Mycologia, 96(2), 2004, pp. 249–259.
q 2004 by The Mycological Society of America, Lawrence, KS 66044-8897
Molecular phylogenetic studies on the Diatrypaceae based on
rDNA-ITS sequences
Francisco Javier Acero
Vicente González
Javier Sánchez-Ballesteros
Vı́ctor Rubio
er with the remaining species of the genus. Eutypella
(excluding Eutypella quaternaria) appeared as an unstable monophyletic group, which was lost when the
sequence alignment was subjected to neighbor-joining analysis. The genus Diatrypella was not associated
with any monophyletic group, suggesting that the
multisporate asci character has appeared several
times during the evolution of the group. Overall, our
study suggests the need to revise many of the concepts usually applied to the classification of members
of the family.
Key words: Creosphaeria, Cryptosphaeria, Diatrypaceae, Diatrype, Diatrypella, Eutypa, Eutypella, ITS sequencing, phylogeny, rDNA sequencing, tandem repeat sequences
Departamento de Biotecnologı́a Microbiana, Centro
Nacional de Biotecnologı́a (CNB-CSIC), Campus
Cantoblanco, Universidad Autónoma de Madrid,
Madrid 28049, Spain
Julia Checa
Departamento de Biologı́a Vegetal, Universidad de
Alcalá de Henares, Madrid 28871, Spain
Gerald F. Bills
Oscar Salazar
Gonzalo Platas
Fernando Peláez1
Centro de Investigación Básica, Merck Sharp and
Dohme de España S. A., Josefa Valcárcel 38, Madrid
28027, Spain
INTRODUCTION
The Diatrypaceae is considered the only family of the
Diatrypales (Ascomycotina) and currently includes
nine accepted genera (Kirk et al 2001). Members of
this family are common worldwide, typically occurring on a broad range of dead or declining woody
angiosperms. Host specificity is variable within the
group, with some species apparently being associated
with one plant genus. For instance, Diatrypella betulina (Peck) Sacc. is known only from Betula, whereas
others, such as Diatrype flavovirens (Pers. : Fr.) Fr.,
have a broad host range. Although some members of
the Diatrypales are considered parasitic, most are accepted to be saprobic. Species like Eutypella parasitica
Davidson & Lorenz, and especially Eutypa lata (Pers. :
Fr.) Tul. & C. Tul., are known to cause severe diseases on economically important plants (Carter et al
1983).
The selection of morphological traits used to discriminate between genera and species within the Diatrypaceae has varied over time. Earlier systematic arrangements of the family (Fries 1823) were based on
stromatal features, and most of the taxa included under the modern concept of the group were recognized primarily as different sections of the genus
Sphaeria Haller. The heterogeneity of the group was
suggested first by Tulasne and Tulasne (1863) and
Currey (1858). An increasing number of diagnostic
characters were added subsequently to delimitate
taxa within the Diatrypaceae. Features such as mor-
Abstract: The order Diatrypales (Ascomycota) contains one single family, the Diatrypaceae. To obtain
insight in the phylogenetic relationships within this
family, the complete sequences of the ITS region
(ITS1, 5.8S rRNA gene and ITS2) of 53 isolates from
the five main genera in the family (Diatrype, Diatrypella, Cryptosphaeria, Eutypa and Eutypella) were determined and aligned for phylogenetic reconstruction. Sequence analysis revealed the presence of tandem repeated motifs 11 nucleotides-long, placed in
homologous positions along the ITS1 region. Parsimony analysis established the existence of nine
monophyletic groups and one branch with a single
isolate of Eutypella quaternata. The phylogenetic relationships established by parsimony analysis did not
correlate well with classical taxonomic schemes.
None of the five genera included in this study was
found to be monophyletic. The genera Diatrype, Eutypa and Cryptosphaeria each were divided into two
groups. Isolates of Diatrype flavovirens appeared in a
clade separated from the one that grouped Diatrype
disciformis and the rest of Diatrype species. The Eutypa strains appeared distributed into two clades, one
grouping Eutypa lata and related species (Eutypa armeniacae, Eutypa laevata, Eutypa petrakii), and anothAccepted for publication September 22, 2003.
1 Corresponding author. E-mail: fernandoppelaez@merck.com
249
250
TABLE I.
Code*
C1C
C2C
C3A
C4C***
C5C***
Species
Cryptosphaeria eunomia var. eunomia (Fr : Fr)
Fuckel.
Cryptosphaeria lignyota (Fr : Fr) Auersw.
Cryptosphaeria pullmanensis
Glawe.
Cryptosphaeria subcutanea (Wahl. : Fr.) F. Rappaz.
Cryptosphaeria eunomia (Fr : Fr) Fuckel. var.
fraxini (Richon) F. Rappaz.
Diatrype bullata (Hoffm. : Fr.) Fr.
Diatrype disciformis (Hoffm. : Fr.) Fr.
Diatrype disciformis (Hoffm. : Fr.) Fr.
Diatrype disciformis (Hoffm. : Fr.) Fr.
Diatrype flavovirens (Pers. : Fr.) Fr.
Diatrype flavovirens (Pers. : Fr.) Fr.
Diatrype flavovirens (Pers. : Fr.) Fr.
Diatrype flavovirens (Pers. : Fr.) Fr.
Diatrype flavovirens (Pers. : Fr.) Fr.
Diatrype macowaniana Thüm
Diatrype polycocca Fuckel.
Diatrype spilomea H. Syd.
Diatrype stigma (Hoffm. : Fr.) Fr.
Diatrype stigma (Hoffm. : Fr.) Fr.
Diatrype undulata (Pers. : Fr.) Fr.
