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Mycology and Plant Pathology |
2USDA-ARS, Systematic Botany and Mycology Lab, Beltsville, Maryland 20705 USA; 4Duke University, Department of Biology, Durham, North Carolina 27708 USA; 5Virginia Polytechnic Institute and State University, Department of Biology, Blacksburg, Virginia 24061 USA
Received for publication March 18, 2004. Accepted for publication September 21, 2004.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Key Words: Agaricales • Crepidotus • Melanomphalia • molecular phylogeny • mushroom systematics • Pleurotellus • Simocybe • Tubaria
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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with several notable exceptions, now known as the euagarics (Hibbett et al., 1997
; Moncalvo et al., 2000
; Moncalvo et al., 2002
).
Phylogenetic systematics of select euagaric lineages has been the subject of many recent studies (e.g., Liu et al., 1997
; Johnson and Vilgalys, 1998
; Drehmel et al., 1999
; Hopple and Vilgalys, 1999
). Comprehensive molecular analyses of the euagarics as a whole was first undertaken by Moncalvo et al. (2000)
, providing a phylogenetic framework for examining evolutionary lineages in the agaric fungi. Their analysis included representative taxa from all of Singer's (1986)
families with the exception of the Gomphidiaceae Maire ex Jülich and the Crepidotaceae (Imai) Singer. Phylogenetic study of the Gomphidiaceae has since been undertaken (Miller and Aime, 2001
; Miller et al., 2002
) although these fungi are now considered to be gilled members of the suilloid (Boletales) lineage and not true agarics. The present study provides the first such analysis to focus on the agaricoid genera of the Crepidotaceae.
The earliest classification for the crepidoti was by Imai (1938)
, who erected the monogeneric tribe Crepidoteae to accommodate those species of agarics with eccentric, lateral, or absent stipes, subdecurrent lamellae, and ocherous or ferruginous spores. In the ensuing years, nine genera gradually came to be included in the Crepidotaceae (Singer, 1951a
, 1962
, 1971
, 1973
). The last edition of The Agaricales in Modern Taxonomy (Singer, 1986
) lists the agaricoid (mushroom-forming) genera Tubaria (W.G. Sm.) Gillet, Melanomphalia M.P. Christ., Simocybe Karst., Crepidotus (Fr.) Staude, and Pleurotellus Fayod, as well as four cyphelloid (without gills) genera, Episphaeria Donk apud Sing. ex Donk, Phaeosolenia Speg., Pellidiscus Donk, and Chromocyphella de Toni and Levi, as the members of this family. No modern systematic treatments of the family have been published as a whole since the works of Singer.
Members of the family as circumscribed by Singer have little or no known economic importance, occur worldwide in a variety of habitats, and are phenotypically diverse. Singer's (1986)
definition of the Crepidotaceae includes a heterogeneous group of genera with pip-shaped, ellipsoid, or globose basidiospores usually without a germ pore, and with pale yellow to dark-brown spore prints. The inamyloid spores may be either smooth walled or ornamented. Hyphae may or may not form clamp connections; cheilocystidia are nearly always present, but pleurocystidia are rare. Species may be pleurotoid, collybioid, omphalinoid, or cyphelloid in habit and are secondary decomposers found on various types of organic debris and wood. Development is not known for all species but is believed to be gymnocarpic or hemiangiocarpic. As a family, these fungi were believed by Singer (1986)
to be related to the Cortinariaceae R. Heim ex Pouzar, Entolomataceae Kotl. and Pouzar, and Paxillaceae R. Maire apud Maire, Dumée and Lutz.
The treatments by many modern authors followed Singer's with minor modifications, while others proposed major revisions to Singer's system, including the abolition of the Crepidotaceae. Most of these treatments include placing some or all of the Crepidotaceae genera within other families, especially the Cortinariaceae and/or the Strophariaceae Singer and A.H. Smith (e.g., Moser, 1978
; Kühner, 1980
; Jülich, 1981
; Bas, 1988
; Breitenbach and Kränzlin, 1995
; Hawksworth et al., 1995
; Kirk et al., 2001
).
Morphological and biological studies of the crepidoti have provided further evidence that makes obvious the need for a critical reassessment of the current classification systems for these fungi. For example, morphological studies, especially of the pileipellis, have suggested that Simocybe might be more closely related to Agrocybe Fayod (Bolbitiaceae Singer) (Romagnesi, 1962
; Watling and Largent, 1976
). Basidiospore germination in members of Crepidotus is markedly different from that in species of Tubaria, suggesting a more distant common ancestry for them than proposed by Singer (Aime and Miller, 2002
). Singer based his transfer of both Tubaria and, later, Melanomphalia into the Crepidotaceae on a single species, M. thermophila (Sing.) Sing. (Singer, 1951a
, 1962
, 1971
); recent study of type and newly collected material has shown this species to be, in fact, a Crepidotus (Aime et al., 2002
). In addition, numerous studies have questioned the validity of delimiting genera based on single morphological characters (e.g., Smith, 1968
; Watling and Largent, 1976
), such as has been done in circumscribing Pleurotellus from Crepidotus, which are delimited solely on the basis of spore pigmentation.
