Molecular phylogeny of Chondrocyclus (Gastropoda: Cyclophoridae), a widespread genus of sedentary, restricted-range snails

摘要

The genus Chondrocyclus Ancey, 1898 contains the majority of southern African members of the Cyclophoridae, a large family of operculate land snails. We present the first molecular phylogeny of the genus based on two mitochondrial genes (16S and CO1) and complement this with an appraisal of morphological characters relating to the shell and soft parts. Worn shells on which some descriptions and records of different species were based appear to be indistinguishable morphologically, creating taxonomic confusion. We show that Chondrocyclus s.l. underwent two major radiations, one Afromontane and the other largely coastal. Accordingly, we recommend a revision recognising two genera. Chondrocyclus s.s. contains four monophyletic lineages, each characterized by a combination of morphological features. The Afromontane group is shown to be a species complex; relationships within this complex could not be resolved due to insufficient DNA sequence data. The molecular data confirms the monophyly of seven currently recognised species and provides evidence for at least twelve undescribed species; the morphological data are broadly consistent with this finding. The morphological data suggest that the two species from countries to the north of South Africa should be removed from the genus, and that Chondrocyclus sensu lato is endemic to South Africa. The historical biogeography of this group of microhabitat specialists with poor dispersal abilities contributes an additional, phylogenetically independent taxon to our understanding of the processes generating biodiversity in southern Africa, a natural laboratory for palaeobiogeography. All taxa are narrow-range endemics, underlining the importance of conserving South Africa's threatened forest habitats.