one last time: haplodiploidy reproduction 0.5 of genome from dad x 1.0 = 0.5 0.5 of genome from mom...
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One last time: haplodiploidy
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
Leafcutter ant queen + workers
Male leafcutter
ant
SEXUAL SELECTIONA 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 SELECTIONDamselflies
SEXUAL SELECTION
Elephant seals
Sexual dimorphism: male and female have different forms
SEXUAL SELECTIONWhy aren’t all species dimorphic?
SEXUAL SELECTIONDimorphism arises from competition for mates
Males produce sperm: cheap
Females produce eggs: expensive
# mates
#kids
BATEMAN PRINCIPLE
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 SELECTIONRole reversal
Greater Painted Snipe
SEXUAL SELECTIONWhich is the limiting sex?
PipefishSeahorse
Sea dragon
SEXUAL SELECTIONParental care
Male may be needed to care for young
SEXUAL SELECTION
Sage grouse Peacock
SEXUAL SELECTION1. Runaway selection: trait initially useful
for survival is exaggerated by sexual selection
Long-tailed Widowbird
SEXUAL SELECTION1. Runaway selection: trait initially useful
for survival is exaggerated by sexual selection
SEXUAL SELECTION2. 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
Natural selection should favor strategies that lead to higher fitness
Every trait has costs and benefits
OPTIMIZING FITNESSGulls “mob” predators that approach nest sites
OPTIMIZING FITNESSHow daring should the gull be?
Distance from predator (m)
1 2 31.5 2.5 3.50.5
Units ofFitness
Cost of action
Benefits of action
Daring mobber
Cautious mobber
OPTIMIZING FITNESS
Optimal strategy:
Benefits - Costs = Maximum
Natural selection should favor optimal strategy
GENE FLOWthe movement of genes from one population to another
“Hide” allele
“Run” allele
TYPES OF SELECTION
1. Directional
Trait
Frequency
Evolutionary change
2. StabilizingMost common: maintains status quo
3. DisruptiveSpeciation
DIRECTIONAL SELECTION
Darwin’s finches
Severe drought 1976-1977
Killed plants with small seeds: birds with larger beaks survived better
Geospiza fortis
10.5 mm 11 mm
Boag and Grant 1981
STABILIZING SELECTION
Human birth weightExtreme light weight and extreme heavy weight both selected against
8 lbs
DISRUPTIVE SELECTIONThree-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; non-random mating