Distribution and conservation status of Grifola frondosa (Polyporales, Basidiomycota) in Ukraine

Grifola frondosa is a nationally red-listed species in Ukraine. In the third edition of the Red Data Book of Ukraine it is assigned to a category Vulnerable (VU). Previously, the fungus was known from 17 localities in nine regions of Ukraine: Cherkasy, Dnipropetrovsk, Donetsk, Kharkiv, Kherson, Kyiv, Sumy, Ternopil, Transcarpatian, and the Autonomous Republic of Crimea. Over the recent decade, G. frondosa has been also recorded in the following eight regions: Chernihiv, Chernivtsi, Ivano-Frankivsk, Khmelnytskyi, Lviv, Rivne, Volyn, Zhytomyr, and Kyiv city. Thus, a number of known up to now localities of G. frondosa increased from 17 to more than 40. However, the expanded number of records is due to additional data recently provided from field observations by amateur mycologists, rather than a result of the increasing population trend of the fungus. Based on the current distribution pattern of G. frondosa in Ukraine, its contemporary conservation status on the national level was evaluated using the IUCN categories and criteria. The species was assessed as Endangered, EN under criteria С2а(і). This is the higher threat category as compared to Vulnerable (VU) in the current edition of the Red Data Book of Ukraine. For conservation purposes, it is necessary to protect the already known sites, to search for new localities of the fungus, and to explore possibilities of its re-introduction into natural habitats. Global distribution and the Red List status of G. frondosa in Europe are briefly discussed. A list of currently known localities of the species in Ukraine and a distribution map of the reported sites are provided.


Introduction
Grifola frondosa (Dicks.) Gray (Polyporales, Basidiomycota) is a rarely recorded fungus in Ukraine and worldwide. It is a wood-inhabiting fungus forming its large annual fruit bodies on the ground near or at the base of old living or dead tree trunks or stumps. As a facultative parasitic or saprotrophic fungus, G. frondosa is capable of degrading lignin components of woody substrates, thus causing white rot or butt rot of tree stems or roots.
In Ukraine, the fungus has been so far recorded mostly on Quercus robur L., occasionally on Fagus sylvatica L. and, according to literature data (Gutsevich, 1940;Sarkina et al., 2003), once on Carpinus betulus L. In the current edition of the Red Data Book of Ukraine this species is listed as Vulnerable (Prydiuk, 2009). Prior to 2009, it was reported from 17 localities in nine regions of Ukraine: Cherkasy, Dnipropetrovsk, Donetsk, Kharkiv, Kherson, Kyiv, Sumy, Ternopil, Transcarpatian Regions, and the Autonomous Republic of Crimea. Recently, the fungus was found to occur in new localities in the western, central and northern parts of Ukraine.
This article presents an update on the current distribution of G. frondosa in Ukraine and results of the re-evaluation of its conservation status on the national level.

Taxonomic notes
Grifola frondosa (Dicks.) Gray, Nat. Arr. Brit. Pl. (London) 1: 643. 1821 The fungus was described as Boletus frondosus Dicks. in 1785 from Britain. In 1821, E. Fries changed the name to Polyporus frondosus (Dicks.) Fr. In the same year, S.F. Gray transferred the species to a new genus, Grifola Gray. Having made that combination, he established for this fungus its currently accepted name, Grifola frondosa. At present the species has over 20 homotypic and heterotypic synonyms. Although this fungus has a nearly worldwide distribution, molecular phylogenetic analysis revealed a strong support for species partition separating eastern North American and Asian isolates, as well as a distinct European lineage of G. frondosa (Shen et al., 2002). Thus, future taxonomic revision may split the species; in that case, the name G. frondosa is to be applied to the European lineage, with other two different names for the North American and Asian populations.
The genus Grifola is placed in the family Meripilaceae (Polyporales) (www.indexfungorum.org/), or in Fomitopsidaceae of the same order (www.mycobank. org/). Recently, based on molecular data (Justo et al., 2017), Grifolaceae Jülich, which appears as sister to Polyporaceae, was restored as an accepted family name to accommodate the genus Grifola.

Global distribution and evaluation
Grifola frondosa is traditionally regarded as a circumpolar species in the Northern Hemisphere where it has its major distribution. In this case, the fungus is considered as native to temperate hardwood regions of Europe, North America, and Asia (Bondartseva, 1998;Ryvarden, Melo, 2014). In North America it can be found in Eastern Canada, northeastern and mid-Atlantic states of the USA, and more rarely in northwestern or southeastern states (Chen et al., 2000). In Asia, it is known to occur in southwestern and northeastern China and northeastern Japan (Yamanaka, 1997;Chen et al., 2000). In the Southern Hemisphere, few records have been reported in Australasia (Australia, New Zealand) (Bondartseva, 1998). Although the fungus has a rather wide geographic distribution, it is a rarely occurring species throughout most of its range.
Since the eastern North American and Asian material may not be conspecific with the European records (see above), the recently proposed assessment of G. frondosa on the global level under the Global Fungal Red-List Initiative (http://iucn.ekoo.se/iucn/species_ view/362177) is based on the European populations.

