New and rare taxa in Agaricus section Bivelares ... - Mycologia

Mycologia, 100(6), 2008, pp. 876–892. DOI: 10.3852/08-019
# 2008 by The Mycological Society of America, Lawrence, KS 66044-8897
New and rare taxa in Agaricus section Bivelares (Duploannulati)
Richard W. Kerrigan 1
Sylvan Research, 198 Nolte Drive, Kittanning,
Pennsylvania 16201
Philippe Callac
INRA, MYCSA (Mycologie et sécurité des aliments) BP
81, 33883 Villenave d’Ornon cedex, France
Luis A. Parra
Avenida Padre Claret 7, 5th G, 09400 Aranda de
Duero, Burgos, Spain
Abstract: Ongoing field and laboratory studies have
led to our recognition of new taxa in Agaricus section
Bivelares, a recent combination and now the earliest
synonym and correct name of section Duploannulati.
Agaricus cupressophilus and A. tlaxcalensis, in the new
Agaricus subsection Cupressorum, and A. agrinferus,
A. devoniensis subsp. bridghamii, and A. subsubensis in
Agaricus subsection Hortenses, are described. Agaricus
subfloccosus is lectotypified. Phylogeny reconstruction
methods with ITS1+2 DNA sequences were used to
determine appropriate placements of the new taxa.
Collectively these new taxa and phylogenetic associations
represent a substantial augmentation and
clarification of our knowledge of section Bivelares;
described, sequenced species-level taxa in the northern
hemisphere are increased from six to 10, a
distinct subsectional lineage is revealed and infraspecific
resolution within A. devoniensis is improved. An
anomalous ITS1+2 sequence is documented in one
collection of A. subsubensis. Preliminary data on
another novel member of Bivelares from France also
are provided. Several of these taxa are rare, highlighting
opportunities and challenges for documenting
biodiversity in this group. Additional comments
on related taxa treated in recent publications are also
provided.
Key words: button mushroom, cultivation,
Cupressus, ITS sequence evolution, phylogeny,
taxonomy
INTRODUCTION
The familiar cultivated button mushroom species
Agaricus bisporus ( J.E. Lange) Imbach and the
cosmopolitan A. bitorquis (Quél.) Sacc. belong to a
relatively small infrageneric group. Several sectional
Accepted for publication 25 August 2008.
1 Corresponding author. E-mail: rwk@sylvaninc.com
876
and subsectional names have been applied to this
group, most often with A. bitorquis (or its heterotypic
synonym Psalliota rodmanii) or A. hortenses (a
heterotypic synonym of A. bisporus) as the type
species (see Challen et al 2003).
Agaricus section Duploannulati Wasser ex Wasser
(1980), typified by A. bitorquis, has been the subject of
two recent phylogenetic reassessments based on
sequence analysis of the ITS1+2 region of the nuclear
rDNA. Challen et al (2003) evaluated six species-level
taxa and several infraspecific entities and restricted
the section to a clade containing the type species, A.
bitorquis, while excluding species that we believe
should be placed in section Chitonioides Romagn.
Didukh et al (2005) extended this analysis with an
emphasis on taxa from Israel, according to Wasser’s
(1980; see also Wasser et al 1976) original, broader
concept of Duploannulati.
Given Singer’s (1975) selection of P. rodmani
(Peck) Kauffman, a synonym of A. bitorquis, as the
type of Kauffman’s (1919) Psalliota section Bivelares,
Bivelares is the oldest epithet for the section
containing A. bitorquis, with priority from 1919.
Consequently a new combination in Agaricus has
been created at the sectional level (Parra 2008).
We have continued to collect and evaluate both
field material and cultures having unresolved affinities
or status. As a result three new species are
described here: Agaricus cupressophilus and A.
tlaxcalensis, both belonging to the new Agaricus
subsection Cupressorum, and A. subsubensis, in
Agaricus subsection Hortenses Heinem. (1956). In
addition we formally treat two entities that were
discussed in our earlier publications, segregating the
new species A. agrinferus from the accumulated
concept of A. subfloccosus ( J.E. Lange) Hlaváček
and recognizing A. devoniensis subsp. bridghamii. Yet
another new member of Bivelares from France
(collection CA103 [INRA]) is given a preliminary
report here. The latter three new taxa (and the
unnamed entity) are placed in subsection Hortenses.
Finally we present comments intended to supplement
information provided in Challen et al (2003).
MATERIALS AND METHODS
Collection, preservation and study methods, and cultural
practices, were routine and have been described elsewhere
(Kerrigan et al 1999). Collection data are given below.
North American material is deposited at SFSU unless
otherwise indicated. CA collections and cultures are housed

at the Collection du Germplasm des Agarics à Bordeaux
(CGAB), France. Cultures were deposited at the American
Type Culture Collection (ATCC) or at CGAB. DNA
sequencing and sequence analysis also has been described
elsewhere (Challen et al 2003). Briefly, PCR amplification of
the ca. 710 nt ITS1+2 nuclear genomic rDNA region, here
defined as beginning at ‘‘position 1’’ with 59-ggaaggat in the
SSU-rRNA gene and ending with gaacttaa-39 in the LSUrRNA
gene, was performed with primers ITS1 or ITS5 and
ITS4, or ITS2 and/or ITS3 as needed (White et al 1990).
Sequences for both strands were determined with an
automated DNA sequencer either at the Nucleic Acid
Facility-Pennsylvania State University, University of Pittsburgh,
McMaster University or INRA and were deposited in
GenBank (accession numbers are given below). Sequences
were aligned with the Clustal W routine followed by manual
inspection and correction and the final alignment was
deposited in TreeBASE (study accession number 5 S2128;
matrix accession number 5 M4027). In the special case of
A. subsubensis JB 101 (discussed below) the ITS1+2
sequence, independently amplified twice and sequenced
twice for verification, was divided into three parts; the first
and third segments were aligned independently for
comparisons but were not used in tree-building. Both
maximum parsimony (MP) trees (FIG. 1; PAUP* v 4.0b8:
Swofford 2000) and a neighbor-joining (N-J) tree (FIG. 2;
MegAlign, Lasergene v. 6; unweighted nucleotide substitution
model) were generated. Evaluation of the nonredundant
sequences, including some that were too short for N-J
analysis, under MP was performed as per Challen et al
(2003) with the following heuristic search settings: random
addition sequence, one tree held at each step during
stepwise addition using the tree-bisection-reconnection
algorithm, branch collapsing if maximum branch length
was zero, gaps treated as missing data, stepwise descent
option not in effect, topological constraints not enforced,
bootstrapping (n 5 1 000 000) and MAXTREES 5 100.
Distinctive DNA sequence characters are reported with
position numeration (see above) specific to individual
sequences. We report such characters when they appear to
be useful in the context of available data; as with any
taxonomic character, new data might lead to a reassessment.
Nomenclature follows Kerrigan et al (2006: 1299) in
agreement with ICBN-2006 (Vienna Code). Rank relationships
presented herein are hypotheses based on all available
data. No single criterion is sufficient to the task; however in
general we have observed in earlier studies (Challen et al
2003, Kerrigan et al 2005) and in ongoing work that
conventionally accepted species of Agaricus generally differ
by two or more ITS DNA characters, whereas infraspecific
taxa differ by two or fewer ITS characters. This emergent,
rough phenetic standard cannot serve as a sole criterion for
defining taxon boundaries and was considered as only a
single line of evidence. In selecting the most appropriate
rank hypothesis we also considered, as available, DNA
sequences from other genes (e.g. from manuscripts in
preparation; see A. subsubensis), morphology (see A.
tlaxcalensis and A. cupressophilus), physiology, cultural
behavior, reproductive mode (for all see A. agrinferus),
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 877
mating studies, other molecular data, ecological and
geographical separation of populations/taxa and any
patterns of association of ITS or other characters among
the isolated populations, evidence for hybrids among
putatively differentiated entities (see A. cupressicola, below,
contra A. xanthodermus and A. moelleri in Kerrigan et al
2006), the state of knowledge and complexity of the
immediate group (see the A. devoniensis clade, below),
nomenclatural practice and precedents, our preference for
conservative rank placements, and, to a lesser (or greater)
extent, the unexpectedly adamant guidance of reviewers.