Diatrype disciformis (Hoffm. : Fr.) Fr.
Diatrype stigma (Hoffm. : Fr.) Fr.
Diatrype stigma (Hoffm. : Fr.) Fr.
Diatrypella favacea (Fr.) Cesati & De Not.
Diatrypella frostii Peck
Diatrypella prominens (Howe) Ell. & Everh.
Diatrypella pulvinata Nits.
Diatrypella quercina (Pers. ex.Fr.) De Not.
ex.Cke.
Strain no.
Host plant
Origin
Collector
GeneBank
accession
code
CBS 216.87
Fraxinus excelsior
Switzerland
F. Rappaz
AJ302417
CBS 273.87
ATCC 52655
Populus tremula
Populus trichocarpa
Switzerland
Washington, USA
F. Rappaz
D.A. Glawe
AJ302418
AJ302419
CBS 240.87
Salix borealis
Norway
F. Rappaz
AJ302420
CBS 223.87
Fraxinus excelsior
Switzerland
F. Rappaz
AJ302421
CBS 215.87
GB 5815
F-091,971
F-091,972
F-091,973
F-091,975
F-091,976
F-093,581
F-093,582
CBS 214.87
CBS 213.87
CBS 212.87
GB 5814
F-091,970
CBS 271.87
CBS 205.87
CBS 211.87
F-101,130
CBS 527.82
ATCC 52484
ATCC 64182
CBS 181.97
F-091,966
Salix sp.
Fagus grandifolia
Fagus sylvatica
Fagus sylvatica
Cytisus purgans
Fagus sylvatica
Cytisus purgans
Castanea sativa
Eucalyptus globulus
Chaenomeles japonica
Acer opalus
Acer campestre
Fagus grandifolia
Fagus sylvatica
Betula sp.
Fagus sylvatica
Quercus sp.
Quercus agrifolia
Betula sp. (dead limb)
Acer sp.
Plantanus sp.
Quercus robur
Quercus faginea
Switzerland
New Jersey, USA
Segovia, Spain
Segovia, Spain
Madrid, Spain
Segovia, Spain
Madrid, Spain
Huelva, Spain
Huelva, Spain
Australia
Switzerland
Switzerland
New Jersey, USA
Segovia, Spain
Switzerland
Switzerland
Irish Republic
Ensenada, Mexico
Netherlands
Unknown
Illinois, USA
Netherlands
Guadalajara, Spain
F. Rappaz
G.F. Bills
J. Checa
J. Checa
J. Checa
J. Checa
J. Checa
J. Checa
J. Checa
F. Rappaz
F. Rappaz
F. Rappaz
G.F. Bills
J. Checa
F. Rappaz
F. Rappaz
F. Rappaz
J. Checa
H.A. van der Aa
D.A. Glawe
D.A. Glawe
H.A. van der Aa
J. Checa
AJ302422
AJ302423
AJ302424
AJ302425
AJ302426
AJ302427
AJ302428
AJ302429
AJ302430
AJ302431
AJ302432
AJ302433
AJ302434
AJ302435
AJ302436
AJ302437
AJ302438
AJ302439
AJ302440
AJ302441
AJ302442
AJ302443
AJ302444
MYCOLOGIA
D6C
D7M
D8M
D9M***
D10M
D11M
D12M***
D13M
D14M
D15C
D16C
D17C
D18M
D19M
D20C
D21C
D22C***
D23M
DL26C***
DL27A
DL28A***
DL29C
DL30M
Isolates used in this study
TABLE I.
Continued
Code*
Huelva, Spain
France
Switzerland
Switzerland
Norway
France
Switzerland
Switzerland
France
Guadalajara, Spain
Almerı́a, Spain
Switzerland
Switzerland
France
J. Checa
F. Rappaz
F. Rappaz
F. Rappaz
F. Rappaz
F. Rappaz
F. Rappaz
F. Rappaz
F. Rappaz
J. Checa
J. Checa
F. Rappaz
F. Rappaz
F. Rappaz
AJ302452
AJ302453
AJ302454
AJ302455
AJ302456
AJ302457
AJ302458
AJ302459
AJ302460
AJ302461
AJ302462
AJ302463
AJ302464
AJ302465
ATCC 64171
CBS 250.87
CBS 221.87
CBS 278.87
GB 4588
Vitus labrusca
Arthrocnemum fruticosum
Alnus glutinosa
Fagus sulvatica
Lindera benzoin
Illinois, USA
France
Switzerland
Switzerland
New Jersey, USA
D.A. Glawe
F. Rappaz
F. Rappaz
F. Rappaz
G.F. Bills
AJ302466
AJ302467
AJ302468
AJ302469
AJ390424
GB 4591
Lindera benzoin
New Jersey, USA
G.F. Bills
AJ390425
ATCC 28120
CBS 622.84
F-091,961
CBS 210.87
CBS 291.87
CECT 20118
CBS 217.87
Prunus avium
Vitis vinifera
Arundo donax
Ulmus sp.
Salix sp.
Tilia sp.
Acer campestre
F-093,584
CBS 286.87
CBS 219.87
CBS 244.87
CBS 245.87
CBS 272.87
CBS 292.87
CBS 209.87
CBS 274.87
F-092,374
F-092,373
CBS 276.87
CBS 277.87
CBS 242.87
DIATRYPACEAE
Cistus ladanifer
Arundo donax
Acer pseudoplatanus
Prunus spinosa
Salix borealis
Quercus ilex
Fraxinus excelsior
Lonicera xylosteum
Ficus carica
Alnus glutinosa
Atriplex halimus
Tilia sp.
