{{Short description|Genus of lichens}} {{Automatic taxobox | image = Myelochroa aurulenta - Flickr - pellaea.jpg | image_caption = The powdery axil-bristle lichen, ''Myelochroa aurulenta'' | taxon = Myelochroa | authority = (Asahina) Elix & Hale (1987) | type_species = ''Myelochroa aurulenta'' | type_species_authority = (Tuck.) Elix & Hale (1987) | synonyms = *''Parmelia'' subsect. ''Myelochroa'' <small>Asahina (1952)</small> *''Parmelina'' sect. ''Myelochroa'' <small>(Asahina) Hale (1976)</small> }}
'''''Myelochroa''''' is a genus of foliose lichens in the family Parmeliaceae. They are commonly known as '''axil-bristle lichens'''. It was created in 1987 to contain species formerly placed in genus ''Parmelina'' that had a yellow-orange medulla due to the presence of secalonic acids. Characteristics of the genus include tightly attached thalli with narrow lobes, cilia on the axils, and a rhizinate black lower surface. Chemical characteristics are the production of zeorin and related triterpenoids in the medulla. ''Myelochroa'' contains about 30 species, most of which grow on bark. The genus has centres of distribution in Asia and North America.
==Taxonomy== ''Myelochroa'' was originally circumscribed by Yasuhiko Asahina as a subsection of section ''Hypotrachyna'' in genus ''Parmelia''.<ref name="Asahina 1952"/> This taxon was later raised to sectional status by Hale in 1976.<ref name="Hale 1976"/> It was promoted to generic status in 1987 by John Elix and Mason Hale. Nineteen species were originally placed in ''Myelochroa'', including the type species, ''M. aurulenta''.<ref name="Elix & Hale 1987"/>
''Myelochroa'' species are commonly known as "axil-bristle lichens".<ref name="Brodo et al. 2001"/>
==Description== ''Myelochroa'' lichens are small- to medium-sized foliose lichens. Their thalli comprises somewhat linear to irregularly shaped lobes. The lobes have simple (unbranched), slender, black cilia on the margin, sparsely or densely distributed. These are sometimes confined to lobe axils, other times they are more evenly distributed. The upper surface of the thallus is grey, or blue-grey, sometimes with a yellow tinge; this yellowish colour, if present, is more likely to be under the apothecia or close to the algal layer. The medulla is yellow-orange. The lower thallus surface is black and covered with mostly unbranched rhizines. The apothecia are lecanorine, with a reddish-brown cup that lacks perforations. The ascospores, which number eight per ascus, are simple, ellipsoid, colourless, and measure 5–8 by 8–14 μm.<ref name="Elix & Hale 1987"/><ref name="Brodo et al. 2001"/>
The upper cortex contains the lichen acids atranorin, chloroatranorin, and secalonic acid. The medulla contains hopane triterpene compounds such as zeorin and leucotylic acid as well as secalonic acid A. The presence of these triterpenes distinguishes this genus from ''Parmelina'', and its segregate genera, including ''Parmelinella'', and ''Parmelinopsis''.<ref name="Elix & Hale 1987"/> secalonic acid A is a yellow pigment that reacts C+ yellow and K+ yellow with lichen spot tests.<ref name="Brodo et al. 2001"/>