New names were recorded in MycoBank (http://www.
mycobank.org) and the assigned unique identifiers are
presented below after the Latin diagnoses in the format MB
######.
DESCRIPTIONS OF TAXA
Agaricus section Bivelares (Kauffman) L.A. Parra
2008. Fung. Europ. 1(1):157.
Type: Psalliota rodmanii (Peck) Lloyd, designated
by Singer, The Agaricales in Modern Taxonomy. 3rd
ed.: 461. 1975.
; Psalliota section Bivelares Kauffman, Agaric.
Michigan: 234. 1919 [‘‘1918’’]. [basion.]
5 Agaricus section Duploannulati Wasser ex Wasser,
Fl. Fung. RSS Ucrain.: 125. 1980. [‘‘Du-
Duploannulatae’’] [nom. illeg., nom. superfl.;
art. 52.1 since Psalliota rodmanii (Peck) Lloyd,
type of the section Bivelares Kauffman (1919) is
cited as a synonym of Agaricus bitorquis (Quél.)
Sacc., the type of the section Duploannulati
designated by Wasser (1980: 125)]
5 Agaricus section Bitorques (Heinem.) Bon &
Cappelli, Doc. Mycol. 13(52): 16. 1983. Type:
Agaricus bitorquis (Quél.) Sacc., designated by
Heinemann, Sydowia 30: 13. 1978.
; Agaricus subsection Bitorques Heinem.,
Sydowia 30: 13. 1978.
Orig. diag.: Annulus double, with thick flocculose
patches on under side. MB 512252.
Delimitation of the section: Schäffer’s reaction
negative, KOH reaction negative (at least away from
the disk), o-tolidine generally blue or negative on
peripheral tissues (pelles, veils, exposed stipe base)
while violet-purple or negative on exposed interior
tissues, a-naphthol generally violet-purple (or rarely
negative) on the basal stipe context while orange to
pink on exposed interior tissues. Exposed context
rufescent: becoming pink or reddish, rarely blood red
or reddish-orange or sordid, or sometimes unchanging
or almost so. Veils forming various types of annuli or
occasionally volva-like basal structures. Stipe cylindrical,
clavate or slightly bulbous, usually not tapering at
the base, stuffed-hollow (having a pith-filled central
cavity) except for Agaricus bitorquis in which it is

878 MYCOLOGIA
FIG. 1. One of six most parsimonius trees from a run of 1 000 000 iterations on a set of nonredundant ITS1+2 sequences
from taxa of Bivelares and other sections of Agaricus. Three trees had the topology shown for the Cupressorum clade, while the
other three trees had the alternative topology shown at the top of the figure. Abbreviations: BERN: A. bernardii; CPCL: A.
cupressicola; CPHL: A. cupressophilus; TLAX: A. tlaxcalensis; DEVO: A. devoniensis (and variants); FRGV: A. fragilivolvatus;
BRID: A. devoniensis ssp. bridghamii; SBPR: A. subperonatus (misapplied); BISP: A. bisporus; BISP BURN: A. bisporus var.
burnettii; BISP EROT: A. bisporus var. eurotetrasporus; SFLC: A. subfloccosus; AGRN: A. agrinferus; BITQ: A. bitorquis; CAPL: A.
capellianus; SBSB: A. subsubensis; XANT: A. xanthodermus; SRTL: A. subrutilescens; SBRF: A. subrufescens; CAMP: A. campestris;
PATR: A. pattersonae. Bootstrap values are based on 1000 replications.
usually about solid. Basidiomata with mild or indistinct
odors, most often like that of Agaricus bisporus, or
occasionally more complex, as in some species of
section Sanguinolenti Jul. Schäff. & F.H. Møller ex L.A.
Parra (a fruity/spicy odor following Kerrigan [1986]).
Cheilocystidia usually present. Spores lacking a rudimentary
apical pore. Culture on routine media such as
PDA or compost extract agar produces ample growth

(relative to cultures of Sanguinolenti). Characteristic
ITS polymorphisms (Challen et al 2003): cttt(k/-)
tCAggta @ 120–121, at (r) tAag (r) a @ 167, ttat (Y )
atac @ 311, attaTattc @473, c(y)c(y) (R) atac @488,
(y)cgtCtgcg @580, and tnag [-8-]gaca @663–670.
We are aware that the sectional name Bivelares has
not been used for many years. However under the
rules of nomenclature Bivelares, as typified by Singer
(1975) has priority over Duploannulati and Bitorques
and is therefore the correct name of the section to
which A. bitorquis belongs. A more complete discussion
is provided by Parra (2008).
Two closely related sections are sect. Xanthoderma-
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 879
FIG. 2. Neighbor-joining tree of all ITS1+2 sequences evaluated in the present study, except (i) the too short sequences for
the New Zealand A. devoniensis variant (GenBank AF059225: ITS1 data are missing) and CA 504 / A/9.1.2, the type of A.
fragilivolvatus (which matches that of DEVO CA 100 / Dv2), and (ii) the highly modified, nonaligning sequence from SBSB
JB-101. The Clustal W alignment was hand corrected. Abbreviations are as in FIG. 1.
tei and sect. Chitonioides. As in sect. Bivelares these two
sections also have negative Schäffer’s reactions
(although in a lapsus in an earlier paper [Challen et
al 2003], those authors wrote that Xanthodermatei is
characterized by positive Schäffer’s reactions, when of
course ‘‘negative’’ was meant [see also Kerrigan et al
2006]).
KEY TO SUBSECTIONS
Pileus margin typically not strongly inrolled in
young basidiomata, with a thin sterile marginal rim
not (or barely) exceeding the lamellae; annulus

880 MYCOLOGIA
thin, ‘‘simple’’, pendant or remaining appended to
the pileus margin, stipe without conspicuous velar
remnants below the annulus; habitat typically
under Cupressaceae, occasionally under other
trees .................. subsection Cupressorum.
Pileus margin strongly inrolled in young basidiomata
(often even in mature basidiomata) with a
thick, sometimes ‘‘swollen’’ rim conspicuously
exceeding lamellae, seldom appendiculate; annulus/veils
various: usually not thin, usually intermediate,
or peronate or occasionally pendant, but if
appearing pendant then sometimes with an ornamented
undersurface or with some velar remnants
towards the base; habitat various including under
Cupressaceae. ............. subsection Hortenses.
See also distinguishing molecular characters (below).
Another helpful field character is a tendency
(only) toward a slender stature in most species of
Cupressorum (or not, in A. cupressicola) vs. a
nonslender stature (with the exception of some A.
devoniensis) in Hortenses. Generally speaking the
pendant annulus in Agaricus (see Kerrigan 1982)
corresponds to the descending (Nauta 2001) or
superous (see Boisselet 1990, Parra 2003, Cappelli
1984) veils of European authors. These terms all
apply to the veils of the new subsection Cupressorum,
but in their strict senses are not typical of subsection
Hortenses.
Agaricus [section Bivelares] subsection Cupressorum
Callac & Kerrigan, subsect. nov.
Stipes cylindricus ad clavatum. Margo pilei non valde
involutus. Annulus superus pendulus, tenuis, simplex. Caro
fracta aurantiascens vel rubescens. Odor inconspectus vel
Agarico bisporo similis. Cheilocystidia praesentia. Sporae
apicis poro destitutae. Cultura in PDA bona. Polymorphismi
propii regionis ITS: in positionibus: ctttGtcag @ 115,
tattgGgAgaag @ 126, 128, ccttCgctg @ 152, tgcaTtgtg @
173, gaaaGcGgtgc @ 181, 183, tgtaGagga @ 491, atctGcact @
600, aggaTtacc @ 689 (ex typi Agarici cupressicolae
sequentia positiones captae, L 5 705 nt). MB 512253.
