Nuclear Large Subunit rDNA Research Articles

Revision of the genus Cryptomonas (Cryptophyceae) II: incongruences between the classical morphospecies concept and molecular phylogeny in smaller pyrenoid-less cells

K. Hoef-Emden. 2007. Revision of the genus Cryptomonas (Cryptophyceae) II: incongruences between the classical morphospecies concept and molecular phylogeny in smaller pyrenoid-less cells. Phycologia 46: 402–428. DOI: 10.2216/06-83.1Previous studies have shown that the nuclear internal transcribed spacer 2 (ITS2) is likely a good marker to identify biological species according to its degree of conservation. Dimorphic strains and a few reports of sexual reproduction indicate the presence of biological species also in cryptophyte taxa. In this study, a reverse ( = DNA-based) taxonomy approach was used to predict putative biological species in the genus Cryptomonas. Of 49 Cryptomonas strains, nuclear ITS2 and partial large subunit (LSU) rDNA sequences were used to determine groups of genetically identical strains. From each group, representative strains (a total of 30 strains) were chosen for improved molecular phylogenetic analyses with combined data sets (nuclear ITS2 and LSU rDNA and nucleomorph small subunit rDNA). To predict putative biological species in Cryptomonas, the secondary structures of the nuclear ITS2 sequences were compared among clades and among strains of the same clade. Mapping light microscopically visible characters of the 49 strains onto the phylogenetic trees revealed conflicts between classical morphospecies and putative biological species. Strains that were identical or almost identical in nuclear ITS2, showed cell shapes representing different morphological species, whereas strains seemingly belonging to the same morphological species were genetically too diverse to represent one biological species. Most of the five putative biological species could solely be identified by molecular signatures. Therefore, five species descriptions were emended by adding molecular signatures as diagnostic characters including a new combination, Cryptomonas commutata (Pascher) Hoef-Emden comb. nov.

Invasion of the French Paleolithic painted cave of Lascaux by members of the Fusarium solani species complex

A major fungal invasion was discovered in the prehistoric painted cave of Lascaux in France in Sep 2001. At least three species of the Fusarium solani complex were isolated and identified with a portion of the translation elongation factor 1α gene (EF-1α), a portion of the nuclear large subunit rDNA (LSU) and nuclear ribosomal intergenic spacer region (ITS). This study represents the first time that Fusarium species have been reported from a cave containing prehistoric paintings. Significant interspecific molecular variability was observed, suggesting that there might have been repeated introduction of the species, possibly carried by water from soils above the cave.

Invasion of the French Paleolithic painted cave of Lascaux by members of the Fusarium solani species complex

A major fungal invasion was discovered in the prehistoric painted cave of Lascaux in France in Sep 2001. At least three species of the Fusarium solani complex were isolated and identified with a portion of the translation elongation factor 1alpha gene (EF-1alpha), a portion of the nuclear large subunit rDNA (LSU) and nuclear ribosomal intergenic spacer region (ITS). This study represents the first time that Fusarium species have been reported from a cave containing prehistoric paintings. Significant interspecific molecular variability was observed, suggesting that there might have been repeated introduction of the species, possibly carried by water from soils above the cave.

Molecular phylogeny of Lactarius volemus and its allies inferred from the nucleotide sequences of nuclear large subunit rDNA

The phylogenetic relationships of Lactarius volemus and its relatives were investigated using the nucleotide sequences of the nuclear-encoded large subunit ribosomal DNA (LSU rDNA). Thirty-six sequences from L. volemus, L. corrugis, and L. hygrophoroides, including three sequences obtained from the GenBank database, were used in this study. Samples studied were divided into four major subclades (A–D) in both neighbor-joining (NJ) and maximum-parsimony (MP) trees. Lactarius volemus and L. corrugis formed one large clade in both NJ and MP trees (bootstrap value, 100%), which was divided into three subclades (A–C). Subclade A included three clusters of L. volemus strains, i.e., velvet, red, and Chinese types. Subclade B included the common and red types of L. corrugis. Subclade C included the common and yellow types of L. volemus. Subclade D included only one type of L. hygrophoroides. An analysis of the fatty acid composition supported the divisions found in the molecular analysis. Analyses of nucleotide sequence, fatty acid composition, morphological characteristics, and the taste of the fruiting bodies all led us to conclude that the common, velvet, red, and Chinese types of L. volemus, and the common and red types of L. corrugis, may each belong to different species, subspecies, or varieties. Further studies with more material from a wide range of regions are required to conduct taxonomic revision of these types. The LSU rDNA region may be a useful tool to investigate phylogenetic relationships within the section Dulces of the genus Lactarius.

