Several general evolutionary predictions are testable at ‘Evolution Canyon’, bec

Question

Several general evolutionary predictions are testable at ‘Evolution Canyon’, because of the sharp interslope microclimatic contrast.

1. The warmer S-slope should harbour more ter restrial, xeric ‘tropical Asian and African’ biota and taxa, in a generally Mediterranean background. By contrast, the cooler and wetter N-slope should harbour ‘temperate European' biota and taxa, across phy- logeny.

2. Species richness across diverse terrestrial phylo genetic lineages is expected to be higher, on average, on the spatiotemporally more heterogeneous and ‘tropical’ S-slope than on the ‘temperate’ N-slope, whereas the opposite is expected for water and shade- dependent cryptogamic plants and fungi.

3. On average, genetic-diversity generating and maintaining mechanisms (mutation, recombination, sexual reproduction, and natural selection) are expected to be higher in terrestrial organisms exposed to higher radiation on the S-slope. This expectation is consistent with the environmental theory of genetic diversity (Van Valen 1965; Soule & Stewart 1970; Nevo 1988). This theory predicts higher genetic diversity as a function of a spatiotemporally more variable and stressful environment.

The 3rd prediction hypothesizes that greater genetic diversity will occur on the slope with more environmental stressors. Why would a scientist expect a more stressful environment to result in greater genetic Variation? Which slope has more environmental stressors? Explain your answer in terms of Selection.

Explanation / Answer

Stressful environmental conditions can be defined as those conditions which lead to reduction in the fitness of a group of population. Stressful condition leads in reduction of population and thus may lead to permanent damage. These stressful conditions result in the isolation of species and thus leads to a direction al evolutionary process resulting in the variation in species. A common example of such activities could be evolution of pesticides resistance insects and resistance of heavy metals in plants.

All this can be attributed to decreased gene flow and increased mutation resulting higer recombination and thus variation.

In terms of slopes S slope has more stresser as compared to N slope due to higher variations in temperature and more environmental stresses due to higher diversity.

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