Typus: Agaricus cupressicola Bon & Grilli in Bon, Doc.
Mycol. 17(67):11. 1987.
Stipe cylindrical, clavate, neither clearly bulbous
nor tapering at the base. Pileus margin not strongly
inrolled, sometimes at least partially appendiculate
with velar remnants. Annulus simple, pendant-superous.
Context becoming orange to red. Odor indistinct
or similar to Agaricus bisporus. Cheilocystidia usually
present. Spores lacking an apical pore. Growth on
PDA good. Schäffer reaction negative; KOH usually
negative, or yellow on disk. Distinctive ITS1+2 region
characters: ctttGtcag @ 115, tattgGgAgaag @ 126, 128,
ccttCgctg @ 152, tgcaTtgtg @ 173, gaaaGcGgtgc @
181, 183, tgtaGagga @ 491, atctGcact @ 600,
aggaTtacc @ 689 (in the LSU) (positions taken from
the A. cupressicola type sequence, L 5 705 nt). Type
species: A. cupressicola Bon & Grilli in Bon, Doc.
Mycol. 17(67):11. 1987. Also included: A. tlaxcalensis
and A. cupressophilus, described below.
Agaricus has a rich association with Cupressaceae.
Several dozen Agaricus species are found under
Cupressus, most particularly C. macrocarpa; more than
30 species have been recorded from a single hectare
of this habitat (Kerrigan 1982). Many Agaricus spp.
from California are known only from groves or
plantations of Monterey cypress, possibly implying a
specific habitat association. On the other hand, where
Cupressus has been introduced, Agaricus usually soon
arrives, and novel, apparently indigenous species are
encountered (Orton 1960, Callac 1994). Considering
the extensive cohabitation of Agaricus (and other
genera of Agaricaceae including Leucoagaricus, Lepiota,
Macrolepiota, Chlorophyllum, Cystoagaricus and
Tulostoma) with Cupressaceae, we speculate that the
ecological association might be ancient.
Thus far three cypress-linked species are known to
belong to subsection Cupressorum (FIGS. 1–2). All are
of slender to medium stature (none have very short
stems), with pendant annuli and rufescent flesh.
Agaricus cupressicola, the type of Cupressorum, was
originally (Grilli 1988) placed in section Sanguinolenti
(type species: A. sylvaticus Schaeff.), and by casual
criteria (simple pendant annulus, red discoloring) A.
tlaxcalensis and A. cupressophilus could be placed
there as well. However we noted that mycelia of these
three species grow well and are white on compost
extract agar or PDA, while A. sylvaticus and other
species of Sanguinolenti grow very slowly and become
brown as the medium around them becomes browner.
We have successfully cultivated A. cupressicola and
A. cupressophilus (A. tlaxcalensis has not been tried).
Phylogenetic analyses indicate that these latter
three species are not close to Sanguinolenti but
instead belong to a single basally joined clade within
section Bivelares. In MP bootstrap analysis, a clade
containing Cupressorum within Bivelares had 96%
support; Cupressorum itself had 99% bootstrap support
(FIG. 1). A neighbor-joining tree also indicated a
sister relationship between subsections Cupressorum
and Hortenses (FIG. 2). On balance we prefer to
recognize these two subsections within Bivelares, while
noting that three of six MP trees obtained did not
include a unified clade containing both subsections.
Comments on A. cupressicola.—Agaricus cupressicola
was first described under Cupressus sempervirens, in
the Abruzzi, in central Italy (Grilli 1988). It is also
relatively frequent on the French Atlantic coast under
C. macrocarpa (Guinberteau et al 1998) and has been
found by Callac under Juniperus phoenicea along the
coast in Portugal. The latter small tree produces a

litter of small branches very similar to those of
Cupressus spp.; such trees might have represented
an ecological niche for cypress-loving species of
Agaricus during the absence of cypresses in continental
Europe after their local extinction during the
glacial period, before their (re)introduction by
humans. Contu (1992) also has encountered Agaricus
cupressicola in coastal sand dunes under Juniperus
phoenicea, and Contu indicated that Heinemann
(pers comm) had found it in Belgium under
broadleaf trees with Taxus baccata. Guinberteau et
al (1998: 26, pl. 3, photo 5) reported it beneath
Robinia. Lanconelli (2003) cited it under Cedrus
atlantica and indicated that Grilli (pers comm) had
found it under Populus. Agaricus cupressicola has
never been found in North America. (Similarly A.
cupressophilus, collected ca. 100 km from the 19th
century Californian refuge area of C. macrocarpa
around Carmel Bay, is not known from Europe and
apparently has not followed the introduction of this
tree.)
We have observed a moderate degree (3/705
characters) of ITS sequence differentiation between
(i) the Italian type specimen (coll. 84.112 deposited
in Grilli’s private herbarium) (GenBank EU363031)
of A. cupressicola and (ii) two collections of French
(CA554: France, Budos, Laulan, 30 Sep 2006, under
Cupressocyparis leylandii, leg. & det. J. Guinberteau:
[GenBank EU363030]; CA72 [5Cp1; GenBank
AJ418769: Challen et al 2003]) and (iii) Greek
(CA99 [5Cp2; GenBank AJ418770: Challen et al
2003]) origin (vouchers and/or strains at CGAB). A
collection from Portugal (CA548: Portugal, Odeceixe,
Monte Novo, 29 Oct 2006, under Juniperus phoenicea
in paleodunes at the top of a coastal cliff (leg. & det.
P. Callac and A. Tancrède [CGAB]: GenBank
EU363029) was heteromorphic for all three of the
sequence characters differing between the French/
Greek and Italian material, suggesting that interbreeding
might be occurring within a single, somewhat
subdivided species. Using these (nonredundant)
sequences, an A. cupressicola clade had 58% bootstrap
support. In N-J trees and in half of the nonredundant
MP trees our A. cupressicola sequences group together.
A speciation process may be in flux among
Mediterranean A. cupressicola.
Two new species in subsection Cupressorum are now
described from North America:
Agaricus tlaxcalensis Callac et G. Mata, sp. nov.
FIGS. 3–7
Figura saepe gracilis. Pileus 2–8 cm pallide brunneogriseus;
primum convexo-cuboideus, conico-campanulatus
fit, deinde plano-convexus cum panditur, modice umbonatus,
radiose fibrillosus, nonnumquam fibrillo-squamulosus,
tactu rufescens. Stipes saepe curvus vel flexuosus (4)5–8(12)
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 881
FIG. 3. Cheilocystidia of A. tlaxcalensis (Holotype,
MATA 681).
cm 3 5–15 mm. Simplex annulus membranaceus ac
descendens. Caro a roseo ad rutilum admodum transit,
deinde siccati sanguinis colorem ducit. Agaricum bisporum
olet. Sporae ellipsoideae, forte ovato-ellipsoideae, (4.5–)
4.8–6.3(–6.9) 3 (3.4–)3.6–4.8(–5.5) mm. Basidia tetrasporigera
(21–27 3 6–8 mm). Cheilocystidia articulosa cylindroutriformiaque
18–30 mm 3 6–12 mm. Sub cupressis lectus.
In septentrionalis Americae superioribus locis situs. HO-
LOTYPUS: ‘‘Mexico, 11 October 2003, MATA 681’’ in
herbario XAL depositur. MB 512234.
Pileus at first cuboidal-convex, becoming conicocampanulate,
later expanding to plano-convex with a
low umbo, 2–8 cm diam; pileipellis beige-gray, exceeding
whitish margin, radially fibrillose, sometimes
fibrillose-squamulose, the background layer concolorous,
rufescent on handling. In drier weather the
surface can become smooth to polished, with concentric
cracks. Lamellae free, ca. 10 per cm at 1 cm
from stipe, at first vinaceous pink, rufescent on
handling, later chocolate brown; margin not distinctive.
