Using Natural History Collections to Determine the Relative Changes in Diversity and Distribution of Freshwater Molluscs in KwaZulu-Natal, South Africa

Abstract

Research using natural history collections to track anthropogenic activities has recently been on the rise. Natural history collections have been utilised beyond their traditional taxonomic and systematic roles, generating data that shape present and future research. We evaluated the value of natural history collections in answering questions about the changes in the occurrence of freshwater mollusc species in KwaZulu-Natal, South Africa, over the past 124 years. The historical records were sourced from four natural history collections databases in South Africa. Specimen records were curated and validated against two independent online platforms. The number of shells and diversity among collections were compared, and trends in the database were analysed. We recorded a significant decline in the number of specimens collected between 1897 and 1960, and after 1980 and 2021, respectively. The majority of freshwater mollusc specimens that were collected belonged to Bulinus tropicus (Krauss, 1848) (307 records), followed by Pseudosuccinea columella (Say, 1817) (270 records) and Radix natalensis (Krauss, 1848) (268 records), while 34% of specimens collected received one observation each. Three species database records exhibited positive observation trends, while two species showed negative database record trends. We also found that potentially declining species database records accounted for 52% of the total freshwater molluscs in KwaZulu-Natal. The broad-scale compositional shift of endemic species and the greater prevalence of invasive species may be exacerbated by inadequate sampling and a lack of long-term monitoring programs at selected sites. We argue that random sampling and donations are insufficient to sustain the growth of these collections. National programs, such as the River Eco-Status Monitoring Programme (REMP) and Freshwater Biodiversity Information System (FBIS), have the opportunity to identify and include new key biodiversity sites for biomonitoring of biodiversity. Thus, an increase in financial and skills investment is advocated to monitor biodiversity and the emergence of future diseases.