On genetic flow and variance and on the place of this in facilitating the evolutionary process
ALLOGENIC – Causing or precipitating environmental change
ECESIS –Establishment of an organism in a new environment
AUTOGENIC – Genetic change to fit new environment
CLINAL VARIATION–Continuous variation over a wide band
NATURAL SELECTION – The circumstances whereby particular individuals can preferentially within a population give rise to offspring due to unique and appropriate genetic makeup.
SUCCESSION – Changes in species makeup within a defined ecosystem over time.
OK, sometime long ago I noted down the following quote:
“Autogenic versus allogenic = succession, dispersal and ecesis versus environmental change.”
And it’s kind of stuck with me, tho’ I forget who I’m actually quoting!
An allogenic phenomenon allows autogenesis followed by ecesis although there could be natural selection from clinal variation within the original population.
Without allogenic change then autogenesis proves selectively disadvantageous or just stocks up the clinal variation.
Succession occurs between species within a fixed climatic and edaphic situation but in response to changes wrought on the ecosystem by the species’ maturation. Primary succession brings about microclimatic variances and the build up of secondary edaphic effects like soil accumulation en route to an eventual climactic state, secondary succession being an ongoing maintenance of an ecosystem’s dynamic equilibrium, always leading back to a previously known climax state. Autogenic change could be expressed during secondary succession or during a period of climatic or other change.
Multi allelic processes. Many enzymes and other products are coded at several different loci in the genome – generally recognised in plants – and this allows far greater flexibility in catering for change. Mutation giving potential for autogenic change at only one of several loci coding for a necessary gene product would probably not to any great extent damage the performance of an organism. If, however, allogenic change occurred then selection for new gene products would show up the existing gene and its now beneficial product. Time might allow for gradual increase in the presence of this gene within the population, within the ecosystem concerned.
What might affect the distribution of such pre-dispositional mutations within a non-allogenic situation? They could arise at random but be non selective passengers. Thus any climax population should consist of individuals loaded with non-related, non-advantageous variations in their genetic codes, possibly maintaining them at below optimal efficiency but giving the population selective adaptability without compromising its established place within the climax community. One could deduce a relationship between the lowered efficiency and the quantity of adaptability needed to allow continued survival of the population.