Stipe subequal, progressively thicker toward the
base, sometimes curved or flexuous, spindly, with a
length up to 2.5 times the width of the pileus, (4)5–
8(12) cm long 3 5–15 mm thick; surface longitudinally
fibrillose, silky, partly rugulose, white, quickly
becoming sordid brown; basal bulb absent but
rhizomorph often present at the base; context white,
becoming strongly red-orange when sectioned, then
vinaceous beige-gray, and finally dried-blood colored.
Odor faint, typical of Bivelares. Veils distinctive, thin,
membranous, sometimes remaining attached to the
pileus margin, forming an apical descending (pendant)
annulus, white then vinaceous brown, persistent.
Spores dark brown at maturity, ellipsoid to ovoideoellipsoid,
(4.5–)4.8–6.3(–6.9) 3 (3.4–)3.6–4.8(–5.5)
mm, mean 5 5.3 3 4.2 mm (N5 240), L/W 5 1.28;
hilar appendix prominent. Basidia tetrasporic, cylindro-clavate,
21–27 3 6.0–8.0 mm; sterigmata 2–3 mm
long. Cheilocystidia present, often in chains of

882 MYCOLOGIA
FIGS. 4–12. Basidiomata. 4–7. Four collections of Agaricus tlaxcalensis under Cupressus benthamii in Tlaxcala State, Mexico;
bars 5 10 cm, to demonstrate variation in proportions. 4–6. In Rancho el Tejocote. 4. 19/07/2001 (not accessioned); 5. 02/
10/2002, GANDARA 377; 6. 10/10/2003, MATA 675. 7. In the National Park of the Malinche, MATA 6817, 11/10/2003:
Holotype. 8. A. cupressophilus. FS-22*: Holotype. Specimens cultivated from culture FS-22, prepared from material from San

oadly cylindrical elements, the terminal element
being cylindrical-utriform; 18–30 mm 3 6–12 mm.
Chemistry: not determined.
ITS1 + 2 sequence (GenBank EU363032–
33): L 5 705 nt (estimated). Distinctive characters:
agagTttggaCtggt @ 486 & 492. The first might be
unique in Agaricus, the second is unique within
Bivelares.
Habit, habitat, known distribution, occurrence:
Isolated, gregarious or cespitose in litter under
planted Cupressus benthamii, at more than 2400 m
altitude in the state of Tlaxcala (Mexico); possibly
frequent.
Specimens examined: MEXICO. Tlaxcala state: National
Park of the Malinche (near the restaurant of the park),
under Cupressus benthamii, 11 Oct 2003, MATA 681, P.
Callac and G. Mata, HOLOTYPE (XAL); Rancho El
Tejocote at 2 km from Cuapiaxtla, under Cupressus
benthamii, 19 Jul 2001, lost specimen, P. Callac and G.
Mata; 02 Oct 2002, GANDARA 377 (XAL), G. Mata; 10 Oct
2003, MATA 675 (XAL), P. Callac and G. Mata; Mycelium
cultures of MATA 675 and MATA 681 both are available at
MYCSA-INRA Bordeaux (CGAB: strains CA 219 and CA 221
respectively).
Etymology: from Tlaxcala state, Mexico.
Agaricus tlaxcalensis is most closely related to A.
cupressicola and A. cupressophilus. It resembles A.
cupressicola in the small size of the sporocarp, the dull
color of the pileus, the simple membranous descending
annulus, the red discoloring when sectioned, the
spore size, and the cypress habitat. It differs by its
more slender, elongated silhouette with a stipe often
curved, the stronger discoloring when sectioned or
touched, the larger basidia (20–25 3 5–6 mm for A.
cupressicola, per Bon [1987]), the cheilocystidia in
chains, which are rather cylindrical-utriform than
broadly clavate (see FIG. 4), and the highland
Mexican geographic distribution. A. tlaxcalensis
differs from A. cupressophilus by its substantially
longer spores and larger cystidia, by its cap that tends
to remains umbonate at maturity, while the cap of A.
cupressophilus tends to become depressed, and
possibly by its geographic distribution because A.
cupressophilus thus far is known only from under
Monterey cypress in coastal California. ITS1+2 sequences
of two A. tlaxcalensis collections consistently
differ from A. cupressicola by seven polymorphisms
and from A. cupressophilus by two polymorphisms. In
r
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 883
view of all of the data A. tlaxcalensis and A.
cupressophilus are best treated as separate species.
Edibility of A. tlaxcalensis is unknown.
Agaricus cupressophilus Kerrigan, sp. nov. FIG. 8
Figura gracilis. Pileus 1–7 cm latus, pallide griseus,
mutabilis, brunnescens. Stipes plerumque aequalis, e farcto
cavus, cavitum amplo, rufescens. Sporae ellipsoideae, (4.2–)
4.6(–4.9) 3 (3.4–)3.7–3.9(–4.2) mm, basidia tetrasporigera,
19–23 3 6–7 mm, cheilocystidia fasciculata, 16–22 3 6–7.5
(–8.0) mm, plerumque cylindro-clavata. HOLOTYPUS: FS-
22*, in herbario SFSU depositur. MB 512229.
Pileus (1–) 4–7 cm diam., convex to broadly
convex, center slightly depressed, margin slightly
incurved; pileipellis glabrous to minutely appressedsquamulose,
the fibrils grayish to gray-brown to buff
or light tan, potentially developing dark brown stains
hours after handling; context (3–)5–8 mm thick,
white becoming sordid vinaceous-flesh color, odor
indistinct to spicy. Lamellae free, close, ca. 13 per cm
at 1 cm from stipe, 2–4 mm broad, margin concolorous
or faintly paler, dull flesh-colored becoming dark
brown. Stipe subequal to subclavate, (5–)10–12 mm
above, (7–)11–20 mm below 3 (1.5–)4–6 cm long;
stipitipellis buff to tan, lustrous-fibrous, coloring as
context or more reddish when injured, potentially
darkening toward the base in age or long after
handling, lacking velar remnants; context lustrousfibrous,
rapidly becoming sordid vinaceous-flesh
color near cuticle and base when exposed, stuffedhollow,
the cavity relatively broad (to 10 mm), filled
with white, unchanging pith. Veils forming a thin,
whitish, subapical to supramedian pendant annulus,
often tending to remain partially attached to the
pileus margin, and/or tearing into radial strands and
fibers, readily collapsing.
Spores dark brown at maturity, ellipsoid, (4.2–)
4.6(–4.9) 3 (3.4–)3.7–3.9(–4.2) mm, mean 5 4.6 3
3.8 mm (N5 30, C 5 1); hilar appendix moderately
prominent; apical pore not evident. Basidia tetrasporic
(some bisporic), cylindro-clavate, 19–23 3 6–7 mm;
sterigmata 3–4 mm long. Cheilocystidia present in
occasional fascicles, mostly about cylindrical to
clavate, sometimes broader, often irregular to somewhat
contorted, 16–22 3 6–7.5 mm, apices sometimes
mucronate, occasional cells to 12–16 mm broad
present; elongated cells arranged parallel to the
margin generally predominate.
Mateo County, California. Scale ca. 0.45 3. 9–10. A. subsubensis. 9. Field collection JB-101, Riverside County, California, which
was cultured and from which holotype JB-101* was cultivated. Scale ca. 0.4 3. 10. A. subsubensis RWK 1789*, cultivated from a
field spore sample from Monterey County, California. Scale ca. 0.7 3. 11. A. agrinferus RWK 1397, Monterey County,
California: Holotype. Scale ca. 0.3 3. 12. A. devoniensis ssp. bridghamii RWK 1899, Clear Creek County Colorado: Holotype.
Credit: 4, 5, 7 P. Callac; 6 G. Mata; 8–12: R.W. Kerrigan. U.S. penny is 18.5 mm diam.

884 MYCOLOGIA
Chemistry: KOH yellow on disk (only); aniline 3
GAA (glacial acetic acid) negative.
ITS1+2 sequence (GenBank EU258676): L 5
708 nt. Distinctive characters: gagg[TG]ggat @ 612–
613.