Given the diverse phenotypes, contradictory proposed classifications, biological differences, and the fact that generic and higher level systematics in the Crepidotaceae have been largely neglected, this study was undertaken to assess phylogenetic relationships for these fungi by analyzing molecular sequence data. Nuclear DNA sequences encoding a portion of the large ribosomal subunit (nLSU) have been shown to be effective at resolving phylogenetic relationships for agarics and related fungi at the generic (e.g., Johnson and Vilgalys, 1998
; Drehmel et al., 1999
; Hopple and Vilgalys, 1999
; Dahlman et al., 2000
) and family or ordinal levels (e.g., Miller et al., 2000
; Moncalvo et al., 2000
, 2002
; Thorn et al., 2000
). Sequences from the type species from each of the five proposed agaric members of the Crepidotaceae were assembled, as were other specific exemplars from each genus selected to cover a broad range of the phenotypic and geographic diversity found within these fungi. The Crepidotaceae sequences were analyzed within a data set chosen to include representatives from all major lineages of dark-spored euagarics including sequences from other families to which various components of the Crepidotaceae have been hypothesized to belong in alternative classifications. Our primary goals were to (1) test the monophyly of the Crepidotaceae s. Singer and evaluate alternative classifications of the family, (2) elucidate phylogenetic relationships and provide a detailed discussion of the taxonomic status for each agaric genus allied in the family by Singer, (3) re-evaluate morphological characters previously used to delimit these genera and identify features that characterize various clades that were detected in this study, and (4) redefine the Crepidotaceae within a phylogenetic framework.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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, phylogenetic lineage according to Moncalvo et al. (2000)
where applicable, and GenBank accession numbers are in Appendix 1 (see Supplemental Data accompanying online version of this article). Sixteen taxa of Crepidotaceae s. Singer, including the type species for each genus, were sampled (GenBank accession numbers AF205669, AF205677, AF205679, AF205685 to AF205686, AF205695, AF205606 to AF205608, AF205610 to AF205612, AF367931 to AF367934); exsiccata used as sources for DNA are also listed in Appendix 1. To assess the relationships of the Crepidotaceae s. Singer within the euagarics, a collection of nLSU sequences were selected from previous studies (Chapela et al., 1994
; Lutzoni, 1997
; Johnson and Vilgalys, 1998
; Hopple and Vilgalys, 1999
; Moncalvo et al., 2000
; Moncalvo et al., 2002
) to include three representatives from each major lineage of dark-spored euagarics (designated Q through W) as identified in Moncalvo et al. (2000)
. Dark-spored euagarics were sampled extensively because all treatments of the Crepidotaceae ally them within this group, and additional sampling of omphalinoid fungi (Moncalvo et al., 2000
, lineage K) was included because preliminary analyses (not shown) suggested an affinity of Melanomphalia with this group. For rooting purposes, outgroup taxa were chosen from within the Boletales (Moncalvo et al., 2000
, lineage AA) because prior phylogenetic analysis of both the nLSU (Moncalvo et al., 2000
) and mitochondrial and nuclear ribosomal subunit DNA sequences (Hibbett et al., 1997
) suggest that the boletes and euagarics are sister lineages, and it has been shown that outgroup choice should, ideally, be confined to taxa sharing a sister group relationship to the ingroup under study (Hopple and Vilgalys, 1999
).
DNA extraction, amplification, and sequencing
Standard DNA isolation methods were used with hexadecyltrimethylammonium bromide extraction buffer (Zolan and Pukkila, 1986
). The 5'-end of the nLSU gene was targeted for sequencing and phylogenetic analysis as this region carries nearly 50% of the phylogenetic signal present within the nLSU molecule (Hopple and Vilgalys, 1999
). Standard amplification and sequencing parameters follow Vilgalys and Hester (1990)
and Moncalvo et al. (2000)
. Amplification was achieved with primer pair 5.8SR/LR7 (Vilgalys and Hester, 1990
) or LR5/ LR0R (Moncalvo et al., 2000
). Primers LR0R, LR3R, LR5, and LR16 (Moncalvo et al., 2000
) were used in sequencing reactions. The four sequence chromatograms generated per sample were compiled using SeqMan II v. 4.03 (DNAStar Inc., 1997
) to produce a single contiguous sequence for each sample.
Phylogenetic analysis
Sequences were manually aligned in PAUP* 4.0b8 (Swofford, 2001
). Gaps were introduced to maintain alignment through regions where indels occurred in one or more sequences. Regions with ambiguous alignment were removed from analysis. Alignments are available from the lead author by request. Analysis was performed on a Power Macintosh OS workstation. Methods for unweighted maximum parsimony analysis (UMP) follow Aime et al. (2002)
. Methods for weighted maximum parsimony analysis (WMP) follow Moncalvo et al. (2000)
and apply a stepmatrix based on dinucleotide frequencies and substitution rate estimates as observed in that work. Support for clades was assessed by calculating bootstrap (Hillis and Bull, 1993
) and jackknife frequencies (Lanyon, 1985
) by performing 1000 replicates of random addition sequence replicates with TBR (tree-bisection-reconnection) branch swapping.
Additionally, constraint analyses were performed to test the probability that different groupings of Crepidotaceae taxa were monophyletic. Topological constraint trees were generated in the following manner. All members of Crepidotus and Pleurotellus were assigned to a single taxset; Simocybe taxa were assigned to a second taxset, and Tubaria taxa was assigned to a third taxset; all other ingroup taxa, with the exception of M. nigrescens, and the two outgroup taxa were assigned to a fourth taxset. No topological constraints were enforced within any taxset. Separate analyses were then run with the following monophyletic constraints between taxsets: (1) no constraints; (2) taxset 1, 2, 3, and M. nigrescens; (3) taxset 1 and 2; (4) taxset 1, 2, and 3; (5) taxset 1, 2, and M. nigrescens; (6) taxset 1 and 3; (7) taxset 1 and M. nigrescens. For each of these analyses, WMP, with weightings based on nucleotide frequencies as already described and using 20 random addition sequence replicates with TBR branch swapping, was conducted in PAUP*. Scores for each of the 20 most parsimonious trees uncovered were recorded for each constraint set. Tree scores were analyzed statistically in JMP v.3.2.1 (SAS Institute Inc., 1997
).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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classification, sequence data from the first 1200-base region of the nLSU molecule indicate that the Crepidotaceae sensu lato (s.l.) is polyphyletic, nor do these data reflect any of the alternative classifications proposed for the genera examined. Both Tubaria (Fig. 1, clade II) and Melanomphalia (Fig. 1, clade III) have originated independently from the core members of the Crepidotaceae s.s. (Fig. 1, clade I). Although strong statistical support via bootstrapping and jackknifing for some of these lineages is low, the conclusions reached by WMP are fully supported by analysis of trees produced by enforcing monophyletic constraints on the genera of the Crepidotaceae s.l. (Appendix 2). A detailed discussion follows.
