Abstract
Ancient mitochondrial DNA sequences were used for investigating the evolution of an entire clade of extinct vertebrates, the endemic tortoises (Cylindraspis) of the Mascarene Islands in the Indian Ocean. Mitochondrial DNA corroborates morphological evidence that there were five species of tortoise with the following relationships: Cylindraspis triserrata ((Cylindraspis vosmaeri and Cylindraspis peltastes) (Cylindraspis inepta and Cylindraspis indica)). Phylogeny indicates that the ancestor of the group first colonized Mauritius where speciation produced C. triserrata and the ancestor of the other species including a second sympatric Mauritian form, C. inepta. A propagule derived from this lineage colonized Rodrigues 590 km to the east, where a second within-island speciation took place producing the sympatric C. vosmaeri and C. peltastes. A recent colonization of Réunion 150 km to the southwest produced C. indica. In the virtual absence of predators, the defensive features of the shells of Mascarene tortoises were largely dismantled, apparently in two stages. 'Saddlebacked' shells with high fronts evolved independently on all three islands. This and other features, such as a derived jaw structure and small body size, may be associated with niche differentiation in sympatric species and may represent a striking example of parallel differentiation in a large terrestrial vertebrate. The history of Mascarene tortoises contrasts with that of the Galápagos, where only a single species is present and surviving populations are genetically much more similar. However, they too show some reduction in anti-predator mechanisms and multiple development of populations with saddlebacked shells.
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- Austin J. J., Ross A. J., Smith A. B., Fortey R. A., Thomas R. H. Problems of reproducibility--does geologically ancient DNA survive in amber-preserved insects? Proc Biol Sci. 1997 Apr 22;264(1381):467–474. doi: 10.1098/rspb.1997.0067. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Caccone A., Gibbs J. P., Ketmaier V., Suatoni E., Powell J. R. Origin and evolutionary relationships of giant Galápagos tortoises. Proc Natl Acad Sci U S A. 1999 Nov 9;96(23):13223–13228. doi: 10.1073/pnas.96.23.13223. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Carson H. L., Lockwood J. P., Craddock E. M. Extinction and recolonization of local populations on a growing shield volcano. Proc Natl Acad Sci U S A. 1990 Sep;87(18):7055–7057. doi: 10.1073/pnas.87.18.7055. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DeSalle R., Templeton A. R. The mtDNA genealogy of closely related Drosophila silvestris. J Hered. 1992 May-Jun;83(3):211–216. doi: 10.1093/oxfordjournals.jhered.a111195. [DOI] [PubMed] [Google Scholar]
- Losos JB, Jackman TR, Larson A, Queiroz K, Rodriguez-Schettino L. Contingency and determinism in replicated adaptive radiations of island lizards . Science. 1998 Mar 27;279(5359):2115–2118. doi: 10.1126/science.279.5359.2115. [DOI] [PubMed] [Google Scholar]
- doi: 10.1098/rspb.1999.0709. [DOI] [PMC free article] [Google Scholar]
- Poinar H. N., Höss M., Bada J. L., Päbo S. Amino acid racemization and the preservation of ancient DNA. Science. 1996 May 10;272(5263):864–866. doi: 10.1126/science.272.5263.864. [DOI] [PubMed] [Google Scholar]
- Posada D., Crandall K. A. MODELTEST: testing the model of DNA substitution. Bioinformatics. 1998;14(9):817–818. doi: 10.1093/bioinformatics/14.9.817. [DOI] [PubMed] [Google Scholar]
- Tamura K., Nei M. Estimation of the number of nucleotide substitutions in the control region of mitochondrial DNA in humans and chimpanzees. Mol Biol Evol. 1993 May;10(3):512–526. doi: 10.1093/oxfordjournals.molbev.a040023. [DOI] [PubMed] [Google Scholar]
- Thomas P., Wong J. G., Almers W. Millisecond studies of secretion in single rat pituitary cells stimulated by flash photolysis of caged Ca2+. EMBO J. 1993 Jan;12(1):303–306. doi: 10.1002/j.1460-2075.1993.tb05657.x. [DOI] [PMC free article] [PubMed] [Google Scholar]