Obligatory group I introns with unusual features at positions 1949 and 2449 in nuclear LSU rDNA of Didymiaceae myxomycetes

Myxomycetes (plasmodial slime molds) belonging to the order Physarales contain obligatory group I introns at positions 1949 and 2449 in their large subunit ribosomal RNA gene. Here, we report 36 group I introns from the Didymiaceae family (order Physarales) from 18 isolates representing three genera and seven species, and have reconstructed both host and intron phylogenies. The introns, named L1949 and L2449, were found in all isolates analyzed, consistent with an obligatory distribution in Didymiaceae. The introns fold at the RNA-level into typical group I ribozyme core structures that are relatively conserved, but contain large and highly variable extension sequences in peripheral domains without any detectable protein coding capacities. Furthermore, the L1949 and L2449 introns have probably become dependent on host factors for folding or activity. This assumption is based on that all introns tested for self-splicing in vitro failed to ligate the flanking exon regions. Phylogenies based on LSU rDNA and intron sequences are consistent with that the L1949 and L2449 introns follow a strict vertical inheritance within Didymiaceae. We suggest that the Didymiaceae L1949 and L2449 introns are well suited as high-resolution markers in genetic assessments at various taxonomic levels, from closely related strains of a single species to separating genera.     

The molecular evolution and structural organization of group I introns at position 1389 in nuclear small subunit rDNA of myxomycetes

The number of nuclear group I introns from myxomycetes is rapidly increasing in GenBank as more rDNA sequences from these organisms are being sequenced. They represent an interesting and complex group of intervening sequences because several introns are mobile (or inferred to be mobile) and many contain large and unusual insertions in peripheral loops. Here we describe related group I introns at position 1389 in the small subunit rDNA of representatives from the myxomycete family Didymiaceae. Phylogenetic analyses support a common origin and mainly vertical inheritance of the intron. All S1389 introns from the Didymiaceae belong to the IC1 subclass of nuclear group I introns. The central catalytic core region of about 100 nt appears divergent in sequence composition even though the introns reside in closely related species. Furthermore, unlike the majority of group I introns from myxomycetes the S1389 introns do not self-splice as naked RNA in vitro under standard conditions, consistent with a dependence on host factors for folding or activity. Finally, the myxomycete S1389 introns are exclusively found within the family Didymiaceae, which suggests that this group I intron was acquired after the split between the families Didymiaceae and Physaraceae.     

In search of monophyletic taxa in the family Desmidiaceae (Zygnematophyceae, Viridiplantae): the genus Cosmarium

Nuclear-encoded small subunit (SSU) rDNA, 1506 group I introns, and chloroplast rbcL genes were sequenced from 97 strains representing the largest desmid genus Cosmarium (45 spp.), its putative relatives Actinotaenium (5 spp.), Xanthidium (4 spp.), Euastrum (9 spp.), Staurodesmus (13 spp.), and other Desmidiaceae (Zygnematophyceae, Streptophyta) and used to assess phylogenetic relationships in the family. Analyses of single genes and of a concatenated data set (3260 nt) established 10 well-supported clades in the family with Cosmarium species distributed in six clades and one nonsupported assemblage. Most of the clades contained representatives of at least two genera highlighting the polyphyletic nature of the genera Cosmarium, Euastrum, Staurodesmus, and Actinotaenium. To enhance resolution between clades, we extended the data set by sequencing the slowly evolving chloroplast-encoded large subunit (LSU) rRNA gene from 40 taxa. Phylogenetic analyses of a concatenated data set (5509 nt) suggested a sister relationship between two clades that consisted mainly of Cosmarium species and included C. undulatum, the type species of the genus. We describe molecular signatures in the SSU rRNA for two clades and conclude that more studies involving new isolates, additional molecular markers, and reanalyses of morphological traits are necessary before the taxonomic revision of the genus Cosmarium can be attempted.     