Habitat, known distribution, occurrence; material
studied: Known only from collection FS-22 (no longer
extant), under Cupressus macrocarpa, USA, CA, San
Mateo County, Pacifica, Skyline Blvd., Fred Stevens,
26 Aug 1990. HOLOTYPE: FS-22*, basidiomata
cultivated from tissue culture ARP 042 of FS-22
(5MYA-4431 at ATCC) at Sylvan Research, Nov 2005
[SFSU]; paratype (second gathering from crop that
produced holotype) [NY]; paratype 5 preserved
culture MYA-4431, ATCC.
Etymology: A cypress-loving species.
The ITS sequence of A. cupressophilus is most
similar to that of the Mexican A. tlaxcalensis, followed
by the European A. cupressicola. The collector of the
only known field specimens, Dr F. Stevens, provisionally
identified the fresh FS-22 material as A. bisporus.
He cultured this material but unfortunately no
voucher was preserved. RFLP analysis done on the
culture by RWK while in the J.B. Anderson lab,
University of Toronto at Erindale, demonstrated that
FS-22 was not A. bisporus or any other RFLPcharacterized
species. An opportunity to obtain the
ITS1+2 DNA sequence later arose, thanks to J.-P. Xu
of McMaster University. Availability of the unique
sequence allowed placement of this entity within the
emergent Cupressorum clade and inspired the successful
attempt to cultivate specimens, from which the
description of the basidiomata was prepared.
The yellow color appearing with KOH on the disk is
unusual, not normally reported for section Bivelares.
This is likely to have been associated with velar
hyphae, which can remain as a substantial but obscure
presence on the disk. We would not be surprised if
this reaction were not observed on other material that
had developed under different (e.g. less humid)
conditions. No other tissue exhibited a yellowing
reaction with KOH.
For a comparison with A. tlaxcalensis see that
species. Edibility is unknown.
Agaricus [section Bivelares] subsection Hortenses
Heinem., Bull. Jard. Bot. Etat 26:22. 1956.
; Agaricus section Hortenses (Heinem.) Bon, Doc.
Mycol. 15(60):9. 1985.
Orig. diag.: Vela complexa. Acies lamellarum semper
cheilocystidiis praedita. Sporae breviter ellipticae, crasse
tunicatae, poro non praeditae. Species ruderales, interdum
halophilae.
Type: Agaricus hortensis (J.E. Lange) S. Imai
[‘‘Agaricus hortensis (Cooke) Pilát’’], designated by
Heinemann, Bull. Jard. Bot. Etat 26:22. 1956.
We regard A. hortensis ( J.E. Lange) S. Imai 1938
(nom. illeg., art. 53.1 non A. [Clitocybe] hortensis
Pers. : Fr., 1801), also known in literature as A.
hortensis (Cooke) Pilát, 1951, to be a heterotypic
synonym of A. bisporus ( J.E. Lange) Imbach 1946.
The correct name for the subsection including A.
bisporus is therefore Agaricus subsect. Hortenses Heinem.
(1956). This subsection is distinguished from
subsect. Cupressorum as noted above: the common
tendency toward complex and/or thickened, even
cottony or somewhat rubbery, often intermediate to
occasionally peronate velar structures, and the pileus
edge strongly involute at least in young basidiomata in
Hortenses are likely to be the most useful macroscopic
characters in this regard. Stature and habitat also can
be useful. DNA ITS1+2 characters have been noted
above. Three new taxa are described:
Agaricus subsubensis Kerrigan, sp. nov. FIGS. 9–10
Pileus 1–9 cm latus, convexus vel undulato-planus, laxe
intertextus, albus, mutabilis, aetate rufobrunneis; contextus
ex albo obscure rufescens vel vinaceus; stipes 5–15(–25) mm
crassus, 0.5–4.5 cm longus, plerumque aequalis, plerumque
solidus; vela alba, friabilis; sporae (5.7–)6.2–6.7(–7.4) 3
(4.3–4.9–)5.3–5.6(–6.2) mm; basidia 24–30 3 7.4–9.2 mm,
bi-, tri-, et tetraspora; cheilocystidia nulla vel cylindrica vel
clavata. HOLOTYPUS: JB-101*, in herbario SFSU depositur.
MB 512226.
Description of JB-101: Pileus broadly convex,
uneven, with inrolled margin, becoming approximately
plane, wavy, 1–9 cm broad; cuticle somewhat loosely
interwoven, more scurfy than glabrous, with concolorous
velar patches toward and on disk, obscurely rimose
toward margin, whitish, becoming light brown (7C4 or
lighter) when dried, or if bruised when young, quickly
turning reddish brown (8D-E8, 9F5), then drying a
mahogany brown (9F6); context semifirm, whitish,
unchanging in a V-shaped zone beneath disk, becoming
sordid above lamellae and pinkish above stipe and
at boundary of sordid and unchanging zones, odor
mild, indistinct, like that of A. bisporus. Lamellae free,
not close, ca. 10–11 per cm at 1 cm from stipe. Stipe
about equal, 5–15 mm 3 0.5–4.5 cm long; cuticle
semismooth beneath velar remnants; context whitish,
almost unchanging or becoming sordid, except
becoming pinkish at cuticles above and below, and
in basal context, with an indistinctly defined central
region of white pith, especially evident and tending to
become hollow near apex, base potentially subtended
by copious stringy mycelia (at least in culture). Veils
forming a narrow, indistinct, band-like, supramedian,
subperonate annulus, more obviously forming a series
of thin broken ring-like remnants on the lower twothird
of stipe, and sometimes velar patches on pileus
(disk).
Spores dark brown at maturity, broadly ellipsoid,
(5.7–)6.2–6.6(–7.2) 3 (4.9–)5.3–5.6(–6.2) mm, mean

5 6.4 3 5.5 mm (N5 30, C 5 1); hilar appendix
unremarkable; no apical pore evident. Basidia tetrasporic,
cylindro-clavate, 24–30 3 7.4–9.2 mm; sterigmata
4–5 mm long. Cheilocystidia absent or basidiolelike,
the lamellar edge bearing basidia and basidiolelike
cells in regions one to several mm long, otherwise
naked, with exposed hyphae oriented parallel to the
edge.
Chemistry: KOH negative; aniline 3 GAA negative;
o-tolidine blue on cuticles and veils, stipe and disk
context near cuticle, stipe pith and basal zone, purple
on lamellae and somewhat obscurely so above basal
context, otherwise unchanging; alpha-naphthol
brownish to scarlet on pileus cuticle, unchanging or
slightly orangish on pileus and stipe context except
becoming purple in portions of lower stipe.
ITS1+2 sequence of the type (GenBank EU131641):
L 5 661 nt, anomalous, with major deletions, substitutions
and/or modified sequence from pos 124
(gggtatA.) to pos 171 (.Gcctgtc), with up to 28
other possible recently modified characters throughout
the ITS. See discussion below, including ITS1+2
sequence of RWK 1789 (GenBank EU257802).
Habit, habitat, known distribution, occurrence;
material studied: USA. California. Riverside County
circa Thermal: JB-101, R.W. Kerrigan 7 Mar 1992
(paratype, SFSU); gregarious, fascicled to cespitose,
in sandy soil in sparsely landscaped area near
dwelling, Sonoran Desert, elevation 26 m [5type
locality]; specimen designated JB-101* (HOLOTYPE,
SFSU; isotypes: NY, MA), cultivated at Sylvan Research,
Kittanning, Pennsylvania, from MYA-2981
(paratype [preserved culture], ATCC), a culture
derived from JB-101; Monterey County, Pacific Grove:
RWK 1789* (SFSU), cultivated at Sylvan Research,
Kittanning, Pennsylvania, from MYA-4432 (preserved
culture, ATCC), derived from RWK 1789 (no longer
extant; collected from soil and Cupressus litter at
Esplanade Park by R.W. Kerrigan).
Etymology: The epithet ‘‘subsubensis’’ honors the
tradition in Agaricus taxonomy of prefixing epithets of
the less-distinctive species with ‘‘sub’’. It is tempting to
say that this species is noteworthy for its lack of
distinguishing macroscopic features.