Molecular phylogeny of <i>Lactarius volemus</i> and its allies inferred from the nucleotide sequences of nuclear large subunit rDNA

The phylogenetic relationships of Lactarius volemus and its relatives were investigated using the nucleotide sequences of the nuclear-encoded large subunit ribosomal DNA (LSU rDNA). Thirty-six sequences from L. volemus, L. corrugis, and L. hygrophoroides, including three sequences obtained from the GenBank database, were used in this study. Samples studied were divided into four major subclades (A–D) in both neighbor-joining (NJ) and maximum-parsimony (MP) trees. Lactarius volemus and L. corrugis formed one large clade in both NJ and MP trees (bootstrap value, 100%), which was divided into three subclades (A–C). Subclade A included three clusters of L. volemus strains, i.e., velvet, red, and Chinese types. Subclade B included the common and red types of L. corrugis. Subclade C included the common and yellow types of L. volemus. Subclade D included only one type of L. hygrophoroides. An analysis of the fatty acid composition supported the divisions found in the molecular analysis. Analyses of nucleotide sequence, fatty acid composition, morphological characteristics, and the taste of the fruiting bodies all led us to conclude that the common, velvet, red, and Chinese types of L. volemus, and the common and red types of L. corrugis, may each belong to different species, subspecies, or varieties. Further studies with more material from a wide range of regions are required to conduct taxonomic revision of these types. The LSU rDNA region may be a useful tool to investigate phylogenetic relationships within the section Dulces of the genus Lactarius.

An overview of the higher level classification of Pucciniomycotina based on combined analyses of nuclear large and small subunit rDNA sequences

In this study we provide a phylogenetically based introduction to the classes and orders of Pucciniomycotina (= Urediniomycetes), one of three subphyla of Basidiomycota. More than 8000 species of Pucciniomycotina have been described including putative saprotrophs and parasites of plants, animals and fungi. The overwhelming majority of these (~90%) belong to a single order of obligate plant pathogens, the Pucciniales (= Uredinales), or rust fungi. We have assembled a dataset of previously published and newly generated sequence data from two nuclear rDNA genes (large subunit and small subunit) including exemplars from all known major groups in order to test hypotheses about evolutionary relationships among the Pucciniomycotina. The utility of combining nuc-lsu sequences spanning the entire D1–D3 region with complete nuc-ssu sequences for resolution and support of nodes is discussed. Our study confirms Pucciniomycotina as a monophyletic group of Basidiomycota. In total our results support eight major clades ranked as classes (Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes, Cryptomycocolacomycetes, Cystobasidiomycetes, Microbotryomycetes, Mixiomycetes and Pucciniomycetes) and 18 orders.

An overview of the higher level classification of Pucciniomycotina based on combined analyses of nuclear large and small subunit rDNA sequences

In this study we provide a phylogenetically based introduction to the classes and orders of Pucciniomycotina (= Urediniomycetes), one of three subphyla of Basidiomycota. More than 8000 species of Pucciniomycotina have been described including putative saprotrophs and parasites of plants, animals and fungi. The overwhelming majority of these (approximately 90%) belong to a single order of obligate plant pathogens, the Pucciniales (= Uredinales), or rust fungi. We have assembled a dataset of previously published and newly generated sequence data from two nuclear rDNA genes (large subunit and small subunit) including exemplars from all known major groups in order to test hypotheses about evolutionary relationships among the Pucciniomycotina. The utility of combining nuc-lsu sequences spanning the entire D1-D3 region with complete nuc-ssu sequences for resolution and support of nodes is discussed. Our study confirms Pucciniomycotina as a monophyletic group of Basidiomycota. In total our results support eight major clades ranked as classes (Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes, Cryptomycocolacomycetes, Cystobasidiomycetes, Microbotryomycetes, Mixiomycetes and Pucciniomycetes) and 18 orders.