Phylogenetic inference
Several methods for evaluating support for phylogenetic clades have been debated and utilized. Decay indices (Bremer, 1988
) are a valuable method of detecting support for branches, but are impractical for large data sets (Moncalvo et al., 2000
). Bootstrap (Hillis and Bull, 1993
) and jackknife (Lanyon, 1985
) values have gained wide acceptance in systematic literature, but in actuality provide an indication only of the degree of support for a particular clade or node given the specific technique and data matrix analyzed (Hillis and Bull, 1993
). In many instances, however, such as when rates of character change are high enough to randomize some characters (i.e., saturation or high homoplasy), bootstrap values can not be used as measures of accuracy or the probability that a given tree or clade represents the true phylogeny (Hillis and Bull, 1993
).
In the present data matrix, >20% of the characters were parsimony-informative. This is well beyond the optimal range of 5–15% (Olmstead and Palmer, 1994
) and, given the broad phylogenetic range sampled and low consistency index, indicates that the variable positions within the matrix are probably saturated by change (Hillis and Huelsenbeck, 1992
). Phylogenetic resolution in parsimony analyses in such instances can be improved by increasing taxon sampling, as the probability increases that more homoplasic characters will be correctly interpreted as such (Olmstead and Palmer, 1994
), although the debate between whether increasing sample size (Graybeal, 1998
; Hillis, 1998
) or increasing character numbers (Kim, 1998
) in phylogenetic analyses is still unresolved. However, further confirmation of the clade I association of Crepidotus and Simocybe and the exclusion of Tubaria from this clade was independently achieved when the number of euagaric taxa in the data set was dramatically increased (see Moncalvo et al., 2002
) and also by increased sampling of nucleotide characters from additional molecules (specifically, the entire nLSU region and SSU regions for a cross-section of exemplar taxa from across the euagarics) (J. M. Moncalvo and M. C. Aime, unpublished data).
An additional method for evaluating the probability that the three crepidotoid lineages uncovered by the parsimony analyses were accurate depictions of phylogeny was devised by comparing tree lengths derived from WMP analysis of the data matrix to tree lengths derived from the same method but with monophyletic constraints imposed on various combinations of crepidotoid genera (Appendix 2, Fig. 2). In all cases, trees derived when Tubaria and or Melanomphalia are constrained within the Crepidotaceae (as defined by the type genus Crepidotus) were significantly (in most cases, P < 0.001) worse phylogenetic hypotheses than that of Crepidotus (including Pleurotellus) and Simocybe as the true familial components (Appendix 2). When Melanomphalia is constrained within the Crepidotaceae, Omphalina becomes part of the dark-spored euagarics, which is in contradiction to all previous classifications and nucleotide-based phylogenetic analyses (Fig. 2a, d, and f). Likewise, when Tubaria is constrained within the Crepidotaceae, Phaeomarasmius and Flammulaster become basal to the family, contrary to previous phylogenetic hypotheses and analyses (Fig. 2a, c, and e).
A detailed taxonomic evaluation of each genus is beyond the scope of this paper; such work has been extensively addressed by other authors. Systematics of Crepidotus will be discussed in a separate paper. A discussion of the other genera of the Crepidotaceae s.l. within a phylogenetic context is herein provided.
Clade I: the Crepidotaceae s.s
Crepidotus and Simocybe are sister taxa representing the Crepidotaceae based on allegiance to the type C. mollis (Fig. 1). The sister lineage to the Crepidotaceae cannot be resolved with these data, nor was it recovered within the expanded analyses of Moncalvo et al. (2002)
, although any sister relationship between the Crepidotaceae s.s. and either the Entolomataceae or the Paxillaceae, as suggested by Singer (1986)
is contraindicated by all analyses. Nor is it likely from these and other analyses (Moncalvo et al., 2002
, and M. C. Aime, unpublished data) that any member of the Strophariaceae s.l. shares a sister relationship with the Crepidotaceae s.s. The most likely candidates in all phylogenetic analyses thus far are that either a component of the Coprinaceae s.l. (Fig. 1) or the genus Inocybe (Fr.) (Moncalvo et al., 2002
) shares a sister relationship with the Crepidotaceae s.s., although neither of these relationships would reflect any previously proposed classification for the Agaricales.
Simocybe
The nomenclatural debate surrounding the group of agarics now conserved and typified under S. centuncula (Greuter et al., 1994
) has been treated previously [Singer, 1973
; Redhead, 1984
as Naucoria (Fr.) Kumm.; Reid, 1984
as Naucoria; Horak and Miller, 1997
]. Approximately 25 species are now allied in Simocybe (Hawksworth et al., 1995
). All known members are saprotrophic. Simocybe is geographically distributed worldwide (Redhead and Cauchon, 1989
) and has been monographed from the Neotropics (Singer, 1973
), lower Pacific (Horak, 1979a
, b
, 1980b
), and the United Kingdom (Reid, 1984
; Watling and Gregory, 1989
as Ramicola Velenovsky).
