Native Seychelles tortoises or Aldabran imports? The importance of radiocarbon dating for ancient DNA studies

Abstract

The living and extinct giant tortoises of the western Indian Ocean islands have been extensively studied in recent times (Bourn et al., 1999; Austin and Arnold, 2001; Palkovacs et al., 2002; Austin et al., 2003; Palkovacs et al., 2003). Currently, indigenous wild populations of Indian Ocean giant tortoises (genus Dipsochelys) occur only on the island of Aldabra, northwest of Madagascar, with most wild tortoises having become extinct on the Seychelles as early as 1800, largely through overexploitation by European sailors and settlers (Stoddardt et al., 1979; Austin et al., 2003). Recent molecular genetic studies on Dipsochelys suggest that there is very little genetic variation among extant Indian Ocean tortoises. Palkovacs et al. (2002) analyzed three mitochondrial genes, 12S and 16S ribosomal RNA (rRNA) and cytochrome b (cyt-b), and found no variation among captive tortoises assigned to three Dipsochelys species. Austin et al. (2003) looked at cyt-b sequences from modern and museum skins of Dipsochelys from the islands of Aldabra and the Seychelles and found ex-