Contact zone of two different chloroplast lineages and genetic guidelines for seed transfer in Quercus serrata and Q. crispula

Within their natural distribution ranges, plant species exhibit genetic
structure which has been created by global climate change and natural
selection over long periods. To conserve local forests with different
genetic structures, genetic guidelines for seed and seedling transfer in
individual species are therefore necessary. Genetic guidelines have been
published for 43 Japanese tree species using population genetic data;
however, for practical use, more detailed genetic borders between
important genetic lineages should be clarified to inform seed collection
and planting. Thus, we investigated in detail the genetic borders between
two important Japanese oak species, Quercus serrata and Q. crispula, in
the Chubu region of Japan using chloroplast and nuclear DNA markers, and
we discuss the factors that influenced border creation using the results
of species distribution modelling (SDM). Two distinct cpDNA haplotypes
were found for each species (northern and southern haplotype) within the
Chubu region of Japan but the difference in nuclear DNA between northern
and southern haplotype populations was very small both in Q. serrata and
Q. crispula. The results of SDM showed that during the LGM Q. serrata was
distributed mostly along the coastline but Q. crispula was distributed not
only along the coast but also in mountainous areas further inland. The
cpDNA genetic borders of these two oak species are complex and seem to
have been influenced by topography and their distribution during the LGM.
We propose and discuss genetic guidelines for these two oak species based
on the results of this study.