Temperature is one of the most significant variables affecting the geographic distribution and physiology of elasmobranchs. Differing thermal gradients across a species’ range can lead to adaptive divergence and differing developmental times, an important consideration for recruitment rates of exploited species. The Critically Endangered common skate (formerly Dipturus batis) has been divided into 2 species, the flapper skate D. intermedius and blue skate D. batis, both of which have undergone dramatic population declines. Here we examine the environmental thermal and geographic distribution of these species, using observations from scientific trawling surveys and recreational angling around the British Isles. As similar-sized specimens of the 2 species can be confused, we validated species identity using molecular genetic techniques. Both species had more extensive geographic ranges than previously reported and different spatial patterns of abundance. The distribution of the blue skate appears to reflect its partiality to thermally less variable and warmer waters, while flapper skate were found in more variable and notably colder areas. The thermal range and current geographic distribution of these species indicate that future projected climate change could have a differential impact on distribution of flapper and blue skate in the north-east Atlantic.

The blue skate (Dipturus batis) has a patchy distribution across the North‐East Atlantic Ocean, largely restricted to occidental seas around the British Isles following fisheries‐induced population declines and extirpations. The viability of remnant populations remains uncertain and could be impacted by continued fishing and by‐catch pressure, and the projected impacts of climate change. We genotyped 503 samples of D. batis, obtained opportunistically from the widest available geographic range, across 6 350 single nucleotide polymorphisms (SNPs) using a reduced‐representation sequencing approach. Genotypes were used to assess the species’ contemporary population structure, estimate effective population sizes and identify putative signals of selection in relation to environmental variables using a seascape genomics approach. We identified genetic discontinuities between inshore (British Isles) and offshore (Rockall and Faroe Island) populations, with differentiation most pronounced across the deep waters of the Rockall Trough. Effective population sizes were largest in the Celtic Sea and Rockall, but low enough to be of potential conservation concern among Scottish and Faroese sites. Among the 21 candidate SNPs under positive selection was one significantly correlated with environmental variables predicted to be affected by climate change, including bottom temperature, salinity and pH. The paucity of well‐annotated elasmobranch genomes precluded us from identifying a putative function for this SNP. Nevertheless, our findings suggest that climate change could inflict a strong selective force upon remnant populations of D. batis, further constraining its already‐restricted habitat. Furthermore, the results provide fundamental insights on the distribution, behaviour and evolutionary biology of D. batis in the North‐East Atlantic that will be useful for the establishment of conservation actions for this and other critically endangered elasmobranchs.

Eleven microsatellites were isolated in the freshwater snail Bulinus forskalii, intermediate host for the medically important trematode Schistosoma intercalatum. Characterization in 60 snails from three populations of B. forskalii from Cameroon revealed 4 to 18 alleles per locus. Low observed heterozygosity but higher expected heterozygosity, high FIS estimates, significant departures from Hardy–Weinberg equilibrium and genotypic linkage disequilibria all indicate that B. forskalii is a preferential selfer. High FST estimates suggest that effective dispersal is limited and genetic drift is an important determinant of genetic structure. The potential utility of the microsatellite primers in other closely related Bulinus species was explored.

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The morphological definition of taxa has proved difficult within the Bulinus forskalii group, which includes intermediate hosts of medically important Schistosoma species in West Africa. Although B. forskalii and B. senegalensis transmit different schistosome species they are conchologically similar and their distributions overlap. Randomly amplified polymorphic DNA (RAPD) allows differentiation of sibling species in the genus Bulinus, but RAPDs are difficult to standardize, impairing their value as a taxonomic tool. Hence, RAPD products diagnostic for either B. senegalensis or B. forskalii from West Africa were cloned, sequenced and a panel of species‐specific primers designed. Sequencing of RAPD products identified a homology in two apparently independent RAPD loci, a problem where RAPDs are indiscriminately scored for phylogenetic analyses. Specificity of primers was confirmed by widespread sampling throughout each species' range. This approach produced a simple, robust, unambiguous PCR‐based species identification strategy for this difficult group.