Singer's (1973)
transfer of Simocybe to the Crepidotaceae is by no means universally accepted. Most early classifications placed S. centuncula and its allies within the Cortinariaceae, and this system is still followed in most modern treatments (e.g., Jülich, 1981
; Bas, 1988
; Hawksworth et al., 1995
; Grgurinovic, 1997
). Such positions can usually be traced to early nomenclaturial difficulties in delimiting Naucoria (mycorrhizal, Cortinariaceae) from segregate genera including Simocybe.
Alternatively, Simocybe has been placed within the Strophariaceae (Kühner, 1980
) or Bolbitiaceae and synonymized with Agrocybe based on striking similarities in pileipellis construction between Simocybe and A. firma (Pk.) Sing. (Romagnesi, 1962
). The present study shows that A. firma and Agrocybe in general have no close affinities to the members of Simocybe (Fig. 1), which is in support of Watling and Largent's (1976)
observation that given the fact that differences in construction also occur in the cuticle of the two taxa, the similarities that exist may be due to convergence and not phylogeny.
Similarities in pileus structure between Tubaria and Simocybe have also been noted (Watling and Largent, 1976
; Vellinga, 1986
). True members of Simocybe all possess numerous pileocystidia terminal cells in the epicutis, which can resemble the velum-producing cells found in the pileipellis of tubarii. The Simocybe pileipellis is of simple construction, however, as in Crepidotus (Watling and Largent, 1976
), and the pileocystidia originate from the pileipellis as differentiated termini whose function is not analogous to that of the similar-appearing cells in Tubaria. Species of Simocybe are gymnocarpic (Horak, 1979a
, 1980b
), and reports of hemiangiocarpy are most likely based on nongeneric elements no longer considered to be allies of S. centuncula as now circumscribed.
Pleurotellus
Pleurotellus was originally typified by Fayod (1889)
based on Berkeley's interpretation of Persoon's description of Agaricus hypnophilus. Later, Fayod became doubtful as to whether he had correctly determined Persoon's taxon and renamed his type collection Pleurotellus graminicola (Donk, 1962
; Nordstein, 1990
). Only two species are commonly accepted in the genus (Hawksworth et al., 1995
), the identity of which are discussed in Nordstein (1990)
, yet the generic concept contains heterogeneous elements (Singer, 1962
; Watling, 1988
). While Orton (1960)
interprets Pleurotellus as white-spored relatives of Pleurotus (Fr.) Kumm., of no affinity to Crepidotus, most consider the two closely related (e.g., Singer, 1961
; Hesler and Smith, 1965
; Watling and Gregory, 1989
; Nordstein, 1990
; Senn-Irlet, 1995
), although opinions vary as to whether Pleurotellus differs from other crepidoti on the generic level.
Proponents of segregating Pleurotellus and Crepidotus do so because of two morphological distinctions: the absence of clamp connections and the very pale-yellow to subhyaline spore print color in Pleurotellus (e.g., Pilát, 1948
; Watling and Gregory, 1989
; Singer, 1951a
, 1962
, 1986
; Pegler and Young, 1972
). Clamp connections, while useful taxonomically for the circumscription of species, are not reliable indicators of phylogeny in many groups (Watling and Largent, 1976
), and Crepidotus contains several lineages that have clamps and others that do not (Aime, 2001
and unpublished data), so the character alone is not unique to Pleurotellus. Therefore, only the single character state of loss of spore pigmentation distinguishes the former from the latter. Pleurotellus, as represented here by the type, P. hypnophilus, is a component of Crepidotus (Fig. 1). Because the use of single characters for circumscribing genera can introduce artificiality into classifications (Smith, 1968
), and P. hypnophilus is in all other characters consistent with Crepidotus, Pleurotellus should be considered congeneric with Crepidotus.
The taxon represented by P. hypnophilus (Pers.:Berk.) Fayod has been reported from all over the world under a large number of synonyms, and the correct specific epithet for it has been the subject of much discussion (Hesler and Smith, 1965
; Nordstein, 1990
; Senn-Irlet, 1995
; Bandala et al., 1999
). The first description that can be unambiguously applied to this taxon is that of Peck (1886)
for Crepidotus herbarum (Pk.) Sacc. However, the older name of Agaricus hypnophilus Pers. ex Berk. takes precedent, if, as has been noted by Singer (1961)
, Berkeley correctly interpreted Persoon's taxon, for which a type no longer exists. Berkeley's type does exist and was the basis for Fayod's establishment of Pleurotellus. Several studies show it to be conspecific with the taxon analyzed in this paper (Singer, 1961
; Donk, 1962
; Horak, 1968
); therefore, the name C. hypnophilus (Pers.:Fr.) Nordstein takes precedent over C. herbarum, as has already been recognized by Nordstein (1990)
.
However, Senn-Irlet (1995)
has investigated the possibility that an older Friesian name, Agaricus epibryus Fr., exists for this taxon. Because no type for A. epibryus apparently exists and the original description (Fries, 1821
) could be applied to many species of Crepidotus or even Pleurotus and allied genera, several differing concepts have been applied to this name in the past (Pilát, 1950
; Singer, 1951b
; Senn-Irlet, 1995
). Senn-Irlet's interpretation was based on that of Quélet (1888)
, and she considers C. herbarum and C. hypnophilus to be synonyms for C. epibryus (Fr.) Quél. (Senn-Irlet, 1995
). Although the argument is convincing, a few problems exist with this interpretation: (1) Quélet's (1888)
description of C. epibryus is as vague as Fries' and could equally fit other taxa within and even outside the confines of Crepidotus, (2) Quélet actually considers A. epibryus as a Crepidotus in works as early as 1872, wherein the spores are described in more detail as being "pruniform," or plum-shaped, which is not the case with the taxon under question here (Quélet, 1872
), and (3) the only substrate given for both Fries' (1821
, 1836–1838)
and Quélet's (1872
, 1888
) taxon is moss, whereas the taxon under question is almost exclusively confined to herbaceous and grassy substrates, and hardwoods, not moss (Peck, 1885; Watling and Gregory, 1989
; Nordstein, 1990
; Bandala et al., 1999
), hence the name C. herbarum and Fayod's later change to P. graminicola.
