Molecular systematics and taxonomic overview of the bird's nest fungi (Nidulariaceae).

Fungi in the Nidulariaceae, otherwise known as 'bird's nest fungi', are among the least studied groups of Agaricomycetes (Basidiomycota). Bird's nest fungi are globally distributed and typically grow on woody debris or animal dung as saprotrophs. This group of fungi is morphologically diverse with ca. 200 described species. Phylogenetic relationships of bird's nest fungi were investigated with four commonly used loci (ITS, LSU, tef, and rpb2). The family was resolved as a monophyletic group with Squamanitaceae as a potential sister taxon. Cyathus and Crucibulum each formed its own independent and well-supported clade. Nidula and Nidularia formed a clade together, but each genus is polyphyletic. Two Mycocalia species included in our analyses were on their own separate branches, indicating that this genus is also polyphyletic. Misidentifications were detected in most genera, suggesting that species concepts need to be revisited and refined throughout Nidulariaceae. Several bird's nest fungi species have global geographical distributions whereas others may have more limited ranges. Basic morphological characters of bird's nest fungi have likely been lost or gained multiple times. The phylogenetic placement of Crucibulum is unclear and the sister lineage of bird's nest fungi is not conclusive. Further studies with data from rare species and additional informative genes are needed to fully resolve the topology of Nidulariaceae and identify its sister group with more certainty.