Genetic structure of Pinus parviflora on Mt. Fuji in relation to the hoarding behavior of the Japanese nutcracker

Pinus parviflora (Japanese white pine) is distributed along a wide range of altitudes between 1100 and 2500 m above sea level (asl) on the northwestern slope of Mt. Fuji in Japan. The seeds of P. parviflora are presumed to be dispersed from the mountainous area to the timberline by the Japanese nutcracker (Nucifraga caryocatactes var. japonica). We aimed to clarify the effect of the nutcracker on the genetic diversity and structures of P. parviflora populations on Mt. Fuji. Leaf samples were collected from eight populations at altitudes between 1100 and 2500 m asl. Using 11 microsatellite markers, we investigated the genetic diversity and structures of P. parviflora populations on Mt. Fuji. The average expected heterozygosity (HE), allelic richness (Aᵣ), and inbreeding coefficients (FIS) of the P. parviflora populations on Mt. Fuji were 0.66, 1.66, and 0.14, respectively, suggesting a lower genetic diversity in comparison with those of P. parviflora populations in other regions of Japan. The genetic structure of the population at the lowest altitude of 1100 m was significantly different from that of the other populations. However, certain individuals in the populations at higher altitudes (2300–2500 m asl) were likely derived from populations at lower altitudes (1100–1500 m asl), probably because of the hoarding behavior of the nutcracker. Our results indicate that seeds carried from low altitudes by nutcrackers have become established at the timberline and have contributed to expanding the distribution and maintaining the genetic diversity of P. parviflora on Mt. Fuji.