EVOLUTIONARY SHIFTS IN 3 MAJOR STRUCTURAL FEATURES OF THE MITOCHONDRIAL GENOME AMONG IGUANIAN LIZARDS

A phylogenetic tree for major lineages of iguanian lizards is estimate d from 1,488 aligned base positions (858 informative) of newly reporte d mitochondrial DNA sequences representing coding regions for eight tR NAs, ND2, and portions of ND1 and COI. Two well-supported groups are d efined, the Acrodonta and the Iguanidae (sensu late). This phylogeneti c hypothesis is used to investigate evolutionary shifts in mitochondri al gene order, origin for light-strand replication, and secondary stru cture of tRNA(Cys). These three characters shift together on the branc h leading to acrodont lizards. Plate tectonics and the fossil record i ndicate that these characters changed in the Jurassic. We propose that changes to the secondary structure of tRNA(Cys) may destroy function of the origin for light-strand replication which, in turn, may facilit ate shifts in gene order.