18S rDNA phylogeny of lamproderma and allied genera (Stemonitales, Myxomycetes, Amoebozoa)

The phylogenetic position of the slime-mould genus Lamproderma (Myxomycetes, Amoebozoa) challenges traditional taxonomy: although it displays the typical characters of the order Stemonitales, it appears to be sister to Physarales. This study provides a small subunit (18S or SSU) ribosomal RNA gene-based phylogeny of Lamproderma and its allies, with new sequences from 49 specimens in 12 genera. We found that the order Stemonitales and Lamproderma were both ancestral to Physarales and that Lamproderma constitutes several clades intermingled with species of Diacheopsis, Colloderma and Elaeomyxa. We suggest that these genera may have evolved from Lamproderma by multiple losses of fruiting body stalks and that many taxonomic revisions are needed. We found such high genetic diversity within three Lamproderma species that they probably consist of clusters of sibling species. We discuss the contrasts between genetic and morphological divergence and implications for the morphospecies concept, highlighting the phylogenetically most reliable morphological characters and pointing to others that have been overestimated. In addition, we showed that the first part (~600 bases) of the SSU rDNA gene is a valuable tool for phylogeny in Myxomycetes, since it displayed sufficient variability to distinguish closely related taxa and never failed to cluster together specimens considered of the same species.     

Molecular taxonomy of Camellia (Theaceae) inferred from nrITS sequences

Camellia, comprising more than 200 species, is the type genus of the family Theaceae. Currently, the interspecies relationship of the economically important genus is still a matter of great debate and controversy. In an attempt to help settle this dispute using molecular phylogeny, we analyzed ITS sequences of 112 species of Camellia. The maximum parsimony and Bayesian trees grouped these species into eight major clades and four isolates. The current study supported the monophyly of sections Thea and Furfuracea, a merged section of Theopsis and Eriandra and the formation of section Oleifera by H, -t. Chang (Flora of Reipulicae Popularis Sinicae. Tomus 49 (3), Science Press, China). The study suggested the polyphyletic nature of the sections Camellia, Paracamellia, Pseudocamellia, and Tuberculata and the paraphyletic nature of the section Chrysantha but did not support the sectional status of the three small sections, Archecamellia, Piquetia, and Sterocarpus. We also discuss the results in terms of morphology, geographic distribution and the results from an earlier molecular phylogeny analysis.     

Molecular phylogeny and morphological evolution of the Acantharia (Radiolaria)

Acantharia are ubiquitous and abundant rhizarian protists in the world ocean. The skeleton made of strontium sulphate and the fact that certain harbour microalgal endosymbionts make them key planktonic players for the ecology of marine ecosystems. Based on morphological criteria, the current taxonomy of Acantharia was established by W.T. Schewiakoff in 1926, since when no major revision has been undertaken. Here, we established the first comprehensive molecular phylogeny from single morphologically-identified acantharian cells, isolated from various oceans. Our phylogenetic analyses based on 78 18S rDNA and 107 partial 28S rDNA revealed the existence of 6 main clades, sub-divided into 13 sub-clades. The polyphyletic nature of acantharian families and genera demonstrates the need for revision of the current taxonomy. This molecular phylogeny, which highlights the taxonomic relevance of specific morphological criteria, such as the presence of a shell and the organisation of the central junction, provides a robust phylogenetic framework for future taxonomic emendation. Finally, mapping all the existing environmental sequences available to date from different marine ecosystems onto our reference phylogeny unveiled another 3 clades and improved the understanding of the biogeography and ecology of Acantharia.     

