Spatial genetic structure links between soil seed banks and above‐ground populations of Primula modesta in subalpine grassland

Abstract

Summary The spatial genetic structure of soil seed banks establishes the initial template for development of spatial genetic structure in above‐ground plants, but is rarely evaluated. We used kinship coefficients to analyse the fine‐scale spatial genetic autocorrelation of plants and of seed banks from different soil depths for Primula modesta at a subalpine fen site on Mt Asama, central Japan. The spatial genetic structure of surface seeds (0–1 cm depth) was significant, while deeper seeds (1–5 cm depth) had no significant genetic structure. We also detected a more pronounced spatial genetic association between the surface seeds and flowering genets than between the deeper seeds and flowering genets. These results suggest that the surface seed bank accounts for a large proportion of the previous season's seed dispersal and therefore represents the transient seed bank, whereas the deeper (persistent) seed bank pools the reproductive output of multiple generations. Directional analysis indicated that secondary dispersal by running water modifies the spatial genetic structure and extends dispersal distances. Over time, this may impact on the spatial pattern of soil seeds, possibly accounting for the absence of spatial genetic structure in deeper seeds. Emerging seedlings and flowering ramets were strongly clustered together at distances up to 20 cm. Surviving seedlings were aggregated at short distances because of the patchy spatial distribution of safe sites for establishment, allowing development and strengthening of the marked fine‐scale spatial genetic structure.