In the past decade much attention has focused on the role that genetics can play in the formation of management strategies in conservation. Here, we describe genetic diversity in the world's largest lizard, the Komodo dragon (Varanus komodoensis), examining the evolutionary relationships and population genetic history of the four islands in southeast Indonesia, which form the vast majority of its range. We identify distinct genetic groups for conservation. The population on the island of Komodo shows by far the largest values of genetic divergence and is proposed that it should be a separate conservation management unit. Other populations, surviving either on small islands with substantially reduced genetic variability, or in isolated patches, are identi¢ed as particularly vulnerable to stochastic threats and habitat loss. Our results provide an example of how data de¢ning intraspeci¢c levels of genetic divergence can provide information to help management plans, ensure the maintenance of genetic variability across populations and identify evolutionary potential within endangered species.

Parthenogenesis, the production of offspring without fertilization by a male, is rare in vertebrate species, which usually reproduce after fusion of male and female gametes. Here we use genetic fingerprinting to identify parthenogenetic offspring produced by two female Komodo dragons (Varanus komodoensis) that had been kept at separate institutions and isolated from males; one of these females subsequently produced additional offspring sexually. This reproductive plasticity indicates that female Komodo dragons may switch between asexual and sexual reproduction, depending on the availability of a mate--a finding that has implications for the breeding of this threatened species in captivity. Most zoos keep only females, with males being moved between zoos for mating, but perhaps they should be kept together to avoid triggering parthenogenesis and thereby decreasing genetic diversity.

Giant tortoises, a prominent symbol of the Galá pagos archipelago, illustrate the influence of geological history and natural selection on the diversification of organisms. Because of heavy human exploitation, 4 of the 15 known species (Geochelone spp.) have disappeared. Charles Darwin himself detailed the intense harvesting of one species, G. elephantopus, which once was endemic to the island of Floreana. This species was believed to have been exterminated within 15 years of Darwin's historic visit to the Galá pagos in 1835. The application of modern DNA techniques to museum specimens combined with long-term study of a system creates new opportunities for identifying the living remnants of extinct taxa in the wild. Here, we use mitochondrial DNA and microsatellite data obtained from museum specimens to show that the population on Floreana was evolutionarily distinct from all other Galá pagos tortoise populations. It was demonstrated that some living individuals on the nearby island of Isabela are genetically distinct from the rest of the island's inhabitants. Surprisingly, we found that these ''non-native'' tortoises from Isabela are of recent Floreana ancestry and closely match the genetic data provided by the museum specimens. Thus, we show that the genetic line of G. elephantopus has not been completely extinguished and still exists in an intermixed population on Isabela. With enough individuals to commence a serious captive breeding program, this finding may help reestablish a species that was thought to have gone extinct more than a century ago and illustrates the power of long-term genetic analysis and the critical role of museum specimens in conservation biology.conservation genetics ͉ evolution ͉ phylogenetics ͉ hybridization ͉ cryptic diversity T he giant tortoises of the Galápagos archipelago (Geochelone spp.) are renowned both for their uniqueness and for their contribution to the development of Darwin's theory of natural selection (1). Fifteen formally described taxa of giant Galápa-gos tortoises are generally recognized, four of which are extinct from the islands of Floreana (G. elephantopus), Santa Fe (Geochelone sp. undescribed), Fernandina (G. phantastica), and Rabida (Geochelone sp. undescribed) (Fig. 1) (2). When Charles Darwin visited the island of Floreana in 1835, he learned that giant tortoises were the staple food source of the recent settlers to the island and that, as a consequence, their numbers had become ''greatly reduced'' (3). Robert Fitz-Roy, captain of the HMS Beagle, remarked that the large number of empty tortoise shells lying about the settlement showed ''what havoc has been made among these helpless animals'' (4). Even before settlers came to Floreana in 1832, there was a long history of tortoise capture and transportation from the island by whalers and buccaneers, who stored the animals in the hulls of their ships for food (2). Darwin reported that single vessels had taken up to 700 individuals at a time. Thus, it is not surprising that the species on Floreana (5) is thought...

Giant Galápagos tortoises represent an interesting model for the study of patterns of genetic divergence and adaptive differentiation related to island colonization events. Recent mitochondrial DNA work elucidated the evolutionary history of the species and helped to clarify aspects of nomenclature. We used 10 microsatellite loci to assess levels of genetic divergence among and within island populations. In particular, we described the genetic structure of tortoises on the island of Isabela, where discrimination of different taxa is still subject of debate. Individual island populations were all genetically distinct. The island of Santa Cruz harboured two distinct populations. On Isabela, populations of Volcan Wolf, Darwin and Alcedo were significantly different from each other. On the other hand, Volcan Wolf showed allelic similarity with the island of Santiago. On Southern Isabela, lower genetic divergence was found between Northeast Sierra Negra and Volcan Alcedo, while patterns of gene flow were recorded among tortoises of Cerro Azul and Southeast Sierra Negra. These tortoises have endured heavy exploitation during the last three centuries and recently attracted much concern due to the current number of stochastic and deterministic threats to extant populations. Our study complements previous investigation based on mtDNA diversity and provides further information that may help devising tortoise management plans.