Nonetheless, a neotype has been established for C. epibryus (Senn-Irlet, 1995
), and this name is now accepted (Bandala et al., 1999
), for the taxon that was previously more commonly known as C. herbarum or P. hypnophilus; the name C. epibryus (Fr.) Quél. s. Senn-Irlet should be applied to it. This species has been previously described and illustrated by Senn-Irlet (1995)
, Bandala et al. (1999)
, Horak (1968
, as P. graminicola), Nordstein (1990
, as C. hypnophilus), and Hesler and Smith (1965
, as C. herbarum).
Clade II: Tubaria and allies
The data presented in this and in Moncalvo et al. (2002)
show this genus to be most closely allied with Phaeomarasmius and Flammulaster, and only distantly related to the members of the Crepidotaceae s.s. (Fig. 1). Basidiospore germination and vegetative morphology of T. furfuraceae were studied by Ingold (1983)
and shown to be considerably different from that of Crepidotus species (Aime and Miller, 2002
), lending additional support to a proposed phylogenetic hiatus between the two genera. Tubaria contains approximately 15 saprotrophic species occurring worldwide in temperate climes (Hawksworth et al., 1995
), and only a few European species have been monographed (Lange, 1938
; Romagnesi, 1940
, 1943
).
Singer (1951a)
transferred Tubaria from the Cortinariaceae to the Crepidotaceae and the rationale behind this decision was discussed in Aime et al. (2002)
. Other authors still ally this genus with the Cortinariaceae s.l. (Romagnesi, 1940
; Vellinga, 1986
; Grgurinovic, 1997
) or place it within the Strophariaceae s.l. (Moser, 1978
). Tubaria has the distinction of being the only genus within Singer's Crepidotaceae in which some members undergo hemiangiocarpic development and have spore prints that may display orange tones. Morphological delimitation and generic concepts between and within Flammulaster, Phaeomarasmius, and Tubaria have been repeatedly evaluated (Romagnesi, 1940
; Watling, 1967
; Kühner, 1969
; Harmaja, 1978
; Moser, 1978
; Horak, 1980a
; Vellinga, 1986
). The present study is in support of the classification of Moser (1978)
which proposes a relationship between the three genera Phaeomarasmius, Flammulaster, and Tubaria.
Numerous characters and character suites have been hypothetical indicators of phylogeny in agarics. The alliance of Tubaria, Flammulaster, and Phaeomarasmius is best understood through the work of Watling and Largent (1976)
, which emphasizes pileipellis anatomy in drawing conclusions about higher-level relationships in the agarics. The members of all three genera possess an unusual pileipellis that contains inflated hyphae occurring in chains, usually encrusted with brown pigment (Watling and Largent, 1976
; Harmaja, 1978
; Vellinga, 1986
). These chains of hyphae appear to be the same elements that give rise to the partial veil present in these species, yet appear to originate from, and be an integral part of, the cutis rather than the stipe. The resulting partial veil is usually fugacious, and persistent in one species (Watling, 1967
). All taxa tested so far are KOH+ on the pileus (Watling, 1967
; Vellinga, 1986
), which appears to be a secondary unifying character.
Clade III: Melanomphalia and its allies
Perhaps the most interesting result of this study is the alliance of Melanomphalia with a subset of the genus Omphalina Quél. Generic affinities for Melanomphalia have never been certain (Lange, 1940
; Montag, 1996
), with the type itself seemingly holding a rather isolated position even within the genus as expanded by Singer (Watling, 1988
). The genus was hypothetically allied with the Gomphidiaceae by Christiansen (1936)
and early authors (Lange, 1940
) and with the Cortinariaceae (Singer, 1955
) until its transfer to the Crepidotaceae (Singer, 1971
) based on similarities between Crepidotus thermophilus (Sing.) Aime, Baroni, and O.K. Miller and some Crepidotus species as previously discussed elsewhere (Aime et al., 2002
).
Similarities between the type, M. nigrescens and some Omphalina have previously been noted (Montag, 1996
). Christiansen (1936)
also recognized similarities between Omphalina and his genus, although the differences in spore pigmentation and ornamentation had always been viewed as too striking to consider other similarities as anything other than evidence of parallel evolution between these genera.
Taxonomically, the omphalinoid fungi have also been a difficult and heterogeneous group to delimit (Bigelow, 1970
; Redhead and Weresub, 1978
; Norvell et al., 1994
), and recent phylogenetic analyses have uncovered three distinct lineages of polyphyletic origin (Lutzoni, 1997
; Moncalvo et al., 2000
). What is extremely interesting is that M. nigrescens, within the confines of this study shows a sister relationship with a clade previously identified as the true Omphalina (Lutzoni, 1997
), which includes lichenized fungi (Fig. 1). This merits closer scrutiny of the phylogeny and ecology of M. nigrescens, which has only been reported on soil (Christiansen, 1936
; Montag, 1996
) or adventitiously on limestone or in association with herbaceous VAM plants (Watling, 1988
), and as such was one of the only non-lignicolous members of the Crepidotaceae s. Singer.
This association is also extraordinary in that it suggests an independent origin of dark spore pigmentation in the euagarics. Historically, much weight has been attached to certain aspects of basidiospore morphology, especially pigmentation, in deriving hypotheses regarding agaric phylogeny. Interestingly, loss of spore wall pigmentation has now been shown through molecular studies to have occurred in several agaric cohorts, such as has occurred in the Agaricaceae (Johnson and Vilgalys, 1998
), and the Crepidotaceae with C. epibryus s. Senn-Irlet, but the acquisition of pigmented spores from an unpigmented ancestor appears to be a rarer phenomenon.