Evolution of dark-spored Myxomycetes (slime-molds): molecules versus morphology

The Myxomycetes are a major component of soil amoebae, displaying a complex life cycle that terminates in the formation of often macroscopic fruiting bodies. The classification of Myxomycetes is controversial and strongly depends on the weight given by different authors to morphological and developmental characters. We used a molecular approach to establish the phylogenetic relationships in the dark-spored orders Stemonitales and Physarales. Twenty-five small subunit ribosomal RNA gene sequences were obtained, with focus on two Stemonitales genera, Lamproderma and Comatricha. Unexpectedly, our results show that Stemonitales are paraphyletic with Physarales arising from within a Lamproderma clade. The genus Lamproderma itself is polyphyletic and can be divided into two distinct clades. Additionally, we found that Comatricha nigricapillitia comprises two cryptic species, both related to Enerthenema. Our study allows the reappraisal of morphological and developmental characters in the light of molecular data and sets foundations for a new classification of Myxomycetes.     

Phylogeny of the fish leeches (Oligochaeta, Hirudinida, Piscicolidae) based on nuclear and mitochondrial genes and morphology

The phylogeny of the Piscicolidae was analysed from combined 18S rDNA, cytochrome c oxidase subunit I (CO-I), nicotinamide adenine dinucleotide dehydrogenase subunit I (ND-I) and morphological data using parsimony. A worldwide distribution of Piscicolidae was represented for the first time. While the family Piscicolidae was supported as a monophyletic group, the traditional subfamilies based on morphology were not supported. The Platybdellinae was polyphyletic and formed four distinct clades, and Bathybdella sawyeri did not group with any other platybdellins. The Piscicolinae was also polyphyletic, also forming four distinct clades. The pontobdellin genus Stibarobdella was shown to be the basal taxon within the Piscicolidae; however, the Pontobdellinae was found to be paraphyletic if Oxytonostoma was included. The genera Aestabdella , Austrobdella, and Malmiana were found to be paraphyletic; the genera Calliobdella, Cystobranchus, and Platybdella were found to be polyphyletic. The species Myzobdella lugubris was not found to be monophyletic. It is proposed that Oxytonostoma be transferred out of the Pontobdellinae, that Aestabdella be synonymized with Pterobdella , that Calliobdella vivida be returned to Cystobranchus , that Gonimosobdella be synonymized with Cystobranchus , and that Piscicolaria be synonymized with Myzobdella . The synonymy of Malmiana and Heptacyclus is confirmed, with Heptacyclus having priority. Piscicola milneri is confirmed to be a separate species from Piscicola geometra .     

Molecular phylogeny of the Blastocladiomycota (Fungi) based on nuclear ribosomal DNA

The Blastocladiomycota is a recently described phylum of ecologically diverse zoosporic fungi whose species have not been thoroughly sampled and placed within a molecular phylogeny. In this study, we investigated the phylogeny of the Blastocladiomycota based on ribosomal DNA sequences from strains identified by traditional morphological and ultrastructural characters. Our results support the monophyly of the Coelomomycetaceae and Physodermataceae but the Blastocladiaceae and Catenariaceae are paraphyletic or polyphyletic. The data support two clades within Allomyces with strains identified as Allomyces arbusculus in both clades, suggesting that species concepts in Allomyces are in need of revision. A clade of Catenaria species isolated from midge larvae group separately from other Catenaria species, suggesting that this genus may need revision. In the Physodermataceae, Urophlyctis species cluster with a clade of Physoderma species. The algal parasite Paraphysoderma sedebokerensis nom. prov. clusters sister to other taxa in the Physodermataceae. Catenomyces persicinus, which has been classified in the Catenariaceae, groups with the Chytridiomycota rather than Blastocladiomycota. The rDNA operon seems to be suitable for classification within the Blastocladiomycota and distinguishes among genera; however, this region alone is not suitable to determine the position of the Blastocladiomycota among other basal fungal phyla with statistical support. A focused effort to find and isolate, or directly amplify DNA from additional taxa will be necessary to evaluate diversity in this phylum. We provide this rDNA phylogeny as a preliminary framework to guide further taxon and gene sampling and to facilitate future ecological, morphological, and systematic studies.     