Prunus avium
Robinia pseudacacia
Eutypa armeniacae Hansford & Carter.
Eutypa armeniacae Hansford & Carter.
Eutypa consobrina (Mont.) F. Rappaz.
Eutypa crustata (Fr : Fr) Sacc.
Eutypa laevata (Nitschke) Sacc.
Eutypa lata (Pers. : Fr.) Tul. & C. Tul.
Eutypa lata (Pers.) Tul. & C. Tul. var. aceris F.
Rappaz
Eutypa lata (Pers. : Fr.) Tul. & C. Tul.
Eutypa leptoplaca (Mont.) F. Rappaz.
Eutypa maura (Fr : Fr) Fuckel.
Eutypa petrakii var. petrakii F. Rappaz.
Eutypa petrakii var. petrakii F. Rappaz.
Diatrype flavovirens (Pers. : Fr.) Fr.
Eutypa astroidea (Fr : Fr) F. Rappaz.
Eutypa lata (Pers. : Fr.) Tul. & C. Tul.
Eutypella caricae (De Not.) Berl.
Eutypella cerviculata (Fr : Fr) Sacc.
Eutypella kochiana Rehm.
Eutypella leprosa (Pers. ex.Fr. : Fr.) Berl.
Eutypella prunastri (Pers. : Fr.) Sacc.
Eutypella scoparia (Schwein. : Fr.) Ellis & Everh.
Eutypella vitis (Schwein. : Fr.) Ellis & Everh.
Eutypella alsophila (Mont.) Berl.
Eutypella cerviculata (Fr : Fr) Sacc.
Eutypella quaternata (Pers. : Fr.) F. Rappaz.
Creosphaeria sassafras (Schweinitz) Ju, Martı́n,
& Rogers
Creosphaeria sassafras (Schweinitz) Ju, Martı́n,
& Rogers
Origin
PHYLOGENY OF THE
Cr91M
AJ302445
AJ302446
AJ302447
AJ302448
AJ302449
AJ302450
AJ302451
Host plant
MOLECULAR
EL57A
EL58C
EL59C
EL60C
Cr90M***
M.V. Carter
H.A. van der Aa
J. Checa
F. Rappaz
F. Rappaz
F. Rappaz
F. Rappaz
Strain no.
ET AL:
E43M***
E44C
E45C***
E46C
E47C
D48C
E49C
E50C
EL51C
EL52M***
EL53M***
EL54C
EL55C
EL56C
Australia
Italy
Almerı́a, Spain
France
Switzerland
Switzerland
France
Species
ACERO
E36A
E37C
E38M
E39C
E40C***
E41T
E42C
Collector
GeneBank
accession
code
* First letter in the strain code refers to the genus, last letter to the source of the isolate: A 5 ATCC; C 5 CBS; T 5 CECT and M 5 Merck, Sharp & Dohme).
** Originally labeled in CBS catalog as Eutypa flavovirens, considered to be a synonym of Diatrype flavovirens (Rappaz 1987a).
*** Strains for which the D1–D2 region of the 28S rRNA was sequenced.
251
252
MYCOLOGIA
phology and disposition of perithecia (Nitschke
1867), type of anamorph (Winter 1887) or asci and
ascospore morphology (Wehmeyer 1926) were incorporated into the descriptions of these organisms.
However, stromatal configuration remains an important diagnostic feature to distinguish among the genera within the family (Glawe and Rogers 1984). Thus,
valsoid configuration, with perithecia converging at
the same point in a poorly developed stroma made
up of mixed tissue or fungal hyphae only, usually is
ascribed to the genus Eutypella (Nitschke) Sacc. Eutypa Tul. & C. Tul. and Cryptosphaeria Ces. & De Not.
show eutypoid stromata, characterized by perithecia
separately reaching the surface of a flat stroma consisting of mixed tissues from the host and the fungus.
These two genera are distinguished by the degree of
immersion of the stroma, which is cortical in Cryptosphaeria, whereas in Eutypa it develops in the wood.
Finally, in Diatrype Fr. and Diatrypella (Ces. & De
Not.) De Not. the stroma is diatrypoid, consisting of
perithecia with short necks that separately reach the
surface of a well-developed stroma made up mostly
of fungal tissues. These two genera are differentiated
by the number of ascospores per ascus; eight in Diatrype and more than eight in Diatrypella.
Unlike other groups of Ascomycetes, anamorph
morphology is almost useless when differentiating
taxa in the Diatrypaceae, either at the genus or at
the species level, because the conidial states in the
Diatrypaceae are indistinguishable relatively (Glawe
and Rogers 1984, Rappaz 1987a). Three form-genera
have been applied to diatrypaceous anamorphs, i.e.,
Cytosporina Sacc., for fungi with enclosed (pycnidial)
conidiomata and filiform conidia; Libertella Desm.,
for those with unenclosed (acervular) conidiomata
and filiform conidia and Naemospora Sacc., for fungi
with unenclosed conidiomata and allantoid conidia
(Glawe and Rogers 1984). However, there has been
a reluctance to assign names to the anamorphs found
in culture (e.g., Glawe and Rogers 1984, Rappaz
1987a) because of the unclear limits among those
form-genera and because many species produce anamorphs of different types. For instance, Eutypella
parasitica produces both pycnidia and acervuli on
both natural substrata and agar media (Glawe 1983).
Likewise, conidial ontogenesis varies highly in the
group and different types of conidiogenesis (e.g.,
sympodial and percurrent) have been reported in
the same strain (Glawe and Rogers 1982a, b). Finally,
conidial morphology relatively is indistinct, ranging
from allantoid to cylindrical or filiform and from
nearly straight to strongly curved.