Characteristics of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) rRNA genes of Apis mellifera (Insecta: Hymenoptera): structure, organization, and retrotransposable elements.

As an accompanying manuscript to the release of the honey bee genome, we report the entire sequence of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) ribosomal RNA (rRNA)-encoding gene sequences (rDNA) and related internally and externally transcribed spacer regions of Apis mellifera (Insecta: Hymenoptera: Apocrita). Additionally, we predict secondary structures for the mature rRNA molecules based on comparative sequence analyses with other arthropod taxa and reference to recently published crystal structures of the ribosome. In general, the structures of honey bee rRNAs are in agreement with previously predicted rRNA models from other arthropods in core regions of the rRNA, with little additional expansion in non-conserved regions. Our multiple sequence alignments are made available on several public databases and provide a preliminary establishment of a global structural model of all rRNAs from the insects. Additionally, we provide conserved stretches of sequences flanking the rDNA cistrons that comprise the externally transcribed spacer regions (ETS) and part of the intergenic spacer region (IGS), including several repetitive motifs. Finally, we report the occurrence of retrotransposition in the nuclear large subunit rDNA, as R2 elements are present in the usual insertion points found in other arthropods. Interestingly, functional R1 elements usually present in the genomes of insects were not detected in the honey bee rRNA genes. The reverse transcriptase products of the R2 elements are deduced from their putative open reading frames and structurally aligned with those from another hymenopteran insect, the jewel wasp Nasonia (Pteromalidae). Stretches of conserved amino acids shared between Apis and Nasonia are illustrated and serve as potential sites for primer design, as target amplicons within these R2 elements may serve as novel phylogenetic markers for Hymenoptera. Given the impending completion of the sequencing of the Nasonia genome, we expect our report eventually to shed light on the evolution of the hymenopteran genome within higher insects, particularly regarding the relative maintenance of conserved rDNA genes, related variable spacer regions and retrotransposable elements.

Detection of potentially valuable polymorphisms in four group I intron insertion sites at the 3'-end of the LSU rDNA genes in biocontrol isolates of Metarhizium anisopliae

BackgroundThe entomopathogenic anamorphic fungus Metarhizum anisopliae is currently used as a biocontrol agent (BCA) of insects. In the present work, we analyzed the sequence data obtained from group I introns in the large subunit (LSU) of rDNA genes with a view to determining the genetic diversity present in an autochthonous collection of twenty-six M. anisopliae isolates selected as BCAs.ResultsDNA fragments corresponding to the 3'-end of the nuclear LSU rDNA genes of 26 M. anisopliae isolates were amplified by PCR. The amplicon sizes ranged from 0.8 to 3.4-kb. Four intron insertion sites, according to Escherichia coli J01695 numbering, were detected- Ec1921, Ec2066, Ec2449 and Ec2563- after sequencing and analysis of the PCR products. The presence/absence of introns allowed the 26 isolates to be distributed into seven genotypes. Nine of the isolates tested showed no introns, 4 had only one, 3 two, and 10 displayed three introns. The most frequent insertion sites were Ec1921 and Ec2449. Of the 26 isolates, 11 showed insertions at Ec2563 and a 1754-bp sequence was observed in ten of them. The most-parsimonious (MP) tree obtained from parsimony analysis of the introns revealed a main set containing four-groups that corresponded to the four insertion sites.ConclusionFour insertion sites of group I introns in the LSU rDNA genes allowed the establishment of seven genotypes among the twenty-six biocontrol isolates of M. anisopliae. Intron insertions at the Ec2563 site were observed for first time in this species.