Molecular Phylogeny of Microsporidians with Particular Reference to Species that Infect the Muscles of Fish

Ribosomal DNA from eight species of microsporidians infecting fish have been sequenced. Seven of these species infect the skeletal muscle of fish ( Pleistophora spp.) and one species infects migratory mesenchyma cells ( Glugea anomala ). These sequences, in addition to other available microsporidian rDNA sequences from a broad range of host taxa, have been used in phylogenetic analysis. This analysis revealed that muscle-infecting microsporidians from fish are a polyphyletic group, indicating that characters supposed to be important in the classification of the genus Pleistophora have to be re-evaluated. One character that probably has a polyphyletic origin is the amorphous coat, which has been extensively used in the definition of this genus. Furthermore, our results showed that the insect parasitizing Pleistophora spp. are not related to the true pleistophorans parasitic in skeletal muscle of fish. Phylogenetic analysis of small subunit rDNA sequences revealed disagreements between the molecular phylogeny and classifications based upon ultrastruclure. Many of the morphological characters claimed to be important in microsporidian classifications appeared to have arisen several times during evolution: for example, the diplokaryon and sporophorous vesicles.     

PRELIMINARY INVESTIGATION OF THE DOUBLE-DIFFUSION TECHNIQUE AS A TOOL IN DETERMINING RELATIONSHIPS AMONG SOME MYXOMYCETES,ORDER PHYSARALES

Double-diffusion technique was used to investigate myxomycete relationships within the order Physarales. Extracts of plasmodia of 22 slime mold isolates were reacted with five antisera produced to Plasmodia of Didymium nigripes, Physarella oblonga, Physarum polycephalum, Physarum gyrosum and Fuligo septica. Two isolates of Fuligo septica tested alike. Four isolates of Physarum pusillum did not test alike, and no valid conclusion of the relationship of this species was possible. These isolates showed strong serological affinity: (1) Physarum gyrosum, Physarella oblonga, two isolates of Fuligo septica, and possibly two isolates of Physarum pusillum, and Physarum tenerum; (2) Physarum polycephalum and Physarum flavicomum; (3) Fuligo septica and many of the species tested; (4) Didymium nigripes and at least one isolate of Didymium iridis. In most cases serologial relationships among species tested did not coincide with current taxonomy based on morphology of fructification.     

Molecular evidence that Langeronia macrocirra and Langeronia cf. parva (Trematoda: Pleurogenidae) parasites of anurans from Mexico are conspecific

The genus Langeronia parasitizing the intestine of several species of anurans is distributed from North to Central America. We identified Langeronia macrocirra and Langeronia cf. parva from the same host and localities, and present here new data not applicable about their tegumental surface by scanning electron microscopy. We compared sequences of the rDNA ITS2 region and mtDNA cox1 gene for the two morphotypes. ITS2 exhibited a high degree of conservation. Phylogenetic reconstruction using cox1 revealed three clades (I, II, and III), which did not correspond to a previous identification or host. Little divergence was found within clades: sequences were identical in clade I, whereas clade II had 0.27% and clade III had 1.08%. Inter-clade divergence reached 8.69% (I vs. III). This pattern of genetic divergence indicated that both taxa probably belong to the same species, so we posit that the morphological changes could be correlated with development. Increasing sample size and geographical coverage will contribute to the taxonomy of the genus based on morphological and molecular evidence, and will open tracks toward the use of DNA barcodes to the genus in Mexico.     

Phylogeny of the genus Aleochara inferred from mitochondrial cytochrome oxidase sequences (Coleoptera: Staphylinidae)

The phylogeny of the genus Aleochara was previously poorly understood due to difficulties with phylogenetic reconstruction by morphological characters. We present here a phylogeny based on the sequences of a 2022-bp fragment of the COI/II genes; 50 Aleochara and 10 outgroup species were included in the analysis. We used parsimony, minimum-evolution, and maximum-likelihood analyses to infer the phylogeny of the group. Our data do not support the commonly assumed sister group relationship between Aleocharini and Hoplandriini. Aleochara is resolved as a monophylum, although A. clavicornis might not belong to the genus. Within Aleochara, there are two large monophyletic clades. Many of the existing subgenera are shown to be para- or polyphyletic; others are likely to be monophyletic. Tinotus morion, previously assigned to the Hoplandriini, is strongly supported as belonging to Aleochara. According to our data, the mesosternal carina that has been used as an important character for classification has arisen and been reduced independently in several clades within Aleochara.     

