Taxonomic revision of the Afrotropical species group with the description of four new species (Coleoptera, Dytiscidae).

We revise the Afrotropical species group, motivated by the discovery of new diversity in Kenya and South Africa. Whilst is mainly a holarctic genus, the group is restricted to high altitude regions of eastern Africa and temperate parts of South Africa, from where we describe the southernmost in the world. The following new species are introduced: from Mount Kenya in central Kenya, a widespread species in South Africa, from the Kamiesberg and northeastern Cederberg ranges in the Northern and Western Cape Provinces of South Africa and from the Agulhas Plain, Western Cape Province, South Africa. We provide a distribution map, a determination key for males, quantitative measurements of diagnostic characters, habitus photos and detailed photos of male genitalia for all described species in the group, as well as images of diagnostic characters and habitats. The presence or absence of an elongated section between the subapical broadening and the base of the apical and subapical teeth of the male aedeagus is a useful novel character, first revealed by our study. In contrast with the most recent revision of Afrotropical , we show that Guignot, 1936 is restricted to eastern Africa; South African records of this species having been based on misidentifications, no species of the group being common to southern and eastern Africa. We speculate that the group may display phylogenetic niche conservatism, being restricted, as an originally temperate taxon, to higher elevations in tropical eastern Africa, but occurring at lower altitudes in temperate South Africa.