Paraphyly of the Pseudophyllidea (Platyhelminthes: Cestoda): Circumscription of monophyletic clades based on phylogenetic analysis of ribosomal RNA

Phylogenetic relationships of cestodes of the order Pseudophyllidea (Platyhelminthes: Cestoda) were examined using sequences of complete small subunit and partial (D1-D3 region) large subunit nuclear rDNA of members of all pseudophyllidean families. The results provide evidence of paraphyly of the order as indicated by previous molecular phylogenetic analyses based on a much lower number of species sequenced. Pseudophyllidean tapeworms represent an artificial assemblage comprising two unrelated clades. “Bothriocephalidea” is formed by four families sensu Bray et al. (1994), namely Bothriocephalidae, Echinophallidae, Philobythiidae and Triaenophoridae, whereas two other families, Diphyllobothriidae and Cephalochlamydidae, give rise to the “Diphyllobothriidea”. The present results indicate that “Bothriocephalidea” forms the most derived clade of all difossate and tetrafossate/bothriate tapeworm lineages which are considered to be basal relative to the rest of tetrafossate/bothridiate and acetabulate cestodes. By contrast, “Diphyllobothriidea”, which includes medically important parasites ( Diphyllobothrium and Spirometra), appeared more basal, without a clearly resolved position within other difossate tapeworm lineages.

Reconstructing the Clavariaceae using nuclear large subunit rDNA sequences and a new genus segregated from Clavaria

Fungi that produce clavarioid fruit bodies have evolved independently many times in the Basidiomycota. The evolutionary significance of this morphology is difficult to interpret because the phylogenetic positions of many clavarioid fungi are still unknown. In this study we examined the phylogenetic diversity of the Clavariaceae sensu lato among Homobasidiomycetidae by adding partial nuclear large subunit ribosomal DNA sequences from clavarioid and corticioid fungi to a large euagaric dataset and analyzing them both together and separately. Our results indicate that the clavarioid morphology has evolved at least five times in the euagarics while the inclusion of type species enabled us to evaluate the taxonomic consequences of this polyphyletic distribution. Although the sampling available at present is incomplete, a qualitative assessment of our phylogenetic hypotheses indicates that the clavarioid habit might not be as evolutionary labile as previously reported. We propose the new genus Alloclavaria to accommodate Clavaria purpurea, which is not related to Clavaria but is derived within the hymenochaetoid clade. The Physalacriaceae and Clavariaceae are redefined to reflect monophyletic groups, and the limits of Clavaria, Clavulinopsis and Ramariopsis should be reconsidered when additional data are available.

Reconstructing the Clavariaceae using nuclear large subunit rDNA sequences and a new genus segregated from Clavaria

Fungi that produce clavarioid fruit bodies have evolved independently many times in the Basidiomycota. The evolutionary significance of this morphology is difficult to interpret because the phylogenetic positions of many clavarioid fungi are still unknown. In this study we examined the phylogenetic diversity of the Clavariaceae sensu lato among Homobasidiomycetidae by adding partial nuclear large subunit ribosomal DNA sequences from clavarioid and corticioid fungi to a large euagaric dataset and analyzing them both together and separately. Our results indicate that the clavarioid morphology has evolved at least five times in the euagarics while the inclusion of type species enabled us to evaluate the taxonomic consequences of this polyphyletic distribution. Although the sampling available at present is incomplete, a qualitative assessment of our phylogenetic hypotheses indicates that the clavarioid habit might not be as evolutionary labile as previously reported. We propose the new genus Alloclavaria to accommodate Clavaria purpurea, which is not related to Clavaria but is derived within the hymenochaetoid clade. The Physalacriaceae and Clavariaceae are redefined to reflect monophyletic groups, and the limits of Clavaria, Clavulinopsis and Ramariopsis should be reconsidered when additional data are available.

