Philopatry in loggerhead turtles Caretta caretta: beyond the gender paradigm

Abstract

Marine turtles have been traditionally considered model organisms to study sexbiased behaviour and dispersal. Although female philopatry has been identified in the loggerhead turtle, with adult females returning to specific locations to nest, studies on the philopatry and breeding migrations of males remain limited. In this study we analysed 152 hatchlings using 15 microsatellite markers. Each individual came from a different nest from samples taken at 8 nesting grounds in the Mediterranean. Our results revealed the existence of 5 genetically differentiated units, mostly due to restricted gene flow for both sexes. This supports existing satellite tracking studies that suggest that mating occurs close to nesting grounds in this region. The 5 management units identified within the Mediterranean included nesting grounds from (1) Libya and Cyprus, (2) Israel, (3) Lebanon, (4) Turkey and (5) Greece. The genetic similarity between distant nesting areas (i.e. Libya and Cyprus) suggests the presence of a more complex pattern of breeding behaviour. Three possible hypotheses, that remain to be tested in future studies, could explain this result: (1) mating might take place in common foraging grounds; (2) mating could occur en route while migrating to/from the breeding grounds; or (3) recent colonisation events could connect the 2 nesting grounds. Overall, our work suggests that widespread male-mediated gene flow between loggerhead nesting grounds is likely to have been previously overstated although opportunistic breeding patterns might connect some widely separated areas.

New genetic insights about hybridization and population structure of hawksbill and loggerhead turtles from Brazil

“…Male sea turtles have uncertain philopatry and probably display greater flexibility in their choice of mating areas (FitzSimmons et al 1997). Similar patterns were found in previous studies using nDNA and are indicative of lack of male philopatry (FitzSimmons et al 1997; Bowen et al 2005; Carreras et al 2011; Vilaça et al 2013; Clusa et al 2018). Thus, the apparently discrepant results for mtDNA and multilocus data could be further explained by male-mediated gene flow between rookeries.…”

Helping decision making for reliable and cost‐effective 2b‐RAD sequencing and genotyping analyses in non‐model species

“…This is a highly valuable characteristic of 2b‐RAD methodology, since not all studies can easily access high quality samples. For instance, marine turtle genetic studies usually rely on sampling of stranded individuals (Clusa et al, 2016) or dead embryos found at nests after excavation (Clusa et al, 2018), due to the complexity of their behaviours and the paucity of individuals. In such cases, a genomic protocol capable of providing optimal results with degraded samples is invaluable.…”

“…Juveniles of D. puntazzo were collected in Blanes ( N = 12) and Xabia ( N = 12) (Spain) during recruitment using hand nets (Figure 1). Samples of C. caretta were taken from bycaught juveniles at the foraging ground off Valencia (Spain) ( N = 9; Figure 1) and from dead hatchlings at the nesting ground west of Sirte (Lybia) ( N = 14; Clusa et al, 2018). We also added a sample collected from a live female turtle nesting in Pulpí (Spain) as positive control (Carreras et al, 2018).…”

“…To facilitate the decision-making process, based on our results, we constructed a flowchart ( Figure 5) and a set of guidelines (Box 1) to help future studies design the most efficient and cost effective protocol to reach their goals. (Clusa et al, 2018), due to the complexity of their behaviours and the paucity of individuals. In such cases, a genomic protocol capable of providing optimal results with degraded samples is invaluable.…”

How many came home? Evaluating ex situ conservation of green turtles in the Cayman Islands

“…Therefore, the natural recovery of isolated populations on the verge of extinction may be difficult, as little migration would be expected from other populations to increase the number of mating adults. This philopatric behaviour, in both females and males (Clusa et al, ), is the basis for a rapid colonization of new potential nesting areas after the first arrival of marine turtles (Carreras et al, ).…”