Geographical Differentiation In Clelandella (Gastropoda: Trochidae) In The Northeastern Atlantic

Abstract

The trochid genus Clelandella is reviewed, taking into account new material collected on northeastern Atlantic seamounts and archipelagos, and in deep water of the Mediterranean. The type species C. miliaris (Brocchi, 1814) is illustrated with topotypic material, and living representatives are reported ranging from north Norway to West Africa and into the Mediterranean. The insular populations of Clelandella are found to constitute discrete groups, which are treated as new species: Clelandella dautzenbergi n. sp. on the Lusitanian seamounts, C. perforata n. sp. in the Meteor group of the central North Atlantic, C. azorica n. sp. in the Azores and C. madeirensis n. sp. in Madeira. Within such groups, differentiation is not appreciable and variability is continuous notwithstanding distances of the order of 200 km. Between such groups, the geographical isolation of the insular populations has resulted in substantial divergence over distances in the range 300– 600 km. A further species, C. myriamae n. sp., was collected on deep-water mud volcanoes of the eastern Mediterranean, and is broadly sympatric with C. miliaris.