Specimens from the desert were easily cultivated;
they fruit prolifically and are therefore better known
to us. These basidiomata tend to be small and
irregularly shaped, with an indistinct pileipellis. They
are unlikely to be deemed attractive. The indelible
rubro-brunnescence of the pileus surface observed in
sound young specimens is an unusual feature
sometimes seen in a few species of sect. Agaricus
and sect. Sanguinolenti (Kerrigan 1986).
RWK 1789 was not recognized initially as conspecific
with JB-101; in addition to its very different
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 885
habitat, it is not easy to cultivate and only a few
basidiomata were obtained from the original culture.
The two collections differ most remarkably in the
divergence of their ITS sequences. The ITS1+2
sequence of JB-101 was obviously anomalous within
its group, and reproducibly so: two independent
amplifications of genomic DNA obtained from
mycelia grown in broth yielded a single shared
sequence with multiple deletions and other alterations.
One segment of the ITS1 is unalignable with
other Agaricus ITS1 sequences. At 661 nt the JB-101
ITS1+2 is much shorter, by about 40–50 nt, than in
any other known Agaricus; whereas in RWK 1789 this
DNA segment is unremarkable at 707 nt long. Even
the alignable portions of JB-101 and RWK 1789 have a
great number of differences between them but also
some unusual shared unique characters. Both sequences
have characteristics of section Bivelares, for
example an 8 nt deletion about 55 nt 59 of the 39 end
of the ITS1+2 region (as we define it). The
phylogenetic situation became clear when uniquely
matching sequences from the LSU, EF1-a, and RPB2
genes were obtained from the two cultures (Kerrigan
and Xu unpubl; GenBank EU284015–20). Thus the
ITS1+2 region of JB101 evidently has been altered in
a major way by an event or process that violates the
assumptions of nucleotide substitution based phylogenetic
analysis. While interesting, such a sequence
cannot be used in a meaningful tree-building
exercise. The phylogenetic and geographical scope
of the altered sequence is not known. However, based
on comparisons of other gene sequences from the
two cultures, we regard it to be an intraspecies event,
hypothetically marking disjunct populations.
This rare species has been collected once (among
an abundance of A. bisporus var. burnettii) near Indio,
California, in desert sand below sea level, and once
(among an abundance of A. bisporus var. bisporus) in
Pacific Grove, California, within meters of the coast
(see Kerrigan 1995, FIG. 3, for site map and position
of RWK 1789). Because the JB-101 material is much
better documented, in part because of its cultivability,
it therefore was selected as the type of the species.
The significance of its anomalous ITS sequence is
unknown; the species concept includes both of the
known ITS sequences. Given the cultural and habitat
differences between the two collections, while keeping
in mind the ITS sequence differences, it remains
possible that two divergent populations or even rare
sister taxa are involved. For that reason a separate
description of cultivated RWK 1789 (FIG. 10) is
provided:
Pileus 4–6.5 cm diam, oval in top view, convex to
broadly convex, becoming subplane or with two
uplifted sides, center slightly depressed, the margin

886 MYCOLOGIA
incurved until maturity, ultimately with semishallow
notched radial fissures; pileipellis glabrous to broadly,
indistinctly appressed-squamose, the squamae large,
obscurely imbricate, apparently due to velar separations,
the surface white when young, becoming
unevenly vinaceous-brown from button stage through
maturity; context (3–)5–8 mm thick, white or whitish
becoming salmon pink-orange to darker vinaceous in
places when cut, odor indistinct, mushroom–like (as
in A. bisporus), of sweet chicory at pileus after velar
rupture. Lamellae free, close (distally) or not (proximally),
with a pronounced bifurcating zone about
1 cm from stipe, ca. 15 per cm at 1 cm from stipe, 1–
2 mm broad, margin concolorous, dull grayish fleshcolored
becoming medium brown. Stipe subequal,
tapering toward base, oval in cross-section, 8–13 3
15–25 mm above, 7–8 mm below 3 3.5–4.5 cm long;
stipitipellis whitish, semilustrous, adorned above the
annulus with broad, appressed, dentate velar patchscales,
these very light buff color, coloring as context
or more orangish when injured; context dull, whitish,
rapidly becoming salmon-orangish to vinaceous color
in places and more sordid overall near base when
exposed, stuffed-hollow, the cavity relatively broad (to
11 mm), wedge-shaped, filled with white, rufescent
pith. Veils forming a short, narrow, submedian
bandlike intermediate annulus, whitish or becoming
brownish on the edge in age, the edge a two-limbed
groove of 1–2 mm width when young, this indistinct
in age, upper and lower annular surfaces smooth,
remaining white.
Spores dark brown at maturity, ellipsoid, sometimes
subglobose, occasionally narrowed toward one end,
(5.7–)6.4–6.7(–7.4) 3 (4.3–4.9–)5.3–5.4(–6.0) mm,
mean 5 6.5 3 5.4 mm (N 5 40, C 5 1); hilar
appendix prominent; no apical pore evident. Basidia
predominantly tri- and bisporic, cylindro-clavate,
24.5–27.5 3 (5.5–)7.5–8.5 mm; sterigmata 3–4 mm
long. Cheilocystidia absent; lamellar margin fertile.
Chemistry: KOH gray-green on pileus surface,
elsewhere indistinct; aniline 3 GAA negative.
ITS1+2 sequence (GenBank EU257802): L 5
707 nt, unique characters: ctgtTcttg @ pos. 191.
Description is of basidiomata cultivated from a
spore culture of RWK 1789 at Sylvan Research, Nov
2005.
This unique collection was taken along with many
others during an unexpected collecting opportunity
under challenging travel conditions. It was only
possible at the time to collect and process air-dried
lamellae bearing viable spores, which later were
germinated, and to record spatial locations within
the site. Growth and basidiomatal development are
slow in this culture. Superficially RWK 1789 bears
some resemblance to A. pequinii, a member of section
Chitonioides; the latter species has a peronate veil,
solid stipe, deeply reddening stipe context, and
abundant cheilocystidia.
Agaricus agrinferus Kerrigan et Callac, sp. nov.
FIG. 11
Pileus 5–8(–10) cm latus, late convexus, mediocriter fuscus
vel raro subalbidus; pileipellis implexa, levis vel paulum
squamosa, continuo integra in margine, cetera autem parte
sordide aurantiaca evadente; stipes subaequalis, 3–8 cm
longus 3 1–2 cm latus, externa parte levi, cetera autem parte
paulum fibrata atque medullosa in medio, colorem sordide
aurantiacum ducit; sporae circa 5.7–6.5 3 4.4–4.7 mm, late
ellipsoideae vel tantum ellipsoideae, basidia tetrasporigera,
cheilocystidia cylindracea forte etiam claviformia, 15–33 3 3–
15 mm. Dispersus sub coniferis crescit in litoris regionibus
parva altitudine. HOLOTYPUS: Point Lobos State Reserve,
Monterey County, California, USA: RWK 1397, 10 Jan 1986, in
herbario SFSU depositur. MB 512235.
Pileus 5–8(–10) cm broad, at first broadly convex,
with moderately inrolled margin, becoming plane,
disk sometimes slightly depressed; surface dry, glabrous
on disk, elsewhere innately fibrillose, color
pallid to sordid (when young) or medium brown, if
brown then becoming appressed fibrillose-squamose,
squamae ca. 10 mm long 3 5–15 mm broad, background
color whitish to pale buff; context white,
becoming reddish near lamellae and stipe apex when
sectioned, firm, up to 10–16 mm thick, odor of A.
bisporus plus fruity/spicy as in some species of
Sanguinolenti after exposure. Lamellae free, close,
up to 10 mm broad, at first pallid to dingy pinkish,
finally dark blackish-brown, margin somewhat pallid.