Phylogeny and a new species of Sparassis (Polyporales, Basidiomycota): evidence from mitochondrial atp6, nuclear rDNA and rpb2 genes

Three nuclear genes, lsu-rDNA (encoding nuclear large subunit rDNA), ITS (encoding the rDNA internal transcribed spacers and 5.8 S rDNA) and rpb2 (encoding the second largest subunit of RNA polymerase II), and the mitochondrial gene atp6 (encoding the sixth subunit of ATP synthase), were sequenced from all recognized Sparassis lineages. Sparassis latifolia sp. nov. from boreal coniferous forests in China is described based on morphological, ecological, geographical and molecular data. The nuclear gene phylogeny strongly supported groups corresponding to morphological differences, geographic distribution and host shifts among species that produce clamp connections, such as S. crispa from Europe, S. radicata from western North America and S. latifolia from Asia. The atp6 phylogeny however showed no divergence among these three species. For clampless Sparassis species, such as S. spathulata from eastern North America, S. brevipes and a new species from Europe, the atp6 phylogeny was congruent with the nuclear gene phylogeny. Sparassis cystidiosa is basal in the nuclear tree but sister to S. brevipes-S. spathulata clade in the ATP6 tree. The differences between the phylogenetic inferences from the atp6 gene and those from nuclear genes within Sparassis species are discussed.

Phylogeny and a new species of Sparassis (Polyporales, Basidiomycota): evidence from mitochondrial atp6, nuclear rDNA and rpb2 genes

Three nuclear genes, lsu-rDNA (encoding nuclear large subunit rDNA), ITS (encoding the rDNA internal transcribed spacers and 5.8 S rDNA) and rpb2 (encoding the second largest subunit of RNA polymerase II), and the mitochondrial gene atp6 (encoding the sixth subunit of ATP synthase), were sequenced from all recognized Sparassis lineages. Sparassis latifolia sp. nov. from boreal coniferous forests in China is described based on morphological, ecological, geographical and molecular data. The nuclear gene phylogeny strongly supported groups corresponding to morphological differences, geographic distribution and host shifts among species that produce clamp connections, such as S. crispa from Europe, S. radicata from western North America and S. latifolia from Asia. The atp6 phylogeny however showed no divergence among these three species. For clampless Sparassis species, such as S. spathulata from eastern North America, S. brevipes and a new species from Europe, the atp6 phylogeny was congruent with the nuclear gene phylogeny. Sparassis cystidiosa is basal in the nuclear tree but sister to S. brevipes-S. spathulata clade in the ATP6 tree. The differences between the phylogenetic inferences from the atp6 gene and those from nuclear genes within Sparassis species are discussed.

Characterization of North American Armillaria species: genetic relationships determined by ribosomal DNA sequences and AFLP markers

SummaryPhylogenetic and genetic relationships among 10 North American Armillaria species were analysed using sequence data from ribosomal DNA (rDNA), including intergenic spacer (IGS‐1), internal transcribed spacers with associated 5.8S (ITS + 5.8S), and nuclear large subunit rDNA (nLSU), and amplified fragment length polymorphism (AFLP) markers. Based on rDNA sequence data, the nLSU region is less variable among Armillaria species than the ITS + 5.8S and IGS‐1 regions (nLSU < ITS + 5.8S < IGS‐1). Phylogenetic analyses of the rDNA sequences suggested Armillaria mellea, A. tabescens and A. nabsnona are well separated from the remaining Armillaria species (A. ostoyae, A. gemina, A. calvescens, A. sinapina, A. gallica, NABS X and A. cepistipes). Several Armillaria species (A. calvescens, A. sinapina, A. gallica, NABS X and A. cepistipes) clustered together based on rDNA sequencing data. Based on the isolates used in this study, it appears that techniques based on IGS‐1, ITS + 5.8S, and/or D‐domain/3′ ends of nLSU are not reliable for distinguishing A. calvescens, A. sinapina, A. gallica and A. cepistipes. However, AFLP data provided delineation among these species, and AFLP analysis supported taxonomic classification established by conventional methods (morphology and interfertility tests). Our results indicate that AFLP genetic markers offer potential for distinguishing currently recognized North American Biological Species (NABS) of Armillaria in future biological, ecological and taxonomic studies.

