Lec13 Mating Systems

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Lec13 Mating Systems

  1. 1. Mating Systems <ul><li>Review of reproductive strategies from previous lecture </li></ul>
  2. 2. Mating Systems <ul><li>Monogamy </li></ul><ul><li>Polyandry </li></ul><ul><li>polygamy </li></ul>
  3. 3. Mating System <ul><li>You should be able to address the following questions: </li></ul><ul><ul><li>What sexual strategies are used in different mating systems? </li></ul></ul>
  4. 4. Mating System <ul><li>You should be able to address the following questions: </li></ul><ul><ul><li>Why is it questionable whether polyandry is adaptive? What factors would make it adaptive and what factors would not? Why are females polyandrous? </li></ul></ul>
  5. 5. Mating System <ul><li>You should be able to address the following questions: </li></ul><ul><ul><li>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? </li></ul></ul>
  6. 6. Mating System <ul><li>You should be able to address the following questions: </li></ul><ul><ul><li>Why is there a high diversity of polygamous sytems? </li></ul></ul>
  7. 7. Mating Systems: What are we talking about? <ul><li>Evolutionary point of view </li></ul><ul><ul><li>What happens in a mating system related to natural selection? </li></ul></ul>
  8. 8. Mating Systems: What are we talking about? <ul><li>Evolutionary point of view </li></ul><ul><ul><li>What factors related to mating systems influence an individuals fitness? </li></ul></ul>
  9. 9. Mating Systems <ul><li>Mating systems primarily refers both to copulation events and offspring produced </li></ul><ul><ul><li>Additional behaviors influence if offspring are produced/survive from copulation </li></ul></ul>
  10. 10. Mating Systems <ul><li>Several factors influence system </li></ul><ul><ul><li>Amount of Parental care </li></ul></ul><ul><ul><li>Availability of other mates </li></ul></ul><ul><ul><li>Frequency of mating with same partner </li></ul></ul>
  11. 11. Operational Sex Ratio <ul><li>OSR – operational sex ratio </li></ul><ul><ul><li>Males ready to mate: females ready to mate </li></ul></ul><ul><ul><li>Ratio of males to females, given they have different energy investments in reproduction </li></ul></ul><ul><ul><li>Biased to sex with lowest reproductive investment in each offspring </li></ul></ul><ul><ul><li>Gives that sex greater potential to increase genetic fitness through polygamous mating </li></ul></ul>
  12. 12. Reproductive Rate <ul><li>What is a reproductive rate? </li></ul><ul><li>What factors influence a reproductive rate? </li></ul>
  13. 13. Potential reproductive rates <ul><li>PRR – potential reproductive rates </li></ul><ul><ul><li>Sex with highest PRR has greatest capacity for polygamy </li></ul></ul><ul><li>Temporal and spatial distribution of mates may alter the potential for polygamy and thus influence mating patterns </li></ul><ul><li>If females only encounter one mate ata a time then monogamous patterns may arise </li></ul>
  14. 14. Monogamy <ul><li>Mate-assistance (male parental investment required) </li></ul><ul><li>Female-enforced monogamy </li></ul><ul><li>Mate-guarding (male mate-guarding is beneficial when females are receptive to males after mating and are rare, and females don’t kill males) </li></ul>
  15. 15. Monogamy: Mate Assistance <ul><li>Hypothesis: monogamy is advantageous to males because ecological factors when there are advantages to: </li></ul><ul><ul><li>parental care of offspring </li></ul></ul><ul><ul><li>protection of offspring </li></ul></ul>
