Population Genetic Structure of Fagus japonica Revealed by Nuclear Microsatellite Markers

Fagus japonica is generally known as one of two beech species native to Japan. It forms intermediate temperate forests that are vertically distributed from the lower part of the cool temperate zone into the upper part of the warm temperate zone, mostly along the Pacific side of Japan. We have studied the genetic diversity and population genetic structure in 16 F. japonica populations distributed throughout its range, using 13 nuclear microsatellite markers. Genetic diversity within populations was found to be high (average \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$H_{\mathrm{E}\,}=0.659$$ \end{document} ), whereas population differentiation was low ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$F_{\mathrm{ST}\,}=0.023$$ \end{document} ; \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$R_{\mathrm{ST}\,}=0.025$$ \end{document} ). However, we detected significant isolation by distance. A neighbor‐joining tree based on genetic distances among the populations reflected the geographic location of the populations and identified three distinct subdivisions, in the northeastern, central, and southwestern regions (the bootstrap values for internal branches between these regions are 87% and 91%). This finding was supported by boundaries detected by Monmonier’s maximum‐difference algorithm. In addition, Bayesian clustering analysis, using multilocus genotypes, revealed two distinct clusters that correlated with the geographical distributions of the populations, consistent with the results of the other analyses. The distribution of the two clusters suggests that, as a result of historical migrations, genetic mixing has occurred between two ancestral populations with different genetic backgrounds.