Vindication of Physcomitrium pygmaeum (Funariaceae), an elusive and endangered moss from North America’s Great Basin

Physcomitrium pygmaeum is an ephemeral moss described in 1871 from a
single collection from Utah, currently considered conspecific with
Physcomitrium pyriforme. The interpretation of the taxon has been
problematic due to its rarity in the field, the elusiveness of the type
material, and an extremely scattered and inconsistent collection record.
Here we present a comprehensive description and assessment of the taxon
following the identification of the original material and lectotype
designation, the examination of all herbarium specimens existing to the
best of our knowledge, the collection of fresh material in Nevada, and the
molecular barcoding of the latter using four plastid and two nuclear loci.
Available information, albeit scant, suggests that this member of the
North American bryoflora should be considered critically endangered
following IUCN criteria.