Red-list status in Europe
In Europe, the reported conservation status of G. frondosa varies across the continent. In many countries the species is nationally red-listed under the threatened categories: Estonia -CR (Lõhmus et al., 2018), Bulgaria, Lithuania, North Macedonia -EN (Gyosheva et al., 2006;Iršėnaitė et al., 2007;Fig. 1. Grifola frondosa. A: registration of parameters of two fruit bodies found at the base of an oak trunk; B, C: fruit bodies of the fungus A B C Karadelev, Rusevska, 2013), Austria, Germany, Latvia, Norway, Poland, Ukraine -VU (Brandrud et al., 2006;Prydiuk, 2009;Matzke-Hajek et al., 2016;Dämon, Krisai-Greilhuber, 2017; http://www.eccf.eu/redlistsen.ehtml). In the Czech Republic, Romania and Sweden this species is listed as NT (Tănase, Adriana, 2005;Antonín et al., 2006;Westling, 2015); in Belarus and Russia it belongs to category 3 (Rare species) (Krasnaya..., 2005,2008). The major threat for G. frondosa is habitat destruction. Old-growth oak forests, particularly large size trees, are highly vulnerable. Many suitable habitats have been destroyed by deforestation, uncontrolled logging for timber in mature forests, replacement of slow-growing oak forests by plantations of fast-growing trees. In addition, in those areas where picking wild mushrooms is traditional, over-harvesting of large edible fruit bodies is also a threat.

In vitro research in Ukraine and worldwide
A large number of in vitro studies in Ukraine and other countries has demonstrated that G. frondosa is rich in a variety of polysaccharides which possess antitumor and immunostimulating activity as well as have antibiotic, antiviral and antioxidant properties (Kodama et al., 2002;Zhou, Wasser, 2004;Bartuv-Tal et al., 2009;Masuda et al., 2010;Linovytska et al., 2011;. Pharmacologically active substances derived from G. frondosa are widely used in pharmacognosy, in food production and as a source of biologically active compounds for dietary supplements. Apart from the advantages of nutritional value and medicinal effect, this fungus is famous for its delicious taste and appealing mushroom aroma. It is widely used in commercial growing and mushroom industry, particularly in Asia and North America. The world leader in production and consumption of G. frondosa is Japan where its annual production is estimated to be about 41,000 tonnes (Mayuzumi, Mizuno, 1997;Yamanaka, 2011).
In Ukraine, 29 strains of G. frondosa of different origin are currently maintained in the IBK mushroom culture collection of the M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, and one strain -in the FCKU culture collection of fungi of the Educational and Scientific Centre "Institute of Biology and Medicine", Taras Shevchenko National University of Kyiv (Bisko et al., 2016.

Distribution in Ukraine
Grifola frondosa forms large (up to 100 cm in diam.) multipileate grayish-brown basidiocarps (Fig. 1). They are easily recognizable and usually much looked after. Apart from literature data, herbarium materials, and our personal field observation results (Fig. 1, A), we have also analysed reports published by amateur mycologists in two social network groups (https://www.facebook. com/groups/Hryby.Ukrayiny/?ref=bookmarks,https:// www.facebook.com/groups/119266158163241/), if and when these newly reported records were confirmed by photographs. Altogether, a number of known up to now localities G. frondosa was expanded from 17 indicated in the current edition of the Red Data Book of Ukraine to over 40. For the first time, the fungus was reported in the following eight regions: Chernivtsi, Chernihiv, Ivano-Frankivsk, Lviv, Khmelnytsky, Rivne, Volyn, Zhytomyr, and Kyiv city. However, the expanded number of the recently reported records is due to additional field observations in appropriate habitats undertaken by amateur mycologists, rather than a result of increasing population trend of the fungus.
Below we provide a list of all currently known localities of G. frondosa in Ukraine. Since the species is nationally red-listed, according to the Ukrainian legislation on the Red Data Book of Ukraine (Zakon…, 2017), its published distribution data do not include information on the exact localities. All reported sites are shown on the map (Fig. 2).

Assessment and conservation status in Ukraine
After having updated its current distribution in Ukraine, we evaluated G. frondosa on the national level using the IUCN Red List Categories and Criteria (IUCN Red List Categories and Criteria, 2012).
The species is assessed under criterion C (Small population size and decline) based on the number of mature individuals. The calculation was made according to the concept of functional individual (Dahlberg, Mueller, 2011), now generally accepted in fungal redlisting. Thus, the currently known number of localities of the fungus is about 40. Since G. frondosa is associated exclusively with old-growth oak trees (or rarely beech trees), maximum actual number of the localities can be increased tenfold, apparently not exceeding 400. For G. frondosa as a lignicolous fungus, sporocarps inhabiting individual tree may represent one functional individual. Since each functional individual should be counted at minimum as two mature individuals, in our case total number of mature individuals is equal to 800. As G. frondosa may not fruit every year under the same tree, if to suggest that one or two fruit bodies under individual tree correspond to four mycelia, the total number of mature individuals would not exceed 1600. In addition, large old-growth oak and beech trees are under long-term ongoing decline. Hence, number of mature individuals is < 2.500; there is an observed, estimated, projected or inferred continuing decline (C2); number of mature individuals in each subpopulation is < 250. Therefore, the species is assessed as Endangered (EN) under criteria С2а(і).

Conclusion
Based on our update on distribution of G. frondosa in the country, the species was assessed nationally as Endangered (EN) which is the higher threat category as compared to Vulnerable (VU) in the current edition of the Red Data Book of Ukraine. It is therefore necessary for conservation purposes to protect the already known sites, to search for new localities of the fungus in appropriate habitats, and to explore potential reintroduction of the strains of local origin into natural habitats. Thus, in the next edition of the Red Data Book of Ukraine, the conservation status of G. frondosa should be indicated as EN С2а(і).