A coastal beach seed bank shows high diversity, but low similarity to the adjacent forest vegetation in an Amazonia Marine Extractive Reserve

Abstract Marine Extractive Reserves (RESEX-Mar) play a fundamental role in conserving Amazoniana coastal biodiversity, maintaining ecosystem services, and supporting the livelihoods of traditional communities. However, the relationship between seed taxonomy and adjacent vegetation remains poorly understood. This study evaluated whether the taxonomic composition of seeds deposited on the beaches of the RESEX-Mar in the municipality of Soure, Brazilian Amazon, reflects the composition and diversity of the adjacent vegetation. A floristic inventory was conducted on the main beaches of the reserve, while seeds were manually collected from the sand during low tide. The vegetation comprised of 20 species distributed across 16 families, with dominance of Rhizophora sp. and a predominance of arboreal habit (50 – 56% of individuals). A total of 786 seeds were recorded, representing 21 plant families, 64 identified species, and 46 morphospecies, exhibiting substantially higher diversity than the vegetation (Shannon 3.90 – 4.13 for seed taxonomy versus 0.79 – 2.29 for vegetation) and high evenness (Pielou ≥ 0.95). Mean seed density did not differ statistically among beaches. The divergence between seeds and vegetation indicated a strong influence of external dispersal, likely shaped by hydrochory. The results demonstrate the genetic potential of the seed bank, characterized as an important propagule reservoir for the ecological restoration of coastal ecosystems. Therefore, it was observed that seed composition does not fully reflect the adjacent vegetation but reinforces the role of Amazoniana coastal ecosystems as biodiversity source areas, highlighting the need for conservation strategies that consider ecological connectivity, monitoring of natural regeneration, and sustainable management of tourism use.