  16. 16. Monogamy: Mate Assistance <ul><li>Example </li></ul><ul><ul><li>Seahorse ( Hippocampus whitei) </li></ul></ul><ul><ul><ul><li>Male seahorse – broods offspring for 3 weeks </li></ul></ul></ul><ul><ul><ul><li>Pouch has room for one clutch of eggs </li></ul></ul></ul><ul><ul><ul><li>PRR of males and females is very similar </li></ul></ul></ul><ul><ul><ul><ul><li>Females can't produce eggs faster than for one male </li></ul></ul></ul></ul><ul><ul><ul><li>Synchrony of reproductive cycle with partner increases male fitness </li></ul></ul></ul><ul><ul><li>Seahorse relative </li></ul></ul><ul><ul><ul><li>Fitness price to break off relationship </li></ul></ul></ul><ul><ul><ul><li>Travel longer distance for new mate </li></ul></ul></ul>
  17. 17. Monogamy: Female Enforced <ul><li>Female-enforced monogamy </li></ul><ul><ul><li>Example birds </li></ul></ul><ul><ul><ul><li>Female pokes holes in eggs of female </li></ul></ul></ul><ul><ul><li>Razor bills </li></ul></ul><ul><ul><ul><li>Rookeries attack females that demonstrate interest in mates </li></ul></ul></ul><ul><ul><li>Burying beetle </li></ul></ul><ul><ul><ul><li>Male and female find a carcass and bury it </li></ul></ul></ul><ul><ul><ul><ul><li>Used to feed larvae </li></ul></ul></ul></ul><ul><ul><ul><li>Male goes to top of mound to release pheremones for a second female </li></ul></ul></ul><ul><ul><ul><li>Female pushes male off perch </li></ul></ul></ul>
  18. 18. Monogamy: Mate Guarding <ul><li>Prevent female from mating with other males </li></ul><ul><li>Advantageous for males if females </li></ul><ul><ul><li>remain receptive after mating </li></ul></ul><ul><ul><li>are widely scattered </li></ul></ul><ul><ul><li>are difficult to locate </li></ul></ul><ul><li>Beneficial if both have high value partner </li></ul><ul><ul><li>e.g., cichlid fish </li></ul></ul><ul><ul><ul><li>Removed male replaced with smaller male </li></ul></ul></ul>
  19. 19. Monogamy: Parental Care <ul><li>Males that invest in parental care should be monogamous </li></ul><ul><ul><li>Little support in mammals </li></ul></ul>
  20. 20. Mating Systems <ul><li>There is a wide range of behavior patterns within polyandry and polygamy </li></ul>
  21. 21. Polyandry <ul><li>Female mates with multiple males </li></ul>
  22. 22. Polyandry <ul><li>Examples </li></ul><ul><ul><li>Honey bees </li></ul></ul><ul><ul><ul><li>Queen honey bees mate with many drones (a dozen); </li></ul></ul></ul><ul><ul><ul><li>drones mate with one queen </li></ul></ul></ul><ul><ul><ul><li>Queens will produce offspring with up to 12 different paternities </li></ul></ul></ul><ul><ul><li>Queen ants </li></ul></ul><ul><ul><ul><li>Ability of ants to select sperm from different males (e.g., alternate generations different paternity, Sweden) </li></ul></ul></ul>
  23. 23. Polyandry: Female Choice <ul><li>Female Choice </li></ul><ul><ul><li>Females avoid extra-pair copulation </li></ul></ul><ul><ul><li>Female solicit extra-pair copulations </li></ul></ul><ul><ul><li>Selected sperm use by females </li></ul></ul><ul><ul><ul><li>Sperm removal by females </li></ul></ul></ul><ul><ul><ul><ul><li>e.g., birds </li></ul></ul></ul></ul><ul><ul><ul><li>Ants control use of which sperm for offspring </li></ul></ul></ul>
  24. 24. Polyandry: Benefits <ul><li>Benefits: Good genes hypothesis </li></ul><ul><ul><li>Guppies </li></ul></ul><ul><ul><ul><li>80% more offspring </li></ul></ul></ul><ul><ul><ul><li>Offspring hatched 9 days sooner </li></ul></ul></ul><ul><ul><ul><li>Mothers were more competent </li></ul></ul></ul><ul><ul><li>Yellow-toothed cavy (wild guinea pig) </li></ul></ul><ul><ul><ul><li>Reduced stillbirths and loss before weaning </li></ul></ul></ul><ul><li>How does sperm competition fit in here? </li></ul><ul><li>Female choice for males in good condition </li></ul>
