Global phylogeography of the critically endangered hawksbill turtle (Eretmochelys imbricata)

Abstract

The hawksbill turtle is a broadly distributed, highly migratory and critically endangered sea turtle species. The paucity of studies restricts the comprehension of its behavior and life history. In this work, we performed a global phylogeographic analysis using a compilation of previously published mitochondrial haplotype data to understand the dynamics and diversity of hawksbill populations worldwide. Our results revealed a complex demographic pattern associated to hawksbill phylogeography since the Pliocene. Isolation by distance is not enough to explain distinct demographic units of hawksbill turtles, which are also influenced by other factors as oceanic currents, coral reef distribution and nesting timing. The foraging aggregations are typically mixed stocks of individuals originating from multiple nesting areas, but there is also a trend of foragers coming from nearby natal beaches. Phylogenetic analysis indicates two highly divergent major lineages split between Atlantic and Indo-Pacific rookeries, but there is also a more recent Atlantic Ocean colonization from the Indo-Pacific Ocean. Long-distance dispersal events are likely responsible for homogenization between distant populations within oceans. Our findings provided new insights about population connectivity, identified gaps that should be prioritized in future research and highlighted the need for international efforts aiming at hawksbill's conservation.

Low Diversity and Strong Genetic Structure Between Feeding and Nesting Areas in Brazil for the Critically Endangered Hawksbill Sea Turtle

“…Regarding the spatial distribution of haplotypes (H), H_1 was shared between all nesting areas, similar to the EiA01 haplotype recorded for Brazil (Vilaça et al, 2013;Arantes et al, 2020). H_10 (FN_BRA, CAR, PUR) and H_11 (FN_BRA, MEX, AUS) were shared by three areas.…”

“…Thus, we demonstrated that the evaluated rookeries were made up of only six haplotypes, all of which were registered exclusively for these areas. Thus, these areas are genetically unique, highlighting their importance for preserving the genetic pool of the endangered species (Santos et al, 2013;Vilaça et al, 2013;Arantes et al, 2020).…”

“…In this context, the use of molecular markers such as mtDNA (control/D-loop region) stands out for being efficient in assessing the genetic structure among reproductive areas (Jensen et al, 2013;López-Barrera et al, 2016;Reis and Goldberg, 2017). Most studies on mtDNA used few bases for sequencing (∼300 bp), but in view of the need to obtain more detailed information about the detection of variation and population structure, longer sequences are being applied for this species (Troëng et al, 2005;LeRoux et al, 2012;Nishizawa et al, 2016;Arantes et al, 2020).…”

New Genetic Insights About Hybridization and Population Structure of Hawksbill and Loggerhead Turtles From Brazil

“…Despite the separation between E. imbricata individuals from Indo-Pacific and Atlantic was not clearly observed in STRUCTURE using nDNA, it was slightly observed in PCA and neighborNet, and strongly detected in the MCC tree. There is a deep genetic divergence between Indo-Pacific and Atlantic mtDNA lineages of E. imbricata dating from the early Pliocene, when the closing of the Isthmus of Panama occurs (Arantes et al 2020). The geographic pattern of separation between ocean basins found with mtDNA was recovered with nuclear data, except for one individual (R0242).…”

“…Other genetic studies including Brazilian sea turtles have investigated their demographic history (Bjorndal et al 2006;Vargas et al 2008;Molfetti et al 2013), population structure (Reis et al 2010a;Vilaça et al 2013;Shamblin et al 2014;Arantes et al 2020), mixed stocks at foraging aggregations (Proietti et al 2009;Reis et al 2010a;Vilaça et al 2013;Proietti et al 2014b) and interspecific hybridization (Lara-Ruiz et al 2006;Reis et al 2010b;Vilaça et al 2012;Proietti et al 2014a;Soares et al 2017Soares et al , 2018. For example, phylogeographic analyses using mtDNA showed significant genetic divergence among three Brazilian rookeries of C. caretta, suggesting the recognition of three different management units (Shamblin et al 2014), while two separate demographic units were recognized for E. imbricata in Brazilian nesting areas (Vilaça et al 2013).…”