In: Sydowia 77, (2025): 271-290; ISSN 0082-0598, DOI 10.12905/0380.sydowia77-2025-0271, Published online on December 17, 2024

Three sphagnicolous species of Arrhenia: one old, one new, one recombined

Andrus Voitk* & Irja Saar

1 Foray Newfoundland & Labrador, 703-7 Tiffany Lane, St John’s, NL, Canada, A1A 4B7
2 Institute of Ecology and Earth Sciences, University of Tartu, J. Liivi 2, 50409 Tartu, Estonia
*e-mail: minaise@nf.sympatico.ca

Voitk A. & Saar I. (2024) Three sphagnicolous species of Arrhenia: one old, one new, one recombined. – Sydowia 77: 271–290.

A cystidiate sphagnicolous Arrhenia, collected in Labrador, led to review of the protologue of Agaricus umbratilis, which described Ag. umbratilis as a black omphalinoid species from wetlands of barrens, characteristic sites for Sphagnum. This species concept matched the black sphagnicolous Arrhenia telmatiaea and its synonym, Arrhenia fusconigra, with no other known lookalikes.
These names were synonymized, giving the earliest and sanctioned name, Ag. umbratilis, priority. Two cystidiate collections of Ag. umbratilis, phylogenetically indistinguishable from the acystidiate populations, were discovered; the cystidiate population was described as a new forma of the species, Arrhenia umbratilis f. cystidiata. The original cystidiate sphagnicolous species of Arrhenia that triggered the review of Ag. umbratilis was a distinct species not matching any other species of Arrhenia, and was described as a new species, Arr. burzynskii. Another sphagnicolous omphalinoid, found on the same collecting trips, matched Peck’s type for Agaricus montanus, and was recombined as Arrhenia montana.

Keywords: systematics, nomenclature, conspecificity, Labrador arrhenias. – 1 new species, 1 new combination, 1 new forma, 2 new synonyma, 1 neotype.