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To investigate the influence of temperature on the length of internesting periods in loggerhead turtles (Caretta caretta) and green turtles (Chelonia mydas), body temperature and water temperature and depth for free-ranging turtles were monitored during internesting periods using micro data loggers. Body mass and clutch size were also measured. The experiments were conducted at nesting beaches in the Japanese archipelago from 1989 through 1996. Internesting interval was significantly negatively correlated with mean body temperature and mean water temperature. Internesting intervals for some turtles exceeded 21 d when they experienced low water temperatures. Arrhenius' equation was used to describe the quantitative relationships, and Q10 values of 3.1 for water temperature and 3.4 for body temperature were calculated. There was no significant relationship between either clutch size or body mass and internesting interval. Body temperatures were kept higher than water temperatures throughout internesting periods, and larger turtles showed a higher mean thermal difference between body temperature and water temperature. The internesting interval could be considered an egg-maturation period for the next oviposition. The rate of pre-ovipositional development of eggs seemed to be accelerated by high body temperature and decelerated by low body temperature.

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...

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Effective conservation of globally distributed marine species relies on identification of demographically independent populations to ensure that management actions are directed at the appropriate scale. This identification is particularly challenging for species with complex life histories when local breeding populations have not been adequately sampled. We used mtDNA to analyze the population structure of loggerhead turtles from a total of 555 samples collected from 12 nesting sites in Japan in the Northwest Pacific, including previously unsampled rookeries in the Ryukyu Archipelago, for a comprehensive coverage of the nesting distribution. We identified a total of 9 haplotypes based on 820 bp of the mtDNA control region, including 5 variants of a single previously described 380 bp haplotype. We discovered that 1 haplotype (CcP1.1) previously rare in the North Pacific is common in the Ryukyu Archipelago. Based on analysis of haplotype frequencies, we found significant differentiation among regionally grouped nesting populations (analysis of molecular variance p < 0.0001, df = 8; pairwise F ST ranging from 0.033 to 0.145). Our results provide evidence to support the recognition of 3 management units (MU) within the NW Pacific Regional Management Unit (RMU). These include (1) the Ryukyu MU that includes Okinawa, Okinoerabu and Amami, (2) Yakushima Island MU and (3) a Mainland MU that includes Bousou, Enshu-nada, Shikoku, Kii and Eastern Kyushu. These new data from Japan will provide important baseline data for global genetic stock assessments and contribute to our understanding of the population structure, ecology and life history of this migratory marine species in the northern Pacific.