Prior work has shown that at least one species previously placed within Melanomphalia is, in fact, a Crepidotus (Aime et al., 2002
), and preliminary study of other taxa currently placed in the genus also suggests that most are more naturally allied within Crepidotus or other genera (M. C. Aime, unpublished data). At present, Melanomphalia appears to be a monotypic genus. The taxonomic disposition of other species currently allied in Melanomphalia and detailed phylogeny are under further investigation.
Redefining the Crepidotaceae
Initially, the macroscopic character of habit delineated Simocybe from Crepidotus. Transfers of some pleurotoid taxa from Crepidotus to Simocybe based on microscopy (Singer, 1973
; Watling, 1988
; Horak and Miller, 1997
), and of some stipitate taxa to Crepidotus (Aime et al., 2002
) have blurred the macroscopic distinctions between the two, but result in a more natural classification based on microscopic characters. Chiefly, Simocybe can be diagnosed from Crepidotus by (1) basidiospores which are always smooth and differ from smooth-spored Crepidotus species in that the adaxial side is typically applanate to depressed; and (2) abundant pileo-, caulo-, and cheilocystidia (the latter two most typically subcapitate), lending a pruinose appearance to these structures macroscopically. Additionally, many Simocybe members have an olivaceous tint to the pileus, lacking in Crepidotus.
The Crepidotaceae s.s. are differentiated from all other euagaric lineages by the following suite of characters: saprotrophic on woody or herbaceous matter; gymnocarpic; spore prints within the pale yellow to brown range, not pink, purple-brown, orange, or black; simple cuticle, although differentiated termini in the form of pileocystidia may be present; cheilocystidia always present; pleurocystidia absent in most taxa and never thick-walled or originating from the lamellar trama; basidiospores entire, with neither a true germ pore nor plage, smooth or ornamented but never angular or reticulate.
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FOOTNOTES |
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The authors thank Roy Watling, Alan Bessette, and Ursula Peintner for the loan of crucial material, and Jean-Marc Moncalvo for laboratory advice and assistance. This study was funded in part by a Sigma Xi Grants-in-Aid-of-Research to MCA, and an ASPIRES fund #232095 from Virginia Tech. Field-work in Japan was supported by a NSF/Monbusho Summer Research Fellowship, #SP-9800003, to MCA. This paper is based in part on a dissertation submitted by the first author to Virginia Tech as one requirement for a Ph.D. degree. 
6 Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture
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LITERATURE CITED |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Aime M. C. T. J. Baroni O. K. Miller Jr 2002 Crepidotus thermophilus comb. nov., a reassessment of Melanomphalia thermophila, a rarely collected tropical agaric. Mycologia 94: 1059-1065
Aime M. C. O. K. Miller Jr 2002 Delayed germination of basidiospores in temperate species of Crepidotus (Fr.) Staude. Canadian Journal of Botany 80: 280-287[ISI]
Bandala V. M. L. Montoya G. Moreno 1999 Two Crepidotus from Mexico with notes on selected type collections. Mycotaxon 72: 403-416[ISI]
Bas C. 1988 Orders and families in agarics and boleti. In C. Bas, T. W. Kuyper, M. E. Noordeloos, and E. C. Vellinga [eds.], Flora Agaricina Neerlandica, vol. 1, 40–49. A.A. Balkema, Rotterdam, Netherlands
Bigelow H. E. 1970 Omphalina in North America. Mycologia 62: 1-32
Breitenbach J. F. Kränzlin 1995 Fungi of Switzerland: Agarics, vol. 4, pt. 2. Edition Mykologia, Lucerne, Switzerland
Bremer K. 1988 The limits of amino acid sequence data in angiosperm phylogenetic reconstruction. Evolution 42: 795-803[CrossRef][ISI]
Chapela I. H. S. A. Rehner T. R. Schultz U. G. Mueller 1994 Evolutionary history of the symbiosis between fungus-growing ants and their fungi. Science 266: 1691-1694
Christiansen M. P. 1936 Melanomphalia n. gen. ny slægt inden for de mørksporede bladhatte. Friesia 1: 287-289
Dahlman M. E. Danell J. W. Spatafora 2000 Molecular systematics of Craterellus: cladistic analysis of nuclear nLSU rDNA sequence data. Mycological Research 104: 388-394[CrossRef][ISI]
DNASTAR, Inc. 1997 SeqMan II, v. 4.03. Madison, Wisconsin, USA
Donk M. A. 1962 The generic names proposed for Agaricaceae. Beihefte Nova Hedwigia 5: 1-320
Drehmel D. R. Vilgalys J. M. Moncalvo 1999 Molecular phylogeny of Amanita based on large-subunit ribosomal DNA sequences: implications for taxonomy and character evolution. Mycologia 91: 610-618[CrossRef][ISI]
Fayod V. 1889 Prodrome d'une histoire naturelle des Agaricines. Annales des Sciences Naturelles (Paris), 7 iteme serie, Botanique 9: 181-411
