Chemical interference along the Mediterranean dune gradient: extracts, BVOCs, and litter legacy effects

Chemical ecology plays a pivotal role in shaping Mediterranean dune plant communities, yet its contribution remains less explored than that of abiotic factors. This study evaluated the allelopathic potential of Teucrium dunense , Helichrysum stoechas , and Crucianella maritima —three characteristic species of Western Mediterranean backdunes—through germination bioassays using aqueous extracts, exposure trials to BVOCs (biogenic volatile organic compounds), and chromatographic analyses of the volatile fraction of leaf litter over a 300-day period. T. dunense extracts exhibited the strongest inhibitory activity, reducing the germination of H. stoechas and C. maritima by over 60% at the highest concentrations, while demonstrating high self-tolerance. In contrast, H. stoechas displayed significant autotoxicity, whereas C. maritima emerged as the most susceptible species. BVOCs emitted by T. dunense also suppressed recipient species' germination. Chemical analysis revealed a profound temporal transformation of the litter, notwithstanding a remarkable persistence of phytotoxic activity. Collectively, these results indicate that chemical ecology significantly drives zonation and coexistence patterns in Mediterranean dunes, with direct implications for the conservation and management of EU habitats 2210 and 2260.