Phylogenetic analysis of Tilletia and allied genera in order Tilletiales (Ustilaginomycetes; Exobasidiomycetidae) based on large subunit nuclear rDNA sequences

The order Tilletiales (Ustilaginomycetes, Basidiomycota) includes six genera (Conidiosporomyces, Erratomyces, Ingoldiomyces, Neovossia, Oberwinkleria and Tilletia) and approximately 150 species. All members of Tilletiales infect hosts in the grass family Poaceae with the exception of Erratomyces spp., which occur on hosts in the Fabaceae. Morphological features including teliospore ornamentation, number and nuclear condition of primary basidiospores and ability of primary basidiospores to conjugate and form an infective dikaryon were studied in conjunction with sequence analysis of the large subunit nuclear rDNA gene (nLSU). Analysis based on nLSU data shows that taxa infecting hosts in the grass subfamily Pooideae form one well supported lineage. This lineage comprises most of the reticulate-spored species that germinate to form a small number of rapidly conjugating basidiospores and includes the type species Tilletia tritici. Two tuberculate-spored species with a large number of nonconjugating basidiospores, T. indica and T. walkeri, and Ingoldiomyces hyalosporus are also included in this lineage. Most of the species included in the analysis with echinulate, verrucose or tuberculate teliospores that germinate to form a large number (>30) of nonconjugating basidiospores infect hosts in the subfamilies Panicoideae, Chloridoideae, Arundinoideae and Ehrhartoideae. This group of species is more diverse than the pooid-infecting taxa and in general do not form well supported clades corresponding to host subfamily. The results of this work suggest that morphological characters used to segregate Neovossia, Conidiosporomyces and Ingoldiomyces from Tilletia are not useful generic level characters and that all included species can be accommodated in the genus Tilletia.

RAPD and large subunit nuclear rDNA sequence analyses of the entomogenous fungus Aschersonia

AbstractEleven isolates within four species of the entomogenous fungus Aschersonia from China, the USA, Japan, the Philippines, Malaysia and Columbia were characterized using 17 RAPD primers. Genetic diversity among these strains of Aschersonia was found. The clustering results showed that the genetic variability among interspecies was more than that among intraspecies of Aschersonia. In the constructed phylogenetic tree, these isolates were not clustered according to their geographic origins or hosts. Furthermore, sequences of the divergent domain at the 5′-end of the large subunit (LSU) in nuclear rRNA from the mitosporic entomogenous fungi were employed to analyse the phylogenetic relationships of 11 Aschersonia isolates. The relationships of interspecies or intraspecies shown in the phylogenetic tree were almost consistent with the results of the morphological study. Different species isolated from different geographic origins could be clearly distinguished in the tree. But there were no close relationships among species isolated from the same family or order of insect hosts. The tree indicated that isolate Aa, belonging to A. aleyrodis, was the same as Aa992 and Aa3.4485. Moreover, results of RAPD analyses were consistent with those of LSU nuclear rDNA analysis for the same isolates tested, which consequently indicates that both methods can be independently applied for classification and identification of Aschersonia.

Phylogenetic analysis of Tilletia and allied genera in order Tilletiales (Ustilaginomycetes; Exobasidiomycetidae) based on large subunit nuclear rDNA sequences

The order Tilletiales (Ustilaginomycetes, Basidiomycota) includes six genera (Conidiosporomyces, Erratomyces, Ingoldiomyces, Neovossia, Oberwinkleria and Tilletia) and approximately 150 species. All members of Tilletiales infect hosts in the grass family Poaceae with the exception of Erratomyces spp., which occur on hosts in the Fabaceae. Morphological features including teliospore ornamentation, number and nuclear condition of primary basidiospores and ability of primary basidiospores to conjugate and form an infective dikaryon were studied in conjunction with sequence analysis of the large subunit nuclear rDNA gene (nLSU). Analysis based on nLSU data shows that taxa infecting hosts in the grass subfamily Pooideae form one well supported lineage. This lineage comprises most of the reticulate-spored species that germinate to form a small number of rapidly conjugating basidiospores and includes the type species Tilletia tritici. Two tuberculate-spored species with a large number of nonconjugating basidiospores, T. indica and T. walkeri, and Ingoldiomyces hyalosporus are also included in this lineage. Most of the species included in the analysis with echinulate, verrucose or tuberculate teliospores that germinate to form a large number (>30) of nonconjugating basidiospores infect hosts in the subfamilies Panicoideae, Chloridoideae, Arundinoideae and Ehrhartoideae. This group of species is more diverse than the pooid-infecting taxa and in general do not form well supported clades corresponding to host subfamily. The results of this work suggest that morphological characters used to segregate Neovossia, Conidiosporomyces and Ingoldiomyces from Tilletia are not useful generic level characters and that all included species can be accommodated in the genus Tilletia.

