Natural and artificial selection — practice question

Collared lizards, Crotaphytus collaris, vary in body length and running speed. An investigation was done to discover whether body length and running speed influenced how many offspring a male lizard sired. A large number of male lizards was trapped during the breeding season. For each lizard, body length was measured, it was chased along a short race track and its top running speed over $1\,\text{m}$ was recorded, and a blood sample was collected and DNA sequences at $10$ different loci were analysed. The lizards were then released back into the place where they had been caught, so that mating could take place. Several weeks later, after the lizards’ eggs had hatched, as many young hatchlings as possible were captured. DNA testing was carried out on each hatchling to identify which male was the father. The results were then used to work out the number of offspring sired by each of the male lizards in the initial sample.