The document discusses different mating systems such as monogamy, polyandry, and polygamy. It addresses factors that influence which system is evolutionarily adaptive, including parental investment, operational sex ratio, reproductive rates, and benefits/risks of each system. Examples are provided for different mating behaviors in species from insects to mammals. The diversity of polygamous systems is also examined, including female defense, resource defense, scramble competition, and leks.

1. Mating Systems Review of reproductive strategies from previous lecture

2. Mating Systems Monogamy Polyandry polygamy

3. Mating System You should be able to address the following questions: What sexual strategies are used in different mating systems?

4. Mating System You should be able to address the following questions: Why is it questionable whether polyandry is adaptive? What factors would make it adaptive and what factors would not? Why are females polyandrous?

5. Mating System You should be able to address the following questions: Is monogamy adaptive? What theories and data indicate it is and is not? What factors may influence whether or not it is adaptive? Why are males ever monogamous?

6. Mating System You should be able to address the following questions: Why is there a high diversity of polygamous sytems?

7. Mating Systems: What are we talking about? Evolutionary point of view What happens in a mating system related to natural selection?

8. Mating Systems: What are we talking about? Evolutionary point of view What factors related to mating systems influence an individuals fitness?

9. Mating Systems Mating systems primarily refers both to copulation events and offspring produced Additional behaviors influence if offspring are produced/survive from copulation

10. Mating Systems Several factors influence system Amount of Parental care Availability of other mates Frequency of mating with same partner

11. Operational Sex Ratio OSR – operational sex ratio Males ready to mate: females ready to mate Ratio of males to females, given they have different energy investments in reproduction Biased to sex with lowest reproductive investment in each offspring Gives that sex greater potential to increase genetic fitness through polygamous mating

12. Reproductive Rate What is a reproductive rate? What factors influence a reproductive rate?

13. Potential reproductive rates PRR – potential reproductive rates Sex with highest PRR has greatest capacity for polygamy Temporal and spatial distribution of mates may alter the potential for polygamy and thus influence mating patterns If females only encounter one mate ata a time then monogamous patterns may arise

14. Monogamy Mate-assistance (male parental investment required) Female-enforced monogamy Mate-guarding (male mate-guarding is beneficial when females are receptive to males after mating and are rare, and females don’t kill males)

15. Monogamy: Mate Assistance Hypothesis: monogamy is advantageous to males because ecological factors when there are advantages to: parental care of offspring protection of offspring

16. Monogamy: Mate Assistance Example Seahorse ( Hippocampus whitei) Male seahorse – broods offspring for 3 weeks Pouch has room for one clutch of eggs PRR of males and females is very similar Females can't produce eggs faster than for one male Synchrony of reproductive cycle with partner increases male fitness Seahorse relative Fitness price to break off relationship Travel longer distance for new mate

17. Monogamy: Female Enforced Female-enforced monogamy Example birds Female pokes holes in eggs of female Razor bills Rookeries attack females that demonstrate interest in mates Burying beetle Male and female find a carcass and bury it Used to feed larvae Male goes to top of mound to release pheremones for a second female Female pushes male off perch

18. Monogamy: Mate Guarding Prevent female from mating with other males Advantageous for males if females remain receptive after mating are widely scattered are difficult to locate Beneficial if both have high value partner e.g., cichlid fish Removed male replaced with smaller male

19. Monogamy: Parental Care Males that invest in parental care should be monogamous Little support in mammals

20. Mating Systems There is a wide range of behavior patterns within polyandry and polygamy

21. Polyandry Female mates with multiple males

22. Polyandry Examples Honey bees Queen honey bees mate with many drones (a dozen); drones mate with one queen Queens will produce offspring with up to 12 different paternities Queen ants Ability of ants to select sperm from different males (e.g., alternate generations different paternity, Sweden)

23. Polyandry: Female Choice Female Choice Females avoid extra-pair copulation Female solicit extra-pair copulations Selected sperm use by females Sperm removal by females e.g., birds Ants control use of which sperm for offspring

24. Polyandry: Benefits Benefits: Good genes hypothesis Guppies 80% more offspring Offspring hatched 9 days sooner Mothers were more competent Yellow-toothed cavy (wild guinea pig) Reduced stillbirths and loss before weaning How does sperm competition fit in here? Female choice for males in good condition

25. Polyandry: Benefits Benefits: Good genes hypothesis Genetic compatibility Number of offspring fertilized by one male was not consistent among females Rooster sperm. Female scorpions more likely to mate with stranger than a male she just mated with

26. Polyandry: Benefits Benefits: Increase material benefit Foraging territory e.g., polyandrous red-winged black-birds can forage on male controlled territories while monogamous birds are chased away Female Galapagos hawks control foraging territory Turn over territory to Multiple males to patrol

27. Polyandry: Benefits Spermatophore Contains nutritional value for female in some species (e.g., butterflies) Can be 15% of male's body weight More males, more spermatophores, more offspring

28. Polyandry: Benefits Parental assistance from more than one mate Female dunnocks Dominant and subordinate male Both males will provide parental care if they have mated with female enough

29. Polyandry: Benefits Protection against dangerous males Primates Reduce infanticide (Hanuman lemurs) Males that have mated with a female will tend to leave her offspring alone

30. Polyandry: Benefits Benefits: Fertility insurance hypothesis Increased likelihood of polyandrous red-winged blackbirds eggs to hatch Pregnancies in Gunnison's prairie dogs Rapid loss of sperm in bearded tit

31. Polyandry:Risks Loss of partner (e.g., for parental care)

32. Polyandry:Risks Venereal Disease Relationship between degree of polyandry and white blood cell count

33. Polygamy Does it make evolutionary sense? See PRR theory

34. Polygamy Diversity of Polygamy Female defense Resource Defense Scramble competition Lek

35. Polygamy Female defense Males fight with other males to monopolize females e.g., elephant seal harems

36. Polygamy Resource Defense Males defend territories with resources that females need to reproduce

37. Polygamy Scramble competition Temporal competition for mates e.g., butterflies Avoid combat Do not control territories

38. Polygamy Lek No food or resource benefits of a lek Very few males mate with females e.g., grouse Similarly bower of bower bird contains few resources for female