4VariacionEvolucion2b copy.pdf - Instituto de Ecología

Tajima D´s (1983)!Compares the diversity as estimated with the allelic frequenciesaccording to the “nucleotidic diversity (π),with the diversity estimated with the segregating sites, (θ).D= (πθ)/square root (variance(πθ))If π & θ are equal, we are in the neutral conditions, No naturalselection!If positive, suggest diversifying/balancing selection, πlarger than θ, in words, some alleles are more common thanexpected, due to their advantages in W, due to selectionsNegative: Indicates directional or purifying selection, πless than θ: alleles in lower frequencies than expected at random,due to selection eliminating them