Understanding lichenicolous heterobasidiomycetes: new taxa and reproductive innovations in Tremella s.l.

Abstract

Four new lichenicolous Tremella species are described and characterized morphologically and molecularly. Tremella celata grows on Ramalina fraxinea, inducing the formation of inconspicuous galls, and having hyphae with incomplete clamps. Tremella endosporogena develops intrahymenially in the apothecia of Lecanora carpinea, having single-celled basidia and clampless hyphae. Tremella diederichiana is the name proposed for a species micromorphologically close to T. christiansenii but inducing the formation of small, pale galls on the thallus and apothecia of Lecidea aff. erythrophaea. Tremella variae grows on Lecanora varia thallus, instead of on the apothecia, as do the other known Tremella species parasitizing Lecanora s.l. Phylogenetic relationships and host specificity of these species are investigated and compared with other taxa that show morphological resemblances, phylogenetic affinities or similar hosts. The formation of mitotic conidia inside old basidia (endospores), which is a poorly known reproductive strategy in the Basidiomycota, is also a distinctive character of Tremella endosporogena. A discussion on the reproductive role and systematic implications of endospores is included.

• endospores
• host specificity
• ITS
• rDNA
• Tremellomycetes

Acknowledgments

The research was supported by grants from The Swedish Taxonomy Initiative (Svenska artprojektet) administered by the Swedish Species Information Center (ArtDatabanken) to MW and the Spanish Ministry of Economy and Competitiveness ( CGL2012-40123) to AM and MW, and ( CGL2013-42498-P and CGL2014-55542-P) to VJR. SPO was supported by the grant CTM2012-38222-C02-02 from the Spanish Ministry of Economy and Competitiveness.