Levels of connectivity between longnose skate (Dipturus oxyrinchus) in the Mediterranean Sea and the north-eastern Atlantic Ocean

Abstract

Sequencing of a partial region of the mitochondrial control region has revealed no shared haplotypes between longnose skate (Dipturus oxyrinchus L.) sampled in the north-eastern Atlantic (Norway and Rockall) and those sampled in the Mediterranean (Mallorca). Bayesian estimation of the migration rate suggests little, if any, gene flow occurs between the regions and that the populations separated 20,000 years ago. These conclusions provide a genetic basis for long-standing observations, based on egg capsule and adult size, that longnose skate in the Mediterranean may be genetically isolated from other stocks. This result has important conservation implications for the threatened longnose skate.

Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

“…In the small-spotted catshark, the lack of significant genetic differentiation between the Atlantic and the western Mediterranean at the mtDNA level contrasts the strong genetic differentiation that was detected in the longnose skate (Griffiths et al, 2011a). Griffiths et al (2011a) found no shared haplotypes between the Atlantic and the Mediterranean collections, possibly because the Atlantic collections (Rockall Bank and off Norway) were geographically very distant from the Mediterranean ones (Mallorca and Menorca).…”

“…Griffiths et al (2011a) found no shared haplotypes between the Atlantic and the Mediterranean collections, possibly because the Atlantic collections (Rockall Bank and off Norway) were geographically very distant from the Mediterranean ones (Mallorca and Menorca). However, the genetic differentiation of both species between the Atlantic and the Mediterranean remains to be clarified with more markers (for example, nuclear) and a more appropriate sampling scheme.…”

“…Comparison with other chondrichthyan species of similar distribution and life history The population genetic pattern found for the small-spotted catshark is not congruent with findings in the thornback ray (Chevolot et al, 2006) and the longnose skate (Griffiths et al, 2011a), although they have a similar geographic distribution and life history traits (Compagno, 1984). For the thornback ray, which also exhibits high degree of site fidelity (Hunter et al, 2005), a single mitochondrial haplotype was identified in the Mediterranean, attributed to a relatively recent expansion following a bottleneck (Chevolot et al, 2006).…”

“…However, a study of the thornback ray, Raja clavata, showed that the Mediterranean populations were undifferentiated, sharing only a single ancestral mitochondrial haplotype, and the respective analyses suggested a strong bottleneck and a subsequent isolation from the Atlantic (Chevolot et al, 2006). Griffiths et al (2011a) did not find any shared haplotypes between Atlantic and Mediterranean samples of the longnose skate, Dipturus oxyrinchus, suggesting the genetic isolation of the Mediterranean from the other stocks. On the other hand, first indications for the genetic differentiation of the small-spotted catshark within the Mediterranean were recently found based on mitochondrial DNA (mtDNA) analysis (Barbieri et al, 2014).…”

Improving the Conservation of Mediterranean Chondrichthyans: The ELASMOMED DNA Barcode Reference Library

“…Geographical genetic breaks need to be accurately accounted for when delineating management and conservation units. Behavioural ecology and life-history traits of demersal and bathydemersal skates and rays [103–105] make this group particularly prone to genetic structuring and several cases have already been documented for the region [73,106,107]. Other studies used different mtDNA markers such as parts of the control region or cytochrome b (see for R .…”