Diversity patterns of the terrestrial snail fauna of Nyungwe Forest National Park (Rwanda), a Pleistocene refugium in the heart of Africa ANNIKA BOXNICK 1 , ANN APIO 2 , TORSTEN WRONSKI 3 * and BERNHARD HAUSDORF 1 1 Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany 2 Department of Wildlife and Aquatic Resource Management, College of Agriculture, Animal Sciences and Veterinary Medicine, University of Rwanda – Nyagatare Campus, PO Box 57, Nyagatare, Rwanda 3 College of Animal Science and Technology, Northwest A&F University, Yangling 712100, PR China Received 4 July 2014; revised 2 September 2014; accepted for publication 2 September 2014 We investigated the land snail fauna of Nyungwe Forest National Park in south-western Rwanda. Fifty plots at altitudes between 1718 and 2573 m were studied. In total, 3461 specimens were collected and were assigned to 102 land snail species. With respect to land snail species, Nyungwe Forest is the richest forest known in Africa. A comparison with other forests in the northern Albertine Rift indicates that land snail species richness in this region is significantly correlated with distance from Pleistocene forest refugia. The high beta diversity in Nyungwe is the result of a high species turnover between sites, which has biogeographical and ecological origins. Nyungwe Forest is situated on the Congo–Nile divide where species of different geographical origin may meet. Moreover, Nyungwe Forest offers a high diversity of habitats because it extends across a wide range of altitudinal zones. Species richness decreased with increasing altitude. It was also correlated with the presence of bare rocks that offer additional microhabitats and shelter. Although the occurrences of different land snail species in Nyungwe Forest were significantly clustered, only a minority of the species could be assigned to a group of species with similar occurrences. The majority of the species respond individualistically to environmental variables. The significant nestedness of the occurrences of the land snail species in Nyungwe was mainly correlated with altitude. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 363–375. ADDITIONAL KEYWORDS: geographical distribution – land snails – species richness. INTRODUCTION In the two past decades local land snail faunas in tropical rainforests in Africa have been thoroughly investigated (Emberton, 1995; de Winter, 1995; Tattersfield, 1996, 1998; Emberton et al., 1997; de Winter & Gittenberger, 1998; Tattersfield et al., 2001, 2006; Seddon et al., 2005; Oke & Alohan, 2006; Fontaine, Gargominy & Neubert, 2007; Wronski & Hausdorf, 2008, 2010) and the assertion that land snails are ‘generally neither diverse nor abundant’ in rainforests (Solem, 1984) has been disproved. However, the factors influencing diversity and com- position of land snail communities in rainforests and the distribution patterns of land snails in Africa are still insufficiently known. The Albertine Rift, running from the northern end of Lake Albert to the southern end of Lake Tanganyika, is a centre of high biodiversity (Pomeroy, 1993; Myers et al., 2000; Plumptre et al., 2007). Thus far, its terrestrial mollusc fauna has been systemati- cally sampled only in the northern part in Uganda (Wronski & Hausdorf, 2008, 2010). The species rich- ness in this region decreases with increasing distance from putative Pleistocene forest refugia (Wronski & Hausdorf, 2008). In the northern part of the Albertine Rift, these Pleistocene montane forest refugia were probably located in the highlands of the eastern Democratic Republic of the Congo (DR Congo) along the western side of the rift and extended to the *Corresponding author. E-mail: t_wronski@gmx.de Biological Journal of the Linnean Society, 2015, 114, 363–375. With 7 figures © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 363–375 363 Downloaded from https://academic.oup.com/biolinnean/article-abstract/114/2/363/2415907 by guest on 13 June 2020