基于16S rDNA和28S rDNA D2基因序列与形态特征联合分析的中国角顶叶蝉亚科系统发育研究（半翅目： 叶蝉科）

首次在国内利用28S rDNA D2区段和16S rDNA基因序列,结合50个形态特征对角顶叶蝉亚科(Deltocephalinae)［半翅目（Hemiptera）: 叶蝉科（Cicadellidae）］19个属进行系统发育分析研究。从无水乙醇浸泡保存的标本中提取基因组DNA并扩增了19个内群和1种外群Typhlocybinae［半翅目(Hemiptera): 叶蝉科(Cicadellidae)］种类的28S rDNA D2基因片段并测序,同时扩增了16S rDNA基因片段并测序11条,采用了GenBank中1个种类的16S rDNA同源序列。采用PAUP*4.0和MrBayes3.0两个分析软件和3种建树方法,利用同源28S D2 rDNA和16S rDNA两个基因序列与形态特征结合进行系统发育分析研究。分析结果表明,二叉叶蝉族Macrostelini是一个单系,并在角顶叶蝉亚科的系统发育中处于基部的位置,是内群中最原始的族;角顶叶蝉族Deltocephalini中除了纹翅叶蝉属Nakaharanus,其余各属构成单系;殃叶蝉族Euscelini内属的归属比较混乱,可能是一个并系群,属间差异有待进一步研究。隆额叶蝉族Paralimnini与顶带叶蝉族Athysanini是姐妹群。带叶蝉属Scaphoideus与纹翅叶蝉属Nakaharanus是姐妹群,二者与木叶蝉属Phlogotettix的关系最近,三者构成一个单系,建议将三者归为带叶蝉族Scaphoideini。研究结果还表明,小眼叶蝉族Xestocephalini和Balcluthini的系统发育位置不明,有待进一步研究。     

Toward a better understanding of the infrageneric relationships in Cortinarius (Agaricales, Basidiomycota)

Research on the molecular systematics of Cortinarius, a species-rich mushroom genus with nearly global distribution, is just beginning. The present study explores infrageneric relationships using rDNA ITS and LSU sequence data. One large dataset of 132 rDNA ITS sequences and one combined da-taset with 54 rDNA ITS and LSU sequences were generated. Hebeloma was used as outgroup. Bayesian analyses and maximum-likelihood (ML) analyses were carried out. Bayesian phylogenetic inference performed equally well or better than ML, especially in large datasets. The phylogenetic analysis of the combined dataset with species representing all currently recognized subgenera recovered seven well-supported clades (Bayesian posterior probabilities BPP > 90%). These major clades are: /Myxacium s.l., /subg. Cortinarius, the /phlegmacioid clade (including the subclades /Phlegmacium and /Delibuti), the /calochroid clade (/Calochroi, /Ochroleuci and /Allutus), the /telamonioid clade (/Telamonia, /Orellani, /Anomali), /Dermocybe s.l. and /Myxotelamonia. Our results show that Cortinarius consists of many lineages, but the relationships among these clades could not be elucidated. On one hand, the low divergence in rDNA sequences can be held responsible for this; on the other hand, taxon sampling is problematic in Cortinarius phylogeny. Because of the incredibly high diversity (~2000 Cortinarius species), our sampling included <5% of the known species. By choosing type species of subgenera and sections, our sampling is strongly biased toward Northern Hemisphere taxa. More extensive taxon sampling, especially of species from the Southern Hemisphere, is essential to resolve the phylogeny of this important genus of ectomycorrhizal fungi.     

