2.6 Influence of landscape on genetic diversity
To reveal the influence of the composition of the landscape types around
each sampling point on the genetic diversity, Arcgis10.2 (ESRI) was used
to create circular buffers with radii of 300 m, 800 m, and 1,000 m and
with each sample point as the center. Then, the proportions of P.
massoniana , C. lanceolata , P. elliottii , mixed forest
(including some hosts), broad-leaved forest, urban, farmland, road,
water, and nudation landscape types in each circular buffer were
calculated. The db-RDA model (Legendre & Anderson, 1999)was used to
analyze whether the ten landscape types at the three scales could
explain the genetic diversity. In addition, to explain the
nonlinear relationship in the db-RDA analysis and explore whether those
variables inhibited or facilitated the genetic diversity of M.
alternatus , a flexible fitting method (GAM) (Lengyel & Podani,
2015)was used to map the explanatory variables over the first two
principal coordinates analysis (PCoA) axes.