Morphological and molecular systematics of Rocky Mountain alpine Laccaria

Abstract

The alpine zone is comprised of habitats at elevations above treeline, and macromycetes play important ecological roles as decomposers and mycorrhizal symbionts here as elsewhere. Laccaria is an important group of ectomycorrhizal basidiomycetes widely used in experimental and applied research. A systematic study of alpine Laccaria species using morphological, cultural and molecular (ribosomal DNA internal transcribed spacer) data revealed five taxa in the Rocky Mountain alpine zone: L. laccata var. pallidifolia, L. nobilis (the first published report for arctic-alpine habitats), L. pumila, L. montana and L. pseudomontana (a newly described taxon similar to L. montana with more ellipsoidal, finely echinulate basidiospores). All occur in the southern Rocky Mountains of Colorado; however, only L. pumila and L. montana were found on the Beartooth Plateau in the northern Rocky Mountains of Montana and Wyoming. All are associated with dwarf and shrub Salix species, with L. laccata var. pallidifolia also associated with Dryas octopetala and Betula glandulosa. Maximum-parsimony phylogenetic analysis of rDNA-ITS sequences for 27 Laccaria accessions supports the morphological species delineations.

• Agaricales
• arctic-alpine macromycetes
• internal transcribed spacer (ITS) sequences
• macrofungi
• molecular phylogenetics
• Tricholomataceae

The authors wish to thank Egon Horak for generously providing additional Rocky Mountain alpine specimens, Laccaria records from arctic-alpine literature sources and invaluable comments on early drafts of the manuscript; Leslie Eddington and Sarah Klingsporn for field assistance; Shirley Gerhardt, Paula Kosted, Vladimir Kanazin, Hope Talbert, and Hussain Abdel-Haleem for consultation on molecular methods; Matt Lavin for consultation on phylogenetic analyses; Nancy Equall for assistance with scanning electron microscopy; and curators at the University of Tennessee Herbarium, Denver Botanical Garden and The Field Museum for loans of herbarium specimens. Funding support was provided by a grant to the second author by the National Science Foundation Biotic Surveys and Inventories Program (# 9971210), and to the first author by the Montana State University College of Agriculture’s Bayard Taylor Fellowship Fund.