==Habitat and distribution== Most ''Myelochroa'' lichens are corticolous. They are largely found in temperate locations, with centre of distribution in eastern Asia and eastern North America. Twelve species of ''Myelochroa'' are found in South Korea.<ref name="Jayalal et al. 2018"/> The type species, ''Myelochroa aurulenta'', is found throughout the world in temperate forests.<ref name="Elix & Hale 1987"/>
==Species== thumb|right|The rock axil-bristle lichen, ''Myelochroa obsessa'' thumb|right|The smooth axil-bristle lichen, ''Myelochroa galbina'', with prominent apothecia *''Myelochroa amagiensis'' {{small|(Asahina) Elix & Hale (1987)}} *''Myelochroa aurulenta'' {{small|(Tuck.) Elix & Hale (1987)}} – widespread *''Myelochroa coreana'' {{small|Y.S.Park (1990)}}<ref name="Park 1990"/> – South Korea; Malaysia *''Myelochroa crassata'' {{small|(Hale) Elix & Hale (1987)}} *''Myelochroa crenulata'' {{small|(J.C.Wei) Hale ex DePriest & B.W.Hale (1998)}}<ref name="DePriest & Hale 1998"/> *''Myelochroa degelii'' {{small|(Hale) Elix & Hale (1987)}} *''Myelochroa denegans'' {{small|(Nyl.) Elix & Hale (1987)}} – Asia; Australia *''Myelochroa entotheiochroa'' {{small|(Hue) Elix & Hale (1987)}} – Asia *''Myelochroa galbina'' {{small|(Ach.) Elix & Hale (1987)}} – Asia; North America *''Myelochroa hayachinensis'' {{small|(Kurok.) Elix & Hale (1987)}} – Jeju Island *''Myelochroa ibukiensis'' {{small|K.H.Moon, Kashiw. & Keis. Kobay. (2013)}}<ref name="Moon et al. 2013"/> – Japan *''Myelochroa immiscens'' {{small|(Nyl.) Elix & Hale (1987)}} *''Myelochroa indica'' {{small|(Hale) Elix & Hale (1987)}} – India *''Myelochroa irrugans'' {{small|(Nyl.) Elix & Hale (1987)}} – Asia *''Myelochroa leucotyliza'' {{small|(Nyl.) Elix & Hale (1987)}} – Asia *''Myelochroa macrogalbinica'' {{small|Divakar, Upreti & Elix (2001)}}<ref name="Divakar et al. 2001"/> – India *''Myelochroa metarevoluta'' {{small|(Asahina) Elix & Hale (1987)}} – Asia; USA *''Myelochroa nothofagi'' {{small|Elix (1996)}}<ref name="Elix 1996"/> *''Myelochroa obsessa'' (Ach.) {{small|Elix & Hale (1987)}} *''Myelochroa perisidians'' {{small|(Nyl.) Elix & Hale (1987)}} – Asia *''Myelochroa radiculata'' {{small|(Kurok.) Divakar & A.Crespo (2010)}}<ref name="Crespo et al. 2010"/> *''Myelochroa rhytidodes'' {{small|(Hale) Elix & Hale (1987)}} *''Myelochroa salazinica'' {{small|Sheng L.Wang, J.B.Chen & Elix (2001)}}<ref name="Wang et al. 2001"/> – China *''Myelochroa sayanensis'' {{small|Otnyukova, Stepanov & Elix (2009)}}<ref name="Otnyukova et al. 2009"/> – Siberia *''Myelochroa siamea'' {{small|Kurok. (1998)}}<ref name="Kurokawa 1998"/> – Thailand *''Myelochroa sibirica'' {{small|Otnyukova, Stepanov & Elix (2009)}}<ref name="Otnyukova et al. 2009"/> – Siberia *''Myelochroa sikkimensis'' {{small|Divakar, Upreti, G.P.Sinha & Elix (2001)}}<ref name="Divakar et al. 2001"/> – India *''Myelochroa sinica'' {{small|Sheng L.Wang, J.B.Chen & Elix (2001)}}<ref name="Wang et al. 2001"/> – China *''Myelochroa subaurulenta'' {{small|(Nyl.) Elix & Hale (1987)}} *''Myelochroa supraflava'' {{small|Canêz & Marcelli (2008)}}<ref name="Marcelli & Canêz 2008"/> – Brazil *''Myelochroa upretii'' {{small|Divakar & Elix (2001)}}<ref name="Divakar et al. 2001"/> – India *''Myelochroa xantholepis'' {{small|(Mont. & Bosch) Elix & Hale (1987)}} – Asia
The taxon once known as ''Myelochroa lindmanii'' {{small|(Lynge) Elix & Hale (1987)}} has been analysed molecularly and shown to belong to the genus ''Parmelinella''.<ref name="Rodrigues et al. 2021"/>
==References== {{Reflist|colwidth=30em|refs=