In this study, the phylogenetic relationships among
53 isolates of the Diatrypaceae were explored based
on the comparison of the sequences of the internal-
transcribed spacer regions ITS1 and ITS2 (including
the 5.8S rRNA gene). The selected isolates represented 35 species from five of the nine accepted genera (Kirk et al 2001) of the Diatrypaceae: Diatrype,
Eutypa, Eutypella, Diatr ypella and Cr yptosphaeria.
Echinomyces Rappaz, Fassia Dennis, Leptoperidia Rappaz and Cryptovalsa Ces. and De Not. ex Fuckel are
not considered here. This was the first time that this
fungal group was subjected to a molecular phylogenetic analysis. The results were compared with morphology-based classification schemes, with the objective of evaluating the phylogenetic significance of
characters such as stromatal morphology, ascospore
number, anamorph and host. In addition, the phylogenetic relationships between Creosphaeria, a member of the Xylariaceae with a Libertella-like anamorph
(Bills and Peláez 1996), and members of the Diatrypaceae were assessed.
MATERIALS AND METHODS
Fungal isolates and culture conditions.—The isolates used in
this work were isolated either by the authors or purchased
from the American Type Culture Collection (ATCC, Rockville, Maryland), the Centraalbureau voor Schimmelcultures (CBS, Utrecht, Netherlands) or the Colección Española
de Cultivos Tipo (CECT, Valencia, Spain). Care was taken
to ensure that the strains obtained from collections had
been deposited or identified by well-known specialists in
this fungal group to minimize the risk of including misidentified strains in the analysis. The isolates, original substrates, geographical origins and collectors are listed in TABLE I. Isolates were grown on liquid complete media (5 g
of each malt extract, yeast extract and glucose L21) in Petri
dishes at 26 C for up to 3 wk and maintained on plates at
4 C on potato-dextrose agar (Oxoid, CM139, Basingstoke,
Hampshire, U.K.).
DNA sequencing.—All procedures used in this study for
DNA purification and ITS amplification have been described previously (Sánchez-Ballesteros et al 2000). Asymmetric PCR amplification was done with a 50:1 molar ratio
between the two primers (Gyllenstein and Erlich 1988).
The primers used for amplification of the D1 and D2 domains of 28S rRNA gene were LR1 (59GTAGGAATACCCGCTG AACT39) as concentrated primer and LR4
(based on primer NL4, O’Donnell 1992) for one strand and
LR4 as concentrated primer and LR1 for the other strand.
The cycling parameters were the same as previously described (Sánchez-Ballesteros et al 2000). PCR products were
analyzed by electrophoresis on 1% agarose gels on TBE
buffer (Sambrook et al 1989) and visualized by staining with
ethidium bromide. The amplified products were sequenced
with an ABI PRISMy Dye Terminator Cycle sequencing Kit
(Perkin Elmer). All samples were sequenced in both directions, using primer LR3 (59 TGACCATTACGCCAGCATCC
39), when LR1/LR4 were used for amplification, and LR2
(based on NL1 primer; O’Donnell 1992), when LR4/LR1
ACERO
ET AL:
MOLECULAR
PHYLOGENY OF THE
were used for amplification. Sequences from each strain
were assembled to obtain the sequence of the entire ITS15.8S-ITS2 region and the 59 region of 28S rRNA gene using
the GCG Fragment Assembly System (Program Manual for
the Wisconsin Package, version 8). All sequences were deposited in GenBank (TABLE I). Alignments were performed
using the CLUSTALW program (Thompson et al 1994) and
deposited in TreeBASE (SN734).
Phylogenetic analysis.—Phylogenetic analysis of the aligned
sequences was performed by the maximum-parsimony
method using the heuristic search algorithm of the Phylogeny Analysis Using Parsimony (PAUP*) program version 4.0
(Swofford 1998). Heuristic search was performed with simple addition of sequences and TBR branch swapping, with
MaxTrees set to 100. All characters were unordered and
equally weighted, with gaps treated as missing data. The
trees were rooted with the ITS sequence of a Neurospora
crassa Shear and B.O. Dodge isolate as outgroup. The data
were resampled with 1000 bootstrap replicates (Felsenstein
1985). To complement the analysis of branch support we
also calculated the decay indexes (Bremer 1994), using the
application SEPAL version 1.01 (Salisbury 1999). Neighborjoining analysis also was applied to the same sequence alignment, using the options DNADIST and NEIGHBOR from
PHYLIP 3.5c package (Felsenstein 1993). The Jukes and
Cantor algorithm was used to estimate the distances between the sequences.
Tandem repeat motifs.—The repeated motifs in the ITS1 region were found using the FINDPATTERNS application
from GCG software Wisconsin Package version 10.0.
RESULTS
The ITS region in the Diatrypaceae were relatively
similar in length across the isolates studied, ranging
from 503 to 521 bp, except five isolates, Diatrypella
prominens, Eutypella kochiana and Eutypella quaternata, which had much longer sequences (540, 539
and 539 respectively), and Eutypella leprosa and Eutypella vitis, which had shorter sequences (491 and
493 respectively). Except those five isolates, the
length of ITS1 ranged from 188 to 199 bp. The size
of the ITS2 ranged from 158 to 168 bp, always shorter than the ITS1.
The analysis of the ITS1 sequences of all the isolates studied of the Diatrypaceae revealed the presence of DNA motifs repeated in tandem. These were
modifications of the 11-nucleotides motif CTACCCTGTAG, found in pure tandem or interspersed in the
ITS1 region, in a number ranging from four to seven
(data not shown). We detected five repetitions in all
the isolates studied, except Diatrypella prominens and
Eutypella quaternata, which had seven repetitions and
Eutypella leprosa and Eutypella vitis with four. The difference in the number of repetitions would account
for the different ITS length of these four isolates.
