Evolutionary Theory (3)

Covers Natural selection (4 tenets), genes and behavior (3 examples), indv. v. group selection (payoffs and variation), and phenotypical plasticity (reaction norms and climate change)

What is behavioral ecology?

How behavior adapted for the environment

What is natural selection? What are the four tenets of natural selection?

Natural Selection: how organisms adapted for the enviornment

4 Tenets:

1. Variation

2. Heritability

3. Competition (excess capacity for growth)

4. Differential reproductive success

What is evolution? What are 3 examples? Which one is not an example?

Evolution: change in relative allele frequencies between generations

Examples:

1. Rover v sitter Retainment in Adult flies

2. Geese mating with MC1R (melanin)

   1. This one is not actually an example because it results in disruptive selection (aa white mates with white and A- blue mates with blue)

3. Warbler migration and restlessness

What is a stable polymorphism? What is negative frequency dependent selection? What is an example of both of these?

1. Stable polymorphism = genetic equilibrium where more than one allele can exist given certain environmental conditions

2. Frequency of one allele goes down as the other goes up, frequency depends on each other

3. Rover v sitter

What an an example of disruptive selection? What is causing this disruptive selection? Is this natural selection? Is this evolution?

1. Lesser snow geese mating with MC1R (melanin).

2. This is caused by positive assortative mating. White (aa) mates only with white and blue (A-) mates only with blue.

3. Yes

4. This is not evolution because allele frequencies remain about the same.

How does multiple genes factor into behavioral distribution? What is an example?

1. Multiple genes makes it more difficult to change the distribution because changing one gene has little impact on the behavior.

2. An example is migratory patterns in warblers.

Explain the migratory/restlessness patterns of German blackcaps, Canary Island blackcaps, and hand-reared blackcaps. What does this show?

1. German = restless in the fall, they migrate

   1. Due to light cues/fixed action pattern

2. Canary Island = not restless, they don’t migrate

3. Hand reared = ¾ restless, ¼ not, but after 3-6 generations of rearing MM together and nMnM together, disruptive selection occurred. That it took this long suggests it was continuous (multiple genes) and that it was difficult to get rid of.

Note: A small population ended up gaining the ability to migrate to Britain and the birds become restless in the direction that their desired location is in.

What is a simple example that group selection doesn’t work? What does this mean?

1. Invading male lions will kill juveniles (not good for species) but it frees females up for mating.

2. This means that adaptive behavior can be maladaptive to others.

Note: It is adaptive for the females to let the males do this because they could die if they don’t. If they die, then both her and her kids die and she has no genes to pass on.

What are two reasons group selection doesn’t work? Explain the example that coincides with both reasons.

1. It’s about the allele, not the population.

   1. Assuming birds lay 2 eggs and that 3 results in not enough resources and that clutch size = genetically determined…

      1. Mean clutch size initially rises b/c it increases fitness but will go back down if the cost of the extra egg leads to a decreased fitness compared to two eggs.

2. It’s about maximized fitness for individual, not population.

   1. Birds lay between 8-9 eggs ( would be better to do ten) but! this leads to an increased mortality in chicks.

   2. 3 Treatments to add 2 kids shows that tradeoffs have many factors and that it can increase mortality to female.

      1. Add two eggs (middle)

      2. Add 2 chicks (highest survivorship)

      3. Induce eggs/chicks (lowest survivorship)

3. Example = Oxford Great Tits

What do the green and yellow lines represent in graphs representing effort and reproductive success?

1. Yellow:

   1. Points along same line: Equal effort

   2. Each line: Levels of lifetime effort

2. Green:

   1. Reproductive success

   2. Shapes of the green lines represent life history traits.

What is an example of individual variation? How does it relate to individual/group selection?

1. Magpies lay between 5 and 8 eggs. Birds that are given 8 but normally lay five have less survivorship compared to when they lay five. (5 normally result in 1, 0 if changed) (8 normally results in 4, 3 if changed).

2. This shows that individual variation is for the individual and NOT for the species.

What is phenotypical plasticity? What is a reaction norm? How are graphs of phenotypic plasticity read?

1. The phenotype of one gene changes with the environment

2. Reaction norm = phenotype plus its relationship with the environment (how does the phenotype normally react to the environment?) (laying date and temperature)

3. Y-axis = average + slope = level of plasticity

How does phenotypic plasticity relate to climate change in the British great tit? The Netherlands population? What could be reasons for this?

1. Laying date has been pushed forward by 14 days in 47 years. Caterpillars also accelerated so they’re still in sync.

2. Laying date has not been accelerating but caterpillars have so they’re not in sync.

3. Reasons could be that British tits use temperature and the Dutch use light, but really it’s because caterpillars emerge in late spring which has changed in both locations while early spring temperatures have only changed in Britain.