How does sexual selection influence animal behavior?

1. How does sexual selection influence animal behavior? A (male) sage grouse

2. 6/10/08: Reproduction: Sexual Selection Lecture objectives: • Be able to define sexual selection and use the theory to generate hypotheses and predictions • Understand why and how male-male competition can select for reproductive-related behaviors and traits • Understand why and how female choice can select for reproductive-related behaviors and traits

3. Darwin recognized that some individuals have a reproductive advantage over others Sexual selection: a form of natural selection that occurs when individuals relative to others of the same sex Sexually selected traits: 1. 2. (males compete; females choose)

4. Sexually selected traits/behaviors arise from… Male-male competition(Intrasexual selection) Female choice(Intersexual selection) - Aggression- Distinct/Alternative mating strategies- Sperm competition- Mate guarding - Parental effort- Nuptial gifts- Ornaments & courtship that don’t include material benefits

5. Male-male competition can select for traits related to aggression over mating

6. Male-male competition can select for alternative mating strategies Marine isopod males alpha beta gamma # females

7. Male-male competition can select for mate guarding Benefits of guarding a female (post-mating)_________as the risk that she will mate again increases Hypothesis: Males millipedes “ride” females as a form of mate guarding Time riding Millipede with pair

8. Male-male competition can select for sperm competition Females in many species will mate with ______________and use their sperm to fertilize her eggs Outcome might be determined by:- - - -

9. Elaborate male genitalia: Females have the opportunity to mate with >1 male Females are mostly monogamous Females have short periods of receptivity Females have longer periods of receptivity Elaborate male genitalia:

10. Female choice can select for males that advertise paternal effort (“I’ll be a good dad!”) signal:Body shaking as an honest signal of paternal effort in 15-spined sticklebacks signal:Song as an honest signal of paternal effortin sedge warblers

11. Female choice can select for nuptial gift-giving A transferred by a male to a female just prior to or during mating * Males that give larger gifts will have a higher reproductive success…because the female leaves as soon as she’s done eating! Gift of a ____: Male hangingflies

12. Nuptial gifts (continued)… Gift of __________ (as a meal): Sexual cannibalism in male redback spiders - Eaten males fertilize more eggs than uneaten males (full female is less likely to mate again soon) - Males have a 20% chance of finding a mate

13. Nuptial gifts (continued)… Gift of _______________:Transfer of alkaloids in spermatophores of moths Hypothesis: PA (-) females will develop after mating with a PA (+) male Utetheisa ornatrix I like a man…er, moth, with high levels of PA!

14. Nuptial gifts (continued)… Gift of ___________Sex is thirst-quenching for female Bruchid beetles Gift of … __________________ Spermatophores: ~10% of male body weight Dehydrated females were more likely to mate Once hydrated, a female was less likely to mate with another male

15. Female choice can select for male ornaments and courtshipthat provide no material benefits Jumping spider courtship Widowbird

16. 1. Healthy mate theory: females choose males who are likely to have good health

17. 2. Good genes theory: females choose males who are likely to have good genes

18. 3. Sexy sons theory: females choose males who are likely to have sexy sons Example: Attractiveness in Drosophila males is __________(sexy males had sexy sons) Son: Time before mating What might make a trait “sexy”? Male: Time before mating

19. Intra and Intersexual selection often go hand-in-hand Function of display? Done in presence of males and females Elephant seals Amazonian river dolphins

20. Sexual conflict arises when males and females have different interests __________________ in orangutans ________________ in Panorpa scorpionflies