Dupontia (Poaceae) in North America

Challenged by work on the Panarctic Flora project and apparent discrepancies in recent taxonomic treatments, the genus Dupontia was studied from herbarium specimens, including types and chromosome vouchers, and by numerical taxonomy, mapping the distribution of morphological characteristics, consideration of chromosome numbers, and field work in the Canadian Arctic. Our results using these techniques show random variability in many characters and differences in plant size that appear to be partly habitat related. The treatment of the genus has varied from the recognition of one variable species to three or more distinct species. Morphological characters, used in the literature to divide the genus Dupontia into more than one taxon, cannot be reliably applied to distinguish most North American plants. Continuous morphological variation in combination with high and variable ploidy levels, effective vegetative growth, and rare sexual reproduction suggests the use of a broad species concept. Until further evidence is available, our results support treating the genus as monotypic.Key words: Poaceae, Dupontia, morphology, chromosome numbers, conditional clustering, contingency tables.

Molecular phylogenetic studies in the genus Amanita

A group of 49 Amanita species that had been thoroughly examined morphologically and anatomically was analyzed by DNA sequence comparison to estimate natural groups and phylogenetic relationships within the genus. Nuclear DNA sequences coding for a part of the ribosomal large subunit were determined and evaluated using neighbor-joining with bootstrap analysis, parsimony analysis, conditional clustering, and maximum likelihood methods. Sections Amanita, Caesarea, Vaginatae, Validae, Phalloideae, and Amidella were substantially confirmed as monophyletic groups, while the monophyly of section Lepidella remained unclear. Branching topologies between and within sections could also partially be derived. Subgenera Amanita and Lepidella were not supported. The Mappae group was included in section Validae. Grouping hypotheses obtained by DNA analyses are discussed in relation to the distribution of morphological and anatomical characters in the studied species.Key words: fungi, basidiomycetes phylogeny, Agaricales, Amanita systematics, large subunit rDNA, 28S.