Seascape Genetics and the Spatial Ecology of Juvenile Green Turtles

Abstract

Understanding how ocean currents impact the distribution and connectivity of marine species, provides vital information for the effective conservation management of migratory marine animals. Here, we used a combination of molecular genetics and ocean drift simulations to investigate the spatial ecology of juvenile green turtle (Chelonia mydas) developmental habitats, and assess the role of ocean currents in driving the dispersal of green turtle hatchlings. We analyzed mitochondrial (mt)DNA sequenced from 358 juvenile green turtles, and from eight developmental areas located throughout the Southwest Indian Ocean (SWIO). A mixed stock analysis (MSA) was applied to estimate the level of connectivity between developmental sites and published genetic data from 38 known genetic stocks. The MSA showed that the juvenile turtles at all sites originated almost exclusively from the three known SWIO stocks, with a clear shift in stock contributions between sites in the South and Central Areas. The results from the genetic analysis could largely be explained by regional current patterns, as shown by the results of passive numerical drift simulations linking breeding sites to developmental areas utilized by juvenile green turtles. Integrating genetic and oceanographic data helps researchers to better understand how marine species interact with ocean currents at different stages of their lifecycle, and provides the scientific basis for effective conservation management.

Potential Biodiversity Connectivity in the Network of Marine Protected Areas in Western Africa

“…Even for mobile species, able to swim actively while performing migrations or ontogenetic shifts in habitat use (Abecasis et al, 2009;Almpanidou et al, 2019), PD alone can explain more than 50% of the variation in genetic dispersal estimates (Kinlan and Gaines, 2003). Taxa without planktonic dispersal stages might also benefit from some aid in transportation by oceanographic currents, as suggested for some taxa like green turtles (e.g., Jensen et al, 2020), but not others (e.g., Briscoe et al, 2016).…”

Marine turtles of the African east coast: current knowledge and priorities for conservation and research

“…Although migratory data of juvenile green turtles are limited (e.g. Sanchez et al 2020), oceanic currents play an important role in the distribution of juvenile green turtles through the WIO (Jensen et al 2020). Four satellite tags deployed on juvenile green turtles in southern Tanzania showed that they stayed close (approximately 10 km) to the capture site (Sea Sense 2017).…”

“…Although research on the genetic structure of coastal populations of green, hawksbill, and loggerhead turtles has been conducted (Bourjea et al 2015b, Fernandes 2015, Anastácio & Pereira 2017, Jensen et al 2020, the experts noted that further work is needed to place the coastal foraging and nesting populations of all 5 species in a regional context (Fig. 4B).…”

Congruence between ocean‐dispersal modelling and phylogeography explains recent evolutionary history of Cycas species with buoyant seeds

“…Recent studies that integrated phylogeographic inference, numerical ocean circulation models, and Lagrangian simulation of individual particle trajectories (van Sebille et al ., 2018) have greatly improved our knowledge of the ecological factors driving evolution in the oceans. These include studies of genetic structure (Bertola et al ., 2020; Sefc et al ., 2020), connectivity and establishment (Jensen et al ., 2020; Nikolic et al ., 2020) of marine organisms. For terrestrial plants, mechanistic dispersal simulations also have been used to predict propagule transoceanic dispersal of mangroves (Van der Stocken et al ., 2019), seagrasses (Smith et al ., 2018) and Urticaceae (Wu et al ., 2018), and to confirm the origin of pre‐Columbian bottle gourds (Kistler et al ., 2014).…”