<ref name="Asahina 1952">{{cite book |last1=Asahina |first1=Yasuhiko |title=Lichens of Japan, II: Genus ''Parmelia'' |year=1952 |publisher=Research Institute for Natural Resources |location=Tokyo |page=74}}</ref>
<ref name="Brodo et al. 2001">{{cite book |first1=Irwin M. |last1=Brodo |first2=Sylvia Duran |last2=Sharnoff |first3=Stephen |last3=Sharnoff |title=Lichens of North America |year=2001 |publisher=Yale University Press |page=447 |isbn=978-0300082494}}</ref>
<ref name="Crespo et al. 2010">{{cite journal |display-authors=6 |last1=Crespo |first1=Ana |last2=Kauff |first2=Frank |last3=Divakar|first3=Pradeep K. |last4=del Prado |first4=Ruth |last5=Pérez-Ortega |first5=Sergio |last6=de Paz |first6=Guillermo Amo |last7=Ferencova |first7=Zuzana |last8=Blanco |first8=Oscar |last9=Roca-Valiente |first9=Beatriz |last10=Núñez-Zapata |first10=Jano |last11=Cubas |first11=Paloma |last12=Argüello |first12=Arturo |last13=Elix |first13=John A. |last14=Esslinger |first14=Theodore L.|last15=Hawksworth |first15=David L. |last16=Millanes |first16=Ana |last17=Molina |first17=M. Carmen |last18=Wedin |first18=Mats |last19=Ahti |first19=Teuvo |last20=Aptroot |first20=Andre |last21=Barreno |first21=Eva |last22=Bungartz |first22=Frank |last23=Calvelo |first23=Susana |last24=Candan |first24=Mehmet |last25=Cole |first25=Mariette |last26=Ertz |first26=Damien |last27=Goffinet |first27=Bernard |last28=Lindblom |first28=Louise |last29=Lücking |first29=Robert |last30=Lutzoni |first30=Francois |last31=Mattsson |first31=Jan-Eric |last32=Messuti |first32=María Inés |last33=Miadlikowska |first33=Jolanta |last34=Piercey-Normore |first34=Michele |last35=Rico |first35=Víctor J. |last36=Sipman |first36=Harrie J.M. |last37=Schmitt |first37=Imke |last38=Spribille |first38=Toby |last39=Thell |first39=Arne |last40=Thor |first40=Göran |last41=Upreti |first41=Dalip K. |last42=Lumbsch |first42=H. Thorsten |title=Phylogenetic generic classification of parmelioid lichens (Parmeliaceae, Ascomycota) based on molecular, morphological and chemical evidence |journal=Taxon |volume=59 |issue=6 |year=2010 |pages=1735–1753 |doi=10.1002/tax.596008 |doi-access=free}}</ref>
<ref name="DePriest & Hale 1998">{{cite journal |last1=DePriest |first1=Paula T. |last2=Hale |first2=Beatrice Wilde |year=1998 |title=New combinations in parmelioid genera (Ascomycotina: Parmeliaceae) |journal=Mycotaxon |volume=67 |pages=201–206 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0067/0201.htm}}</ref>
<ref name="Divakar et al. 2001">{{cite journal |last1=Divakar |first1=P.K. |last2=Upreti |first2=D.K. |last3=Elix |first3=John A. |year=2001 |title=New species and new records in the lichen family Parmeliaceae (Ascomycotina) from India |journal=Mycotaxon |volume=80 |pages=355–362 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0080/0355.htm}}</ref>
<ref name="Elix & Hale 1987">{{cite journal |last1=Elix |first1=John A. |last2=Hale |first2=Mason E. |year=1987 |title=''Canomaculina'', ''Myelochroa'', ''Parmelinella'', ''Parmelinopsis'' and ''Parmotremopsis'', five new genera in the Parmeliaceae (lichenized Ascomycotina) |journal=Mycotaxon |volume=29 |pages=233–244 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0029/0233.htm}}</ref>
