New locality of Hymenochaete cruenta in the Olbina nature reserve and revisiting of distribution of this fungus in Poland

Hymenochaete cruenta is a saprotrophic fungus, grown mainly on the bark of dead branches and trunks of Abies trees and thus the distribution of this fungus in Poland and other European countries is closely connected with natural range of silver fir. Despite its wide range, H. cruenta is considered as rare in the whole area of its occurrence. In this paper, we present a new locality of H. cruenta, discovered in May and September 2016 in the Olbina nature reserve (southern Wielkopolska Lowland, Kalisz Forest District). Ecological notes and macroand microscopic feature of basidiocarps of this fungus are presented. Additionally, the current distribution of H. cruenta in Poland comprising 78 localities is provided. The rank of H. cruenta among threatened species categories in different European countries is discussed. It seems that the species is rare and threatened in Poland, and it should be still classified as “vulnerable” on the red list of macrofungi. The significance of H. cruenta for diversity of mycobiota and the necessity of further research on the dynamic of occurrence of H. cruenta inside and outside of the natural range of A. alba is underlined.


Introduction
The widespread, but uncommon fungi of the genus Hymenochaete Lév.(Hymenochaetales, Basidiomycota) are represented worldwide by about 130 species.Most of them have been noted in tropical and subtropical regions, less frequently in the northern temperate areas.The species of this genus occur on dead wood, mostly of deciduous trees and shrubs, and less often on conifers.All species cause white fibrous or pocket rot [1][2][3].
The purpose of this paper is to present ecological notes and the current distribution of H. cruenta in Poland, supplemented with new locality of this species from the "Olbina" nature reserve, situated close to the northern border of natural occurrence of A. alba.Additionally macro-and microscopic feature of basidiocarps of this fungus are presented.

Material and methods
Specimens of H. cruenta were collected in the Olbina Reserve in May and September 2016.The description of the basidiocarp morphology and ecological characteristics of this species are based on original material, accompanied by information from literature.The microscopic structure were observed and measured using Olympus BX53 light microscope (LM), supplied with an Olympus DP26 digital camera, and the scanning electron microscope Zeiss EVO LS10 (SEM).Spore, basidia, and setae sizes in the descriptions are based on 20-30 measurements.Size ranges of the microscopic features are given as follows: (minimum value-)first decile-ninth decile(-maximum value).SEM micrographs were taken in the Center for Molecular Biology and Biotechnology, Environmental Testing Laboratory, University of Szczecin (Poland).The specimens were identified by examining macroscopic and microscopic features, using monographs by Breitenbach and Kräzlin [16] and Bernicchia and Gorjón [17].
Distribution of H. cruenta in Poland is presented on the cartogram map according to the ATPOL gird square system as used by Wojewoda [18].The cartogram map is based on our investigations and all available published and unpublished data.In order to illustrate the changes in the distribution of this species, we presented the localities in three different periods: before 1950, in years 1951-2002, and after 2002.The fungal nomenclature and its synonyms follows Index Fungorum database [19], and the names of vascular plants follows Mirek et al. [20].The nomenclature of plant communities are given according to Matuszkiewicz [21].The collected specimens of H. cruenta are deposited in the Herbarium of the Department of Botany and Nature Conservation, Szczecin University (SZUB), and in the Institute of Dendrology, Polish Academy of Sciences in Kórnik, (Poland).

