1. Lecture 7. Sexual Selection

2. Costs of sex Cost of meiosis Cost of producing males Cost of courtship and mating

3. Benefits of sex Protection against mutations (Muller’s ratchet) Protection against environmental changes (Raffle hypothesis) Protection against biotic fluctuations (Red Queen hypothesis)

4. ”Now here, you see, it takes all the running you can do to keep in the same place.” The Red Queen hypothesis

5. Why do male and female gametes differ in size? Geoffrey Parker et al.: divergent evolutionary selection favoured two types of gametes:  small and mobile (sperm)  sedentary and packed with nutrients (eggs)

7. Darwin (1871, p256): “We are, however, here concerned only with that kind of selection, which I have called sexual selection. This depends on the advantage which certain individuals have over other individuals of the same sex and species, in exclusive relation to reproduction.”

8. Sexual selection 1. More individuals are produced than manage to reproduce 2. Individuals differ in their ability to compete with others for mates or to attract members of the opposite sex  Result: the evolution of traits that enhance reproductive success while decreasing survivorship

9. What about these

10. Inrasexual Selection Members of one sex compete among themselves for access to members of the other sex Competition before mating Competition after mating Competition following conception

11. Bruce effect in rodents The pregnancy of a recently inseminated female is terminated upon exposure to an unfamiliar male

12. Male infanticide in langur monkeys.

13. Male infanticide in lions

14. Explain This ?

15. Intersexual Selection  Members of one sex (mostly males) ‘advertise’ that they are worthy of an investment.  Members of the other sex (usually females) choose among them.

16. Sexually selected “ornaments” of males Darwin argued that sexual selection via female choice was responsible for the evolution of male displays and plumage

17. The widowbird (Euplectes progne), a species the size of a blackbird that is endowed with a half-meter long tail Sexual selection for tail length in long-tailed widowbirds (Andersson 1982)

18. Mate-choice copying in the guppy (Poecilia reticulata ) One female’s choice of a mate affects another female’s choice

19. Male zebra finch

24. Fluctuating asymmetry: The extent of asymmetry in bilaterally symmetrical traits Sailfin Molly (Poecilia velifera)

25. Normal HighPerfect