Phytoliths in Fynbos plants and soils: Implications for South African archaeological and palaeoecological research

The exceptional biodiversity and rich archaeological and palaeontological record of the Fynbos biome provide an important context for investigating past environmental changes and human–plant interactions through palaeobotanical evidence. Here, we use phytoliths to improve the identification and interpretation of fossil phytolith records in South Africa. We analysed 22 plant species from Restionaceae and Proteaceae, together with 69 modern soil samples from 34 Fynbos localities representing 14 vegetation units across the Greater Cape Floristic Region. Restionaceae produced abundant and morphologically distinctive S pheroids and characteristic E longate claviform phytoliths, providing useful indicators of the family. Papillae-like phytoliths occurred in both Restionaceae and Proteaceae, highlighting the potential for similar morphologies to occur across different plant families. In modern soils, S pheroids and restio phytoliths were among the most abundant morphotypes and together provided a clear signal of Limestone Fynbos, even at low concentrations. Their distribution also reflected broader regional vegetation and climatic gradients across the GCFR. Soil phytolith assemblages vary widely among and within vegetation types, with substantial variability at small spatial scales (~ 100 m), indicating pronounced micro-scale heterogeneity. Grass phytoliths were ubiquitous across Fynbos vegetation types. However, although their distribution in the Fynbos biome does not follow a single, consistent west–east pattern, lower frequencies of O blong and R ondel phytoliths are observed towards the eastern GCFR. Overall, our study shows how modern phytolith assemblages reflect Fynbos vegetation composition and regional environmental gradients, while also highlights the importance of considering taphonomic and spatial variability when interpreting fossil phytolith records in the GCFR.