Characterizing genetic variation by retrospective genotyping of trophy or historical artifacts from endangered species is an important conservation tool. Loss of genetic diversity in top predators such as the white shark Carcharodon carcharias remains an issue, exacerbated in this species by declining, sometimes isolated philopatric populations. We successfully sequenced mitochondrial DNA (mtDNA) D-loop from osteodentine of contemporary South African white shark teeth (from 3 jaws), and from 34 to 129 yr old dried cartilage and skin samples from 1 Pacific Ocean and 5 Mediterranean sharks. Osteodentine-derived sequences from South African fish matched those derived from an individual's finclips, but were generally of poorer quality than those from skin and cartilage of historical samples. Three haplotypes were identified from historical Mediterranean samples (n = 5); 2 individuals had unique sequences and 3 shared the contemporary Mediterranean haplotype. Placement of previously undescribed mtDNA haplotypes from historical material within both the Mediterranean and Pacific clades fits with the accepted intraspecific phylogeny derived from contemporary material, verifying our approaches. The utility of our methodology is in its provision of additional genetic resources from osteodentine (for species lacking tooth pulp) and cartilage of rare and endangered species held in often uncurated, contemporary and historical dry collections. Such material can usefully supplement estimates of connectivity, population history, and stock viability. We confirm the depauperate haplotype diversity of historical Mediterranean sharks, consistent with founding by a small number of Pacific colonizers. The consequent lack of diversity suggests serious challenges for the maintenance of this top predator and the Mediterranean ecosystem.
Bibliographical noteThis work was supported by Aberdeen University, the Marine Biological Association and Save Our Seas Foundation (SOSF). We thank Mr Oliver Crimmen, Dr Colin MacLeod, Dr Sharon Mitchell and Patricia Crombie for their support, Dr Takashi Sawada for valuable comments on elasmobranch tooth formation and Professor Richard Aspden for use of the freezer mill for grinding osteodentine. Thanks to Steffano Vanni, Giuseppe Guarrasi, Enrico Bellia, Helmut Wellendorf, Radek Šanda, Peter Adamik and Georges Lenglet for allowing access to material from museum and private collections.
- Carcharodon carcharias
- Mitochondrial DNA
- Museum specimens
- White shark