<ref name="Elix 1996">{{cite journal |last1=Elix |first1=John A. |year=1996 |title=New species in the lichen family Parmeliaceae (Ascomycotina) from Australasia and Oceania |journal=Mycotaxon |volume=59 |pages=407–417 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0059/0407.htm}}</ref>
<ref name="Hale 1976">{{cite journal |last1=Hale, Jr. |first1=Mason E. |title=A Monograph of the Lichen Genus ''Pseudoparmelia'' Lynge (Parmeliaceae) |journal=Smithsonian Contributions to Botany |volume=33 |page=15 |year=1976 |url=https://www.biodiversitylibrary.org/page/52065142}}</ref>
<ref name="Jayalal et al. 2018">{{cite journal |last1=Jayalal |first1=Udeni |last2=Joshi |first2=Santosh |last3=Oh |first3=Soon-Ok |last4=Koh |first4=Young Jin |last5=Hur |first5=Jae-Seoun |title=A taxonomic study of the genus ''Myelochroa'' in South Korea |journal=Mycobiology |volume=40 |issue=4 |year=2018 |pages=217–224 |doi=10.5941/MYCO.2012.40.4.217|pmid=23323045 |pmc=3538967 |doi-access=free }} {{OA}}</ref>
<ref name="Kurokawa 1998">{{cite journal |last1=Kurokawa |first1=S. |year=1998 |title=A new record and a new species in ''Myelochroa'' (Parmeliaceae) |journal=Journal of Japanese Botany |volume=73 |issue=1 |pages=12–14 |url=http://www.jjbotany.com/pdf/JJB_073_12_14.pdf}}</ref>
<ref name="Marcelli & Canêz 2008">{{cite journal |last1=Marcelli |first1=Marcelo P. |last2=Canêz |first2=Luciana S. |year=2008 |title=Novelties on Southern Brazilian Parmeliaceae |journal=Mycotaxon |volume=105 |pages=225–234 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0105/0225.htm}}</ref>
<ref name="Moon et al. 2013">{{cite journal |last1=Moon |first1=K.H |last2=Kashiwadani |first2=H |last3=Kobayashi |first3=K. |year=2013 |title=A new species of ''Myelochroa'' (Parmeliaceae, Lecanorales) from Shiga Prefecture, Central Japan |journal=Journal of Japanese Botany |volume=88 |pages=140–143}}</ref>
<ref name="Otnyukova et al. 2009">{{cite journal |last1=Otnyukova |first1=Tatyana N. |last2=Stepanov |first2=Nikolay V. |last3=Elix |first3=John A. |year=2009 |title=Three new species of Parmeliaceae (Ascomycota) from Siberia |journal=Mycotaxon |volume=108 |issue=1 |pages=249–256 |doi=10.5248/108.249|hdl=1885/50596 |s2cid=85913429 |hdl-access=free }}</ref>
<ref name="Park 1990">{{cite journal |last1=Park |last2=Yun Sil |year=1990 |title=The macrolichen flora of South Korea |journal=The Bryologist |volume=93 |issue=2 |pages=105–160 |doi=10.2307/3243619 |jstor=3243619}}</ref>
<ref name="Rodrigues et al. 2021">{{cite journal |last1=Rodrigues |first1=Andressa S. |last2=Canêz |first2=Luciana S. |last3=Lorenz |first3=Aline P. |title=''Canoparmelia amazonica'', ''Myelochroa lindmanii'' and ''Parmelinella salacinifera'' belong to ''Parmelinella'' (Parmeliaceae) |journal=The Bryologist |pages=352–361 |volume=124 |issue=3 |year=2021 |doi=10.1639/0007-2745-124.3.352|s2cid=237773315 }}</ref>
<ref name="Wang et al. 2001">{{cite journal |last1=Wang |first1=Sheng-Lan |last2=Chen |first2=Jian Bin |last3=Elix |first3=John A. |year=2001 |title=Two new species of the lichen genus ''Myelochroa'' (Parmeliaceae, Ascomycota) from China |journal=Mycotaxon |volume=77 |pages=25–30 |url=http://www.cybertruffle.org.uk/cyberliber/59575/0077/0025.htm}}</ref>
}}
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Category:Parmeliaceae Category:Lichen genera Category:Lecanorales genera Category:Taxa described in 1952 Category:Taxa named by Yasuhiko Asahina