Phylogenetic analysis of the distribution of deadly amatoxins among the little brown mushrooms of the genus Galerina

Some but not all of the species of 'little brown mushrooms' in
the genus Galerina contain deadly amatoxins at concentrations equaling
those in the death cap, Amanita phalloides. However, Galerina's ~300
species are notoriously difficult to identify by morphology and the
identity of toxin-containing specimens has not been verified with DNA
barcode sequencing. This left open the question of which Galerina species
contain toxins and which do not. We selected specimens for toxin analysis
using a preliminary phylogeny of the fungal DNA barcode region, the
ribosomal internal transcribed spacer (ITS) region. Using liquid
chromatography/mass spectrometry, we analyzed amatoxins from 70 samples of
Galerina and close relatives, collected in western British Columbia,
Canada. To put the presence of toxins into a phylogenetic context, we
included the 70 samples in maximum likelihood analyses of 438 taxa, using
ITS, RNA polymerase II second largest subunit gene (RPB2), and nuclear
large subunit ribosomal RNA (LSU) gene sequences. We sequenced barcode DNA
from types where possible to aid with applications of names. We detected
amatoxins only in the 24 samples of the G. marginata s.l. complex in the
Naucoriopsis clade. We delimited 56 putative Galerina species using
Automatic Barcode Gap Detection software. Phylogenetic analysis showed
moderate to strong support for Galerina infrageneric clades Naucoriopsis,
Galerina, Tubariopsis, and Sideroides. Mycenopsis appeared paraphyletic
and included Gymnopilus. Amatoxins were not detected in 46 samples from
Galerina clades outside of Naucoriopsis or from outgroups. Our data show
significant quantities of toxin in all mushrooms tested from the G.
marginata s.l. complex. DNA barcoding revealed consistent accuracy in
morphology-based identification of specimens to G. marginata s.l. complex.
Prompt and careful morphological identification of ingested G. marginata
s.l. has the potential to improve patient outcomes by leading to fast and
appropriate treatment.