Behavior: Levels of Explanation Recall N. Tinbergen Proximate: Mechanisms (How? Most Biology) Ultimate: Adaptive Significance (Why?) Example, Compare

Male White-crowned Sparrow Zonotrichia leucophrys Breeding Territoriality

Territoriality: How? Spring: Increases in Day-length Compared to Circadian Clock Transmitted to Hypothalamus “Right time”: Neuro-hormones Released, Target Anterior Pituitary

Territoriality: How? Anterior Pituitary Releases Gonadotropins into Bloodstream, Target Testis Testis Releases Steroid Hormones Secondary Sexual Characteristics, Reproductive Behavior: Territoriality Mechanisms: More Description than Prediction

Territoriality: Why? Adaptive Value Fitness: Survival & Reproduction Defending Resources (Food, Nest Site) By Excluding Conspecifics Advances Reproductive Success

Territoriality: Why? Defended Resources on Territory Attracts Mate, Food for Offspring Single-Pair Territory Greater Reproductive Success Than Alternatives Assume Natural Selection & Adaptation

Territoriality: Why? Understand Significance of Individual Behavior and Mating Systems Model Benefits & Costs of Territoriality Predict: Why Individuals Territorial or Not Understand Behavioral Diversity

Functional Significance of Behavior Research Strategies 1. Comparative Method 2. Hypothetico-Deductive Method: Predictive Modeling

Functional Significance of Behavior Comparative Method Cuvier: Anatomy, Paleontology Newton Era

Comparative Method Comparative Anatomy for Phylogeny Applied to Behavior: Initially for Phylogeny, Later: Correlate Behavior with Environment Across Series Populations, Species, … Does same environment produce same behavior?

Comparative Method Correlations of Behavior & Environment Suggest Hypotheses re Adaptation Correlation Not Causality Secondary to H-D method: Phenotypic Gambit

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

Biological Evolution Change in Gene Frequencies thru Time What Drives Evolution? MutationMigration (Gene Flow) Genetic DriftMeiotic Drive Natural Selection

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

Natural Selection Phenotypic Variance Within Population Genetic Variation: Contributes to Phenotypic Variance Phenotypes Heritable Different Phenotype: Different Fitness

Levels of Selection Gene Individual: Natural Selection Darwinian Fitness Family: Kin Selection Inclusive Fitness Group, Deme, Species

Selection and Adaptation Natural Selection: Individual Fitness Result: Population Adapts Mean Fitness Increases Fitness Variance Declines Phenotype “Optimized”

Selection and Adaptation Directional Selection (favor 1 extreme) Destabilizing Selection (favor extremes) Optimizing (Stabilizing) Selection

Optimizing Selection

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

Phenotypic Gambit Constructing Model for Optimal Behavior Incorporate Hypothesis: Behavior and Fitness Math: Deduce Prediction, Then Test If we can predict, we understand. Assigned: Review this lecture; Read next lecture.

Introductory Topics  How do we invoke the concepts of Natural Selection to predict behavior?  What is “optimizing selection?” How do we apply the notion of optimizing selection in the “Phenotypic Gambit?”  How do we distinguish the comparative method from deductive modeling as ways to understand behavior?

Phenotypic Gambit Natural Selection Acts on Behavior – As with Anatomy & Physiology “Phenotypic Gambit” ~Ignore Details of Evolutionary Genetics ~Ignore (Unnecessary) Details of Mechanisms ~Optimization Model, Predict Outcome of Selection

Adaptation Selection on Individuals  Population Adapts Fixed Environment  Optimizing Selection: ~Mean Fitness Increases ~Fitness Variance Decreases Phenotype “Optimized;” Optimization Models

Optimality Theory Question In Behavioral Ecology  Strategy Set (behavior, animal can do)  Constraints (environment, animal can’t do)  Objective Function Hypothesize Currency of Fitness Deduce Optimal Solution, Prediction

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

Optimality Theory Identify Applicable Constraints Total Time (or Energy) Available Physiological Requirement Possible vs Impossible (Cannot Search for Food & Handle Food Simultaneously)

Optimality Theory Listing Constraints: “Phenotypic Gambit” Ignore Genetic Constraints, Usually Don’t Know What They Are

Optimality Theory Construct Objective Function Maps Any Feasible Behavior onto An Hypothesized “Currency of Fitness” Hypothesis: Increase in Currency Will Increase Survival, Reproduction … Test Understanding Deduce Prediction(s)

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