You Learned How Freshwater Stickleback Populations Have Lost Their Body

Essay

You learned how freshwater stickleback populations have lost their body armor through positive selection of a low-armor Eda allele, which is found at low frequency in marine populations. Draw (a) a phylogenetic tree that would support the hypothesis that the low-armor phenotype arose once and then spread throughout freshwater populations and (b) a phylogenetic tree that would support the hypothesis that the phenotype arose independently multiple times in freshwater populations.