Answer:
Option A
Step-by-step explanation:
Options
A. most populations were fixed for a single genotype, but genotypes varied among populations
B. average heterozygosity was declining steadily over time
C. individual populations were polymorphic for several loci and most populations were genetically similar to one another
D. all populations were fixed for the same allele at each locus studied
Solution
As per the study conducted by Templeton, it was found that human affect the biodiversity at all biological levels such as genetic, ecosystem, species etc. and behind genetic variation two important factors are genetic drift and gene flow.
Both the gene flow and genetic drift produce opposite results as genetic drift increase variation with in the species but decrease variation with in the local population and the opposite of this happens in gene flow.
Genetic drift has actually lead to speciation of collared lizards among themselves for a specific genotype
Hence, option A is correct