| dc.description.abstract | Successful resolution of the nomenclature and taxonomy of batoid fish complicated by the high degree of morphological and ecological conservatism in this group. However, both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) phylogenies have been utilised to resolve batoid phylogenies and even to identify cryptic species. As a result, the number of ray species described in recent decades has dramatically increased- although questions still remain regarding the taxonomic status of many batoid species. In chapter one of this thesis, the importance of taxonomy in skate conservation and management is reviewed. In chapter two, control region (CR) and cytochrome oxidase I (COI) sequencing of the blue skate (Dipturus batis) and the flapper skate (Dipturus intermedius) from across the Northeast Atlantic was performed, in order to clarify their geographical distribution. Although now formally recognised as distinct species, before 2010 these two taxa were classified together as the critically endangered ‘common skate’, D. batis. Although this has important conservation implications, their protection is currently being hindered by a lack of spatiotemporal data. In the present study, the blue skate generally appears to be more common than the flapper skate, with a distribution extending from Rockall and Iceland to the Western Approaches and the Celtic Sea. Whilst the flapper skate appears most frequent around northern Scotland, the North Sea and Ireland, novel data also suggests that it may have once had a much wider distribution. For the first time, this species was identified in the Azores, where unique haplotypes were also isolated, potentially highlighting the genetic distinctiveness of the population in this region. In chapter three, nextRAD and mtDNA (concatenated CR and COI) sequencing were utilised to explore the phylogenetics of several vulnerable species of European skate. Whilst the current designation of the Madeiran skate (Raja maderensis) and the thornback ray (Raja clavata) as distinct species wasn’t fully supported, genetically distinct populations were identified in the Azores and surrounding seamounts. The presence of a cryptic Dipturus species in the Azores wasn’t supported, as suggested by previous work on the longnosed skate (Dipturus oxyrinchus). However, Azorean longnosed skate and flapper skate were distinct from their geographically proximate counterparts, and may represent distinct populations. The uniqueness of the Azores highlights the importance of seamounts as ‘hotspots’ of biodiversity, which has important implications for marine protected areas that include these batoid species as a protected feature. In addition to resolving these phylogenies, this thesis also offered an opportunity to comment on the utility of mtDNA and nextRAD sequencing for batoid phylogenetics, the latter of which has never been applied to skates and rays before. | en_GB |