THE PHYLOGENY OF CAULERPA BASED ON RDNA INTERNAL TRANSCRIBED SPACER SEQUENCES

Phylogenetic hypotheses for the pantropical marine green algal genus, Caulerpa , were inferred based on analyses of nuclear-encoded rDNA internal transcribed spacer (ITS) sequences. Results of these analyses were used to assess the correspondence between rDNA phylogeny and traditional sectional taxonomy, to identify synapomorphic morphological characters (including assimilator morphology and chloroplast ultrastructure), and to examine marine biogeographic hypotheses for the genus. Ribosomal DNA ITS sequences were aligned for thirty-three species and intraspecific taxa of Caulerpa. Results indicate limited correspondence between phylogeny and sectional taxonomy for the genus, (e.g., the sections Filicoideae and Sedoideae were not monophyletic). In contrast, chloroplast morphology could be mapped to the tree topology with limited homoplasy. Pantropical isolates of the filicoidean species, Caulerpa sertularioides and Caulerpa mexicana each formed monophyletic groups. Caulerpa reyesii was included as a derived taxon within the Caulerpa taxifolia clade, suggesting that these species were conspecific and affirmed the lack of correspondence between phylogeny and assimilator morphology. Isolates and various intraspecific taxa of Caulerpa racemosa did not form a monophyletic group. Instead, these taxa formed a heterogeneous assemblage with other sedoidean and filicoidean taxa. Within the C. sertularioides clade, Caribbean and Atlantic isolates formed a basal paraphyletic group, whereas eastern and western Pacific isolates formed a more derived monophyletic group. Therefore, these results are not consistent with an Indo-West Pacific origin of this species.     

Rapid PCR-based method for detection and differentiation of Didymiaceae and Physaraceae (myxomycetes) in environmental samples

Ecological studies of myxomycetes have been limited by the absence of universal cultivation techniques and the lack of life stage independent identification methods. We designed a novel PCR primer pair for the specific amplification of small subunit ribosomal RNA gene of Didymiaceae and Physaraceae. The primers produced amplicons from 192 fruiting body samples belonging to 10 genera. Twenty-four samples yielded longer fragments and sequence analysis revealed the presence of intron(s). As for the exonic regions, while sequence heterogeneities within a single species/varietas/forma were frequently observed, identical sequences were obtained only from identical species/varietas. The effectiveness of this primer pair in the analysis of morphologically unidentifiable samples was confirmed with the applications to samples of environmental plasmodium/sclerotium and soil. Denaturing gradient gel electrophoresis analysis was also tested with the soil samples. The results presented here demonstrate this PCR-based method can facilitate further ecological studies of Physaraceae and Didymiaceae in the environment.     

Molecular phylogeny of diploid Hordeum species and incongruence between chloroplast and nuclear datasets

The phylogeny of diploid Hordeum species has been studied using both chloroplast and nuclear gene sequences. However, the studies of different nuclear datasets of Hordeum species often arrived at similar conclusions, whereas the studies of different chloroplast DNA data generally resulted in inconsistent conclusions. Although the monophyly of the genus is well supported by both morphological and molecular data, the intrageneric phylogeny is still a matter of controversy. To better understand the evolutionary history of Hordeum species, two chloroplast gene loci (trnD-trnT intergenic spacer and rps16 gene) and one nuclear marker (thioreoxin-like gene (HTL)) were used to explore the phylogeny of Hordeum species. Two obviously different types of trnD-trnT sequences were observed, with an approximately 210 base pair difference between these two types: one for American species, another for Eurasian species. The trnD-trnT data generally separated the diploid Hordeum species into Eurasian and American clades, with the exception of Hordeum marinum subsp. gussoneanum. The rps16 data also grouped most American species together and suggested that Hordeum flexuosum has a different plastid type from the remaining American species. The nuclear gene HTL data clearly divided Hordeum species into two clades: the Xu+H genome clade and the Xa+I genome clade. Within clades, H genome species were well separated from the Xu species, and the I genome species were well separated from the Xa genome species. The incongruence between chloroplast and nuclear datasets was found and discussed.     

