Lec9 Adaptation

Animal Behavior:
Adaptation

ANIMALEHAVIOR LEC 3

ANIMAL BE

ANIM

Animal Behavior, Lec. 9, BIOL 4518

Chapters 6 and 9

Homework in quiz on Blackboard

Due Thursday

Midterms

Expectations

So far...

First part of course

tools to ask evolutionary questions:

mechanisms of speciation,

history of ethology and animal behavior,

two ways of looking at animal behavior (proximate and ultimate)

hypothesis development (e.g., if, then statements) to test explanations for behavior,

how to collect data to test hypotheses (lab)

basics of animal behavior:

relative magnitude of influence of genes and environment

introduction to social insects

physics of communication, orientation/navigation etc.

2nd half

Second half of the quarter

Examine ULTIMATE questions more deeply

The sorts of questions we will ask include:

Is that an adaptation?

Current theories

Attempt to explain broad classes of behaviors across many species

Examine data that do/do not support

Discuss cases of observations of animal behavior in more detail.

2nd half Evaluation

Tests

Forming a detailed argument

nuances of the argument

Using detailed information to support/not support the hypothesis

Example test question:

Provide both sides of the argument of XY and Z topic, and defend your conclusion.

Concepts in 2nd half of class

Key words

Fitness

Inclusive fitness

Cost benefit analysis

Altruism

Honest signals

Theories:

Optimality theory

Game theory

Outline

Adaptations (behavioral)

Phylogenies

Fitness

Phylogenies and adaptations

What is a phylogeny?

How is it constructed?

Is there only one phylogeny?


Does it matter which traits are used to make the phylogeny?


Weak phylogenetic relationship but the same characteristic!

Convergent Evolution

Similar selection pressure

Examples

Quoll (marsupial) and human cat (placental)

Saber toothed tiger marsupial!!!

Doesn't require animals being in the same habitat


Strong phylogenetic relationship but different characteristics

Divergent evolution

Shared ancestry but different behavior

Doesn't require animals being in the same habitat

What is fitness?

Fitness is the reproductive success. Several ways to measure it, but the best is to measure the number of offspring (F1) that produce viable offspring (F2).

What is fitness?

What can reduce your fitness?

How measure fitness?

Fitness can be less precisely measured as the

number of offspring produced, or the

number of copulations, or the

number of surviving offspring

None of these measurements measure the full chain required for fitness

How measure fitness?

Relative fitness

Fitness of individual with one trait vs fitness of an individual with another trait

What is an adaptation?

Definition: trait which has been positively selected for and increases the relative fitness of an individual

What is an exaptation?

Human hand vs. bat wing?

Exaptation: trait originally selected for one purpose and different selection pressures resulted in the current use. Potential explanation for why something may not be the best design if you were starting from scratch

e.g. human knees not necessarily the best design for extensive bipedal walking; joint wears out, highly susceptible to damage, etc.

How do you determine just so vs. adaptation?

Is that an adaptation?

To find out you construct a hypothesis and test

The test design is important, however!

When does the trait increase fitness?

In rare extreme environment/events

In a typical environment/event?

For example:

a trait which does not appear to confer a fitness advantage in typical environment, may confer high advantage in a rare event.

Rocky intertidal example

Context is crucial to correct determination of whether the trait is selected for/is an adaptation

Example of testing whether behavior is adaptive

Projectile caterpillar poop!


Gazelles

Stotting behavior

Leap into air and show white rump?

Is this adaptive?


Hypotheses:

Alarm signal:

Social cohesion:

Confusion effect:

Pursuit deterrence:


Solitary gazelle stots

Grouped gazelles stot

Stotters show rump to predator

Stotters show rump to gazelles


Data

Lone gazelle stots when approached by cheetah

Stotting gazelles orient rump to predator and not to gazelles


Conclusion

Pursuit deterrence

Example of Darwinian puzzle

Traits whose benefits are unlikely to be balances by the negatives

Bright coloration by insects

Monarch

Milkweed toxins

Butterflies regurgitate

Wings rejected

Mimics

Optimality

Behavioral decisions (strategies) are chosen to maximize reproductive success

Examples of fitness measurements proxies:

Energy gain per time

Energy loss per time

Being predated

Used as a test to see whether you have accurately assessed the selection pressures

Optimal foraging theory

Behavioral decisions of foraging:

Where should I search?

For what prey?

For how long?

At what time of day?

What is being optimized?

Caloric intake per time

Others?

Does a behavior have to be optimal to be adaptive?

Is efficiency required?

Game Theory

Unconscious maximization of reproductive success

Behavioral decisions (strategies) are chosen to maximize reproductive success

Costs and benefits are weighed

Social context each individual is maximizing its own success (or genes)

Example of Game Theory

Assume most individuals are solitary

Selfish herd (Hamilton)

Individuals try to get into the center of the group

Use other individuals as shields

What would happen over evolutionary time?

Would this be selected for over other traits?

Does it still work if everyone uses it?

Game theory: 2 different strategies in a species

Individuals in the same species are known to specialize on different prey items

Why hasn't the behavior with the higher fitness replaced the other over evolutionary time?

Small differences can have big impacts

Behavior exhibited depends on context


How can two strategies coexist in a population?

Frequency dependent selection

The fitness of one genotype depends on the frequency of other genotypes in the

Frequency of fish-stealing genotype in the population

0.25

0.5

0.75

1.0

0


Fitness of phenotypes

high

low

medium

Fish stealer

Fish hunters

4

8

12

4

12

4

4

12

0

16

8

8

16

12

4

0


0.25

0.5

0.75

1.0

0



high

low

medium

Fish stealer


0.25

0.5

0.75

1.0

0



high

low

medium

Fish hunter

Fish stealer


0.25

0.5

0.75

1.0

0



high

low

medium

Fish hunter

Fish stealer

Equilibrium point

Lec9 Adaptation

Technology

Transcript of Lec9 Adaptation