The phylogenetic distribution of resupinate forms across the major clades of mushroom‐forming fungi (Homobasidiomycetes)

Phylogenetic relationships of resupinate Homobasidiomycetes (Corticiaceae s. lat. and others) were studied using ribosomal DNA (rDNA) sequences from a broad sample of resupinate and nonresupinate taxa. Two datasets were analysed using parsimony, a ‘core’ dataset of 142 species, each of which is represented by four rDNA regions (mitochondrial and nuclear large and small subunits), and a ‘full’ dataset of 656 species, most of which were represented only by nuclear large subunit rDNA sequences. Both datasets were analysed using traditional heuristic methods with bootstrapping, and the full dataset was also analysed with the Parsimony Ratchet, using equal character weights and six‐parameter weighted parsimony. Analyses of both datasets supported monophyly of the eight major clades of Homobasidiomycetes recognised by Hibbett and Thorn, as well as independent lineages corresponding to the Gloeophyllum clade, corticioid clade and Jaapia argillacea. Analyses of the full dataset resolved two additional groups, the athelioid clade and trechisporoid clade (the latter may be nested in the polyporoid clade). Thus, there are at least 12 independent clades of Homobasidiomycetes. Higher‐level relationships among the major clades are not resolved with confidence. Nevertheless, the euagarics clade, bolete clade, athelioid clade and Jaapia argillacea are consistently resolved as a monophyletic group, whereas the cantharelloid clade, gomphoid‐phalloid clade and hymenochaetoid clade are placed at the base of the Homobasidiomycetes, which is consistent with the preponderance of imperforate parenthesomes in those groups. Resupinate forms occur in each of the major clades of Homobasidiomycetes, some of which are composed mostly or exclusively of resupinate forms (athelioid clade, corticioid clade, trechisporoid clade, Jaapia). The largest concentrations of resupinate forms occur in the polyporoid clade, russuloid clade and hymenochaetoid clade. The cantharelloid clade also includes many resupinate forms, including some that have traditionally been regarded as heterobasidiomycetes (Sebacinaceae, Tulasnellales, Ceratobasidiales). The euagarics clade, which is by far the largest clade in the Homobasidiomycetes, has the smallest fraction of resupinate species. Results of the present study are compared with recent phylogenetic analyses, and a table summarising the phylogenetic distribution of resupinate taxa is presented, as well as notes on the ecology of resupinate forms and related Homobasidiomycetes.

The Crepidotaceae (Basidiomycota, Agaricales): phylogeny and taxonomy of the genera and revision of the family based on molecular evidence

Advances in phylogenetic systematics have clarified the position of most major homobasidiomycete lineages. In contrast, the status of the Crepidotaceae, a historically controversial family of dark-spored agarics, remains unaddressed. In this paper, current morphology-based classifications of the agaric genera of the Crepidotaceae were evaluated by parsimony and constraint analyses of sequence data from the nuclear large subunit rDNA. Taxa analyzed included the type species for each agaric genus allied in the family by Singer: Crepidotus, Simocybe, Pleurotellus, Tubaria, and Melanomphalia. Contrary to traditional classifications, results suggest that the crepidotoid fungi have three separate origins within the euagarics. The Crepidotaceae sensu stricto (s.s.) includes Crepidotus and Simocybe and represents a separate lineage of dark-spored euagarics. Pleurotellus is congeneric with Crepidotus. Results indicate the exclusion of both Tubaria and Melanomphalia from the Crepidotaceae s.s. Tubaria is allied with the strophariaceous taxa Phaeomarasmius and Flammulaster, while Melanomphalia has arisen from within a lineage of light-spored omphalinoid euagarics representing an independent acquisition of basidiospore pigmentation. Other pleisiomorphic and newly uncovered synapomorphic characters are discussed in detail along with the taxonomic status of each genus, and a revised family description is provided.