DNA Sequence Analyses Reveal Abundant Diversity, Endemism and Evidence for Asian Origin of the Porcini Mushrooms

Abstract

The wild gourmet mushroom Boletus edulis and its close allies are of significant ecological and economic importance. They are found throughout the Northern Hemisphere, but despite their ubiquity there are still many unresolved issues with regard to the taxonomy, systematics and biogeography of this group of mushrooms. Most phylogenetic studies of Boletus so far have characterized samples from North America and Europe and little information is available on samples from other areas, including the ecologically and geographically diverse regions of China. Here we analyzed DNA sequence variation in three gene markers from samples of these mushrooms from across China and compared our findings with those from other representative regions. Our results revealed fifteen novel phylogenetic species (about one-third of the known species) and a newly identified lineage represented by Boletus sp. HKAS71346 from tropical Asia. The phylogenetic analyses support eastern Asia as the center of diversity for the porcini sensu stricto clade. Within this clade, B. edulis is the only known holarctic species. The majority of the other phylogenetic species are geographically restricted in their distributions. Furthermore, molecular dating and geological evidence suggest that this group of mushrooms originated during the Eocene in eastern Asia, followed by dispersal to and subsequent speciation in other parts of Asia, Europe, and the Americas from the middle Miocene through the early Pliocene. In contrast to the ancient dispersal of porcini in the strict sense in the Northern Hemisphere, the occurrence of B. reticulatus and B. edulis sensu lato in the Southern Hemisphere was probably due to recent human-mediated introductions.

New species and distinctive geographical divergences of the genus Sparassis (Basidiomycota): evidence from morphological and molecular data

“…1), and closely related species or species pairs were found in Eurasia, East Asia-North America, or Europe-North America in each clade, indicating that broad historical exchange of Sparassis could exist in the Holarctic region. This is in accordance with observations on many ectomycorrhizal fungi, such as Boletus (Dentinger et al 2010;Feng et al 2012), Chroogomphus (Li et al 2009) and Amanita (Geml et al 2006(Geml et al , 2008Zhang et al 2004), and many other fungi (Halling 2001;Mueller et al 2001;Petersen and Hughes 2007;Redhead 1989). This suggests allopatric speciation events have contributed a lot to the current distribution patterns of plants (Donoghue and Smith 2004) and some fungal groups (e.g.…”

“…Du et al 2012;Feng et al 2012;Li et al 2011;Liang et al 2011;Yang 2011;Yang et al 2012;Zeng et al 2012), rich collections of Sparassis were made. Taxonomy and biogeographic distribution of East Asia Sparassis species were revised based on morphological examination and molecular phylogenetic analyses.…”

Fungal DNA barcoding

“…As DNA barcode sequences increase, barcode-based species identification is becoming increasingly common and the barcode sequences are generating many new species hypotheses. For example, ITS sequences helped reveal divergent lineages within the commercially important wild edible mushrooms Thelephora ganbajun (Sha et al 2008), Russula vinosa , and Boletus (Feng et al 2012). Similar findings have been reported for other organisms such as the root-knot nematodes where DNA barcoding information at four loci identified limitations in species identification based on a single barcode and the usefulness of multiple loci in revealing several new lineages within quarantine root-knot nematodes (Meloidogyne spp.)…”

“…Several efforts have been made to distinguish closely related fleshy mushrooms (e.g., Cai et al 2012;Feng et al 2012;Cao et al 2012;Buyck et al 2014). For example, Cai et al (2012) analyzed 28 isolates representing eight poisonous species of Amanita and their two close allies that are not poisonous but edible.…”

Revisiting the morphology and phylogeny ofLactifluuswith three new lineages from southern China

“…The diversity of Lactifluus in Asia, comprising both morphologically distinct species and cryptic species, appears to be much higher than was thought. The above studies and some other studies on different groups of fungi in the same region (Feng et al 2012, Li et al 2010, Li et al 2011, Halling et al 2012, de Crop et al 2014a suggest that subtropical-tropical Asia will be a key region assessing the actual species diversity in Lactifluus and therefore will contribute greatly to a better understanding of the evolution and distribution of this genus.…”