A New Fossil Tortoise, with Remarks on the Origin of South American Testudinines

Auffenberg, Walter

doi:10.2307/1441604

Cited by 40 publications

(38 citation statements)

References 3 publications

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“…Giant tortoises colonized the Seychelles at least three separate times (29). Fossil giant tortoises are known from mainland South America, and morphological analysis of these and extant species are consistent with a clade containing giant tortoise fossils and G. chilensis (30).…”

Section: Discussionmentioning

confidence: 69%

Origin and evolutionary relationships of giant Galápagos tortoises

Caccone

Gibbs

Ketmaier

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

160

156

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Perhaps the most enduring debate in reptile systematics has involved the giant Galá pagos tortoises (Geochelone nigra), whose origins and systematic relationships captivated Charles Darwin and remain unresolved to this day. Here we report a phylogenetic reconstruction based on mitochondrial DNA sequences from Galá pagos tortoises and Geochelone from mainland South America and Africa. The closest living relative to the Galá pagos tortoise is not among the larger-bodied tortoises of South America but is the relatively small-bodied Geochelone chilensis, or Chaco tortoise. The split between G. chilensis and the Galá pagos lineage probably occurred 6 to 12 million years ago, before the origin of the oldest extant Galá pagos island. Our data suggest that the four named southern subspecies on the largest island, Isabela, are not distinct genetic units, whereas a genetically distinct northernmost Isabela subspecies is probably the result of a separate colonization. Most unexpectedly, the lone survivor of the abingdoni subspecies from Pinta Island (''Lonesome George'') is very closely related to tortoises from San Cristó bal and Españ ola, the islands farthest from the island of Pinta. To rule out a possible recent transplant of Lonesome George, we sequenced DNA from three tortoises collected on Pinta in 1906. They have sequences identical to Lonesome George, consistent with his being the last survivor of his subspecies. This finding may provide guidance in finding a mate for Lonesome George, who so far has failed to reproduce.

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Section: Discussionmentioning

confidence: 69%

Origin and evolutionary relationships of giant Galápagos tortoises

Caccone

Gibbs

Ketmaier

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

160

156

View full text Add to dashboard Cite

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“…Two calibration points were specified using normally distributed priors. Based on the fossil species C. hesternus from the middle Miocene La Venta Fauna of Colombia, thought to be close to the last common ancestor of C. carbonarius and C. denticulatus [48], the split between these two species was identified with La Ventan age, 13.5-11.8 million years ago (mya) [49,50]. Accordingly, the node age was set to a mean of 12.55 mya with a standard deviation of 0.6.…”

Section: (F ) Phylogenetic Analyses and Molecular Datingmentioning

confidence: 99%

Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoiseChelonoidis alburyorum

et al. 2017

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Ancient DNA of extinct species from the Pleistocene and Holocene has provided valuable evolutionary insights. However, these are largely restricted to mammals and high latitudes because DNA preservation in warm climates is typically poor. In the tropics and subtropics, non-avian reptiles constitute a significant part of the fauna and little is known about the genetics of the many extinct reptiles from tropical islands. We have reconstructed the near-complete mitochondrial genome of an extinct giant tortoise from the Bahamas (Chelonoidis alburyorum) using an approximately 1 000-year-old humerus from a water-filled sinkhole (blue hole) on Great Abaco Island. Phylogenetic and molecular clock analyses place this extinct species as closely related to Galápagos (C. niger complex) and Chaco tortoises (C. chilensis), and provide evidence for repeated overseas dispersal in this tortoise group. The ancestors of extant Chelonoidis species arrived in South America from Africa only after the opening of the Atlantic Ocean and dispersed from there to the Caribbean and the Galápagos Islands. Our results also suggest that the anoxic, thermally buffered environment of blue holes may enhance DNA preservation, and thus are opening a window for better understanding evolution and population history of extinct tropical species, which would likely still exist without human impact.

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“…Fossil evidence was used for inferring minimum ages of two nodes within the Chelonoidis phylogeny. The age of the type stratum of C. hesterna (Auffenberg, 1971), the ancestral species of C. carbonaria and C. denticulata (Auffenberg 1971), served as prior constraint for the split between the latter two species. Chelonoidis hesterna originates from the Middle Miocene deposit of La Venta, Colombia (mean age 12.55 mya; Flynn and Wyss 1998).…”

Section: Molecular Datingmentioning

confidence: 99%

Red- and yellow-footed tortoises, Chelonoidis carbonaria and C. denticulata (Reptilia: Testudines: Testudinidae), in South American savannahs and forests: do their phylogeographies reflect distinct habitats?

Vargas‐Ramírez

Maran²,

Fritz

2010

Org Divers Evol

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Using sequence data of the mitochondrial cytochrome b gene, we investigated phylogeographic differentiation of the Amazonian tortoise species Chelonoidis carbonaria and C. denticulata. While C. carbonaria is generally restricted to savannah habitats and adjacent forests, C. denticulata is associated with wet tropical and subtropical forests. Our study suggests a correlation between distinct habitat preferences and phylogeography of the two species. In Maximum Parsimony, Maximum Likelihood and Bayesian analyses, haplotypes of C. carbonaria cluster in several distinct clades reflecting the species' patchy distribution in savannah habitats. By contrast, haplotypes of C. denticulata are only weakly differentiated; a finding also confirmed by parsimony network analysis. This suggests that the contiguous Amazonian rainforest allows gene flow between populations of the forest-dwelling C. denticulata throughout the range, but significantly impedes gene flow in C. carbonaria. The phylogeographic structure and extant distribution pattern of C. carbonaria is supportive of former Amazonian rainforest fragmentation, enabling the dispersal of savannah species. Based on fossil calibration, we dated divergence times for the C. carbonaria clades using a relaxed molecular clock, resulting in average estimates ranging from 4.0-2.2 mya. This implies that the onset of rainforest fragmentation could predate the Pleistocene considerably. Furthermore, our findings call for further research on geographic and taxonomic variation in C. carbonaria and for a reassessment of the conservation status of the distinct genetic units.

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A New Fossil Tortoise, with Remarks on the Origin of South American Testudinines

Cited by 40 publications

References 3 publications

Origin and evolutionary relationships of giant Galápagos tortoises

Origin and evolutionary relationships of giant Galápagos tortoises

Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoiseChelonoidis alburyorum

Red- and yellow-footed tortoises, Chelonoidis carbonaria and C. denticulata (Reptilia: Testudines: Testudinidae), in South American savannahs and forests: do their phylogeographies reflect distinct habitats?

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