Phylogenomics, biogeography, and trait evolution of the Boletaceae (Boletales, Agaricomycetes, Basidiomycota)

Abstract

The species-rich porcini mushroom family Boletaceae is a widespread and well-known group of ectomycorrhizal (ECM) mushroom-forming fungi that has eluded intrafamilial phylogenetic resolution despite many attempts using morphological traits and multi-locus molecular datasets. In this study, we present a genome-wide molecular dataset of 1764 single-copy gene families from a global sampling of 418 Boletaceae specimens. The resulting phylogenetic analysis has strong statistical support for most branches of the tree, including the first statistically robust backbone. The enigmatic Phylloboletellus chloephorus from non-ECM subtropical forests in northwestern Argentina is recovered as an early diverging lineage within the Boletaceae. Time-calibrated branch lengths estimate that the family first arose in the early-to-mid Cretaceous and underwent a rapid radiation in the Eocene, possibly when the ECM nutritional mode arose with the emergence and diversification of ECM angiosperms. Biogeographic reconstructions reveal a complex history of vicariance and episodic long-distance dispersal correlated with historical geologic events, including Gondwanan origins and cladogenesis patterns that parallel its fragmentation. Ancestral state reconstruction of morphological traits predicts that the ancestor of the Boletaceae was lamellate with ornamented basidiospores, contrary to the most common bolete sporocarp morphology. Transition rates indicate that the lamellate hymenophore and sequestrate sporocarp are reversible traits. Together, this study represents the most comprehensively sampled, data-rich molecular phylogeny of the Boletaceae to date, enabling robust inferences of trait evolution and biogeography in the group.