Anegada iguana hatchlings
Ecological Implications of Population Genetic Analyses of Caribbean Iguanas
The eight species of rock iguanas (genus Cyclura), the Lesser Antilles iguana Iguana delicatissima, and many Caribbean island populations of the common iguana Iguana iguana have been drastically reduced due to a number of human-related threats. As a consequence, all Caribbean iguana species are protected by inclusion in the Convention on International Trade in Endangered Species (CITES) Appendix I or II.
The Zoological Society of San Diego has long understood the need to protect these endangered iguanas and their habitats and this focus was underscored with the 2000 appointment of Conservation Research Postdoctoral Fellow Dr. Glenn Gerber. Dr. Gerber has focused on the rock iguana species of Anegada Island (Cyclura pinguis) and the Turks and Caicos Islands (Cyclura carinata), enlisting the help of several CRES divisions in addressing conservation research needs such as recovery of wild populations and captive breeding.
Because genetic studies have become major components in characterizing biological diversity in the wild, and for management of captive populations, the Genetics Division was asked to share in this collaborative effort. A key objective of the Anegada project was to evaluate kinship in the Zoological Society's small captive population of iguanas by comparing their genetic variation to that found in the wild iguanas. Because the molecular markers known as microsatellites have been useful in assessment of genetic diversity and kinship evaluation, microsatellite genotyping and analysis were used to evaluate the suitability of the captive individuals to serve as the basis for a genetically healthy captive breeding program. Screening of the Cyclura pinguis microsatellite library found over 20 informative loci, and these were used on DNA from the six captive potential founders as well as two groups of wild iguanas: randomly captured animals (assumed to be unrelated) and hatchlings from marked nests (assumed to be siblings). Using a statistical approach, three separate pairs of related individuals were identified within the captive cohort, and this information is now being used to design a management plan that will maximize genetic diversity in the captive collection.
The genetic diversity found in the wild population on Anegada was surprisingly high and, despite their critically low number of about 200 individuals, they do not appear to be inbred when compared to other species. While these are preliminary data, they are encouraging results for the conservation of this species. An exploratory screening using the Cyclura pinguis microsatellite library was done on the Turks and Caicos iguanas, and early results were promising. With the designation of a new position, genetic work can continue on the Anegada iguana, be increased for the Turks and Caicos iguana, and be applied to questions concerning other species of Caribbean iguanas.
Continuing analysis of the wild Anegada population, including recently collected samples, will confirm parentage and relatedness among alleged siblings and on cohorts from different years, providing valuable information for monitoring the genetic health of the wild population over time. For the Turks and Caicos iguanas, genetic analysis is proposed on samples from a nesting study of known clutch mates, their dams, and a pool of all potential sires to determine parentage and quantify variation in male mating success.
Another project will examine changes in the genetic makeup of four new island populations (established via translocation) as compared to their respective island source populations. The approach to these studies will be to continue the microsatellite screening of Cyclura carinata to try and identify at least 20 informative loci. The Cyclura pinguis library will also be used to screen other Caribbean iguana species of interest; positive results would allow for relatedness and other genetics studies that can aid in conservation management decisions across the entire group.