DIATRYPACEAE
253
The different ITS length of E. kochiana is not due to
a different number of tandem repeat motifs. This isolate also had five repetitions, and in this case the larger size is explained by insertions of one or more nucleotides along the whole ITS1 region.
The aligned sequences showed a percentage of nucleotide divergence of up to 22.1% for the complete
ITS region, with up to 30.5% and 31% divergence in
the ITS1 and the ITS2, respectively. The 5.8 S rRNA
gene was conserved among all the strains, except E.
kochiana, which had a C/T transition at position 120.
One of the 70 most-parsimonious trees derived
from the analysis of the whole ITS1-5.8S-ITS2 region
is shown in FIG. 1. The complete alignment was 616
bp, with 304 constant characters, 205 parsimony-informative positions and 107 parsimony-uninformative
positions. The length of the tree was 1006 steps, with
CI 5 0.489, RI 5 0.681, and RC 5 0.333.
The most basal branch in the tree separated the
Creosphaeria isolates from a monophyletic group that
included all the Diatrypaceae sensu stricto isolates
studied, although the bootstrap support for this main
branch was only moderate (70%). The next division
in the tree left Eutypella quaternata alone in a branch.
Above this clade it was possible to distinguish nine
groups, seven of them supported by high bootstrap
and decay indexes (groups 1–5, 7 and 8). All the
groups consisted of members from the same genus,
except groups 1, 3 and 8, which contained strains
from different genera. The tree did not allow resolving the relationships further among those nine
groups, because none of the larger clades observed
were supported by bootstrap analysis.
Group 1 was taxonomically the most heterogeneous, although it had one of the highest bootstrap
values. It contained two branches, one with Diatrype
macowaniana and Eutypella caricae and another with
Diatrypella frostii and Diatrypella prominens, and both
branches were supported by high bootstrap values.
Group 2 clustered all the isolates belonging to Diatrype flavovirens. Group 3 included the Eutypa species
analyzed more distant to Eutypa lata (Eutypa leptoplaca, Eutypa consobrina, Eutypa maura, Eutypa crustata
and Eutypa astroidea), together with Diatrype polycocca and Eutypella prunastri. Group 4 clustered three
of the five strains analyzed of genus Cryptosphaeria
(Cryptosphaeria lygniota, Cryptosphaeria pullmanensis
and Cryptosphaeria subcutanea). Group 5 included
two Diatrypella species, Diatrypella pulvinata and Diatrypella favacea. Group 6 contained sequences of the
strains of Eutypa lata and related taxa, but this group
was not supported by bootstrap analysis. Two Eutypa
armeniacae isolates and one Eutypa lata isolate were
in this group with identical sequences along the
whole region. The next two branches included Eu-
254
MYCOLOGIA
FIG. 1. One of the 70 most equally parsimonious phylogenetic trees generated from the alignment of the ITS1-5.8S-ITS2
region of 55 isolates from the Diatrypaceae. Bootstrap support values are indicated (when more than 50%) at the base of
the corresponding clade (above the line), together with decay indexes (below the line). Codes used for character mapping.
Number of ascospores per ascus: C eight, ● more than eight. Type of stroma: m eutypoid, M diatrypoid, q valsoid. Type of
anamorph: C, Cytosporina; L, Libertella; AA, conidiomata acervular, conidia allantoid (sensu Rappaz 1987a); AC, conidiomata
acervular, conidia straight to moderately curved (sensu Rappaz 1987a); PC, conidiomata pycnidial, conidia straight to moderately curved (sensu Rappaz 1987a); S, sterile in cultures, no anamorph described (Rappaz 1987a); U, anamorph unknown,
species not studied in Rappaz (1987a). Host: ANG Angiosperms (broad host range), I Aceraceae, II Poaceae, III Platanaceae,
IV Oleaceae, V Moraceae, VI Rosaceae, VII Salicaceae, VIII Fagaceae, IX Betulaceae, X Chenopodiaceae.
ACERO
ET AL:
MOLECULAR
PHYLOGENY OF THE
typa laevata and Eutypa lata var. aceris. The clade also
included other two Eutypa lata and two Eutypa petrakii var. petrakii isolates. Group 7 clustered the remaining two isolates of genus Cryptosphaeria (two varieties of Cryptosphaeria eunomia) not included in
Group 4. The most populated clade was Group 8,
which clustered 11 isolates of genus Diatrype and Diatrypella quercina. All Diatrype disciformis isolates appeared together in a cluster, with identical ITS sequences. The nearest isolate to the Diatrype disciformis group was Diatrype quercina. A second branch
clustered three Diatrype stigma isolates (D23M, D22C
and D19M) and another branch clustered Diatrype
spilomea, Diatrype bullata and another Diatrype stigma
strain (D18M). Diatrype undulata appeared in a basal
branch as the most external isolate. Most Eutypella
species were clustered in Group 9, but genetic distances in this group were much higher than in the
other groups. This was not considered a reliable
monophyletic group because it was not supported by
bootstrap analysis. Three main branches were in this
clade. One included two Eutypella cerviculata isolates.
A second cluster grouped Eutypella alsophila and Eutypella scoparia, with Eutypella kochiana next to them,
alone in a single branch. The last branch grouped
Eutypella leprosa and Eutypella vitis.
