What is the standing genetic variation?
Standing genetic variation is when there is more than one allele at locus in the population at the time-point in question. When an allele goes to fixation there is no standing genetic variation at the locus until new mutations occur. Loci where alleles are not fixed are described as having standing genetic variation.


  "Standing genetic variation: the presence of more than one allele at a locus in a
  population."


from Barrett and Schluter 2007