Rhizocarpon lavatum and R. reductum (Rhizocarpaceae, Ascomycota), two misunderstood taxa found in the Gorce Mts (Polish Carpathians)

Based on collections of P. Czarnota deposited in the GPN herbarium, 8 species of Rhizocarpon are reported from the Gorce Mountains. Two of them, R. lavatum and R. reductum are reported from the Gorce Mts for the first time, instead of erroneously determined R. obscuratum . This species was previously misinterpreted due to taxonomic and nomenclatoric uncertainties.


INDRODUCTION
New concepts of taxa and changes in nomenclature have triggered my studies on genus Rhizocarpon.The present paper is the part of the taxonomic revision of representatives of the genus Rhizocarpon in Poland.The paper has been aimed to clarify the actual status of the species belonging to this genus, based on the latest innovations (Fryday 2000;Ihlen 2004).In particular, it is focuses on solving the problem of a group of species interpreted earlier as Rhizocarpon obscuratum (Ach.)Massal.
According to Fryday (2000) the specimens upon which Lecidea petraea var.obscurata Ach., the basionym of Rhizocarpon obscuratum (Ach.)Massal., is based are shown to be mostly referable to the species currently known as R. lavatum (Fr.)Hazsl.Rhizocarpon reductum Th.Fr. is resurrected to accommodate specimens with small ascospores previously referred there.The name Rhizocarpon obscuratum, which previously had an unclear relation to R. lavatum is formally excluded, because it proved to be synonym of Fuscidea lygaea (Ach.)V. Virth & Vězda (Ihlen 2004).Consequently, the name R. reductum (Fryday 2000) has been used for the specimens of this complex producing stictic acid, and R. lavatum for the specimens lacking lichen substances.

MATERIAL AND METHODS
The study is based on the taxonomic revision of Paweł Czarnota's collection made in the Gorce Mts in the years 1994-2005 and stored in the herbarium of the Gorce National Park in Poręba Wielka (GPN).The nomenclature of species is based on taxonomic studies by Ihlen (2004).The species have been named according to Santesson et al. (2004).The pigments Arnoldiana-brown, Atra-brown, Atra-red (sensu Meyer, Printzen 2000) and Macrocarpa-green (sensu Fryday 2002) were recognized.Chemical analyses were performed using a thin-layer chromatography (Orange et al. 2001) with the use of solvents A and C. Localities are given in the system ATPOL adapted for lichens (Cieśliński, Fałtynowicz 1993).
Microscopic measurements of anatomical features (ascospores length, breadth in μm and number of cells per ascospore) were made as characteristic of the diagnostic manual for Rh.lavatum and Rh.reductum.All ascospore measurements were made on mature ascospores and were also granted a definitively on the basis of the 24 spores measured for each species.All published specimens of the six species were previously correctly identified and their localities are in the following papers: Glanc (1960), Czarnota (2000), Czarnota et al. (2005) and Czarnota & Wojnarowicz (2008).
Revised specimens from morphological, anatomical and chemical features matches the description of R. reductum by Fryday (2000) and Ihlen (2004).
Taxonomic and nomenclatural remarks.Rhizocarpon reductum sometimes resembles some forms of R. lavatum with small apothecia, but the presence of stictic acid usually makes it distinct.A comparison of the main features distinguishing Rhizocarpon lavatum and R. reductum is presented in the Table 1.
The distinction of the two species -Rhizocarpon lavatum and R. reductum is related to the changes in the taxonomy of Rhizocarpon obscuratum auct.non (Ach.)Massal.complex, with hyaline and muriform ascospores (Fryday 2000;Ihlen 2004).
Rhizocarpon lavatum is similar to R. reductum, a name resurrected for the species previously commonly referred to R. obscuratum (Ach.) A. Massal.(Fryday 2000).Basionym for R. obscuratum, Lecidea petraea var.obscurata Ach. has been show to be based on a mixed type (Fryday 2000) and to be regarded as a synonym of Fuscidea lygaea (Ach.)V. Virth & Vězda (Ihlen, Fryday 2002;Ihlen 2004).An examination of the specimens upon which Rhizocarpon obscuratum is based revealed that they are mostly referable to the species currently knows as R. lavatum.Rhizocarpon reductum is resurrected for specimens formely placed under 'R.obscuratum' with small ascospores and the thallus containing stictic acid, whereas specimens with larger ascospores and a thallus lacking lichen substances are more referred to R. lavatum (Fryday 2000).

Table 1
Comparison of the main features separating Rhizocarpon lavatum and R. reductum