Russulaceae of the Pakaraima Mountains of Guyana. IV. New species forming a distinct lineage of Lactarius subg. Plinthogalus

ABSTRACT

The Neotropics have recently emerged as an important region for studies of tropical ectomycorrhizal (ECM) fungi. Specific neotropical areas with high ECM host tree densities have ECM fungal diversities rivaling those of higher-latitude forests. Some forests of the Guiana Shield are dominated by endemic ECM trees of the Fabaceae, including species of Dicymbe (subfam. Detarioideae), Aldina (subfam. Papilionoideae), and Pakaraimaea (Cistaceae). One of the most species-rich ECM fungal families present in each of these systems is Russulaceae. Long-term sampling in forests in Guyana’s Pakaraima Mountains has revealed a number of species of the Russulaceae genera Lactarius, Lactifluus, and Russula. In this study, we document a previously unknown, distinct lineage of Lactarius subg. Plinthogalus containing eight species from the Guiana Shield. Here, we describe five of these species from Guyana as new to science: Lactarius humiphilus, Lactarius mycenoides, Lactarius guyanensis, Lactarius dicymbophilus, and Lactarius aurantiolamellatus. Morphological descriptions, habit, habitat, and known distribution are provided for each new species. Sequence data for the barcode internal transcribed spacer (ITS) locus are provided for types and most other collections of the new taxa, and a molecular phylogenetic analysis based on the ITS, 28S, and RPB2 (second-largest subunit of the RNA polymerase II) loci across the genus Lactarius corroborates their morphology-based infrageneric placement. The discovery of this lineage changes our insights into the biogeography and evolutionary history of Lactarius subg. Plinthogalus.

KEYWORDS:

• Gondwana
• Guiana highlands
• Neotropics
• Russulales
• tropical fungi
• 5 new taxa

ACKNOWLEDGMENTS

Research permits were granted by the Guyana Environmental Protection Agency. Field assistance was provided by members of the Patamona Amerindian community, including Chris Andrew, Francino Edmund, and Luciano Edmund. Additional field assistants included Mei Lin Chin, Piakai Henkel, Dillon Husbands, Rachel Koch, and Jessie Uehling. Kennan Mighell, Sarah Norvell, and Aida Vasco-Palacios provided specimens used in the study. Field photos were kindly provided by Todd Elliott and Noah Siegel.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

SUPPLEMENTARY MATERIAL

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00275514.2022.2125712

Additional information

Funding

We thank the following funding sources: National Science Foundation (NSF) (DEB-0918591, DEB-1556338), National Geographic Society’s Committee for Research and Exploration grants (6679-99, 7435-03, and 8481-08 to T.W.H.), NSF (DEB-0732968 to M.C.A.), and the Kits van Waveren Foundation (to J.N.).