Molecular phylogeny of Zygomycota based on EF-1alpha and RPB1 sequences: limitations and utility of alternative markers to rDNA

Earlier molecular phylogenetic analyses based on nuclear small subunit ribosomal DNA (nSSU rDNA) suggest that the Zygomycota are polyphyletic within the Chytridiomycota. However, these analyses failed to resolve almost all interordinal relationships among basal fungi (Chytridiomycota and Zygomycota), due to lack of sufficient characters within the nSSU rDNA. To further elucidate the higher-level phylogeny of Zygomycota, we have sequenced partial RPB1 (DNA dependent RNA polymerase II largest subunit) and EF-1alpha (translation elongation factor 1 alpha) genes from 10 and 3 zygomycete fungi, respectively. Independent molecular phylogenetic analyses were performed based on each sequence by distance and maximum likelihood methods. Although deep phylogenetic relationships among basal fungi still remain poorly resolved using either gene, the RPB1-based phylogeny identified a novel monophyletic clade consisting of the Dimargaritales, Harpellales, and Kickxellales. This result suggests that regularly formed septa (cross walls that divide hyphae into segments) with a lenticular cavity are plesiomorphic for this clade, and indicates the importance of septal pore ultrastructure in zygomycete phylogeny. In addition, a peculiar mucoralean genus Mortierella, which was considered to be distantly related to the other Mucorales based on previous nSSU rDNA analyses, was resolved as the basal most divergence within the Mucorales, consistent with traditional phenotypic-based taxonomy. Although the taxa included in our analysis are restricted, the monophyly of each order suggested by nSSU rDNA phylogeny is supported by the present RPB1-based analysis. These results support the potential use of RPB1 as an alternative marker for fungal phylogenetic studies. Conversely, the overall fungal phylogeny based on EF-1alpha sequence is poorly resolved. A comparison of numbers of observed substitutions versus inferred substitutions within EF-1alpha indicates that this gene is much more saturated than RPB1. This result suggests that the EF-1alpha gene is unsuitable for resolving higher-level phylogenetic relationships within the Fungi.     

Phylogeny of the Pluteaceae (Agaricales, Basidiomycota): taxonomy and character evolution

The phylogeny of the genera traditionally classified in the family Pluteaceae (Agaricales, Basidiomycota) was investigated using molecular data from nuclear ribosomal genes (nSSU, ITS, nLSU) and consequences for taxonomy and character evolution were evaluated. The genus Volvariella is polyphyletic, as most of its representatives fall outside the Pluteoid clade and shows affinities to some hygrophoroid genera (Camarophyllus, Cantharocybe). Volvariella gloiocephala and allies are placed in a different clade, which represents the sister group of Pluteus, and a new generic name, Volvopluteus, is proposed to accommodate these taxa. Characters such as basidiospore size and pileipellis structure can be used to separate Pluteus, Volvariella and Volvopluteus. The genus Pluteus is monophyletic and includes species with partial veil traditionally classified in the genus Chamaeota. The evolution of morphological features used in the infrageneric taxonomy of the genus, such as metuloid cystidia and pileipellis structure, was analyzed. Agreement between the molecular phylogeny and morphological subdivision of Pluteus is, generally speaking, good, though some rearrangements are necessary: (i) species with non-metuloid pleurocystidia and pileipellis as a cutis are placed either in sect. Celluloderma, together with the species characterized by a hymenidermal pipeipellis, or in sect. Pluteus, with the metuloid bearing species; (ii) subdivision of sect. Celluloderma according to the presence/absence of cystidioid elements in the pileipellis is not supported by molecular data.