The giant Galapagos tortoises (Geochelone elephantopus) at one time consisted of 15 recognized subspecies, five of which have vanished within the last few centuries. The ten remaining subspecies are highly endangered, threatened today primarily by human-released feral animals. These tortoises present an ideal model system for defining evolutionary significant units (ESU's) in the context of clearly declining populations with a complex taxonomic history. Modern DNA technology provides the opportunity to conduct detailed conservation-genetic studies of these tortoises. The Charles Darwin Research Station located in the Galapagos is about to undertake, for the first time, as complete a census as possible of all living giant tortoises, covering two to three subspecies per year over the next five years. For eight of the ten extant subspecies, it is likely that all animals will be located, measured, weighed, marked, sexed, etc. This proposal is to add the relatively minor procedure of drawing small amounts of blood for DNA analysis. The major types of variation studied will be hypervariable regions associated with nuclear microsatellites and RFLP (restriction fragment length polymorphism) variation in mtDNA (mitochondrial DNA), thus providing both Mendelian and maternal lineage data. Sequence data will be collected from a more limited number of individuals for phylogenetic purposes.
The resulting data will address questions at the population level to higher-level phylogenetic/historical analysis. In addition, the baseline genetic data will be provided for an ongoing release program on one of the islands. While these will be the primary studies done in the laboratory, a major part of the proposal is to archive all DNA and blood to have it available to future projects; the kind of survey about to be conducted on these remarkable animals is unlikely to be repeated in the foreseeable future so this archived material will have long term value.
