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Sexual Selection

Sexual Selection. Motivation Sexual Dimorphism is Frequent. The sexual dimorphism in. Scarlet Tanagers, male, female Wesern Tanagers, male female. long-tailed widowbirds. Human males and females differ in height. Why this sexual dimorphism. Selection on survivorship and reproduction

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Sexual Selection

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  1. Sexual Selection

  2. Motivation • Sexual Dimorphism is • Frequent

  3. The sexual dimorphism in Scarlet Tanagers, male, female Wesern Tanagers, male female long-tailed widowbirds

  4. Human males and females differ in height

  5. Why this sexual dimorphism Selection on survivorship and reproduction Ability to obtain mates: Sexual Selection: Different reproductive success due to variation among individuals in success at getting mates If there is heritable variation in a trait that affects to ability to obtain mates, then variants with higher success at obtaining mates will become more common over time

  6. II. Limits to reproduction differ between the sexes

  7. Guess What? With few exceptions, females invest much more time and energy in the production of young

  8. Asymmetries in sexual reproduction in rough-skinned newts

  9. Asymmetries in sexual reproduction in rough-skinned newts females males

  10. Exception to the Rule?” Asymmetries in sexual reproduction in broad-nosed pipefish Male with Kids (in pouch)

  11. Males Females

  12. Consequences of Asymmetric Limits on Fitness • Members of the sex subject to strong sexual selection will be competitive (Male-male competition) • Members of the sex subject to weak sexual selection will be choosy (Female Choice) • Bateman’s rule, males limited by access to mates, females limited by resources

  13. III. Natural Selection Limits Sexual Selection e.g., marine iguanas

  14. Larger iguanas expend more energy on metabolism

  15. Male marine iguanas in combat

  16. Large territorial males

  17. Alternative mating strategies in coho salmon

  18. IV. Male Access to Females Sperm Competition

  19. Sperm competition in damselflies

  20. Sperm Swimming Speeds Sperm morphology in rodents All for one and one for All!

  21. Infanticide

  22. V. Evidence for Sexual Selection on Traits

  23. Long tail feathers are a ball-and-chain for male red-collared widowbirds

  24. Female red-collared widowbirds prefer long-tailed males

  25. VI. Fisher’s Run Away Sexual Selection An example from UMD

  26. How runaway selection works in theory

  27. VII. Good genes model of sexual selection

  28. Are male gray tree frogs that give long calls genetically superior to males that give short calls??

  29. Courtship and mating in hangingflies

  30. VIII. Origin of Trait Selection Water mite waiting in ambush for a copepod, male has found her

  31. A phylogeny of the water mite Neumania papillator and several related species. The boxes above the tips of the branches indicate which species have net-stance and which species have male courtship trembling. A colored box indicates the trait is present; an open box indicates the trait is absent. The two versions of the phylogeny show the two most likely scenarios for the evolution of these two traits. Redrawn from Proctor (1992).

  32. Lilies from from SW Aust.

  33. IX. Sexual Selection in Plants

  34. X. SEXUAL SELECTION IN HUMANS Kipsigis men and women

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