Morphological and genetic diversification of Russula floriformis, sp. nov., along the Isthmus of Panama

ABSTRACT

Species of Russula are ubiquitous members of ectomycorrhizal fungal communities in tropical ecosystems. However, an important part of the total tropical diversity of this genus and its biogeographic patterns is unknown due to the lack of studies on Russula in tropical ecosystems. We combined molecular, morphological, ecological, and biogeographic data to elaborate concepts for two new subspecies of R. floriformis (subsection Substriatinae). Russula floriformis subsp. floriformis and R. floriformis subsp. symphoniae are described as new from montane forest dominated by Quercus and/or Oreomunnea (Fagales) from Colombia and Panama, respectively. Phylogenies were constructed using nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS), D1–D2 domains of nuc 28S rDNA (28S), and partial regions of the second largest subunit of RNA polymerase II (rpb2) and translation elongation factor 1-alpha (tef1). Similar environmental conditions, similar morphology, and an ITS sequence similarity higher than 99% with only three different positions indicate that these two subspecies are closely related. Detailed observations of microscopic structures and analyses of further DNA loci, however, revealed morphological and molecular characteristics that allow distinguishing the two subspecies of R. floriformis. Spatial distribution and phylogenetic proximity of the two Russula subspecies and their ectomycorrhizal hosts, i.e., species of Quercus, suggest that their diversification is a result of comigration, adaptation, and geographic isolation along the Isthmus of Panama during the Pliocene and Pleistocene.

KEYWORDS:

• Allopatry
• Basidiomycota
• cryptic species
• ectomycorrhizal diversity
• Fagaceae
• Juglandaceae
• new species and subspecies
• Russulales
• tropical montane forest
• 3 new taxa

ACKNOWLEDGMENTS

M.V. thanks the Plant Science and Biodiversity Centre of the Slovak Academy of Sciences for their logistic support. We thank David Escobar and Nelly Maldonado from the Chicaque Natural Park for their support during field work in Colombia and Jim Dalling, Ben Turner, Carmen Velasquez, Orlando Cáceres, Tina Antje Hofmann, and Manlio Cuevas for their support during field work in Panama. Also, we thank Adriana Garcia and Lida Triviño for their assistance during the laboratory work and Nicolas Luna and Frasella de Martino for support with the study area map. Annemieke Verbeken is thanked for letting us perform parts of the molecular work in her laboratory. The Panamanian Environmental Ministry (MiAmbiente) is thanked for issuing permits for collection (SE/PH-4-18) and export (SEX/H-2-18) of fungi. We thank three anonymous reviewers, the associate editor Andy Wilson, and executive editor Brandon Matheny for their valuable comments.

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Additional information

Funding

M.V. thanks the IAPT Research Grant Round 2019 for their financial support. Partial funding for A.C. was provided by the Robert L. Gilbertson Mycological Herbarium Grant (University of Arizona). Sequencing and other laboratory work of the Slovak team were funded by the National Slovak research project APVV 15-0210.