1. Evolution of Reproductive Behavior Continued

2. Sexual Selection
Darwin: “the advantage which certain individuals have over others of the same sex and species, in exclusive relation to reproduction”
Accounts for costly courtship rituals and elaborate morphology
Time, energy, developmental trade offs, visibility to enemies
Slightly different from regular natural selection which emphasizes enhancing survival (a special case)
Pipefish. Why do they demonstrate sexual selection vs just male female roles? Importance of these examples of role reversals.

3. Developmental Cost Dung beetle: horns or eyes?
Horns win fights, but probably not all because the others can see better.

4. When males compete Dismantle bowers Defense Outright fighting
Body size is selected
Body weapons are selected
Speed
Horns, antlers, tusks
Clubbed tails or spiny legs
Sexual selection for the trait of watching and guarding the bower, willingness to fight to defend territory because loss of territory leads to loss of opportunity to mate. In fights, winners tend to mate more often so traits that enhance winning are sexually selected.

5. Speed is sexually selected

6. Convergent Evolution of body weapons

7. Dominance
Battle for a short time early on to establish a dominance hierarchy
Alpha-male reproduces more
Fights less: threatening displays discourage would-be battles
Savanna baboons
Subordinate males will challenge alpha
Males get bitten and infected > females
Is it worth it?
Initial studies found that males all mated about the same amount. Explain?!

8. Mating success
Effects on mating success measured in many troups over many breeding seasons in a Kenya preserve.

9. And genetic success Gentoyping by PCR
Key feature is to mate when the female is in estrous. And guard her from other males during her fertile period.

10. Advantage, but limited
Reasons: subordinates show willingness and ability to care for a female’s offspring—she seeks him out next time
Subordinates form male-male friendships and gang up on the alpha, forces him to surrender the female he has been guarding (18/28 cases observed in a pack of 8 males). Alternative tactics. Compensation.

11. Conditional Mating Strategies
Evolve when circumstances are such that individual variation leads to differential success
Evolution favors flexibility, so that when social or physiological constraints become apparent, an individual can select a behavioral tactic that gives them the best chance for success
It is conditional because the same animals can adopt multiple different strategies over its lifespan depending on the conditions, socially or environmentally.

12. Conditional Strategies
Even the playing field for disadvantaged members
Why would this be selected for?
Male horseshoe crabs swim and grab onto females (attached) or are solo, satellite males that crowd around paired couples hoping to mate with the female after the attached male releases her. Expt: wrap claws in plastic, put males at sea. Make note of the condition of the male, health of eyes, shell, etc. Poor condition males more likely to be satellite maters—have higher success than poor condition males that try to attach to females and fail.
Main point: lesser males have greater success adopting a different strategy than using the strategy of higher males.

13. Alternate Mating Strategies Example: Faster sperm transfer
Small male iguanas “pre-ejaculate” so that when they mount a female, on the fly, ‘old’ sperm can be immediately transferred before a larger male pulls him off.

14. Example: Body parts trade-off
Uses small body size to sneak up and inseminate a female with more sperm than a larger horned male could.

15. DQ 7.8
Roosters exhibit male dominance hierarchies, with dominant males having greater copulatory success.
Dominant males transfer more and faster sperm to females with red combs on head
Subordinate males transfer same # and quality sperm to all mates
How does sexual selection explain these differences?
What would happen if two dominant males were placed together until one became subordinate? (Use conditional strategy theory)

16. Panorpa Scorpionfly: 3 strategies
Secrete saliva on a leaf, wait for female to come by and eat it
Defend a dead insect, a very delectable food gift for a female
Grab and force to mate
Who is most successful? Most copulations?
Why? How would you test it?

17. Each tries to maximize fitness—dominant, more mates, give best female best sperm—assume red comb is better female. Subordinate, fewer mates, maximize each mating by giving equal quality sperm
Newly subordinate male will start to produce fewer sperm and give equal quality to all mates
2 dead crickets, 10 males, 10 females in a cage. Different sized males. Test: remove largest males, observe behavior of remaining males