ABSTRACT To consider and evaluate the effectiveness of strategies for genetic variation preservation of populations of targeted species, it is important to examine which components of gametic heterogeneity have a greater impact on the genetic diversity of the next generation. Here, we investigated gene dispersal patterns in dispersed seeds and the relative levels of genetic diversity and differentiation for within-population and immigrant groups of both paternal and maternal gametes in a natural population of Abies firma during three reproductive events (mast years). Accurate paternity and maternity analyses, genotyping 630 seeds (1,260 tissue samples) and 331 candidate adult trees in total, were performed by analyzing 12 nuclear microsatellite loci of both diploid biparental embryos and haploid maternal megagametophytes. We found that 53.7% of paternal gametes and 15.3% of maternal gametes were of immigrant origin, indicating substantial gene flow for both parentages. Of the three components of gametic heterogeneity (immigration, parentage, and year) of the seeds, differences in gene-flow categories (within-population vs. immigrant gametes) showed the largest variation (mean F ST = 0.030). Differences in gametes between paternal and maternal parentages had the second-largest variation (0.012), and variation among three mast years was the lowest (0.006). Diverse immigrant gametes derived from nearby populations at the landscape level and the differences in paternal and maternal reproductions of adult trees are considered to make the main contributions to the overall genetic variability of dispersed seeds of A. firma.