Fries E. 1821 Systema mycologicum I. Lunde, Sweden (Johnson Reprint Corp., USA, 1952)
Fries E. 1836–1838 Epicrisis systematis mycologici, synopsis hymenomycetum. Uppsala, Sweden (Shiva Offset Press Reprint, India, 1989)
Graybeal A. 1998 Is it better to add taxa or characters to a difficult phylogenetic problem?. Systematic Biology 47: 9-17
Greuter W. F. R. Barrie H. M. Burdet W. G. Chaloner V. Demoulin D. L. Hawksworth P. M. Jorgensen D. H. Nicolson P. C. Silva P. Trehane J. McNeill [eds.] 1994 International code of botanical nomenclature (Tokyo code). Regnum Veg. 131, Koeltz Scientific Books, Königstein, Germany
Grgurinovic C. A. 1997 Larger fungi of South Australia. The Botanic Gardens of Adelaide and State Herbarium, Adelaide, Australia
Harmaja H. 1978 Phaeomarasmius confragosus—an agaric to be transferred to Tubaria. Karstenia 18: 55-56
Hawksworth D. L. P. M. Kirk B. C. Sutton D. N. Pegler 1995 Ainsworth and Bisby's dictionary of the Fungi, 8th ed. CAB International, New York, New York, USA
Hesler L. R. A. H. Smith 1965 North American species of Crepidotus. Hafner Publishing Company, New York, New York, USA
Hibbett D. S. E. M. Pine E. Langer G. Langer M. J. Donoghue 1997 Evolution of gilled mushrooms and puffballs inferred from ribosomal DNA sequences. Proceedings of the National Academy of Sciences, USA 94: 12002-12006
Hillis D. M. 1998 Taxonomic sampling, phylogenetic accuracy, and investigator bias. Systematic Biology 47: 3-8
Hillis D. M. J. J. Bull 1993 An empirical test of bootstrapping as a method for assessing confidence in phylogenetic analysis. Systematic Biology 42: 182-192[CrossRef][ISI]
Hillis D. M. J. P. Huelsenbeck 1992 Signal, noise, and reliability in molecular phylogenetic analyses. The Journal of Heredity 83: 189-195
Hopple J. S., Jr. R. Vilgalys 1999 Phylogenetic relationships in the mushroom genus Coprinus and dark-spored allies based on sequence data from the nuclear gene coding for the large ribosomal subunit RNA: divergent domains, outgroups, and monophyly. Molecular Phylogenetics and Evolution 13: 1-19[CrossRef][ISI][Medline]
Horak E. 1968 Synopsis Generum Agaricales (die Gattungstypen der Agaricales). Beiträge zur Kryptogamenflora der Schweiz 13: 1-741
Horak E. 1979a New species of Simocybe Karsten (Agaricales) from Papua New Guinea. Sydowia, Annales Mycologici Series II 32: 123-130
Horak E. 1979b Additional species of Simocybe (Agaricales) from Sabah and Australia. Sydowia, Annales Mycologici Series II 32: 181-184
Horak E. 1980a Fungi Agaricini Novazelandiae. VIII. Phaeomarasmius Scherffel and Flammulaster Earle. New Zealand Journal of Botany 18: 173-182
Horak E. 1980b Fungi Agaricini Novazelandiae. X. Simocybe Karsten. New Zealand Journal of Botany 18: 189-196[ISI]
Horak E. O. K. Miller Jr 1997 A new species of Simocybe from North America. Mycotaxon 62: 225-229[ISI]
Imai S. 1938 Studies on the Agaricaceae of Hokkaido. II. Journal of the Faculty of Agriculture Hokkaido Imperial University 43: 238-243
Ingold C. T. 1983 Homing on basidiospores and production of oidia in Tubaria furfuracea. Transactions of the British Mycological Society 80: 363-364[ISI]
Johnson J. R. Vilgalys 1998 Phylogenetic systematics of Lepiota sensu lato based on nuclear large subunit rDNA evidence. Mycologia 90: 971-979[CrossRef][ISI]
Jülich W. 1981 Higher taxa of basidiomycetes. Bibliotheca Mycologica 85: 1-485
Kim J. 1998 What do we know about the performance of estimators for large phylogenies?. Trends in Ecology and Evolution 13: 25-26
Kirk P. M. P. F. Cannon J. C. David J. A. Stalpers 2001 Dictionary of the Fungi, 9th ed. CAB International, Wallingford, UK
Kühner R. 1969 Une Agaricale peu connue: Tubaria confragosa (Fr.) comb. nov. Travaux du Laboratoire de la Jaysinia 3: 67-71
Kühner R. 1980 Les Hyménomycètes agaricoïdes (Agaricales, Tricholomatales, Pluteales, Russulales): Etude generale et classification. Bulletin Mensuel de la Société Linnéenne de Lyon 49: 1-1027
Lange J. E. 1938 Studies in the Agarics of Denmark. XII. The genus Tubaria. Dansk Botanisk Arkiv 9: 26-29
Lange J. E. 1940 Flora agaricina Danica, vol. V. Recato, Copenhagen, Denmark
Lanyon S. 1985 Detecting internal inconsistencies in distance data. Systematic Zoology 34: 397-403[CrossRef]
Liu Y. J. S. O. Rogers J. F. Ammirati 1997 Phylogenetic relationships in Dermocybe and related Cortinarius taxa based on nuclear ribosomal DNA internal transcribed spacers. Canadian Journal of Botany 75: 519-532[ISI]
Lutzoni F. M. 1997 Phylogeny of lichen- and non-lichen-forming omphalinoid mushrooms and the utility of testing for combinability among multiple data sets. Systematic Biology 46: 373-406[CrossRef][ISI][Medline]
Miller O. K., Jr. M. C. Aime 2001 Systematics, ecology, and world distribution in the genus Chroogompus (Gomphidiaceae). In J. K. Misra and B. W. Horn [eds.], Trichomycetes, other fungal groups: Robert W. Lichtwardt commemoration volume, 315–333. Science Publishers, Inc., Enfield, New Hampshire, USA
