Die verspreiding en habitat van Chambardia wahlbergi en Chambardia petersi (Bivalvia: Iridinidae) in Suid–Afrika

Abstract

Based on the data in the database of the National Freshwater Snail Collection (NFSC), the distribution and habitat of Chambardia wahlbergi and Chambardia petersi, are presented and discussed. Although the distribution of these two species overlaps extensively in the Limpopo and Mpumalanga Provinces, contrary to reports in literature, specimens of C. wahlbergi were also collected in the North West Province and the Free State Province in the west-flowing Vaal River, as well as in Gauteng. The majority of samples of both species were collected in rivers and dams, in water conditions described as perennial, standing, clear and fresh. Multivariate analyses indicated that temperature, altitude and waterbodies played a significant role in the geographical distribution of both species. Although little is known of the conservation status of these species, it is categorised as of least concern in the revised edition of the UCN Red Data List (Seddon et al. 2011). The majority of records of both species in the database of the NFSC date from work done during the previous century in the Kruger National Park (KNP). More recent surveys by the authors in the KNP revealed a decline in the number of positive sites, as well as the number of specimens per site. This data suggest that there might be reason for concern regarding their conservation status. The fact that exceptionally large specimens of C. wahlbergi were collected, mostly by chance, on several occasions in the west-flowing Vaal River as recently as 2007 emphasises the need to conduct extensive mollusc surveys, as during the previous century, to update the documented geographical distribution and to monitor the progress of exotic invader species