Encalada SE et al. (1996) Mol. Ecol., 5:473-483

The herbivorous green turtle (Chelonia mydas) is distributed circumglobally in tropical and subtropical oceans (Carr 1967). Within each ocean basin, mature females travel from feeding grounds to nesting beaches in reproductive migrations that span hundreds or thousands of kilometers (Mortimer & Carr 1987; Limpus et al. 1992). Despite this high dispersal potential and broad geographical distribution, tagging studies show strong segregation of females among the different nesting beaches (Carr et al. 1978; Balazs 1980; Limpus et al. 1992). These discrete populations are not separated by obvious geographical or climatic barriers, but instead appear to be shaped by the female's strong nest site fidelity, a process by which females return faithfully to the same rookery to nest in consecutive breeding seasons (Carr 1967). How might these behavioural aspects of sea turtle life history, as well as other demographic factors influence the current geographical distribution of green turtle lineages?

An earlier survey of green turtle population structure with mitochondrial (mt) DNA restriction fragment length polymorphisms (RFLPs) revealed a fundamental bifurcation of mtDNA lineages between Atlantic-Mediterranean and Indo-Pacific nesting colonies and a marked geographical structuring of mtDNA genotypes among Atlantic rookeries (Bowen et al. 1992). This approach is too few to resolve intraoceanic phylogeographic patterns and certain aspects of population structure. Herein, To resolve the phylogeography and population genetic structure of Atlantic and Mediterranean populations of green turtles is analyzed by mtDNA sequences. Analysis of sequence variation over 487 base pairs of the control (D-loop) region identified 18 haplotypes among 147 individuals from nine nesting populations. Pairwise comparisons of haplotype frequencies distinguished most nesting colonies, indicating significant genetic differentiation among rookeries and a strong propensity for natal homing behaviour by nesting females. The sequence data reveal a gene genealogy that distinguishes two groups of haplotypes corresponding to (i) the western Caribbean and Mediterranean, and (ii) eastern Caribbean, South Atlantic and West Africa. The data suggest that phylogeographic patterns in Atlantic Ocean may be interpreted in terms of female nest site fidelity and episodic dispersal events. The distribution of mt DNA haplotypes within the region is thus explained by the geological and climatic alternations (glacial and interglacial) over the last million years.

Reference:

Bowen BW et al. (1989) An odyssey of the green turtle: Ascension Island revisited. Pro. Natl. Acad. Sci. USA, 86:573-576.

Norman JA et al. (1994) Mitochondrial DNA control region polymorphisms: genetic markers for ecological studies of marine turtles. Mol. Ecol., 3:363-373.

http://mail1.ntttc.edu.tw/~leochang/turtle.html; http://www.gio.gov.tw/info/ecology/specific/tutl_c.html