Fine-scale spatial genetic structure and intra-specific interactions of Populus nigra within a natural river corridor along the lower Allier River (France)

•We investigated the fine-scale spatial genetic structure (at a metre scale) in three cohorts in a natural population of Populus nigra and assessed the links with the intra-specific interactions in early-life stages.•We found a significant fine-scale spatial genetic structure in patches of young P. nigra but not in older cohorts. This indicates a shift in intra-specific interactions from positive to negative with time.•Facilitation processes are enhanced by the presence of significantly more clones of P.nigra in the edges of recruitment bands and in more disturbed portions of the alluvial bars. Competition occurs later through self-thinning.•Studying FSGS for different age cohorts is thus a valuable tool to study the intra-specific interactions and how they change through different life stages.