A population of wildflowers (species Lupinus texensis) growing in a prairie was studied for two alleles at a single gene locus: allele A and allele a. In 2015, the population consisted of 10 000 individuals, and the allele frequencies were: frequency of A = 0.70, frequency of a = 0.30. In 2016, a severe wildfire killed 98% of the plants, leaving only 200 survivors. The surviving plants were distributed randomly with respect to their genotype. Researchers then monitored the population as it recovered. The allele frequencies in the surviving population (immediately after the fire) were: frequency of A = 0.85, frequency of a = 0.15.
Describe the change in allele frequencies and explain how the bottleneck event contributed to this change. Refer to the concepts of genetic drift and natural selection in your answer.