Miller O. K. M. C. Aime F. Comacho U. Peintner 2002 Two new species of Gomphidius from the Western United States and Eastern Siberia. Mycologia 94: 1044-1050
Miller S. L. T. M. McClean J. F. Walker B. Buyck 2000 A molecular phylogeny of the Russulales including agaricoid, gasteroid and pleurotoid taxa. Mycologia 93: 344-354[CrossRef][ISI]
Moncalvo J. M. F. M. Lutzoni S. A. Rehner J. Johnson R. Vilgalys 2000 Phylogenetic relationships of agaric fungi based on nuclear large subunit ribosomal DNA sequences. Systematic Biology 49: 278-305[CrossRef][ISI][Medline]
Moncalvo J. M. R. Vilgalys S. A. Redhead J. E. Johnson T. Y. James M. C. Aime V. Hofstetter S. J. W. Verduin E. Larsson T. J. Baroni R. G. Thorn S. Jacobsson H. Clémençon O. K. Miller Jr 2002 One hundred and seventeen clades of Euagarics. Molecular Phylogenetics and Evolution 23: 357-400[CrossRef][ISI][Medline]
Montag K. 1996 Zur kenntnis von Melanomphalia nigrescens Christiansen 1936 ein seltener braunsporer, erstmals in Deutschland gefunden. Zeitschrift für Mykologie 62: 75-78
Moser M. 1978 Keys to agarics and boleti (Polyporales, Boletales, Agaricales, Russulales), 4th ed. Roger Phillips, London, UK
Nordstein S. 1990 The genus Crepidotus (Basidiomycotina, Agaricales) in Norway. Synopsis Fungorum 2, Fungiflora, Oslo, Norway
Norvell L. L. S. A. Redhead J. F. Ammirati 1994 Omphalina sensu lato in North America, 1–2. 1. Omphalina wynniae and the genus Chrysomphalina. 2. Omphalina sensu Bigelow. Mycotaxon 50: 379-407[ISI]
Olmstead R. G. J. D. Palmer 1994 Chloroplast DNA systematics: a review of methods and data analysis. American Journal of Botany 8: 1205-1224
Orton P. D. 1960 New check list of British agarics and boleti. Transactions of the British Mycological Society 43: 159-459
Peck C. H. 1886 New York species of Pleurotus, Claudopus and Crepidotus. Annual Report of the Trustees of the State Museum of Natural History 39: 58-73
Pegler D. N. T. W. K. Young 1972 Basidiospore form in British species of Crepidotus. Kew Bulletin 27: 311-323[CrossRef]
Pilát A. 1948 Evropské druhy trepkovitek Crepidotus Fr. Atlas Hub Evropska, Prague, Czech Republic
Pilát A. 1950 Revision of the types of some extra-European species of the genus Crepidotus Fr. Transactions of the British Mycological Society 33: 215-249
Quélet L. 1872 Les Champignons du Jura et des Vosges, vol. I. Sociâetâe d'âemulation de Montbâeliard, Montbâeliard, France
Quélet L. 1888 Flore mycologique de la France et des pays limitrophes. Octave Doin Publisher, Paris, France (A. Asher and Co. reprint, Amsterdam, Netherlands, 1962)
Redhead S. A. 1984 Mycological observations, 4–12: on Kuehneromyces, Stropharia, Marasmius, Mycena, Geopetalum, Omphalopsis, Phaeomarasmius, Naucoria and Prunulus. Sydowia 37: 246-270
Redhead S. A. R. Cauchon 1989 A new Simocybe from Canada. Sydowia 41: 292-295
Redhead S. A. L. K. Weresub 1978 On Omphalia and Omphalina. Mycologia 70: 556-567[CrossRef][ISI]
Reid D. A. 1984 A revision of the British species of Naucoria sensu lato. Transactions of the British Mycological Society 82: 191-237
Romagnesi H. 1940 Essai sur le genre Tubaria W. Sm. Revue de Mycologie 5: 29-43
Romagnesi H. 1943 Études complémentaires sur le genre Tubaria et sur deux Naucoria tubarioïdes. Revue de Mycologie 8: 26-35
Romagnesi H. 1962 Les Naucoria du groupe Centunculus (Ramicola Velen). Bulletin Trimestriel de la Societe Mycologique de France 78: 337-358
SAS Institute, Inc. 1997 JMP, version 3.2, professional ed. Cary, North Carolina, USA
Senn-Irlet B. 1995 The genus Crepidotus in Europe. Persoonia 16: 1-80
Singer R. (1949) 1951a The "Agaricales" (mushrooms) in modern taxonomy. Lilloa 22: 5-832
Singer R. 1951b Type studies on Basidiomycetes V. Sydowia, Annales Mycologici 5: 445-475
Singer R. 1955 Le genre Melanomphalia Christiansen. Revue de Mycologie 20: 12-17
Singer R. 1961 Type studies on Agarics IV. Sydowia, Annales Mycologici Ser. II 15: 133-151
Singer R. 1962 The agaricales in modern taxonomy, 2nd ed. J. Cramer, Weinheim, Germany
Singer R. 1971 A revision of the genus Melanomphalia as a basis of the phylogeny of the Crepidotaceae. In R. H. Petersen [ed.], Evolution in the higher basidiomycetes, 441–474. The University of Tennessee Press, Knoxville, Tennessee, USA
Singer R. 1973 Neotropical species of Simocybe. Beihefte Nova Hedwigia 44: 485-517
Singer R. 1986 The agaricales in modern taxonomy, 4th ed. Koeltz Scientific Books, Koenigstein, Germany
Smith A. H. 1968 Speciation in higher fungi in relation to modern generic concepts. Mycologia 60: 742-755[CrossRef][ISI]
Swofford D. L. 2001 PAUP*: phylogenetic analysis using parsimony (*and other methods), beta version 4.0b8. Sinauer Associates, Sunderland, Massachusetts, USA
