Green turtle ddRAD raw sequencing data

The occasional westward transport of warm water of the Agulhas Current,
‘Agulhas leakage’, around southern Africa has been suggested to facilitate
tropical marine connectivity between the Atlantic and Indian oceans, but
the ‘Agulhas leakage’ hypothesis doesn’t explain the signatures of
eastward gene flow observed in many tropical marine fauna. We investigated
an alternative hypothesis: the establishment of a warm-water corridor
during comparatively warm interglacial periods. The ‘warm-water corridor’
hypothesis was investigated by studying the population genomic structure
of Atlantic and Southwest Indian Ocean green turtles (N = 27) using 12,035
genome-wide single nucleotide polymorphisms (SNPs) obtained via ddRAD
sequencing. Model-based and multivariate clustering suggested a
hierarchical population structure with two main Atlantic and Southwest
Indian Ocean clusters, and a Caribbean and East Atlantic sub-cluster
nested within the Atlantic cluster. Coalescent-based model selection
supported a model where Southwest Indian Ocean and Caribbean populations
diverged from the East Atlantic population during the transition from the
last interglacial period (130 – 115 thousand years ago; kya) to the last
glacial period (115 – 90 kya). The onset of the last glaciation appeared
to isolate Atlantic and Southwest Indian Ocean green turtles into three
refugia, which subsequently came into secondary contact in the Caribbean
and Southwest Indian Ocean when global temperatures increased after the
Last Glacial Maximum. Our findings support the establishment of a
warm-water corridor facilitating tropical marine connectivity between the
Atlantic and Southwest Indian Ocean during warm interglacials.