Friday, October 3, 2014

Genetic Polymorphism

Thoughts

When selecting a plant from its natural habitat, say from Aswan, to transplant elsewhere, it is a good idea to select from a location that would provide the characteristics you desire in the plant (ex: lower elevation to be more drought tolerant ... etc.)

Digest

  • "The distinction between local ecotypes and polymorphic populations is not always a clear one."
  • Genetic polymorshipsm was defined by Edmund Brisco Ford in 1940 as: "the occurrence together in the same habitat of two or more discontinuous forms of a species in such proportions that the rarest of them cannot merely be maintained by recurrent mutation or immigration".
  • Transient polymorphisms occur when conditions in a habitat change so that one form is being replaced by another.
  • In contrast to transient polymorphism, many polymorphisms are actively maintained in a population by natural selection, and there are a number of ways in which this may occur:
    • Heterozygotes may be of superior fitness, but continually generate less fit homozygotes within the population
    • Presence of gradients of selective forces favoring one morph at one end of the gradient and another form at the other
    • There may be frequency-dependent selection in which each of the morphs of a species is fittest when it is rarest
    • Selective forces may operate in different directions within different patches in the population

Questions

  1. What is the difference between polymorphism and ecotypes?
  2. What is polymorphism?
  3. What are ecotypes?