Postia caesia complex (Polyporales, Basidiomycota) in temperate Northern Hemisphere

Abstract

Taxonomy of the Postia caesia complex is revised based on morphology and two genetic markers, ITS and tef1. In total, we recognize 24 species, multiplying the known species diversity in the complex. We provide descriptions for 20 temperate Northern Hemisphere taxa. Identity of the core species, P. caesia, is re-established, and a neotype from the type locality is selected. Four new combinations are proposed, and 10 new species are described:

Cryptic species diversity in polypores: the Skeletocutis nivea species complex

“…This is in accordance with other comparable studies on polypores (e.g. Otrosina and Garbelotto 2010, Spirin et al 2015, Han et al 2016, Song and Cui 2017, Spirin et al 2017, Miettinen et al 2018). Notable exceptions here include S. semipileata , which has a circumpolar distribution and S. nivea , which ranges longitudinally from northern China to New Zealand.…”

“…Carlson et al 2014, Miettinen et al 2018) who conclude that tef1 is more variable between species than ITS and provides greater resolution in separating species. Still, unique character state combinations can be identified from ITS sequences even for the most closely related species in the S. nivea complex.…”

The unbearable lightness of sequenced-based identification

“…It needs to be mentioned here that species recognition in Antrodiella is based on very slight sequence differences (which is also the case for many other polypores, see Miettinen et al 2018), in this case mostly in the ITS2. The two identical sequences we obtained for A. cf.…”

“…Because the use of molecular sequence data (Miettinen et al 2018) suddenly revealed the existence of many 'cryptic' northern hemisphere species, the ARCS-which contained many morphology-based records for Postia/ Oligoporus species-decided to eliminate all records from this Atlas in the absence of available sequence data to identify these Postia records from Switzerland more reliably. Our sequence therefore suddenly becomes the first positive species identification for the country in this species complex.…”

“…-Are dependent on the chosen similarity cut-off for species recognition. The often applied 97% similarity cut-off (Lindahl et al 2013;Selosse et al 2016) is certainly too low for most mushrooms as suggested by several recent taxonomic revisions (Bazzicalupo et al 2017;Yuan 2014;Miettinen et al 2018;Ö rstadius et al 2015). -Can be affected by contamination problems, e.g.…”