In summary, parsimony analysis of the whole ITS15.8S-ITS2 region revealed little correlation between
the molecular data and the morphological criteria
classically used for delimiting genera within the Diatrypaceae because no genus could be shown to be
monophyletic. Group 1 contained members of Diatrype, Eutypella and Diatrypella as a well supported
monophyletic group just like Group 8, which contained taxa from Diatrype and Diatrypella. The moderately well-supported Group 3 contained species of
Eutypa, Diatrype and Eutypella. The Cryptosphaeria
species were placed in two separate groups. Also, the
Diatrype flavovirens isolates formed a well-supported
group, separate from the remaining species of Diatrype. Finally, Eutypella quaternata was excluded from
the clade containing the remaining Eutypella species
(Group 9), although this group was not supported by
bootstrap analysis.
Neighbor-joining analysis of the same alignment
resulted in a tree that upheld the topology of the
nine main clusters resolved in the parsimony tree except Group 9, whose members were segregated in
two groups. The internal topology of the strongly
supported branches resolved by parsimony analysis
also was maintained (data not shown).
Sequences from the D1-D2 region of the 28S rRNA
gene from a subgroup of representative species also
were obtained to complement the phylogenetic analysis. The size of this region was 556 bp for the 12
DIATRYPACEAE
255
isolates analyzed except Eutypella kochiana, with 561
bp. The alignment of these sequences revealed that
this region was conserved highly. Only 33 positions
from the alignment were parsimony informative,
making impossible any reliable reconstruction of the
phylogenetic relationships from these data.
DISCUSSION
One of the most interesting findings in this work is
the detection of tandem-repeat sequence patterns in
the ITS1 region. The presence of this type of sequences in fungal genomes is well documented (Andersen and Torsten 1997, Giraud et al 1998, Zézé et
al 1999), but its occurrence in the ITS regions has
been reported only recently. These motifs previously
have been reported for Eutypa lata by DeScenzo et
al (1999), although in this work the number of repetitions varied among isolates, whereas in our study
the number of motifs was consistent among strains
from the same species. These tandem-repeat sequences have been found in the ITS region of many
members of the Xylariales but not in other fungal
groups (Platas et al 2001). In the Diatrypaceae they
were located in the ITS1 region at homologous positions, between positions 55–65 and 111–155. Such
repeats are lost easily or incorporated by mechanisms
of slipping strand mispairing (Platas et al 2001).
Our molecular data poorly correlated with the
morphological criteria used for delimiting genera
and species within the Diatrypaceae, suggesting that
the current taxonomical schemes in the Diatrypaceae
might not reflect the natural relationships and limits
of the genera traditionally placed in this group. Parsimony analysis of the ITS sequences seem to support
a monophyletic origin for the family, although the
bootstrap support is weak.
Genus Eutypa.—Our molecular data suggested that
genus Eutypa is polyphyletic. The species analyzed appeared distributed in two separate groups. This is
consistent with the heterogeneity of the genus hypothesized by many authors, most likely as a consequence of the low number of diagnostic features exhibited. Although without bootstrap support, each
Eutypa clade associated with some Cryptosphaeria species, in agreement with the presumed relationship
between the two genera suggested by their similarity
in stromatal morphology (Wehmeyer 1975, Glawe
and Rogers 1984).
The distribution of taxa within Group 6 in the phylogenetic trees suggests a large sequence variability
among the strains belonging to Eutypa lata and related taxa. This taxon could be regarded as a species
complex, where delimitation of individuals repre-
256
MYCOLOGIA
senting Eutypa lata sensu stricto could be difficult, given that this species is reported commonly from a
large number of plant hosts and old descriptions of
the species often lack enough diagnostic characters.
Within this group we found a robust subclade containing one strain of Eutypa lata and two strains of
Eutypa armeniacae showing identical sequences. Although this could support the hypothesis that both
species are synonyms, as suggested by several authors
(Glawe 1992, Rappaz 1987a), two other Eutypa lata
isolates are peripheral to this subclade. DeScenzo et
al (1999) assessed the genetic diversity in a group of
Eutypa lata-like isolates from California using ITS sequencing and AFLP fingerprint and their results supported the separation of the two species. The next
two branches in Group 6 included Eutypa lata var.
aceris, which differs from Eutypa lata only in cultural
features and Eutypa laevata, a taxon considered by
Rappaz (1987a) as a possible variant of Eutypa lata
with smaller ascospores and habitat restricted to Salix
spp. The high homology between one of the Eutypa
lata (E43M) and one of the Eutypa petrakii isolates
(E46C) is remarkable.
Group 3 contained the Eutypa species less related
to the Eutypa lata complex. The inclusion of Diatrype
polycocca in this clade is intriguing. Our molecular
data suggest that Diatrype polycocca is highly related
to species of Eutypa, but Rappaz (1987a) described
Diatrype polycocca unambiguously as a member of genus Diatrype, with a diatrypoid stroma. It is interesting to note that this species shows a pycnidial anamorph, similar to the typical Eutypa anamorphs,
whereas the species of Diatrype in Group 8 usually
produce a Libertella-like anamorph (i.e., with unenclosed conidiomata). Another species in this clade
not ascribed to Eutypa is Eutypella prunastri. Tiffany
and Gilman (1965) have suggested that Eutypella prunastri should be considered as belonging to genus
Eutypa, and our data provide additional support for
that suggestion.
Genus Cryptosphaeria.—Our molecular analysis suggests a polyphyletic origin for genus Cryptosphaeria.
The five species analyzed appear distributed in two
separate clades (groups 4 and 7), each related to one
of the two Eutypa clades. For the species studies,
there is an apparent correlation between this segregation and their host plant range. Thus, the three
species included in Group 4 commonly are recorded
from members of the Salicaceae, whereas the two
taxa included in Group 7 are typical from the Oleaceae. Within Group 4, Cryptosphaeria subcutanea
and Cryptosphaeria lignyota were grouped together.
