Phylogeography of the Caribbean rock iguana (Cyclura): Implications for conservation and insights on the biogeographic history of the West Indies

The Caribbean rock iguana, Cyclura, has had an unstable intrageneric taxono my and an unclear phylogenetic position within the family Iguanidae. We use mtDNA sequence data to address these issues and explore the phylogeographi c history of the genus. ND4 to leucine tRNA sequence data were collected fr om multiple individuals of each of the eight species of Cyclura (including 15 of 16 subspecies) and from four localities of Iguana iguana (representat ive of this species' broad geographic range). This data set was combined wi th sequence data from Sites et al. (1996, Mol. Biol. Evol. 13, 1087-1105) a nd analyzed under maximum-parsimony and maximum-likelihood optimization cri teria. The ND4 region provided good resolution for the majority of nodes, a s indicated by high bootstrap support. In agreement with several recent mol ecular studies, Cyclura is recovered as monophyletic and is not closely rel ated to any other genus, whereas Iguana is strongly supported as the sister taxon to Sauromalus. This result is statistically more likely than other p ublished hypotheses of Iguanid relationships. Cyclura shows a southeast to northwest speciation sequence in the Caribbean, with the most ancient linea ge on the Puerto Rican Bank. The amount of interspecific sequence divergenc e within Cyclura (maximum 11.4%) is very high in comparison to data from ot her iguanid taxa at this locus, suggesting that this group either has been in the Caribbean for a very long time or has gone through a very rapid rate of evolution at this locus. Using dates from other published studies, we c alculate a molecular clock that suggests that Cyclura colonized the Caribbe an between 15 and 35 mya. Several questions regarding subspecific taxonomy are raised in the analysis and await further investigation using a more rap idly evolving marker such as nuclear microsatellites. (C) 2000 Academic Pre ss.