Giant Galápagos tortoises; molecular genetic analyses identify a trans-island hybrid in a repatriation program of an endangered taxon

We report here that an analysis of an additional 473 captive-bred tortoises released back to the island reveals an individual (E1465) that exhibits nuclear microsatellite alleles not found in any of the 15 breeders. Statistical analyses incorporating genotypes of 304 field-sampled individuals from all populations on the major islands indicate that E1465 is most probably a hybrid between an Espa？ola female tortoise and a male from the island of Pinzón, likely present on Espa？ola due to human transport.Removal of E1465 as well as its father and possible (half-)siblings is warranted to prevent further contamination within this taxon of particular conservation significance. Despite this detected single contamination, it is highly noteworthy to emphasize the success of this repatriation program conducted over nearly 40 years and involving release of over 2000 captive-bred tortoises that now reproduce in situ. The incorporation of molecular genetic analysis of the program is providing guidance that will aid in monitoring the genetic integrity of this ambitious effort to restore a unique linage of a spectacular animal.Conservation genetics is a relatively new, yet growing field of research that can have immediate impact on practical issues confronting efforts to conserve biodiversity. Technical developments of molecular procedures directly applicable to genetic analysis of virtually any organism have made important contributions to these efforts. Here we present a unique example of the use of molecular conservation genetics to detect genetic contamination of an otherwise successful captive breeding-repatriation program of a once critically endangered species.The genetically distinct population of giant Galápagos tortoises (Geochelone hoodensis, at times considered a subspecies of G. nigra) occupying the island of Espa？ola in the extreme southeastern region of the Galápagos archipelago was in grave danger of extinction in the late 1960s due to hunting activities from sealin