Consider substitutions accumulating at neutral loci (i. e., the fixation of mutations due to drift) in populations of two organisms, milkweed beetles with a huge population and mountain lions with a small population. In which organism would you expect substitutions to accumulate at a higher rate

substitutions will accumulate faster in mountain lions

Explanation:

Genetic drift is the stochastic change in the allele frequencies in a population due to random sampling events. Genetic drift is known to produce the fixation of alleles (where allele reaches a frequency of 1) or loss of neutral genetic diversity in a population. Genetic drift conducts a population towards genetic uniformity over time. Neutral substitution refers to the emergence of a previously non-existent gene variant that arises by neutral mutations (i.e mutations that do not confer an adaptive advantage), which may be subsequently fixed or lost by genetic drift. The rate of neutral allele fixation is higher in smaller populations because drift (random sampling) is maximized, whereas in populations with infinite size fixation cannot be achieved. In consequence, neutral substitutions will accumulate faster in small populations than in large populations.