# Current Problems of Forest Protection (25-27 October 2022, Katowice Poland)
## 1 Introduction
Some sources state that this mistletoe has not been recorded in Poland, while others state that it was seen over 130 years ago near Czestochowa, Busko, Bukowina. Oak mistletoe was mentioned in a 19 th Century publication by Wladyslaw Spaust, who confirmed that the plant was rare in present-day Poland. In recent years, this species has not been studied in Poland. Currently, a high population density of _L. europaeus_ is found in neighbouring countries of Poland: Slovakia and the Czech Republic. Its occurrence has also been confirmed in Germany and Ukraine. The occurring climatic changes increase the probability of _L. europaeus_ spreading. The type of host plant, age, origin and biosocial status are probably also important. The presence of this mistletoe may be influenced by habitat fragmentation, herbivory and topography. The spread of this species is favoured by ornithochory. The fruits of mistletoe are fed to various bird species, which transport them over long distances. Considering the threat that _L. europaeus_ poses to oak stands in Poland, it is important to create a model of the potential occurrence of this mistletoe in case of subsequent climate changes. An inventory of stands on the border between Poland and Slovakia and betweenPoland and the Czech Republic is important as part of the risk assessment of this semiparasite. Continuous monitoring should be conducted to determine how to most effectively reduce the incidence of _L. europaeus_. The risk should not be ignored, especially in a situation when the area of mistletoe in coniferous stands is expanding and the share of hardwood stands in the forest area of our country is increasing. oak mistletoe; climate changes; semi-parasitic plant; deciduous stands  
**Taxonomic Status of Mistletoe Found in _Pinus sylvestris_ Stands in Poland Based on Molecular Studies  
Katarzyna Sikora  
Forest Research Institute, Sekocin Stary, Poland  
* Correspondence: k.sikora@ibles.waw.pl  
Forestry is one of the sectors particularly affected by the threats posed by changing climatic conditions, as evidenced by a deterioration in the health of tree stands due to the synergistic effect of numerous abiotic and biotic factors. Of particular importance in the context of the observed changes in the health status of _Pinus sylvestris_ stands is the mass occurrence of mistletoe (_Viscum album_ L.), which in the past was of little economic importance. Based on the diversity of host plants and the biochemical and genetic characteristics of mistletoe, three subspecies within _Viscum_ species have been identified to date, only one of which, _V. album_ ssp. _austriacum_, can parasitize on _Pinus_. The process of new species formation or speciation may occur as a result of parasite adaptation to the host race. The studies conducted so far have shown the taxonomic distinctiveness of mistletoe at the subspecies level, adaptation to the host race and high genetic variability between populations from different European countries. The regional differences in the intensity of mistletoe occurrence on Scots pines observed in Poland suggest the need to understand the population structure of _V. album_ ssp. _austriacum_ and confirm its taxonomic status. In a study conducted at the Forest Research Institute, five molecular markers were analysed, including nuclear (ITS1) and chloroplast loci (trnL intron, trnL-trF IGS, trnH-trnK, ccmp4). The barcode ITS was used in the study because of its broad application in taxonomic analyses. The chloroplast loci, on the other hand, provided the basis for analysing variation among mistletoe populations. For the study, leaves of mistletoe shrubs were collected at sites of the Regional Directorates of State Forests in Wrochaw, Gdansk and Lodz, as well as in Kampinoski National Park. Sequences of 372 bp (ITS1), 541 bp (trnL intron), 303 bp (trnL-trnF IGS), 245 bp (trnH-trnK) and 321 bp (ccmp4) were obtained. The sequences of the ITS1 region, trnL-trnF IGS and trnH-tmK were identical in all specimens examined.