Biology 338: Lecture 20Spring 1997

Cooperative Breeding

  1. What do "helpers" do?

  2. Do "helpers" really enhance group reproductive success?
    1. Scrub jays
    2. Silver-backed jackals
    3. Grey-crowned babblers

  3. Who are the "helpers" helping?

  4. How does helping evolve?
    1. Two-step process
      1. Ecological/demographic constraints necessitate staying at home
      2. Net fitness gains by helping > net fitness gains by not helping
    2. Observational/experimental support
      1. Scrub jays
      2. Seychelles warblers

  5. Vertebrates vs. invertebrates

  6. Case study: Paper wasps
    1. Natural history
    2. Why do subordinate females help?
      1. Subfertility of the subordinate foundress
      2. Joint defense against predation
      3. Economic synergism
      4. Survivorship insurance
    3. Social contracts