Genetic diversity is arguably the most important aspect of the genetic analysis of single populations. In this chapter we have looked at methods for quantifying genetic diversity and also at some of the factors that influence genetic diversity. An overview of the main factors that influence the genetic diversity of populations is shown in Figure 3.14. Note that although factors that reduce genetic diversity outnumber those that increase it, levels of genetic diversity within most populations remain high. It should be evident from Figure 3.14 that we have not yet discussed one key process that increases within-population

Mutation \

Balancing selection

ÎGenetic diversity

Sexual reproduction / _

Directional selection

┬┐Genetic diversity


Small population -size

TGenetic drift t

TGenetic drift

Immediate loss of alleles t lNe

~ Population -bottlenecks

Variance in """" reproductive success, uneven sex ratio

Figure 3.14 An overview of some of the main factors that influence levels of genetic diversity within populations genetic diversity, and that is gene flow. We have excluded gene flow so far because it involves interactions between multiple populations, but it is an extremely important factor in population genetics and will be a main topic of discussion in the next chapter, which is concerned with the genetics of multiple populations.

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