Marine turtle species exhibit differences in characteristics that could affect their sensitivity to climate change, such as size, generation time, diet, and thermal preferences. Research on nesting turtles has also shown that there are often multiple maternal lineages within a species, some spanning whole ocean basins and others much more restricted. These geographic differences could also have influenced past responses to climate change. We compiled data from 23 marine turtle lineages and compared the observed data to many simulated datasets to determine whether lineages were stable, expanding, or contracting over time. We then looked at which factors best predicted past population history and genetic diversity. We found evidence for population expansion in 60% of the lineages, with the remaining lineages stable over time. A co-expansion model showed that the lineages that expanded did so in a highly synchronous manner after the last Ice Age. Geographic factors (ocean basin and range extent) were much better predictors of population history and genetic diversity than species traits. So, where you were mattered more than who you were in determining response to global warming. This can inform conservation planning for these species and other marine organisms in the face of climate change.

For the full article: Reid BN, Naro‐Maciel E, Hahn AT, FitzSimmons NN, Gehara M. Geography best explains global patterns of genetic diversity and postglacial co‐expansion in marine turtles. Mol Ecol. 2019;28:3358–3370. https://doi.org/10.1111/mec.15165