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Abstract
Natalina sensu lato includes some of the largest carnivorous snails in the world and represents an important African radiation of the Gondwanan land snail family Rhytididae. It comprises the taxa Natalina, Afrorhytida and Capitina, all three of which we treat as full genera. We provide a comprehensive revision of each genus, and update the species-level taxonomy extensively in the light of new molecular and morphological data. Detailed comparative morphological observations are provided for the distal reproductive tract (including spermatophores for the first time in this family), pulmonary cavity, mantle edge, radula and suprapedal gland. In addition, we present a summary of biological and ecological data including information on habitat preferences, feeding, prey and mating behaviour. Although the genera are well circumscribed in terms of both morphological and molecular data, morphology is usually highly conserved within genera. Yet surprising cryptic diversity is evident within the described species and restricted-range endemism is more frequent than was previously thought, with significant implications for conservation. The widespread common cannibal snail, Natalina cafra (Férussac, 1821), is shown to comprise four cryptic, allopatric lineages. For the most part, we recognise this cryptic diversity at the level of subspecies. In some cases where populations from disjunct, lime-rich habitats exhibit a significantly different shell morphology, it is difficult to evaluate whether and to what extent this is genetically or environmentally determined. Spermatophores exhibit considerable phylogenetically consistent morphological variation and may eventually prove to be an important source of new taxonomic characters. The geographic distributions of the respective lineages are interpreted in the light of phylogenetic data, current regional vegetation patterns, and historical environmental phenomena, so as to identify biogeographic trends. Some lineages are clearly forest-associated specialists and have fragmented, narrowly-endemic distributions resulting from cyclical changes in forest cover during the Plio-Pleistocene, but there is also strong evidence for regional endemism associated with other vegetation types, notably Albany Thicket. Observations on the conservation status of all taxa are provided.New subgenus: Natalina (Tongalina). New species: Afrorhytida burseyae, Capitina calcicola. New subspecies: Afrorhytida kraussi oraria, Natalina cafra amathole, Natalina cafra natalensis, Natalina quekettiana dracomontana, Natalina quekettiana lucaris, Natalina quekettiana montistempli. New synonyms: Natalina compacta Connolly, 1939 = Natalina cafra cafra (Férussac, 1821); Natalina coerneyensis Melvill & Ponsonby, 1894 and Natalina insignis Melvill & Ponsonby, 1907 = Afrorhytida knysnaensis (Pfeiffer, 1846); Natalina liliacea Preston, 1912 = Afrorhytida kraussi kraussi (Pfeiffer, 1846); Natalina arguta Melvill & Ponsonby, 1907 = Afrorhytida trimeni Melvill & Ponsonby, 1892. Revised status: Helix (Aerope) eumacta Melvill & Ponsonby, 1892 is considered a subspecies of Natalina cafra (Férussac, 1821). Lectotypes designated for Aerope beyrichi Martens, 1890 [= Natalina] and Helix schärfiae Pfeiffer, 1861 [= Capitina schaerfiae].
Highlights
Carnivorous snails of the family Rhytididae represent some of the most spectacular of all lands snails
Ten genera are recognised in Australia (Smith 1998), and nine or ten in New Zealand (Barker 2005; Spencer et al 2006), and Solem (1959) recorded five in Austronesia
The studied material is kept in the following institutions: ELM – East London Museum, East London, South Africa; BMNH – Natural History Museum, London, UK; MNHN – Muséum National d’Histoire Naturelle, Paris, France; MNHU – Museum für Naturkunde der Humboldt-Universitat, Berlin, Germany; MVM – Museum Victoria, Melbourne, Australia; NMSA – Natal Museum, Pietermaritzburg, South Africa; ISNB – Institut Royal des Sciences Naturelles de Belgique, Brussels, Belgium; RMNH – National Museum of Natural History, Leiden, The Netherlands; SAMC – South African Museum, Cape Town, South Africa; SMFD – Senckenberg Museum, Frankfurt, Germany
Summary
Carnivorous snails of the family Rhytididae represent some of the most spectacular of all lands snails. As animals with limited capacity for dispersal, their patterns of endemicity have potential to contribute valuable information to the growing pool of data regarding the evolutionary biogeography of the southern African low-vagility fauna (Griswold 1991; Hamer & Slotow 2000; Tolley et al 2006; Daniels et al 2009) This revision is based on a sound phylogenetic framework incorporating a great deal of new data (both molecular and morphological, Moussalli et al 2009), we are acutely aware of the fact that our knowledge of the diversity of larger rhytidids in southern Africa is still embryonic. It can only be expected that similar unrecognised taxa exist in southern Africa, within the more deeply divergent complexes for which we currently have insufficient material
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