Mitochondrial DNA sequence evolution in sharks: rates, patterns, and phylogenetic inferences

Abundant representation of sharks in the fossil record makes this group asuperb system in which to investigate rates and patterns of molecularevolution and to explore the strengths and weaknesses of phylogeneticinferences from molecular data. In this report, the molecular evolution ofthe cytochrome b gene in sharks is described and the information related toresults from phylogenetic analysis of the data evaluated in the light of aphylogeny derived independently of the molecular data. Across divergentlineages of sharks there is evidence for significant substitution ratevariation, departure from compositional equilibrium, and substantialhomoplasy; nevertheless, the signal of evolutionary history is evident inpatterns of shared transversions and amino acid replacements.