Evolution of Animal Mitochondrial Dna: Relevance for Population Biology and Systematics

In the past decade, mitochondrial DNA (mtDNA) analysis has become established as a powerful tool for evolutionary studies of animals. These studies, recently reviewed by Avise (8) and Wilson et al (149), have used mtDNA analyses to provide insights into population structure and gene flow, hybridization, biogeography, and phylogenetic relationships. Major advances have been made in our understanding of the molecular biology of animal mtDNA (reviewed in 7, 28). A powerful synergism exists between the two fields of research: Evolutionary studies provide comparative data on mtDNA organization and function, and molecular investigations can, and should, improve the level of sophistication of evolutionary studies that use mtDNA. Here we focus on molecular aspects of animal mtDNA that are especially relevant to its use in evolutionary studies. Thus, we consider the form and frequency of three types of change in mtDNA: base substitution, length variation, and sequence rearrangement. Attention is also given to the nature and possible consequences of interactions between nuclear and mitochondrial (mt) genes. In the concluding sections, we discuss the way in which the knowledge of molecular processes allows informed use of mtDNA variation in evolutionary studies. Only animal mtDNAs are considered. The molecular biology and evolution of chloroplast DNA and nonmetazoan mtDNAs have been reviewed elsewhere (41, 66, 111, 121, 123).