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Nucleotide sequences of mitochondrial genes (ND1, ND2, COI, and tRNAs) were determined for 38 samples representing 15 taxa of tropidurid lizards from the Galapagos Islands and mainland South America. Phylogenetically informative characters (759 of 1956) were analyzed under Bayesian, maximum likelihood, and parsimony frameworks. This study supports the hypothesis that tropidurid lizards dispersed to the Galapagos on at least two separate occasions. One dispersal event involved an eastern Galapagos clade (Microlophus habelii and M. bivittatus, on Marchena and San Cristobal islands, respectively) the sister taxon of which is M. occipitalis from coastal Ecuador and Peru; the closest mainland relative of the western Galapagos clade was not unambiguously identified. The wide-ranging M. albemarlensis is revealed to be a complex of weakly divergent lineages that is paraphyletic with respect to the insular species M. duncanensis, M. grayii, and M. pacificus. [Copyright &y& Elsevier]