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Chapter 23
Why do high rates of evolutionary change and a limited number of character states cause
problems for parsimony analyses? (Page 458)
Answer: In parsimony analyses of phylogenies, the least complex explanation is favored.
High rates of evolutionary change and few character states complicate matters. High rates
of evolutionary change, such as occur when mutations arise in noncoding portions of
DNA, can be misleading when constructing phylogenies. Mutations arising in noncoding
DNA are not eliminated by natural selection in the same manner as mutations in coding
(fiunctional) DNA. Also, evolution of new character states can be very high in
nonfunctional DNA and this can lead to genetic drift. Since DNA has only four
nucleotides (four character states) it is highly likely that two species could evolve the
same derived character at a particular base position. This leads to a violation of the
assumptions of parsimony – that the fewest evolutionary events lead to the best
hypothesis of phylogenetic relationships – and resulting phylogenies are inaccurate.