New insights into the evolutionary history of white sharks, Carcharodon carcharias

Authors


  • Editor: Luiz Rocha

Abstract

Aim

To determine the genetic structure of the white shark population around the South African coastline and, by including data from animals sampled elsewhere in the world, to provide new insights into white shark evolution at the global scale.

Methods

Mitochondrial and microsatellite analyses were performed on 302 free-ranging white sharks collected from five sites along the South African coastline. This was augmented with 58 GenBank sequences originating from five distinct global populations. Genetic diversity, local population sub-structuring analyses and global phylogeographical patterns were determined.

Results

Four mtDNA haplotypes restricted to South Africa were recovered. One common haplotype was shared by 89% of all the individuals and was 13 bp different from the second most common haplotype shared by 10% of the remaining sharks. No local geographical sub-structuring was evident for either mtDNA or nuclear DNA. Both data sets show a remarkably low level of genetic diversity (mtDNA:= 0.205, π = 0.0027; nDNA: Na = 7.6, Ho = 0.675). At the global scale, three distinct geographical clades were detected which could not be connected with 95% confidence in the haplotype network.

Main conclusions

Results indicate that the observed South African mtDNA biogeographical pattern and diversity levels may be a consequence of a severe bottleneck or a recent colonization event from one or two sources. Globally, the population of white sharks can be differentiated into three mtDNA clades confined to (1) the Mediterranean and Indo-Pacific Oceans (Australia and California), (2) the North West Atlantic (Florida) and Indian Ocean (South Africa), and (3) a single divergent haplotype restricted to South Africa. The pattern is most likely the result of a combination of site philopatry, isolation by distance, infrequent long-distance dispersal, isolated founder events and the closure of the Isthmus of Panama.

Ancillary