Taxonomic status and genetic differentiation of Hyrcanian Castanea based on noncoding chloroplast DNA sequences data

Abstract

The taxonomy and phylogenetic relationships among Castanea species were investigated using sequence data from the chloroplast trnL-F and trnH-psbA intergenic spacer regions. Samples included Castanea specimens of uncertain taxonomic affinity that were collected in the Hyrcanian forest of northern Iran. The trnL-F data were more informative than trnH-psbA, having seven parsimony-informative sites. A low level of haplotype diversity was detected within Hyrcanian samples and the whole species of the genus Castanea. In the trnL-F dataset, Castanea sativa and Castanea mollissima have unique character states that differentiate them from other species of Castanea. The genus Castanea was recovered as a monophyletic with high to moderate support when inferred from combined trnH-psbA and trnL-F spacer data. Two main lineages received minimal support in the trnL-F analysis, whereas trnH-psbA could not distinguish different species of Castanea from each other. Finally, low levels of haplotype diversity was found within small remnant stands of Castanea in the Hyrcanian forest, indicating that genetic erosion may increase the extinction risk for these valuable trees.