Localities in Poland
Until now, H. cruenta has been recorded in Poland at 78 localities.The oldest records come from the Sudetes (the Foothills Izerskie, near Lubań) from 1933 [33].It is also the western-most stand in our country.In the years 1951-2002, this species was reported from 51 localities.A full list of localities and a distribution map are given by Wojewo da et al. [5].After 2002, 26 new localities were found (Fig. 3).
A new locality of H. cruenta was discovered in the "Olbina" nature reserve (southern Wielkopolska Lowland: Kalisz Forest District, forest section No. 405, ATPOL grid square Cd-97; Fig. 3).The reserve was established in 1958, in order to "preserve a fir tree locality at its northern natural limit" [66].According to Górski [67], the forest communities of this reserve belong to continental mixed forest Festuco ovinae-Pinetum (Juraszek 1928) Kobendza 1930, in variant with A. alba, and corresponding to Świętokrzyski-type fir forest.These phytocoenoses are composed by mature tree stands, predominated by Pinus sylvestris trees with a significant admixture of A. alba and Picea abies.species, recorded in the mountains more frequently than in uplands or lowlands (e.g., [5,23,32,36]).According to Parmasto [23], H. cruenta grows especially on the bark of various species of the genus Abies, and its occurrence on Picea is doubtful.It has also been found on an angiosperm tree in Argentina [34] and on Quercus leucotrichophora in India [32].Moreover, this species has been reported from some other angiosperm trees, like Juglans, Neopanax, Pyrus, and Rhododendron.According to Parmasto [23] and Dai and Niemelä [79] these findings rather belong to another species of Hymenochaete, i.e., H. sphaericola, characterized by similar basidiomata.Hymenochaete sphaericola differs from H. cruenta by longer setae and broader basidiospores, as well as by the hymenophore without a violet tint.These species have also different areas of distribution though they are partly overlapping in Asia (e.g., China, Japan, and Russian Far East) and Australia.Identification to the species level of some specimens of Hymenochaete is sometimes difficult because majority of specimens are sterile, or have deformed basidiospores and grows on wood, which are difficult to classify.Only on few specimens of H. cruenta found in the Olbina Reserve basidiospores were observed.It seems that this species can be more easily recognized in the field by its substrate preferences than by basidiospores characteristics.
The distribution of H. cruenta in Poland and other European countries is associated with the occurrence of A. alba.This is probably the main reason that H. cruenta is mostly reported from the southern part of our country, mainly from the mountains (Fig. 3), which are the most natural habitat for silver fir.The "Olbina" natural reserve, where the new locality of H. cruenta was discovered, is situated close to the northern border of natural occurrence of A. alba in Poland [80].It is interesting that in Poland this European mountain tree species found also excellent conditions for growth and development 400 km north of its native range in the lowlands of Pomerania (northern Poland) [81].However, despite extensive mycological surveys on this area, H. cruenta has not been found there until now.The reasons of absence of this species in Pomeranian fir forest remains an open question.
Another question is the rank of H. cruenta among threatened species categories.In some European countries, this fungus is regarded as an endangered and red-listed species.It has the status of "vulnerable" in Switzerland [15], "near threatened" -in the Czech Republic [9], and in Germany classified as threatened of varied threat categories in particular federal states [10][11][12][13][14].In Poland, H. cruenta has been recognized as an endangered species not only on a regional scale but also countrywide.It is included on regional red lists of macrofungi in the Polish Carpathians (category "rare", [82]) and the Świętokrzyskie Mts (category "rare" [83], category "near threatened" [7]).In the Polish red list of macrofungi it is placed into the category "vulnerable" [8].It seems, based on the available published and unpublished data, that the species is rare and threatened in our country, and it should be still classified as "vulnerable" on the red list of macrofungi in Poland.
Hymenochaete cruenta is certainly an important element of diversity of mycobiota in Polish forests.In the context of recovery of growth of A. alba since the beginning of the 1980s after the decrease of SO 2 emissions and recent climate change, the dynamic of occurrence of H. cruenta inside and outside of the natural range of silver fir requires further research.

Fig. 1
Fig. 1 Morphological features of Hymenochaete cruenta basidiocarps.a-c Plan view of basidiocarps growing on dead branches of Abies alba.d The edge of basidiocarps.e Setae on the surface of basidiocarp.Scale: a-c 1 cm; d 50 µm; e 10 µm.Photographs: T. Leski.

Fig. 3
Fig. 3 Distribution of Hymenochaete cruenta in Poland.Blue point -locality before 1950; black points -localities reported between the years 1951-2002; red points -localities found after 2002; red starnew locality in the Olbina Reserve; green line -northern border of natural occurrence of Abies alba in Poland [80].