The species aggregate in Nordic countries - phylogeny and species delimitation.

Mycologists have always been curious about the elaborate morphotypes and shapes of species of the genus . The small, black, cupulate specimens have mostly been assigned to a broadly defined morpho-species. Recent phylogenetic analyses, however, have revealed an aggregate of species hidden under this name. We performed a multispecies coalescent analysis to re-assess species limits and evolutionary relationships of the species aggregate in the Nordic countries. To achieve this, we used morphology and phylogenetic evidence from five loci - heat shock protein 90 (), translation elongation factor 1-alpha (), RNA polymerase II (), and the 5.8S and large subunit (LSU) of the nuclear ribosomal DNA. All specimens under the name in the larger university fungaria of Norway, Sweden and Denmark were examined and barcoded, using partial and/or as the preferential secondary barcodes in . Additional fresh specimens were collected in three years (2015-2018) to obtain morphological data to aid in species discrimination. The species aggregate consists of seven phylogenetically distinct species, nested in three divergent lineages, and in the /alpina-corium lineage, and in the /alpestris-nannfeldtii lineage, and as a weakly supported sister to the /alpestris-nannfeldtii lineage. Among the seven species, the ribosomal loci expressed substantial variation in evolutionary rates, suggesting care in the use of these regions alone in delimitation of species. Altogether, 469 out of 496 available fungarium specimens were successfully barcoded.