They are closely related species, according to Rappaz
(1987a). The two varieties of Cryptosphaeria eunomia
included in Group 7 showed enough genetic variability to be distinguished from each other. They
have been reported to be macroscopically identical,
except that var. fraxini posses a distinctive ascospore
septum (Rappaz 1987a). Although they appeared
grouped, the nucleotide divergence rate between
them was relatively high (4.8%), compared with other groups in the study. This would support maintaining these two varieties as distinct taxa.
Genus Diatrype.—Parsimony and neighbor-joining
analyses suggests a polyphyletic origin for the genus,
or at least that Diatrype flavovirens should be segregated from the rest of the species of the genus analyzed. Thus, the strains studied here grouped in two
distinct clades, one of them containing sequences
from Diatrype flavovirens strains and the other including the remaining Diatrype spp. studied (except
Diatrype polycocca and Diatrype macowaniana). The
systematic position of Diatrype flavovirens (Group 2)
has been reported to be unclear, because it exhibits
morphological characters intermediate between Diatrype and Eutypa. Rappaz (1987a) considered Diatrype flavovirens difficult to delimitate because of the
limits between well-developed and poorly developed
diatrypoid stromata. Our data suggests that it could
be considered a taxon different from both Diatrype
and Eutypa, but further molecular analyses involving
other genes is required to assign the members of this
taxon to an independent genus.
Group 8 contained the remaining species of Diatrype, including Diatrype disciformis, the type species
of the genus. The sequence of Diatrypella quercina
also was included in this group. This taxon has been
considered a Diatrypella because of its multisporate
asci, but Wehmeyer (1926) discussed the convenience of including this species in Diatrype. In addition, Ruhland (1900) pointed out that Diatrypella
quercina could be considered under the concept of
Diatrype because of the strongly developed ectostromata and Croxall (1950) later distinguished it from
other Diatr ypella species because of its strongly
curved ascospores. The molecular data presented
here suggest that Diatrypella quercina should be considered a member of Diatrype despite its multisporate
asci.
All species included in Group 8 have been reported as related to some degree. In addition, Diatrype
disciformis clearly was separated from the remaining
Diatrype species. All isolates belonging to this taxon
showed identical ITS sequences, despite their different geographic origins, and they were arranged together in a monophyletic group with a high bootstrap index. In contrast, the isolates of Diatrype stigma
did not cluster in a monophyletic group, suggesting
ACERO
ET AL:
MOLECULAR
PHYLOGENY OF THE
that this might be a species complex as hypothesized
by several authors. Thus, Wehmeyer (1926) and Nitschke (1867) found differences in conidial sizes in
different collections of Diatrype stigma, suggesting
that more than one species were included under this
epithet. Likewise, Glawe and Rogers (1984) considered five groups for Diatrype stigma based on ascospore size, conidial size and stromatal features. Rappaz (1987b) considered three taxa for Diatrype stigma: Diatrype stigma sensu stricto, Diatrype decorticata
and Diatrype undulata. Our study does not include
Diatrype decorticata, but FIG. 1 suggests a clear distinction between Diatrype stigma sensu stricto and Diatrype undulata. On the other hand, Diatrype bullata
and Diatrype disciformis also were seen as similar to
Diatrype stigma by Wehmeyer (1926) and Rappaz
(1987b) because of their similar stromatic development. Nevertheless, our analysis did not resolve the
relationships among these species.
Genus Diatrypella.—The five isolates of Diatrypella included in this study were distributed into three different clades with high statistical support, in some
cases (groups 1 and 8) together with members of other genera. This would suggest that the multisporate
ascus trait might have appeared independently several times during the evolution of the Diatrypaceae.
Group 5, containing Diatrypella pulvinata and Diatrypella favacea, the type species of genus Diatrypella,
could be the representative group of the genus, provided that any character, other than the number of
spores per ascus, were used to define this genus. The
small nucleotide divergence between these two isolates (1.1%) would suggest that they are related closely or even conspecific. The sequencing of additional
genes and isolates from these species would be required to confirm this possibility. As already mentioned, Diatrypella quercina should be considered a
member of genus Diatrype. Finally, the two Diatrypella species in Group 1 probably should be considered
out of the concept of the genus, according to its relative position in the tree. It is interesting to note that
Group 1 includes species from three different genera, with very low percentages of divergence, suggesting close affinities among the four taxa. The similarity between the sequences of Diatrype macowaniana and Eutypella caricae is particularly striking
(0.2%). Although we cannot rule out the possibility
that the nomenclatural heterogeneity in this clade
could be due to strain misidentifications, our data
suggest at least the need of a taxonomic revision of
these species.
Genus Eutypella.—The clade containing most of the
species from genus Eutypella (Group 9) appeared as
an unstable monophyletic group in the analysis of the
DIATRYPACEAE
257
entire ITS region, with low bootstrap values (FIG. 1).
