Abstract
Armillaria is a globally distributed fungal genus most notably composed of economically important plant pathogens that are found predominantly in forest and agronomic systems. The genus sensu lato has more recently received attention for its role in woody plant decomposition and in mycorrhizal symbiosis with specific plants. Previous phylogenetic analyses suggest that around 50 species are recognized globally. Despite this previous work, no studies have analyzed the global species richness and distribution of the genus using data derived from fungal community sequencing datasets or barcoding initiatives. To assess the global diversity and species richness of Armillaria, we mined publicly available sequencing datasets derived from numerous primer regions for the ribosomal operon, as well as ITS sequences deposited on Genbank, and clustered them akin to metabarcoding studies. Our estimates reveal that species richness ranges from 50 to 60 species, depending on whether the ITS1 or ITS2 marker is used. Eastern Asia represents the biogeographic region with the highest species richness. We also assess the overlap of species across geographic regions and propose some hypotheses regarding the drivers of variability in species diversity and richness between different biogeographic regions.
Highlights
While the importance that fungi play as mutualists, decomposers, and pathogens is undisputed, researchers are just beginning to disentangle the processes that shape their global species richness and distribution (Tedersoo et al, 2014)
Public data sets which contributed to the high-throughput internal transcribed spacer region 1 (ITS1) and internal transcribed spacer region 2 (ITS2) region sequences in this study consisted of six different primer pair combinations: fITS7/ITS4, gITS7/ITS4, ITS1F/ITS2, ITS1F/ITS4, ITS3/ITS4, and ITS5/ITS2
Of the ITS1 region species clusters, sequences from the Sequence Read Archive (SRA) database clustered into five species clusters, all of which contained sequences queried from NCBI-Genbank
Summary
While the importance that fungi play as mutualists, decomposers, and pathogens is undisputed, researchers are just beginning to disentangle the processes that shape their global species richness and distribution (Tedersoo et al, 2014). One such globally important group is the armillarioid clade – a lineage composed of the mushroom-forming genera Armillaria and Desarmillaria, along with the sequestrate genus Guyanagaster. Desarmillaria – which was recently separated from Armillaria on the basis of morphological and molecular characters (Koch et al, 2017; Heinzelmann et al, 2019) – is representative of the exannulate mushroom-forming species within the clade. While Guyanagaster – representative of the sequestrate species – is a member of the armillarioid clade (Henkel et al, 2010; Koch et al, 2017), the discussion of the armillarioid clade will only refer to species of Armillaria and Desarmillaria, and when necessary, Guyanagaster will be referenced
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