Abstract
An account is given of the geographical distribution and habitats of the South African representative of the genus Corbicula Muhlfeld 1811, formerly known as C. africana (Krauss, 1848) but currently regarded as conspecific with the Asian clam, C. fluminalis (Muller, 1774). Data pertaining to 390 samples of C. fluminalis africana (Krauss, 1848) were extracted from the database of the National Freshwater Snail Collection (NFSC) and statistically analysed. Details of each habitat, as well as mean altitude and mean annual temperature and rainfall for each locality, were processed to determine chi-square and effect size values. An integrated decision tree constructed from the data indicated that temperature, altitude, current speed and type of water-body seemed the more important factors that significantly influenced the distribution of this species in South Africa. In spite of the fact that C. fluminalis africana is relatively widespread in South Africa and was recovered from a wide range of habitat types and water-bodies, it has, to our knowledge, not yet been reported to cause problems in cooling circuits as experienced elsewhere in the world. It is proposed that the feasibility to exploit this species for monitoring heavy metal pollution in freshwater biotopes should be investigated in view of reports from elsewhere in the world that it has the ability to accumulate metals such as copper, lead, zinc and manganese.
Highlights
The distribution of the bivalve genus Corbicula was reported by Pilsbury and Bequart in 1927 as widespread over the AfroTropical Region, Madagascar, south-eastern Europe, southern and eastern Asia, the indo-Malayan Region, eastern Australia and Tasmania
African representatives of the genus Corbicula were separated by Haas (1936) into two groups, one with a smooth ligament plate (4 species), the other with a crenulated ligament plate (1 species)
This author is of the opinion that the many species of Corbicula previously described as being from Africa should be included in only 2 species groups, namely the C. fluminalis-group and the C. astartina-group, the latter group restricted to Africa
Summary
The distribution of the bivalve genus Corbicula was reported by Pilsbury and Bequart in 1927 as widespread over the AfroTropical Region, Madagascar, south-eastern Europe, southern and eastern Asia, the indo-Malayan Region, eastern Australia and Tasmania. After studies on the freshwater bivalves of Africa, Mandahl-Barth (1988) came to the conclusion that these were the only 2 species of this genus represented in South Africa, but regarded the previously known C. africana as conspecific with the widespread Asian clam, C. fluminalis and considered it as a defendable subspecies, C. fluminalis africana (Krauss 1848). Defendable subspecies occur in east and central African lakes, namely C. fluminalis cunningtoni (Smith 1906) in lake Victoria and C. fluminalis tanganyicensis (Crosse 1881) in lake Tanganyika These are the subspecies of Corbicula acknowledged by Appleton and Curtis (2007) in their account of the freshwater bivalves of Namibia and Botswana. As well as mean altitude and mean annual air temperature and rainfall for each locality, were processed to determine chi-square and effect size values
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