Page 1 - Chrysoula_al_2010

Proc. R. Soc. B (2011) 278, 1679–1686
doi:10.1098/rspb.2010.1856
Published online 17 November 2010

Antipodean white sharks on a

Mediterranean walkabout? Historical

dispersal leads to genetic discontinuity
and an endangered anomalous population

3,†
3,†
Chrysoula Gubili 1,2,† , Ras¸it Bilgin , Evrim Kalkan ,
¨
1,†
4,†
S. Unsal Karhan , Catherine S. Jones , David W. Sims 2,5 ,
7
6
1,
Hakan Kabasakal , Andrew P. Martin and Leslie R. Noble *
1
Institute of Biological and Environmental Science, University of Aberdeen, Tillydrone Avenue,
Aberdeen AB24 2TZ, UK
2
Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK
3
Institute of Environmental Sciences, Bog ˘azic¸i University, Hisar Campus, Bebek, Istanbul TR-34342, Turkey
4
Department of Biology, Faculty of Science, Istanbul University, Vezneciler, Istanbul TR-34134, Turkey
5
Marine Biology and Ecology Research Centre, Marine Institute, School of Marine Sciences and Engineering,
University of Plymouth, Plymouth PL4 8AA, UK
6
Ichthyological Research Society, Atatu ¨rk Mahallesi, Mentes¸og ˘lu Caddesi, Idil Apartment no. 30/4,
¨
Umraniye, Istanbul TR-34764, Turkey
7
Department of Ecology and Evolutionary Biology, N122 Ramaley, University of Colorado,
Boulder, CO 80309, USA
The provenance of white sharks (Carcharodon carcharias) in the Mediterranean is both a conundrum and
an important conservation issue. Considering this species’s propensity for natal philopatry, any evidence
that the Mediterranean stock has little or no contemporary immigration from the Atlantic would suggest
that it is extraordinarily vulnerable. To address this issue we sequenced the mitochondrial control region
of four rare Mediterranean white sharks. Unexpectedly, the juvenile sequences were identical although
collected at different locations and times, showing little genetic differentiation from Indo-Pacific lineages,
but strong separation from geographically closer Atlantic/western Indian Ocean haplotypes. Historical
long-distance dispersal (probably a consequence of navigational error during past climatic oscillations)
and potential founder effects are invoked to explain the anomalous relationships of this isolated ‘sink’
population, highlighting the present vulnerability of its nursery grounds.
Keywords: Mediterranean; white shark; mitochondrial DNA; conservation; climate change; migration

1. INTRODUCTION natal female philopatry, such navigational errors may
The movement of marine megafauna around the result in a founding population becoming closely associ-
globe has significant and lasting consequences for ecosys- ated with a new location, often outside the normal
tems, especially where those species are top predators home range of the source population or well beyond the
[1,2]. Some are known to undertake long transoceanic species’ usual distribution. Once established as a top
migrations [3–6], with an attendant risk of navigational predator in a new location such founders may become
error. Observations that water temperature appears to effectively isolated, making them a vulnerable yet highly
influence the movements of many marine species, includ- significant component of the ecosystem.
ing sharks [7,8], has led to the suggestion that thermal A wide-ranging species inhabiting sub-polar to tropical
fronts may act as navigational cues during migration seas of both hemispheres, the great white shark,
[9]. Such cues are easily disrupted during periods of Carcharodon carcharias (Linneaus, 1758) has been docu-
climate change, producing anomalous distributions of mented in the Mediterranean [11,12]. The oldest white
some species [10]. Most of these instances probably shark material preserved in Europe dates from 1640 to
go unnoticed, or remain little more than a historical anec- 1660; however, the capture date and locality are unknown
dote, having no significant or lasting effect on the species’ [13]. Records of Mediterranean white sharks date back to
global distribution or on the ecosystem in which they the 1820–1850s, mainly from Italy [14] or Sicily [11].
become resident [2]. However, for species exhibiting However, the first legitimate scientific record of Mediter-
ranean white sharks probably dates to 1901, when a 4.5 m
female caught off the coast of Capo San Croce, Augusta,
eastern Sicily was dissected, revealing three human
* Author for correspondence (l.r.noble@abdn.ac.uk).
† corpses [15]. White sharks are recorded from all coasts
These authors contributed equally to the study.
of the Mediterranean western basin, most frequently the
Electronic supplementary material is available at http://dx.doi.org/
10.1098/rspb.2010.1856 or via http://rspb.royalsocietypublishing.org. eastern side, with the most consistent reports in the
Received 30 August 2010
Accepted 27 October 2010 1679 This journal is q 2010 The Royal Society