Juvenile loggerhead turtles (Caretta caretta)

Restriction-site analyses of mitochondrial DNA (mtDNA) from the loggerhead sea turtle (Caretta caretta) reveal substantial phylogeographic structure among major nesting populations in the Atlantic, Indian, and Pacific oceans and the Mediterranean sea. Based on 176 samples from eight nesting populations, most breeding colonies were distinguished from other assayed nesting locations by diagnostic and often fixed restriction-site differences, indicating a strong propensity for natal homing by nesting females. Phylogenetic analyses revealed two distinctive matrilines in the loggerhead turtle that differ by a mean estimated sequence divergence p = 0.009, a value similar in magnitude to the deepest intraspecific mtDNA node (p = 0.007) reported in a global survey of the green sea turtle Chelonia mydas. In contrast to the green turtle, where a fundamental phylogenetic split distinguished turtles in the Atlantic Ocean and the Mediterranean Sea from those in the Indian and Pacific oceans, genotypes representing the two primary loggerhead mtDNA lineages were observed in both Atlantic-Mediterranean and Indian-Pacific samples. We attribute this aspect of phylogeographic structure in Caretta caretta to recent interoceanic gene flow, probably mediated by the ability of this temperate-adapted species to utilize habitats around southern Africa. These results demonstrate how differences in the ecology and geographic ranges of marine turtle species can influence their comparative global population structures.

The holotype (MHM-K2) of the Eocene cheloniine Tasbacka danica is arguably one of the best preserved juvenile fossil sea turtles on record. Notwithstanding compactional flattening, the specimen is virtually intact, comprising a fully articulated skeleton exposed in dorsal view. MHM-K2 also preserves, with great fidelity, soft tissue traces visible as a sharply delineated carbon film around the bones and marginal scutes along the edge of the carapace. Here we show that the extraordinary preservation of the type of T. danica goes beyond gross morphology to include ultrastructural details and labile molecular components of the once-living animal. Haemoglobin-derived compounds, eumelanic pigments and proteinaceous materials retaining the immunological characteristics of sauropsid-specific β-keratin and tropomyosin were detected in tissues containing remnant melanosomes and decayed keratin plates. The preserved organics represent condensed remains of the cornified epidermis and, likely also, deeper anatomical features, and provide direct chemical evidence that adaptive melanism – a biological means used by extant sea turtle hatchlings to elevate metabolic and growth rates – had evolved 54 million years ago.

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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...