Stipe 3–8 cm long 3 1–2 cm broad, equal to
subclavate, occasionally ventricose (in culture), interior
white, quickly becoming orange-red, ultimately
red after longitudinal sectioning, in median transverse
section becoming orangish, stuffed-hollow;
surface glabrous, or minutely floccose or with
fibrillose zones below, white, coloring as above when
incised; base firmly rooted in litter and/or soil. Veils
forming a supramedian, white intermediate-type
annulus with a pendant aspect, sheathing upward
and with a broadly flaring limb, unrolling with the
pileus margin, upper surface smooth to striate, lower
surface interwoven to scurfy, sometimes subtended by
one or two small limbs, margin thin, uneven;
universal veil also sometimes leaving a scale ring
above the base of the stipe. Spores (4.5–5.3–)5.7–
6.5(–7.1–7.5) 3 (4.1–)4.4–4.7(–5.3–6.0) mm, dark
brown, broadly ellipsoid to ellipsoid, hilar appendix
semiprominent, no apical pore evident. Basidia 17–
28.5 3 (4–)7–9(–12) mm, clavate to cylindro-clavate,
tetrasporic; sterigmata 1–4 mm long. Cheilocystidia
15–33(–45) 3 3–15 mm, clustered, not abundant;
lamellar margin primarily composed of hyphae
oriented parallel to the margin, sterile.

Chemistry: KOH negative; aniline 3 HNO3 negative;
o-tolidine blue on basal context of stipe,
elsewhere violet; alpha-naphthol purple on basal
context of stipe, elsewhere pinkish-orange to orange,
weakly so on pileus context.
Habit, habitat, known distribution, occurrence:
Solitary to subgregarious under Cupressus macrocarpa
in California, and under that tree and others in low
elevation coastal areas of the U.K. and France. Fall–
winter.
ITS1+2 sequence (GenBank EU257801 and
AF432888 for RWK 1397 and FS-5 respectively;
see also ITS1 sequences AJ418738-42, for RWK
1397, Sf5, FS-10, FS-13, and WAT1 respectively:
Challen et al 2003): L 5 703 nt. Distinctive characters:
atgtTattg @ pos 259, vs C for A. subfloccosus, is
unique within Bivelares.
Material examined: USA. California. San Francisco
County: RWK 738, 770b, 770c, 770*, 775, 884, 1117, 1140,
1040*, 1153, 1175, FS-2 (5ARP 003, 5ATCC 66250), FS-5
(5ARP 006, 5ATCC 66253), FS-13 (5ARP 030); San Mateo
County: RWK 969, 1192, FS-10 (5ARP 020, 5ATCC 76561),
FS-29 (5ARP 073, 5ATCC 200200); Monterey County: RWK
1030, 1397 (TYPE: SFSU; Paratype: ATCC MYA-3441
[preserved culture]), 1819, [1910 or 1911], NW-1 (5ARP
205); UK. Scotland: ATCC 34842; England: W4 II* (5ATCC
200593), W4 IV*, A 119* (5ATCC 200592), A 11*; France:
Sf2 (5CA47), Sf5 (5CA70). (See also Kerrigan et al 1999,
Challen et al 2003.) All California collections were made
under Cupressus macrocarpa.
Etymology: ager/agri: territory, land; inferus: lower.
The epithet refers to the distribution of the species
at elevations of about 5–200 m at middle northern
latitudes.
This mushroom was discussed in detail and figured
by Kerrigan et al (1999). At that time we showed that,
based on morphological, cultural, and molecular
(RFLP, isozyme) characters, this lowland entity was
phylogenetically distinct from the highland, spruce/
fir/pine associated form of A. subfloccosus (see
Cappelli 1984, Parra and Suárez 2002, Kerrigan et al
1999; this association is frequent but not absolute).
Both entities have been referred to A. subfloccosus by
various authors. We also indicated that the two
entities might be sister species, however without
sequence data it was difficult to be confident of the
best rank-relationship for them.
We further noted the problem presented by the
lack of a type specimen for Lange’s taxon. Lange
(1926) mentioned only this syntype: ‘‘Hollufga˚rd
forming large fairy-rings in naked ground in plantation
of Picea, Aug. 1915’’. No original specimens of
Psalliota subfloccosa exist in the Copenhagen Natural
History Museum (H. Knudsen pers comm; Kerrigan
et al 1999), therefore a lectotype designation is in
order:
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 887
Agaricus subfloccosus (J.E. Lange) Hlaváček, Mykol.
Sborn. 28(4–6):67. 1951 [‘‘subflocosus’’]
Lectotype (hic designatus): [icon] ‘‘Psall. hortensis
v. subfloccosa JEL.’’, in Lange, Danmarks Agaricaceer:
plate 647 (unpubl), deposited in the Copenhagen
Natural History Museum.
Remarks: Plate 647 was reproduced by Lange
(1939) as plate 139 D as Psalliota subfloccosa and
the original plate is currently shown on the Copenhagen
Botanical Museum web site at http://130.225.211.
158/agaricina/FMPro?-db5agaricina.fp5&-format5
flagar-storbillede.htm&-sortfield5fadtavle&-op5cn&
FADogCurrent5Agaricus%20subfloccosus&-max5
15&-recid533495&-find5
Briefly the key field characters useful in differentiating
A. agrinferus from A. subfloccosus are: the
former has an interwoven pileipellis that is usually
not pronouncedly scaly nor rimose toward the margin
(as in the latter) and is most often a somewhat darker
medium-brown (except in rare specimens with a
nearly white pileus when young) than the pallid to
lighter brown of the latter; A. agrinferus has a
relatively uniform stipe context, vs. the more fibrous
stipe context of A. subfloccosus; the two species are
separated by habitat and by elevation differences
reaching hundreds or thousands of meters at middle
latitudes in the northern hemisphere.
Although these two lineages differ at only one
position in their ITS sequences, the rank of species
was chosen for A. agrinferus because both species are
homothallic and their genomes and lineages therefore
are phylogenetically isolated, as indicated by the
nonreticulating pattern of RFLP markers within and
between the two species (Kerrigan et al 1999); they
are homomictic analogues of asexual species. The
single ITS character difference is consistent among
studied strains: compare with GenBank AJ418743,
AJ418745–47, AF432887, and EU131638–40 for A.
subfloccosus collections SUB1, RWK 1542, 21552,
21553, 21441, LAPAG 113, RWK 1568, 21993 and
21994 respectively. The two phylogenetic lineages
however are much more substantially diverged: the
observed extent of RFLP molecular marker dissimilarity
between the two sister species is 92% 6 2% SE
(Kerrigan et al 1999). Abundant diverging cultural
and molecular features, as well as the agreement of
characters within each species found on both sides of
the Atlantic, also were evaluated (Kerrigan et al
1999).
Morphologically the two species are quasicryptic
under some conditions. Because both species are
homothallic, and each comprises multiple nonrecombining
sublineages (genets) (Kerrigan et al 1999), the
process of homogenization that occurs within an outcrossing
species via independent association of most

888 MYCOLOGIA
traits in each generation is absent. Instead, homothallic
(homomictic) species can diverge into genets
that increasingly vary among themselves with respect
to the presence of various traits that might useful for
recognition of the species (e.g. absent in one vs.
present or absent in the other); hence we describe
‘‘tendencies’’ when presenting characteristics of
these species (see Stebbins 1950).
We believe that Lange (1926) described the
Pinaceae-associated entity as P. hortensis subfloccosa,
the basionym of A. subfloccosus. His material was
collected from ‘‘large fairy-rings’’ in a ‘‘plantation of
Picea’’ in Denmark. Danish material that we examined
had the nuclear RFLP genotype of the Pinaceaeassociated
entity, confirming its existence in the
region of the type locality (Kerrigan et al 1999). In
Denmark spruce will grow near sea level, while to the
south it occurs, along with this highland mushroom,
in montane settings. Finally, although macroscopic
differences between the two entities are subtle and
inconsistent, Lange’s (1939) figures of Psalliota
subfloccosa more closely resemble material of the
Pinaceae-associated entity, particularly with respect to
the more fibrous appearance of the stipe context. We
accept this interpretation.
