Population structure of the loggerhead turtle Caretta caretta, a large marine carnivore that exhibits alternative foraging behaviors

Abstract

Information on population genetic structure is fundamental for recognizing management units of endangered species (Moritz 1994). Because population genetic structure depends on both the resolution and the inheritance modes of genetic markers, it should be analyzed through the combined use of multiple mark- ABSTRACT: Knowledge of detailed population genetic structure is crucial to conserve and manage endangered species effectively. Size-related variation in feeding-habitat use (neritic vs. oceanic) by adult loggerhead turtles Caretta caretta has been reported within several populations, and sympatric population subdivision was suspected. In the present study, genetic differences between the 2 feeding-habitat groups within 2 Japanese nesting sites were assessed, using 5 microsatellite loci and mitochondrial (mt) DNA sequences. There were no genotypic or haplotype differences between the feeding-habitat groups, which were defined by egg-yolk stable isotope ratios and body size, at both nesting sites, suggesting that both neritic and oceanic individuals belong to the same genetic population. Differences in feeding-habitat use are unlikely to be a limiting factor for gene flow between feeding-habitat groups and were thought to be the result of phenotypic plasticity rather than population subdivision. Gene flow among 5 nesting sites was assessed by pooling these feeding-habitat groups at each nesting site. Significant genetic structure by female natal homing was observed at the mtDNA level. However, no significant structure was found at the microsatellite DNA level, suggesting male-mediated gene flow caused by migration through courtship areas. Although nesting beaches are connected by male-mediated gene flow, which might have evolved as a mechanism to avoid genetic fragmentation by natal homing, extirpated beaches would not be easily recolonized from other nesting populations due to female philopatry. Therefore, conservation of individual nesting beaches is still needed to maintain the overall genetic diversity of Japanese loggerheads.KEY WORDS: Alternative life histories · Microsatellite DNA · Mitochondrial DNA · Phenotypic plasticity · Reptile · Caretta caretta Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 424: [273][274][275][276][277][278][279][280][281][282][283] 2011 ers. Sequences of maternally inherited mitochondrial (mt) DNA and microsatellites of biparentally inherited nuclear DNA are the markers commonly used in recent wildlife population genetics (Frankham et al. 2002). In principle, due to their faster rate of evolution, the resolution of microsatellites is greater than that of mtDNA sequences. Nevertheless, in some cases, population differentiation inferred from mtDNA sequences is stronger than that from microsatellites (e.g. FitzSimmons et al. 1997b, Bowen et al. 2005, Carreras et al. 2007, Chen et al. 2008, Lukoschek et al. 2008, Okello et al. 2008, Caparroz et al. 2009, Hefti-Gautschi et al. 2009, Portnoy et al. 2010, and this has been attributed...

Foraging dichotomy in loggerhead sea turtles Caretta caretta off northwestern Africa

“…As no genetic differences between oceanic and neritic foragers nesting in the same area have been reported to date (Watanabe et al 2011), they cannot be considered 2 independent populations, rather just the result of phenotypic plasticity. It is probable that turtles exploiting less productive habitats will grow more slowly than turtles exploiting more productive habitats (Hatase et al 2010;McClellan et al 2010, Piovano et al 2011.…”

Genetic composition of loggerhead turtle feeding aggregations: migration patterns in the North Pacific

“…1; Hatase et al 2002a, Watanabe et al 2011, and (2) 2 geographic groups of these rookeries, the northern rookeries, i.e. Minabe and Kamouda, and the southern rookeries, i.e.…”

“…An 817 bp fragment was used in the analyses of the Sanriku samples, but a shorter 350 bp fragment, trimmed from the 817 bp fragment, was used for all other analyses, including published data from the nesting rookeries (Bowen et al 1995, Hatase et al 2002a, Watanabe et al 2011. Sequence alignments were performed using CLUSTALW in MEGA v5.1 (Tamura et al 2011).…”

“…Once the loggerhead turtles near Baja California grow to 50−75 cm in straight carapace length (SCL), they return and recruit to the feeding areas around Japan as large juveniles (Nichols et al 2000, Polovina et al 2004. When female turtles mature, they are thought to nest in their natal regions, resulting in significant genetic differentiation among loggerhead sea turtles in the 5 Japanese rookeries (Hatase et al 2002a, Watanabe et al 2011. Rookeries in Japan and those in the Southern Hemisphere do not share common haplotypes (Bowen et al 1995, Hatase et al 2002a, Boyle et al 2009, indicating that there is little or no gene flow between them.…”

“…Bowen et al 1994, Encalada et al 1998, Hatase et al 2002a has afforded an opportunity to link feeding aggregations back to their nesting region of origin and to estimate the contribution of genetically differentiated nesting rookeries to feeding aggregations by using mixed-stock analysis (MSA; Pella & Masuda 2001, Bolker et al 2003. The significant genetic differentiation of loggerhead turtles in Japanese rookeries (Hatase et al 2002a, Watanabe et al 2011) presents an opportunity to link the feeding aggregation to specific Japanese rookeries by using mtDNA haplotypes and MSA.…”