Environmental correlates of non-marine ostracod (Crustacea: Ostracoda) assemblages of the Eastern Cape (South Africa)

The present study investigates the ecology and distribution of ostracod species and assemblages from 62 inland waterbodies in the Eastern Cape province of South Africa and tests the influence of two major climatic zones (Arid steppe climate BS and Warm temperate humid climate Cf) and two primary catchments (Kowie and Great Fish Rivers), as well as broad gradients of altitude and several local environmental factors. Distance-based linear models were used to test these species-environment relationships and indicated that eight variables (water temperature, pH, conductivity, waterbody size, habitat type, altitude, hydrological-drainage, climate) individually showed significant correlations with the response ostracod dataset of 35 species. However, owing to substantial collinearity, the most parsimonious model identified only two predicting variables (climatic zone and water pH) which best explained variation in ostracod assemblage composition. The assemblages of the two climatic zones differed significantly, with Plesiocypridopsis newtoni and Sarscypridopsis ochracea being most commonly found in the BS climates, while Sarscypridopsis trigonella and Physocypria capensis occurred most frequently in the Cf climates. Finally, tolerance ranges to water pH and electrical conductivity for 21 ostracod species are provided to facilitate application of ostracods in further biodiversity and water-quality assessments, as well as in palaeo-environmental reconstructions.