  25. 25. Polyandry: Benefits <ul><li>Benefits: Good genes hypothesis </li></ul><ul><ul><li>Genetic compatibility </li></ul></ul><ul><ul><li>Number of offspring fertilized by one male was not consistent among females </li></ul></ul><ul><ul><ul><li>Rooster sperm. </li></ul></ul></ul><ul><ul><li>Female scorpions more likely to mate with stranger than a male she just mated with </li></ul></ul>
  26. 26. Polyandry: Benefits <ul><li>Benefits: Increase material benefit </li></ul><ul><ul><li>Foraging territory </li></ul></ul><ul><ul><ul><li>e.g., polyandrous red-winged black-birds can forage on male controlled territories while monogamous birds are chased away </li></ul></ul></ul><ul><ul><li>Female Galapagos hawks control foraging territory </li></ul></ul><ul><ul><ul><ul><li>Turn over territory to Multiple males to patrol </li></ul></ul></ul></ul>
  27. 27. Polyandry: Benefits <ul><ul><li>Spermatophore </li></ul></ul><ul><ul><ul><li>Contains nutritional value for female in some species (e.g., butterflies) </li></ul></ul></ul><ul><ul><ul><li>Can be 15% of male's body weight </li></ul></ul></ul><ul><ul><ul><li>More males, more spermatophores, more offspring </li></ul></ul></ul>
  28. 28. Polyandry: Benefits <ul><li>Parental assistance from more than one mate </li></ul><ul><ul><li>Female dunnocks </li></ul></ul><ul><ul><li>Dominant and subordinate male </li></ul></ul><ul><ul><li>Both males will provide parental care if they have mated with female enough </li></ul></ul>
  29. 29. Polyandry: Benefits <ul><ul><li>Protection against dangerous males </li></ul></ul><ul><ul><ul><li>Primates </li></ul></ul></ul><ul><ul><ul><li>Reduce infanticide (Hanuman lemurs) </li></ul></ul></ul><ul><ul><ul><ul><li>Males that have mated with a female will tend to leave her offspring alone </li></ul></ul></ul></ul>
  30. 30. Polyandry: Benefits <ul><li>Benefits: Fertility insurance hypothesis </li></ul><ul><ul><li>Increased likelihood of </li></ul></ul><ul><ul><ul><li>polyandrous red-winged blackbirds eggs to hatch </li></ul></ul></ul><ul><ul><ul><li>Pregnancies in Gunnison's prairie dogs </li></ul></ul></ul><ul><ul><li>Rapid loss of sperm in bearded tit </li></ul></ul>
  31. 31. Polyandry:Risks <ul><li>Loss of partner (e.g., for parental care) </li></ul>
  32. 32. Polyandry:Risks <ul><li>Venereal Disease </li></ul><ul><ul><li>Relationship between degree of polyandry and white blood cell count </li></ul></ul>
  33. 33. Polygamy <ul><li>Does it make evolutionary sense? </li></ul><ul><ul><li>See PRR theory </li></ul></ul>
  34. 34. Polygamy <ul><li>Diversity of Polygamy </li></ul><ul><ul><li>Female defense </li></ul></ul><ul><ul><li>Resource Defense </li></ul></ul><ul><ul><li>Scramble competition </li></ul></ul><ul><ul><li>Lek </li></ul></ul>
  35. 35. Polygamy <ul><li>Female defense </li></ul><ul><ul><li>Males fight with other males to monopolize females </li></ul></ul><ul><ul><ul><li>e.g., elephant seal harems </li></ul></ul></ul>
  36. 36. Polygamy <ul><li>Resource Defense </li></ul><ul><ul><li>Males defend territories with resources that females need to reproduce </li></ul></ul>
  37. 37. Polygamy <ul><li>Scramble competition </li></ul><ul><ul><li>Temporal competition for mates </li></ul></ul><ul><ul><ul><li>e.g., butterflies </li></ul></ul></ul><ul><ul><li>Avoid combat </li></ul></ul><ul><ul><li>Do not control territories </li></ul></ul>
  38. 38. Polygamy <ul><li>Lek </li></ul><ul><ul><li>No food or resource benefits of a lek </li></ul></ul><ul><ul><li>Very few males mate with females </li></ul></ul><ul><ul><ul><li>e.g., grouse </li></ul></ul></ul><ul><ul><li>Similarly bower of bower bird contains few resources for female </li></ul></ul>

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