An ecologically important genus of mushrooms

North America

The genus Laccaria comprises an important part of the North American mycota north of Mexico. Nineteen species are recognized from the study area. Laccaria laccata is further divided into two varieties. Discussions regarding the distribution, presumed ectomycorrhizal hosts, and biology of these taxa are provided along with data on select extralimital taxa. In addition to an examination of North American material, an attempt was made to examine all extant type specimens. Descriptions of these collections are offered. To facilitate further work on the genus, a tentative key to the world taxa of Laccaria is presented.

Extensive collecting was undertaken in much of the continental United States and southern Canada. Comparative material was collected in Costa Rica, South America and Sweden. Data were obtained on basidioma and somatic culture mat morphology, intercollection pairing reactions and restriction fragment length polymorphisms of mtDNA and rDNA. Cytological data and in vitro ectomycorrhizal synthesis data were also obtained and used to further characterize the genus. Taxa were delimited so that they are presumably monophyletic and are diagnosable by a unique combination of character states, either morphological or molecular. Data from intercollection pairings were used in conjunction with the other data sets and did not outweigh information from the other analyses. Results of cladistic analyses were concordant with the hypothesis that Laccaria is a monophyletic assemblage of taxa with at least one synapomorphy (echinulate basidiospores with echinulae formed by perpendicular microtubules) supporting its monophyly. However, it was not possible to develop a fully resolved, robust hypothesis of phylogeny within the genus because of a pausity of characters, inability to polarize some of these characters and problems in choosing appropriate outgroup(s). As expected, there was a high degree of homoplasy detected within the employed data set and it will be necessary to utilize either extensive restriction site mapping or sequencing of selected macromolecules to develop a robust hypothesis of phylogenetic relationships within this genus. Although synapomorphies were not found to support the recognition of sections in the genus, two metasections, Laccaria and Amethystina, are recognized for logistic reasons and to provide a hypothesis to be tested during future analyses.

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