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?
Phylogenies and adaptations
Does it matter which traits are used to make the phylogeny?
Phylogenies and adaptations
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
Phylogenies and adaptations
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!
Example of testing whether behavior is adaptive
Gazelles
Stotting behavior
Leap into air and show white rump?
Is this adaptive?
Example of testing whether behavior is adaptive
Hypotheses:
Alarm signal:
Social cohesion:
Confusion effect:
Pursuit deterrence:
Example of testing whether behavior is adaptive
Solitary gazelle stots
Grouped gazelles stot
Stotters show rump to predator
Stotters show rump to gazelles
Example of testing whether behavior is adaptive
Data
Lone gazelle stots when approached by cheetah
Stotting gazelles orient rump to predator and not to gazelles
Example of testing whether behavior is adaptive
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
Game theory: 2 different strategies in a species
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
Game theory: 2 different strategies in a species
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
Frequency of fish-stealing genotype in the population
0.25
0.5
0.75
1.0
0
Game theory: 2 different strategies in a species
Fitness of phenotypes
high
low
medium
Fish stealer
Frequency of fish-stealing genotype in the population
0.25
0.5
0.75
1.0
0
Game theory: 2 different strategies in a species
Fitness of phenotypes
high
low
medium
Fish hunter
Fish stealer
Frequency of fish-stealing genotype in the population
0.25
0.5
0.75
1.0
0
Game theory: 2 different strategies in a species
Fitness of phenotypes
high
low
medium
Fish hunter
Fish stealer
Equilibrium point
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