on predators. F

The evolution of faster escape responses by guppies is likely to cause selection favoring faster capturing ability in predators.      T

The geographic mosaic theory of coevolution would predict that there is variation across the landscape in Trinidad in how strongly the reciprocal selection is acting on predators and on guppies.      T

If dispersal by guppies up and down the barrier waterfalls increased, you would expect the escape responses in the high and low predation populations to become more similar because of increased gene flow.     T

The longer that guppies co-occur with predators, guppies should continue to evolve faster and faster escape responses at the same rate.     T