A Genetic Exploration in a Last Refuge: The Common Angelshark (Squatina squatina) in the Canary Islands

The common angelshark ( Squatina squatina ) has been extirpated from nearly the entirety of its historical eastern North Atlantic and Mediterranean range and is listed as ‘Critically Endangered’ by the IUCN Red List of Threatened Species. Currently, only a single known remnant population of any abundance exists, occurring within the waters surrounding the Canary Islands. Nothing is known about the genetic population dynamics of this species. To assess the common angelshark’s genetic connectivity and diversity, tissue samples (n = 509) were collected between 2009-2016 from three separate islands within the archipelago: Gran Canaria and Tenerife – which are separated by a deep ocean channel (~3000 m) which potentially serves as a barrier to dispersal for this benthic species, and Lanzarote. To date, DNA sequences have been obtained from four mitochondrial loci [control region (CR) (n = 233), Cytochrome c oxidase subunit 1 (COI) (n = 16), NADH dehydrogenase subunit 4 (ND4) (n =28), and NADH dehydrogenase subunit 2 (ND2) (n =4)] revealing exceptionally low genetic diversity across all regions, as identical haplotypes were found in nearly all analyzed individuals. Additionally, next-generation sequencing has been used to develop a species-specific library for novel microsatellites and preliminary screening of each of 18 markers has shown these loci to be monomorphic across 16 individuals. Further screening of additional loci (mitochondrial and microsatellite) and individuals is ongoing. Such potentially low levels of genetic diversity may have far reaching implications for the persistence of this species and ultimately underscore the common angelsharks’ highly vulnerable state.