Taxonomists describe new species of fungi based on phenotypic differences reflected in morphology and ecology, and genetic differences, usually by comparison of conserved genes (like the ITS and LSU regions of ribosomal DNA). The challenge for taxonomists is to find a happy medium between lumping and splitting species. Species boundaries that are too broad cannot distinguish among actual differences (such as pathogenicity and geographic range), and lose meaning when too narrow and many names are applied across intraspecific variation. The ITS region is a biological gem. It can be amplified with universal primers across the fungal kingdom, it is interspecifically variable (usually), and intraspecifically conserved (usually). I fell in love with the ITS region working on smut fungi and rust fungi, both of which are more easily amplified with ITS primers than any other genes. But the ITS is not a Cinderella fit for all Fungi, there is not enough variation among species of Ascomycota (e.g., the ITS is not variable enough to distinguish species of Fusarium), and some familiarity is needed to understand the limitations of the ITS region in different groups. The Psilocybe subaeruginosa species complex has grown based on variation in the ITS region, phenotypic variability, and geographic range. It includes P. cyanescens, P. australiana, P. eucalypta, P. tasmaniana, P. azurescens, P. makarorae, P. weraroa, and P. allenii, the latter two described on differences in rDNA. Below is a phylogenetic hypothesis based on an alignment of the ITS region including all of the 86 sequenced genomes of P. subaeruginosa from Australia, and sequences taken from GenBank of other taxa in the complex. The ITS region is intraspecifically variable across the complex in Australia. This variation makes P. cyanescens, P. azurescens, and P. allenii paraphyletic in regard to P. subaeruginosa. A taxonomic solution would be to either call everything P. subaeruginosa, or potentially describe more and more species to reflect groupings. This 'splitting' option is unsatisfactory because it would not match the population analyses posted previously (essentially the relationships among ITS do not reflect population networks based on >1.5 million SNPs). My opinion is that P. subaeruginosa is one phenotypically variable species with a widespread distribution caused by saprotrophic invasions in the northern hemisphere. Describing more species in the complex ultimately adds more future synonyms.
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Designer Shrooms @ Funky Fungus on 1st July 2023
I started a gig at Funky Fungus as Chief Scientific Officer to make designer shrooms Our research on Psilocybe
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