Friday, October 3, 2014

Genetic Polymorphism


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.)


  • "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


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