| Study and Review Hint for question 8 Review section 14.2, The Phylogeny of Whales. Interpreting character changes in DNA sequences is more complex than it might appear. Suppose two taxa differ in a DNA sequence at one base position. Given that there are only 4 bases, how do we know whether that one base difference represents a single mutation or multiple mutations? Might a reversal have created a homoplasy? To evaluate these possibilities, investigators must specify models of DNA evolution in their analyses; these models make explicit assumptions about rates of change, which types of base substitutions are most likely, etc. So once again, there's more to phylogeny inference than meets the eye! |