The importance of museum collections in determining biodiversity patterns, using a freshwater mussel Unio caffer (Krauss 1848) as an example

Background: Two recent distributional maps of the African freshwater mussel Unio caffer (Krauss 1848) in South Africa represented an incomplete picture compared to the records held by the national museums. Objectives: This study is partly in response to them, with the aim to compare and contrast the distribution maps of the published papers with the distribution records held by the national museums. Method: We requested the distribution records of U. caffer from four South African museums. We visited and worked on the U. caffer collections of three of these museums to confirm the taxonomic identity of their specimens and gather occurrence records. We also extracted the distributional records from the two published maps, and plotted all these records using the geographic information system, ESRI ArcGIS. Results: The distribution map based on the museum records showed that this species occurred in all nine provinces of the country, thus revealing a much broader historical occurrence than previous known. Conclusion: This study demonstrates the crucial function of museums, natural history collections in facilitating understanding about biodiversity patterns using U. caffer distribution as an example. However, as museum records mainly show historical occurrence, there is a need to conduct further studies to assess the current population trends of this species. Although the current International Union for Conservation of Nature (IUCN) conservation assessment of this species is Least Concern, pressures on native fish, which host the larval stages of this mussel, and the declining environmental conditions of rivers in the country may affect the conservation status in the near future.