Evolutionary history of the sequestrate genus Rossbeevera (Boletaceae) reveals a new genus Turmalinea and highlights the utility of ITS minisatellite-like insertions for molecular identification

Abstract

The sequestrate (truffle-like) basidiomycete genera Rossbeevera, Chamonixia, and Octaviania are closely related to the epigeous mushroom genera Leccinum and Leccinellum. In order to elucidate the properties and placement of several undescribed sequestrate taxa in the group and to reveal the evolutionary history of Rossbeevera and its allies, we conducted phylogenetic analyses based on three nuclear (ITS, nLSU, EF-1α) and two mitochondrial DNA loci (ATP6 and mtSSU) as well as precise morphological observations. Phylogenetic analyses of three nuclear loci suggest a complex evolutionary history with sequestrate fruiting bodies present in several clades, including a previously unrecognized sister clade to Rossbeevera. Here we propose a new sequestrate genus, Turmalinea, with four new species and one new subspecies as well as two new species of Rossbeevera. The three-locus nuclear phylogeny resolves species-level divergence within the Rossbeevera-Turmalinea lineage, whereas a separate phylogeny based on two mitochondrial genes corresponds to geographic distance within each species-level lineage and suggests incomplete lineage sorting (ILS) and gene introgression within several intraspecific lineages of Rossbeevera. Furthermore, topological incongruence among the three nuclear single-locus phylogenies suggests that ancient speciation within Rossbeevera probably involved considerable ILS. We also found an unusually long, minisatellite-like insertion within the ITS2 in all Rossbeevera and Turmalinea species. A barcode gap analysis demonstrates that the insertion is more informative for discrimination at various taxonomic levels than the rest of the ITS region and could therefore serve as a unique molecular barcode for these genera.

Can we use environmental DNA as holotypes?

“…Introgression and incomplete lineage sorting have been documented in other Leccinoideae genera, namely Rossbeevera T. Lebel et al and Turmalinea Orihara & N. Maek., and may have been overlooked in other groups (Orihara et al 2016). However, this kind of phenomenon, although problematic in species identification and phylogenetic analysis should not commonly result in false-positives in mgDNA species delimitation (i.e., wrongly considering divergent sequences as belonging to different species), except in the case of incomplete concerted evolution of the ITS sequences.…”

Dating the emergence of truffle-like fungi in Australia, by using an augmented meta-analysis

“…in New Zealand, the diverse truffle flora is mostly epigeal). Further, although the majority of sequestrate fungi in Australia appears to have transitioned locally, Octaviania and Rossbeevera, two sequestrate genera of Boletaceae, were already sequestrate when they arrived in Australia from Asia (Orihara et al 2016). Therefore, conditions in Australia did not influence their sequestration, but must have been conducive to the establishment of these species following their dispersal.…”

­­­Multi-locus phylogenies reveal three new truffle-like taxa and the traces of interspecific hybridization in Octaviania (Boletales)

“…As far as we know, however, the present study is the rst case that demonstrated interspeci c hybridization in sequestrate basidiomycetes based on molecular evidence. Given the multiple traces of introgression among intraspeci c lineages shown by Orihara et al (2016a) and the interspeci c hybridization within Octaviania discussed here, it appears that the sequestrate genera in the Leccinoideae may be less reproductively isolated when the two lineages have been ecologically isolated (e.g. there is therefore no need for reproductive isolation to reinforce species boundaries).…”