The diversification of land iguanas from the Galápagos lslands: a new form of iguana traces the origin of the modern Galápagos land iguanas

The land iguanas (genus Conolophus) of the Galápagos Islands are among the most significant representatives of the fauna from that archipeiago. Their evolution consists primariiy of a history of extinctions and recolonizations, most of which left few traces in the fossil record and in the genes of the remnant populations. We used a 2.2kb sequence of mtDNA and nine microsatellite DNA loci to investigate pattems of genetic diversification and times of divergence between all extant populations. We also included the genetic analyses of a rare form of land iguana (that we refer to as rosada) from the Wolf Volcano on Isabela island. Both mtDNA and microsatellites indicated major differentiation between western and central islands. MtDNA data indicated that the current patterns and levels of genetic differentiation are not completely consistent with the age ofthe presently emerged isiands. At the base ofthe evolution and diversification of the Galápagos land iguanas, stem two lineages: the first led to the lineages ofthe extant lanci iguanas, while the second led only to the rosada form. The estimated time of such a divergence event predated the age of the oldest extant island. Despite the remarkable diversification found in the mtDNA haplotypes, microsatellite data indicate possible incomplete genetic isolation due to occasional introgression between the rosada and the syntopic yellow form. An alternative scenario that proposes a recent diversification of the rosada from populations that already had colonized Isabela was not supported by the analysis.