COMMENTARY

Rediscovery of an ‘‘extinct’’ Gala´pagos tortoise

James F. Parham* Biodiversity Synthesis Center, The Field Museum, 1400 South Lake Shore Drive, Chicago, IL 60605; and Department of Herpetology, California Academy of Sciences, 55 Music Concourse Drive, Golden Gate Park, San Francisco, CA 94118

ver the past three centuries, dants of Floreana tortoises actually still humans have demonstrated exist (albeit not on Floreana) (Fig. 1B). increasing scientific curiosity That it is still possible to find such an about biodiversity. During important result within a well studied Othis time, we developed a classification group of species is at first surprising. scheme that accelerated the description But, in fact, it is the detailed genetic and codification of species (1), profound studies of Gala´pagos tortoises by the new theories to explain diversity (2), Yale University-led team (10–12) that explicit frameworks of taxonomic study provided the necessary background to (3), and DNA-based methods for char- achieve this insight. Poulakakis et al. acterizing lineages (4). Despite these augment and use their genetic database academic advancements, the progress of to address lineage diversity from a pop- biological discovery has struggled to ulation genetics perspective, applying keep pace with an increasingly modified appropriate markers and methods to natural environment, because the past elucidate the ancestry of extant individ- 300 years have also witnessed the expo- uals. But their work is more than a well nential growth of human population executed genetic survey of a celebrated ϫ 8 ϫ 9 (from 6 10 to 6 10 ) and concomi- clade. One of the salient aspects of their tant anthropogenic impacts on bio- study is the incorporation of data from diversity. Human-mediated extinctions, long-dead Floreana tortoises into their translocations, and genetic pollution genetic database. By using historic DNA obscure and erode natural patterns of techniques, Poulakakis et al. are able to distribution and variation (which is espe- sequence museum specimens from Flo- cially true for economically and calori- reana. Without the incorporation of cally valuable species, like turtles). A these specimens, the true ancestry of the study by Poulakakis et al. (5) in this is- Floreana descendants would still be a sue of PNAS wrestles with all three of mystery. Indeed, their study is another these complicating factors and provides shining example of the irreplaceable an excellent example of the resources role of museum specimens for biodiver- and methodologies required to tease sity science. No matter how fast and apart patterns resulting from natural powerful genomics becomes, we always and artificial processes. In doing so, this need museums to inform, identify, and study reaches an astonishing conclusion: Fig. 1. Gala´pagos tortoises. (A) A subfossil spec- compare our findings (13). Older, his- A species that we thought was eaten to imen of the species from Floreana Island (Field toric collections are especially valuable, extinction still survives...inpart. Museum of Natural History no. 13525). Until the study by Poulakakis et al. (5), the Floreana species irreplaceable even, because they archive The species in question is a Gala´pa- was only known from museum specimens such as biological data from a time when life on gos giant tortoise, one of 15 species (13 this one. (B) A living descendant of the ‘‘extinct’’ formally described) from the famous Earth was more abundant and diverse. Floreana species from Isabela Island (photo by C. The discovery of Foreana tortoise de- archipelago (5). The Gala´pagos Islands Ciofi). are well known for bearing the fauna scendants is unexpected, but the circum- that helped inspire Darwin to develop stances that led to the preservation of his landmark theory of natural selection Santa María or Charles), in 1835, within this lineage are nothing short of ironic. (2). The giant tortoises should be given years of the putative extinction of its It was, after all, the massive harvest of partial credit for this inspiration, be- endemic form (7). Both Darwin and the Floreana tortoises that ultimately led to cause the diagnostic phenotypes on each captain of the HMS Beagle remarked the persistence of this lineage. Whereas island provided Darwin with a clear ex- on the depredated carcasses and scarcity turtle populations may be vulnerable to ample of regional variation and adapta- of the Floreana tortoise, seeing no live decimation, individual animals are dura- tion (6). But even as Darwin observed tortoises themselves (6, 7). In the case ble and capable of surviving great physi- these tortoise populations, they were of Floreana, the ultimate result of hu- cal hardship (such as desiccation and declining precipitously. Humans had man activities, extirpation, preceded starvation in the hull of a ship). This already altered the tortoises’ habitat by scientific observation and collection. preservation potential, combined with a introducing numerous feral mammals, Consequently, much of what we know wide appreciation for the taste of tor- but primarily reduced their numbers about the Floreana species is based on toise flesh, made Gala´pagos animals a through direct harvest for consumption subfossil skeletal remains from caves (8, highly sought after source of protein for [even Darwin ate tortoises (6)]. Darwin 9) (Fig. 1A). Because extinction is a per- and the tortoises exemplify the afore- manent phenomenon, the Floreana tor- mentioned challenge of biologists to un- toise seemed destined to remain another Author contributions: J.F.P. wrote the paper. cover and record biological patterns sad footnote in biodiversity registers, The author declares no conflict of interest. while humans simultaneously obscure lost like the dodo. See companion article on page 15464. them. In fact, Darwin arrived at one of The report by Poulakakis et al. (5) *E-mail: jparham@fieldmuseum.org. the islands, Floreana (also known as provides new data showing that descen- © 2008 by The National Academy of Sciences of the USA

www.pnas.org͞cgi͞doi͞10.1073͞pnas.0808013105 PNAS ͉ October 7, 2008 ͉ vol. 105 ͉ no. 40 ͉ 15227–15228 Downloaded by guest on September 27, 2021 19th-century whalers, pirates, and other al.’s results. The Floreana castaways did The story of the Floreana tortoise is a seafarers (7, 14, 15). Historical accounts not maintain reproductive isolation so great example of how complex it can be of hundreds of animals being harvested their living descendants result from the to establish natural patterns while they for a single ship are known (15), as are interbreeding with native Isabelan tor- are being simultaneously distorted by reports of these tortoises being thrown toises. Thus, the heartwarming rediscov- human actions. The study by Poulakakis overboard to lighten loads (16) or other- et al. (5) contends with a range of dele- wise being moved among islands (7). It terious impacts (extirpation, transloca- was this haphazard harvest and translo- Descendants of Floreana tion, genetic pollution) and demon- cation that has inadvertently preserved strates many of the tools and methods Floreana DNA into modern times. tortoises actually still biologists use to see through them to the underlying patterns (long-term While the endemic population of Flo- exist (albeit not study, cutting-edge genetic techniques, reana tortoises was eaten into oblivion, biodiversity collections). Some biological Poulakakis et al. (5) found their genetic on Floreana). patterns may be too modified to re- signature preserved on a different is- cover, but we have the best chance of land. The most likely explanation is that knowing what was (and was not) lost Floreana tortoises were, for some rea- when we combine modern genetic tech- son, moved there Ͼ150 years ago. ery of this ‘‘extinct’’ Gala´pagos tortoise niques with traditional museum-based The new home of these translocated is tempered somewhat by the realization approaches. individuals, Isabela, is the largest Ga- that the lineage is genetically compro- la´pagosisland and home to five endemic mised. The conservation and genetic ACKNOWLEDGMENTS. My work on how humans species of giant tortoise (each associated rehabilitation of the Floreana tortoise impact turtle diversity is supported by the John D. and Catherine T. MacArthur Foundation, the with a volcano). Herein lies one of the should prove challenging, but is cer- Alfred P. Sloan Foundation, and the Turtle Con- more interesting aspects of Poulakakis et tainly worthwhile. servation Fund.

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