Phylogeography, Genetic Diversity, and Management Units of Hawksbill Turtles in the Indo-Pacific

Abstract

Hawksbill turtle (Eretmochelys imbricata) populations have experienced global decline because of a history of intense commercial exploitation for shell and stuffed taxidermied whole animals, and harvest for eggs and meat. Improved understanding of genetic diversity and phylogeography is needed to aid conservation. In this study, we analyzed the most geographically comprehensive sample of hawksbill turtles from the Indo-Pacific Ocean, sequencing 766 bp of the mitochondrial control region from 13 locations (plus Aldabra, n = 4) spanning over 13500 km. Our analysis of 492 samples revealed 52 haplotypes distributed in 5 divergent clades. Diversification times differed between the Indo-Pacific and Atlantic lineages and appear to be related to the sea-level changes that occurred during the Last Glacial Maximum. We found signals of demographic expansion only for turtles from the Persian Gulf region, which can be tied to a more recent colonization event. Our analyses revealed evidence of transoceanic migration, including connections between feeding grounds from the Atlantic Ocean and Indo-Pacific rookeries. Hawksbill turtles appear to have a complex pattern of phylogeography, showing a weak isolation by distance and evidence of multiple colonization events. Our novel dataset will allow mixed-stock analyses of hawksbill turtle feeding grounds in the Indo-Pacific by providing baseline data needed for conservation efforts in the region. Eight management units are proposed in our study for the Indo-Pacific region that can be incorporated in conservation plans of this critically endangered species.

Are we working towards global research priorities for management and conservation of sea turtles?

“…Perhaps the biggest recent genetic advances have been made in the Indian and Pacific Oceans, for green (e.g. Dutton et al 2014a,b, Nishizawa et al 2014b, Bourjea et al 2015a, Jensen et al 2016), hawksbill (e.g. Gaos et al 2016, Vargas et al 2016 loggerhead (e.g.…”

A Piece of a Puzzle of Haplotypes for the Indian Ocean Hawksbill Turtle

“…Alterations on haplotype frequencies on a nesting beach are of conservation concern; but knowing the causes implies completely understanding the RMU to which that rookery belongs, which for the WIO is still difficult. This exercise can be done with the published papers about the haplotypes discovered so far (see [32] …”

Advances in the Application of Genetics in Marine Turtle Biology and Conservation

“…Perhaps the most important advances to this field have been made through expanded sample collections that provide key insights informing designation of units to conserve on a global scale, such as Evolutionary Significant Units (ESUs), Distinct Population Segments (DPSs), and Regional Management Units (RMUs; see Box 2, Table 1 for definitions and applications of conservation units). As sample coverage continues to improve for all species in parallel with better analytical tools, marine turtle studies continue to explore questions of past glacial refuges (e.g., Hamabata et al, 2013;Naro-Maciel et al, 2014a), colonization routes (Dutton et al, 2014a;Shamblin et al, 2014;Gaos et al, 2016), and multiple colonization events that create such complexity in marine turtle phylogeographic patterns (e.g., Dethmers et al, 2006;Vargas et al, 2016). The field of marine turtle phylogeography will undoubtedly continue to advance in coming years with the development of genomic approaches and novel analytical tools.…”

“…• How isolated or connected are rookeries from one another through the exchange of nesting females? Population structure analyses of nesting females across regions of interest (mtDNA haplotypes and/or fine-scale nuclear markers a ) Examples since comprehensive review in Jensen et al (2013a) include: Dutton et al (2014b), Shamblin et al (2014), Vargas et al (2016), Gaos et al (2016), and Matsuzawa et al (2016) • How does male-mediated gene flow influence population structure among rookeries? Population structure analyses, various methods including: sampling nesting females, hatchlings and/or males in-water at breeding grounds (fine-scale nuclear markers; mtDNA haplotypes under specific circumstances b ) Wallace et al (2010b); references for information specific to each species is listed within the table.…”

“…However, examination of functional genomic regions (MHC loci) in loggerhead turtles suggested that locally adapted pools of MHC alleles at the margins of the population distribution combined with male-mediated gene flow may be key to sustaining adaptive potential across the entire rookery (Stiebens et al, 2013a,b). As diversity is increasingly characterized across more marine turtle species and geographical regions (e.g., Ng et al, 2014;Vargas et al, 2016) and capacity to assess both neutral and adaptive genomic variation expands, our understanding of how human activities might impact marine turtle genomic diversity and ultimately long-term resiliency will continue to advance.…”