A Taxonomic Study of the Genus Myelochroa in South Korea

Myelochroa (Asahina) Elix & Hale is a common foliose lichen genus found on the Korean Peninsula. Since it was first recorded nearly two decades ago, no detailed taxonomic or revisionary study of the genus has been conducted. Thus, the current study was conducted to carry out a detailed taxonomic and revisionary study of Myelochroa in South Korea. This study was based on specimens deposited in the Korean Lichen Research Institute (KoLRI). Detailed taxonomic studies and a literature review confirmed the presence of twelve species of Myelochroa from S. Korea, including one new record, Myelochroa xantholepis (Mont. & Bosch) Elix & Hale. Descriptions of each species with their morphological, anatomical and chemical characters together with a key to all known Myelochroa species are presented.


Introduction
The genus Myelochroa, which was segregated from the genus Parmelina Hale by Elix and Hale [1], with the 19 species that are distributed in temperate zones and the higher altitudes in tropical regions [2]. The species belonging to Myelochroa have adnate to closely adnate thalli with rather narrow lobes, cilia on the axils and a rhzinate black lower surface without an erhizinate margin. Additionally, the genus is characterized chemically by the production of zeorin and related triterphenoids in the yellow medulla [2].
Myelochroa currently consists of c. 30 species, with East Asia and North America being the main centers of distribution [3]. In South Korea, the first detailed taxonomic study of this genus was conducted by Park in 1990 [4], who described 11 species. However, some of her findings have synonymized and the actual number of species has been reduced to eight. The lichen checklist of South Korea published by Hur et al. [5], reported eleven species, Myelochroa aurulenta (Tuck.) Elix [1], Hale [6], Elix [7,8], Kurokawa and Arakawa [2], and Divakar and Upreti [9].

Materials and Methods
This study was based on specimens deposited in the Korean Lichen Research Institute (KoLRI). The lichen samples were identified using stereo and light microscopes, while a dissecting microscope (Nikon SMZ645; Nikon, Tokyo, Japan) was used to identify morphological characteristics of the thallus, reproductive structures, color, size and shapes. Additionally, a compound microscope (Zeiss Scope. A1; Carl Zeiss, Oberkochen, Deutshland, Germany) was used to investigate the anatomy of thalli and fruiting bodies. Spot test reactions were carried out on the thallus under a compound microscope, and thin layer chromatography (TLC) was performed in solvent systems A (toluene : dioxin : acetic acid = 180 : 45 : 5) and C (toluene : acetic acid = 85 : 15) [10]. All examined localities of specimens were mapped using the open source GIS software Quantum GIS 1.7.0 (QGIS). Voucher specimens have been deposited in the herbarium of the Lichen and Allied Bio-resource Center at the KoLRI, Sunchon *Corresponding author <E-mail : jshur1@sunchon.ac.kr> This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. National University, South Korea.
Remarks: This species is very close to M. leucotyliza, but differs in having galbinic acid and salazinic acid in the medulla. According to Kashiwadani et al. [19], this is a very rare species that has also been reported from a single location on Jeju Island on the bark of Carpinus species. Specimens examined: 041255 (Mt. Backwoon) (Fig.  3C).

Myelochroa indica
Species excluded from this study. The following taxa have been reported from South Korea based on earlier publications by different authors. Some of these have not been found to date or have been synonymized as other taxa. However, the details are provided with this paper for the species of Myelochroa coreana Y. S. Park 1990