Explanations for Behavior

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Explanations for Behavior

• Proximate Mechanisms (How?)
• Ultimate Adaptive Significance (Why?)

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Male White-crowned Sparrow
Zonotrichia leucophrys
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Territoriality How?

• Spring Increases in day-length
• Compared to Circadian Clock
• Transmitted to Hypothalamus
• Right time Neurohormones Released,
• Target Anterior Pituitary

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Territoriality How?

• Anterior Pituitary Releases Gonadotropins
• into Bloodstream, Target Testis
• Testis Releases Steroid Hormones
• Secondary Sexual Characteristics,
• Reproductive Behavior

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Territoriality Why?

• Adaptive Value
• Fitness Survival Reproduction
• Defending Resources (Food, Nest Site)
• By Excluding Conspecifics
• Advances Reproductive Success

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Territoriality Why?

• Defended Resources on Territory
• Attracts Mate, Food for Offspring
• In Environment, Single-Pair Territory Greater
  Reproductive Success
• Than Alternatives
• Understand Significance of Individual Behavior
• and Mating Systems
• Infer Consequences for Population Growth

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Functional Significance of Behavior

• 1. Comparative Method
• 2. Hypothetico-Deductive Method
• Predictive Modeling

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Functional Significance of Behavior Comparative
Method

Cuvier Anatomy, Paleontology
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Comparative Method

• Comparative Anatomy
• to
• Behavior Phylogeny, Originally
• Later Correlate Behavior with Environment
• Across Series Populations, Species,

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Comparative Method

• Correlations of Behavior Environment
• Suggest Hypotheses re Adaptation
• Correlation Not Causality
• Secondary to H-D method
• Phenotypic Gambit

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Phenotypic Gambit

• Selective Evolution Favors Certain Alleles
• Commonly Natural Selection on Individuals
• Result Populations Adapt to Environment
• Evolutionary Genetics ? Optimization Model

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Biological Evolution

• Change in Gene Frequencies thru Time
• What Drives Evolution?
• Mutation Migration (Gene Flow)
• Genetic Drift Meiotic Drive
• Natural Selection

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Natural Selection

• Change in Gene Frequencies Due to Variation in
  Lifetime Reproductive Success Among Individual
  Phenotypes
• Survival and Fecundity ? Fitness
• Inclusive Fitness
• Different Phenotypes ? Different Genes

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Natural Selection

• Phenotypic Variance Within Population
• Genetic Variation
• Contributes to Phenotypic Variance
• Phenotypes Heritable
• Different Phenotype Different Fitness

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Levels of Selection

• Gene
• Individual Natural Selection
• Darwinian Fitness
• Family Kin Selection
• Inclusive Fitness
• Group, Deme

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Selection and Adaptation

• Natural Selection Individual Fitness
• Result Population Adapts
• Mean Fitness Increases
• Fitness Variance Declines
• Phenotype Optimized

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Selection and Adaptation

• Directional Selection (favor 1 extreme)
• Destabilizing Selection (favor extremes)
• Optimizing (Stabilizing) Selection

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Optimizing Selection
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Optimality Theory

• Hypothetico-Deductive Method
• Functional Questions
• Optimality Models to Predict Behavior
• Assume Optimizing Selection
• Optimal, best, metaphor for adaptation

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Optimality Theory

• Constructing Model for Optimal Behavior
• Incorporate Hypothesis
• Behavior and Fitness
• Math Deduce Prediction, Then Test
• If we can predict, we understand.

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Optimality Theory

• Question, From Behavioral Ecology
• Strategy Set
• Constraints
• Objective Function
• Hypothesize Currency of Fitness
• Deduce Optimal Solution, Prediction

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Optimality Theory

• Identify Strategy Set
• List Possible Behaviors
• Discrete (Eat some prey, reject others)
• Continuous (Time in food patch)

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Optimality Theory

• Identify Applicable Constraints
• Total Time Available
• Physiological Requirement
• Possible vs Impossible
• (Cannot Search for Food
• Handle Food Simultaneously)

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Optimality Theory

• Listing Constraints Phenotypic Gambit
• Ignore Genetic Constraints,
• Usually Dont Know What They Are

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Optimality Theory

• Construct Objective Function
• Maps Any Feasible Behavior onto
• An Hypothesized Currency of Fitness
• Hypothesis Increase in Currency Will
• Increase Survival, Reproduction

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Optimality Theory

• Currency of Fitness
• Rate of Energy Gain While Foraging
• Probability of Starving
• Offspring Produced/Year
• Maximize Fitness Currency by
• Optimizing Behavioral Strategy