One last time haplodiploidy Leafcutter ant queen workers

One last time: haplodiploidy Leafcutter ant queen + workers Male leafcutter ant reproduction 0. 5 of genome from dad X 1. 0 = 0. 5 + 0. 5 of genome from mom X 0. 5 = 0. 25 r = 0. 75

SEXUAL SELECTION A type of natural selection that acts differently on males and females of the same species Traits that increase mating success are selected for Pheasants

SEXUAL SELECTION Damselflies

SEXUAL SELECTION Sexual dimorphism: male and female have different forms Elephant seals

SEXUAL SELECTION Why aren’t all species dimorphic?

SEXUAL SELECTION Dimorphism arises from competition for mates Males produce sperm: cheap Females produce eggs: expensive BATEMAN PRINCIPLE # kids # mates

BATEMAN PRINCIPLE The sex that invests most in reproduction is a limiting resource that opposite sex competes for Female is usually limiting sex (expecially in mammals), but not always

SEXUAL SELECTION Role reversal Greater Painted Snipe

SEXUAL SELECTION Which is the limiting sex? Seahorse Sea dragon Pipefish

SEXUAL SELECTION Parental care Male may be needed to care for young

SEXUAL SELECTION Sage grouse Peacock

SEXUAL SELECTION 1. Runaway selection: trait initially useful for survival is exaggerated by sexual selection Long-tailed Widowbird

SEXUAL SELECTION 1. Runaway selection: trait initially useful for survival is exaggerated by sexual selection

SEXUAL SELECTION 2. Handicap principle: ornaments show that males are high-quality Ornaments expensive to produce, only males in good condition can have them Ornamental males less likely to have disease

SEXUAL SELECTION Satin bowerbird

OPTIMIZING FITNESS Every trait has costs and benefits Natural selection should favor strategies that lead to higher fitness

OPTIMIZING FITNESS Gulls “mob” predators that approach nest sites

OPTIMIZING FITNESS How daring should the gull be? Daring mobber Benefits of action Units of Fitness Cautious mobber Cost of action 0. 5 1 1. 5 2 2. 5 3 3. 5 Distance from predator (m)

OPTIMIZING FITNESS Optimal strategy: Benefits - Costs = Maximum Natural selection should favor optimal strategy

GENE FLOW the movement of genes from one population to another “Hide” allele “Run” allele

TYPES OF SELECTION 1. Directional Frequency Evolutionary change Trait 2. Stabilizing Most common: maintains status quo 3. Disruptive Speciation

DIRECTIONAL SELECTION Darwin’s finches Geospiza fortis Severe drought 1976 -1977 Killed plants with small seeds: birds with larger beaks survived better Boag and Grant 1981 10. 5 mm 11 mm

STABILIZING SELECTION Human birth weight Extreme light weight and extreme heavy weight both selected against 8 lbs

DISRUPTIVE SELECTION Three-spined sticklebacks Dolph Schluter benthic limnetic Descended from common ancestor Selection favored large fish near shore and small fish in open water Assortative mating led to speciation Assortative mating: Like mates with like; nonrandom mating