“Northern tetraploids” clarified: A study of dactylorchids (Dactylorhiza, Orchidaceae) from North European Russia

Despite numerous phylogenetic studies in recent decades, dactylorchids still remain taxonomically a poorly resolved group, which is especially a case for the vast territory of Russia. The massive morphological sampling effort was made towards the better understanding of dactylorchids in northern (from 50° latitude) European Russia. Previous study revealed that the majority of plants of Dactylorhiza maculata group from North European Russia belong to plants which combine D. maculata s.str. and Dactylorhiza fuchsii genomes. We applied results of previous molecular studies in the region as “anchors” to establish species identity using advanced multivariate classification techniques, Random forest and recursive partitioning. With Random forest, most samples were successfully discriminated so it became possible to attribute them to the known species. We also found that the majority of our Arctic samples with likely combined genomes comprise the separate group, to which we propose the name Dactylorhiza psychrophila. With recursive partitioning, we were able to create the dichotomous key which could be used for discrimination of Dactylorhiza species from the area of our study.