Moreover, such arrangement was not conserved in
the neighbor-joining tree (data not shown). It also is
interesting to note that several of the strains analyzed
showed large differences in length in the ITS1 region, in some cases with a different distribution of
the tandem-repeat sequences. This was the most heterogeneous group at the sequence level, with nucleotide divergence percentages ranging between 3.2
and 22.1%. In fact, the appearance of monophyly
could be caused by a ‘‘long-branch attraction’’ phenomenon (Maley and Marshall 1998). This group
also included species from other ancient genera
(e.g., Quaternaria Tul. and C. Tul, Scoptria Nitschke)
lately synonymized under Eutypella to maintain name
stability (Rappaz 1987a, 1989). However, some of the
relationships among the isolates analyzed are conserved and well supported. Thus, the two strains of
Eutypella cerviculata clustered together, Eutypella leprosa and Eutypella vitis also were grouped, and there
was a third group with Eutypella alsophila, Eutypella
scoparia and Eutypella kochiana. Rappaz (1987a) reported that Eutypella kochiana was close to Eutypella
alsophila, although the former had smaller ascospores. However, Eutypella alsophila appeared more
related to Eutypella scoparia than to Eutypella kochiana in the phylogenetic trees. Furthermore, both Eutypella scoparia and Eutypella alsophila showed a similar distribution pattern of tandem-repeat motifs
(data not shown). Moreover, Eutypella kochiana was
the only isolate in this study with a different nucleotide in the 5.8S rRNA gene and with five additional
nucleotides in the 59 region of 28S rRNA. To get insight to the implications of such observations, the sequencing of other isolates of Eutypella kochiana
would be desirable.
Our analysis suggests that Eutypella quaternata
(EL60C) should be considered a member of a different genus. This taxon was described as the type species of the genus Quaternaria (as Quaternaria quaternata) and later proposed to be included in genus
Eutypella (Rappaz 1987a, Eriksson 1988). Molecular
data support maintaining Quaternaria as an independent genus, as proposed by Gams (1994).
Genus Creosphaeria.—One of the goals of this work
was to assess the phylogenetic relationships between
Creosphaeria and members of the Diatrypaceae. Creosphaeria is classified within the Xylariaceae, but its Libertella-like anamorph (Bills and Peláez 1996) suggests
that it could have affinities with the Diatrypaceae
(Rappaz 1987a). A previous study based on ITS sequences revealed that Creosphaeria sassafras was peripheral to other members of the Xylariaceae (Sánchez-Ballesteros et al 2000). However, our phyloge-
258
MYCOLOGIA
netic reconstruction did not reflect a clear link between this genus and the Diatrypaceae. In the
parsimony analysis the two Creosphaeria sassafras, sequences appeared in a basal node, out of the main
clade that included all the sequences of the Diatrypaceae. Although based on the number and position
of the tandem repeat motifs in the ITS1 region, Creosphaeria sassafras would be closer to the Diatrypaceae
than to the Xylariaceae (data not shown), the phylogenetic relevance of this finding is unknown. In any
case, and although more sequence-based work would
be desirable to clarify the systematic placement and
evolutionary affinities of the genus, our results suggest maintaining Creosphaeria out of the Diatrypaceae.
Molecular phylogeny and morphological traits.—Most of
the monophyletic clades identified in the phylogenetic trees were homogeneous with respect to the
type of stromata of the species clustered within. The
exceptions were groups 1 and 3, which contained
taxa showing different stromatal types. However, the
groups containing taxa with diatrypoid or eutypoid
configuration were intermingled along the cladogram. The valsoid type was apparently more homogeneous because all of the Eutypella species (except
Eutypella prunastri and Eutypella caricae) were arranged in a group, although without bootstrap support. Likewise, species of Eutypa and Cryptosphaeria,
which share a similar type of stromata, were grouped
together but also lacking bootstrap support. However, the data presented here are insufficient to draw
any conclusions about the evolutionary relationships
among the stromatal configurations used to define
genera in the Diatrypaceae. Our results suggest a possible polyphyletic origin for these stromatal types; the
three main types seem to have appeared several times
along the natural history of the group. Likewise, the
number of ascospores per ascus is not a character
associated with any monophyletic group.
In the phylogenetic trees presented here, we have
mapped the anamorphs for the species studied based
on two sources. The database ANATELEO (http://
www.cbs.knaw.nl/databases/anateleo.html) provides
anamorph epithets for some of these species. These
have been incorporated in the trees and referred to
as Cytosporina or Libertella. However, the anamorphs
for most of the species studied have not been named
in the literature. In those cases we have assigned a
code defining the type of conidiomata and conidia,
as described by Rappaz (1987a). The distribution of
species in FIG. 1 does not reveal any apparent overall
correlation with their anamorphs. The segregation of
Diatrype flavovirens from other Diatrype spp. correlates with its different anamorph Cytosporina-like,
with pycnidial conidiomata, compared with the anamorphs with conidiomata unenclosed produced by
the members of Group 8. However, this apparent correlation is weakened by the observation that Diatrype
flavovirens is known to produce pycnidia on the host
but unenclosed conidiomata in agar media (Glawe
1983).
Like morphological characters, host range did not
show any apparent correlation with the distribution
of species in the phylogenetic trees. Species with
broad host range appeared distributed across the
cladogram and those with restricted host range were
not clustered.
In summary, this work presents a preliminary assessment of the phylogenetic relationships among
genera of the family Diatrypaceae by sequencing of
the ITS region. Our molecular phylogenetic analysis
shows little correlation with the current morphological concepts used for delimiting genera in the family.
The current generic divisions within this family might
not reflect the natural relationships among different
taxa.
In addition to its contribution to the understanding of the systematics of the Diatrypaceae, our work
may be a useful tool for the identification of diatrypaceous fungi in culture, which is hampered by the
fact that anamorphs are almost indistinguishable and
not always produced in culture. PCR primers have
been designed recently that are useful in the rapid
identification of Eutypa lata in culture (Lecomte et
al 2000). Although the design of primers for the
identification of other species would require sequencing more isolates from diverse geographic locations, our work provides a foundational database
that can be used as a reference to compare sequences
of unknown isolates of this important family.
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