The population genetic structure of Cyclura carinata carinata (Sauria : Iguanidae)

Cyclura carinata carinata, the Turks and Caicos islands rock iguana, is critically endangered. This research was conducted to define the relative importance of specific barriers to gene flow among populations of C. c. carinata and to provide useful information for future conservation efforts. Previous behavioral studies of C. c. carinata and the geological history of the Turks and Caicos islands suggest that the present genetic structure among populations has been affected by two different rates of dispersal: the rate of dispersal over water and the rate of dispersal over land. It was hypothesized that the importance of these barriers to gene flow is correlated with the water depth between and the geographic distance between island populations. These hypotheses were tested by calculating genetic identities between island populations from allele frequencies at two microsatellite loci that are polymorphic in C. c. carinata. Regression analyses showed that a linear relationship between geographic distance and one transformation of genetic identity was only marginally significant. However, island populations located in the same geographic region tend to cluster genetically in a phylogenetic tree. Further, Mantel tests showed that genetic identities and geographic distances between island populations were not randomly associated. These analyses suggest that geographic distance between islands has greatly influenced the genetic structure of these populations, but may not have a direct relationship with genetic distance. This evidence suggests that the historical genetic structure of these populations is decaying due to genetic drift. Presumably, this structure arose after these island populations were isolated by rising sea levels associated with the present interglacial period.