Altitudinal Genetic Diversity and Differentiation ofQuercus crispulain the Chichibu Mountains, Central Japan

Abstract

In order to elucidate the three‐dimensional genetic structure of Quercus crispula in mountainous regions, the level and distribution of genetic variation were evaluated within and among 19 populations at altitudes ranging from 850 to 1750 m in and around the Chichibu Mountains, central Japan, using seven microsatellite markers. Compared with populations at intermediate altitudes (1000–1500 m), both the expected heterozygosity and allelic richness were significantly weaker for the populations at the lower (≤1000 m) altitudes and not significantly but slightly weaker for the populations at the higher (≥1500 m) altitudes. These results suggest that the lower and higher populations have relatively little diversity because they are peripheral populations, growing in environments (midtemperate and subfrigid forests, respectively) that are close to the environmental limits of the species. In addition, other factors, such as historical movements, may also be partially responsible for the weak diversity in the populations at the lower (≤1000 m) altitudes. According to a multiple regression analysis, there was no significant isolation by distance among the populations along either horizontal ($$R^{2}=0.00$$, $$P=0.69$$) or vertical axes ($$R^{2}=0.01$$, $$P=0.17$$). The genetic differentiation was low (overall fixation index $$F_{\mathrm{ST}\,}=0.013$$), and virtually no genetic variance attributable to differences in altitude was detected.