Post-fire clumping of seedlings of Cape Proteaceae species: ecological, evolutionary and conservation implications

Background Spatial clumping of plants results in intense competition. Aims We analysed the extent of clumping of Proteaceae seedlings across the Cape Floristic Region after fire. Methods To demonstrate the extent of clumping in 23 species, we analysed the seedling and adult densities in 290 post-fire surveys each of 100 × 1 m2 plots using standard indices of clumping. Key results We detected clumping of Cape Proteaceae seedlings, whereas parent plants were less clumped. The clumping is not due to limited safe sites for seedlings because the number of plots at a site with at least one seedling was positively related to the number of seedlings at the site. Sites with seedlings were enriched in nutrients relative to those without. Conclusions The possible benefits of clumping are saturation of granivores and co-location of buried seeds with nutrient-rich patches of fire-derived ash and debris. A cause of clumping is seeds sticking together. Clumping, which is strongly intraspecific, has implications for trait evolution and the dominance of reseeders over resprouters. Strong clumping reduces the usefulness of the widely used seedling:parent index to determine whether fires were favourable or not. Implications Clumping has implications for understanding seed dispersal distances, seedling versus adult traits, fire responses and demography.