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The position of several endemic and rare species in Agaricus sect. Duploannulati and the limits of the section were investigated by analysis of sequence data from the ribosomal DNA ITS. The results supported the recognition of two groups, which we treat as subsections Chitonioides and Duploannulati. Most of the species studied proved to belong to subsect. Chitonioides. Species excluded from the section, as well as other potential members of sect. Duploannulati, are considered. Morphological traits deemed important for identification of A. nevoi, A. pequinii, A. gennadii, A. rollanii, and A. padanus are discussed. Taxonomic positions of these species in morphologically-based systems and according to molecular systematics data are compared and analyzed.
Current classifications of the Lyophylleae and the importance of siderophilous granulation in the basidia for the classification of agaricoid fungi were evaluated using parsimony analyses of sequence data from the nuclear ribosomal large subunit gene (nLSU), the internal transcribed spacer region of the nuclear ribosomal array (ITS), and the mitochondrial ribosomal small subunit gene (mtSSU). These three different data partitions were phylogenetically congruent on the basis of the Mickevich–Farris statistical test, but not from the ILD and the Templeton tests. Bootstrap supports for nodes in phylogenetic trees generated from combined nLSU, ITS, and mtSSU sequence data were generally higher than those in trees generated from individual data sets. This suggests a lack of major conflict in the phylogenetic signal among the different data sets. We conclude that the Mickevich–Farris test is more appropriate for estimating congruence and combinability between different sources of molecular data than the more widely used ILD and Templeton tests, at least when the different data sets have their respective resolution power at different depths in the phylogeny. Results of the combined analyses show that the Entolomataceae are a sister group to a clade composed of the Lyophylleae, Termitomyceteae, and Tricholomateae p.p. This implies that presence of siderophilous granulation in the basidia of agaric fungi has probably a single origin, and would have been lost in the Tricholomateae. Inclusion of the Termitomyceteae within the Lyophylleae suggests homology of the macro type granulation. Because the exact placement of Tricholomateae pro parte remains uncertain, it remains unclear whether the Lyophylleae (including Termitomyceteae) are monophyletic or paraphyletic. Within the Lyophylleae, genera Lyophyllum and Calocybe are shown to be artificial, as are Lyophyllum sections Lyophyllum, Difformia, and Tephrophana. Four main natural groups of Lyophylleae have been identified that should serve as a basis for developing a more natural classification system for these fungi.
Ecologically important ectomycorrhizal (EM) associations are poorly known from equatorial rain forests of South America. Recent field studies in the Pakaraima Mountains of western Guyana revealed previously undocumented forests dominated by EM leguminous trees, with a rich assemblage of EM mycobionts. Along transects, basidiomes from 75 species or morphospecies of putatively EM fungi were spatially associated with leguminous host trees. These fungi belonged to the basidiomycete families Boletaceae, Amanitaceae, Russulaceae, Cortinariaceae, Cantharellaceae, Clavulinaceae, and Entolomataceae, all of which are poorly documented from the lowland neotropics. Ectomycorrhizas were confirmed on D. corymbosa, D. altsonii, and D. jenmanii (Caesalpiniaceae, tribe Amherstieae), and a fourth species, Aldina insignis (Papilionaceae). The tribe Amherstieae contains most of the EM leguminous species forming monodominant forests in Guineo-Congolian Africa. Dicymbe species constituted the first record of EM Amherstieae in the New World. A variety of other co-occurring caesalpiniaceous trees failed to exhibit ectomycorrhizas. Transect surveys indicated that D. corymbosa and D. altsonii were: (1) highly clumped and dominant at specific sites; (2) occurred on soils with widely varying chemical and textural characteristics; and (3) the most important hosts for EM fungi in the local landscape. Dicymbe species have life history attributes, including the ectomycorrhizal habit, which enhance their competitive abilities irrespective of soil conditions. The spatial restriction of EM fungal basidiomes indicated that discrete groves of EM trees harbour an important component of regional macromycete diversity.
Collybia, as understood by Antonin & Noordeloos, comprises four species: C. racemosa, C. tuberosa, C. cirrhata and C. cookei.
Collybia tuberosa, C. cirrhata and C. cookei are morphologically similar and are primarily distinguished from each other by the
presence or absence and the colour of sclerotia. All four share a common and unique habitat. Phylogenetic reconstructions using
DNA sequences of the ribosomal ITS1–5.8S–ITS2 support four distinct clades, each corresponding to a morphological species, with
the C. tuberosa, C. cirrhata and C. cookei clades forming a larger group. Analyses of ribosomal Large Subunit DNA sequences
confirmed that Collybia tuberosa, C. cirrhata and C. cookei formed a monophyletic group. In both analyses, the C. racemosa sequence
was highly divergent from those of the other three species of the complex and we propose a separate genus name, Dendrocollybia,
for this species. Simple diagnostic RFLP patterns were identified for the four species and were used to validate morphological
designations and distributions.
Genetic relationships were investigated among several populations of Pleurotus tuberregium from Nigeria, Papua New Guinea and
New Caledonia. Intrastock mating compatibility studies using progeny from two collections demonstrated a tetrapolar mating system
for P. tuberregium. Interstock matings among the geographically distinct populations were compatible. All isolates were found to be
intersterile with tester strains of other Pleurotus species, showing that P. tuberregium represents a unique intersterility group in
Pleurotus. Nucleotide sequences of the ITS region of the rDNA gene were determined for 30 isolates and used to infer phylogenetic
structure of populations. Phylogenetic analysis shows that African and Australasian-Pacific isolates form at least two distinct
evolutionary lineages. Higher genetic divergence was observed among ITS sequences from the Australasian-Pacific region than
among African isolates, which suggests a possible origin of P. tuberregium in the Australasian-Pacific region.
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