Macroevolution

vocabulary:  niche, species, speciation, sympatry, allopatry, reinforcement, hybridization
  1. Species concepts
    1. biological
    2. evolutionary (phylogenetic)
  2. Macroevolution
    1. speciation
      1. allopatry:  separation of populations by habitat, mating behavior, etc.
      2. sympatry:  a matter of degree
      3. mutation:  changes in ploidy level
      4. reinforcement and hybridization
    2. Examples
Study questions

1. Which of the following statements do scientists currently regard as correct?

  1. The length of time necessary for two separate populations of a single species to diverge genetically to the point at which they can no longer interbreed depends in part on how different their environments are.
  2. When remote new habitat is created, such as the Galapogos Islands, there are many unoccupied niches. The first animals and plants that arrive can fill many ecological roles, and may rapidly evolve into different species that fill each of these roles. This is called diversification.
  3. Convergent evolution is when two closely related species utilize their bodies and their environment in the same fashion.
2.  Many biologists believe that allopatry is a matter of scale:  for some organisms, very small distances might suffice.  What is an example of an organism where a allopatric speciation might occur over a very short distance?  What is an example of an organism where allopatric speciation might require very large distances?

3.  The soapberry bug example in the text book (pg. 454) is presented as an example of sympatric speciation.  Use it to discuss why "sympatry" and "allopatry" are end-points on a continuum.

4.  The soapberry bugs mate on their host plants. This is not true for many insects, for instance many butterflies group into "leks" on hilltops.  How might this story be different, if mating occured at a common area such as a hilltop?

5.  Categorize each of the following as "prezygotic" or "postzygotic"  isolation.
  1. Female crickets only respond to males that "sing" the appropriate song.
  2. Male moths are only attracted to females producing a particular chemical perfume (pheromone)
  3. Mules, products of horses mated with donkeys, are sterile.
  4. Flowers of many plants prevent the pollen from germinating, thereby preventing the male nucleus from reaching the egg.
  5. In two species of wolf spiders, matings can be forced by "drugging" the female - the males will mate with females from either species.  Hybrid males have very low mating success, as they have mixed courtship behavior that pleases no females.

6.  Allopatry is defined in your textbook as physical isolation through geographic isolation.  Can you think of other environmental factors that might produce physical isolation of reproductive individuals without geographic isolation?

Answers