In contrast Bohus (1994) published the illegitimate
name A. cappellianus Bohus (;A. bohusianus L.A.
Parra 2005) (non A. cappellianus Hlaváček 1987),
based on an Hungarian type believed to correspond to
A. subfloccosus ss. Cappelli (1984, Pl. 26). Both Cappelli
and Bohus placed their mushroom(s) in section
Sanguinolenti, and our study (Parra unpubl) of the
relevant material illustrated by Cappelli (1984, Pl. 26)
indicates that it is a pale collection of A. sylvaticus. Our
attempt to study the type material of Bohus (BP) was
unsuccessful; however his description, particularly the
spore size of 5.2–7 3 3.5–4.5 mm, is a better fit to A.
sylvaticus than to Lange’s A. subfloccosus. Therefore it
appears that no new name actually has been typified by
specimens of the montane, Pinaceae-associated A.
subfloccosus, simplifying the correct application of the
original name to such material.
In much of Europe south of Scandinavia and in
North America A. subfloccosus occurs from 500 m to
more than 1700 m above sea level, typically with Picea
(Italy, Switzerland, Canada, USA) or other Pinaceae
(Spain). It can be common in the bottoms of
glaciated valleys in Alberta, Canada (e.g. Banff ca.
1400 m and, farther north, Jasper ca. 1100 m), where
it may form arcs (partial fairy-rings). In Colorado it
occurs with spruce or with broadleaf trees and shrubs
in urban parks at 1600 m (Denver: M. Shaw, G.
Pickett and R. Kerrigan, pers obs). Parra and Suárez
(2002) report it with Pinus and Populus at 1500 m in
Spain.
In contrast the lowland entity that is known from
Scotland into France and from California usually
occurs near the coast and is most commonly
associated with Cupressus. We describe this entity
here as A. agrinferus. Like A. subfloccosus it consists of
homothallic genets; however each genet may be more
widely distributed in A. agrinferus (Kerrigan et al
1999).
Agaricus agrinferus has sometimes been (incorrectly)
called A. subperonatus ( J.E. Lange) Sing. (see
Kerrigan et al 1999 for literature review). The latter
species, recently proposed to be synonymous with A.
cappellianus Hlaváček (;A. vaporarius [Pers.] Imbach
1949, nom. illeg., non A. vaporarius Schrank
1789) (e.g. Nauta 2001; Parra 2003, 2005, 2008), has
been consistently illustrated with radially oriented
brown fibrils in appressed scales on the pileus surface
(Lange 1939, Essette 1964, Bon 1988, Cortecuisse and
Duhem 1994). Close inspection of fresh A. agrinferus
reveals that the fibrils of the pileipellis are highly
interwoven, not radially arranged (Kerrigan 1986); it
is a distinct entity. Based on our review of its ITS1
sequence, strain WC721 from the PSUMCC (provided
by RWK as FS-2/ARP003, from a collection by F.
Stevens in San Francisco, California), deposited by
Geml et al (2004) in GenBank (AY484698), belongs
to A. agrinferus, consistent with our own evaluation of
this culture (Kerrigan unpubl).
Agaricus devoniensis subsp. bridghamii Kerrigan,
subsp. nov. FIG. 12.
Pileus 3–7.5 cm latus, convexus demum late convexus,
fibrillis adpressis, albus demum sordidus; contextus albus,
immutabilis; stipes 5–8 cm longus, 1–1.5(–2.0) cm crassus,
subaequalis, e farcto cavus; contextus albus; velum peronatum,
inferus; sporae (4.8–5.3–)6.0–6.6(–7.3–7.4) 3 (4.3–
4.8–)5.1–5.5(–5.9) mm; basidia 19–23(–29) 3 9–10 mm,
tetrasporigera; cheilocystidia (12.5–)20–31 3 11–12.5(–15–
19) mm, equalis vel clavata vel subglobosa. HOLOTYPUS:
RWK 1899: Colorado, Clear Creek Picnic Area, Clear Creek
County, 16 Jul 1995: in herbario SFSU depositur. MB
512227.
Pileus broadly convex, 3–7.5 cm broad, margin
initially inrolled, disk slightly depressed in age;
surface glabrous or obscurely appressed-fibrillose,
color whitish or with irregular sordid brownish areas;
context white, virtually unchanging when cut, later
(or in age) becoming brownish near lamellae and
stipe, to 1.5 cm thick, odor mushroomy, unremarkable.
Lamellae free, close, drab when young, obscurely
if at all marginate (paler), later dark blackishbrown.
Stipe approximately equal, slightly broader at
base and sometimes at pileus, 5–8 3 1–1.5(–2.0) cm,
surface finely erect-fibrillose above veils, glabrous or
innately fibrillose below, basal 5 mm covered with
substrate; Veils submedian, peronate, sheathing, with
a flaring upper margin and a flaring, or appressed, or

obscure lower margin, all weak and soon collapsing;
context white, or obscurely rufescent in places,
becoming brownish near pileus, with a 3–5 mm broad
pith-filled central cavity.
Spores dark brown, broadly ellipsoid (Q 5 1.13–
1.16 to 1.24–1.26), (4.8–5.3–)5.9–6.6(–7.3–7.4) 3
(4.3–4.8–)5.0–5.5(–5.9) mm, the mean 6.21 3
5.20 mm, (N 5 120, C 5 3); hilar appendix not
prominent; apical pore not evident. Basidia clavate or
cylindro-clavate, 19–23(–29) 3 9–10 mm, mostly tetrasporic,
the sterigmata acute, to 4 mm long. Cheilocystidia
in scattered to semicontinuous fascicles, mostly
broadly clavate to subglobose or almost pyriform,
otherwise quasi-cylindrical, 20–27 3 11–12.5(–15) mm.
Chemistry: unavailable.
ITS1+2 sequence (GenBank AF432890–
91, EU131637): L 5 707 nt. Distinctive characters:
gtgaTaaca @ 180 and actcActtg @ 530 distinguish the
subspecies.
Habit, habitat, known distribution, occurrence:
Solitary or in small groups, under Picea, in fairly level
areas in valley bottoms, at middle to high elevations in
the eastern Rocky Mountains of Colorado and Alberta.
Material studied: USA. Colorado. Clear Creek County
Near Empire: Clear Creek Picnic Area, elev. 2900 m. Under
Picea, 16 Jul 1995, RWK 1899 (HOLOTYPE [SFSU];
paratypes: preserved culture MYA-2671 [ATCC]); Mizpah
Campground, elev. 3000 m. Under Picea, 16 Jul 1995, RWK
1900 (NY), preserved culture 5 MYA-2672 [ATCC]);
CANADA. Alberta. Canmore. Bow River Recreation Area
campground, elev. 1300 m. Under Picea, 5 Aug 1990, RWK
1664 (SFSU).
Etymology: The name honors Joseph Bridgham,
one of 19th century North America’s foremost
illustrators of fungi and other natural subjects, who
illustrated several Agaricus spp. for the Icones Farlowianae
(Farlow 1929).
Two ITS characters unify subsp. bridghamii contra
devoniensis; one of these characters is unique within
the section and possibly the genus. This level of
ITS1+2 sequence divergence of subsp. bridghamii
from A. devoniensis P.D. Orton subsp. devoniensis,
which itself is somewhat heterogeneous as presently
constituted (Challen et al 2003, Callac et al 2006; see
FIG 1), is in the rank-range of both established species
and varieties in the section. Because the morphological
differention of the two entities is slight and
because subsp. devoniensis at least comprises one or
more heterothallic, out-crossing populations (Callac
et al 2006), and furthermore because the ‘‘devoniensis
clade’’ is a complex group with additional undescribed
entities of uncertain rank, we believe that it is
more conservative and appropriate at present to
recognize bridghamii at subspecific (vs. species) rank.
Considering the other extreme, the physiological
differentiation of the two subspecies is greater than
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 889
what is seen among isolated populations or even
varieties in related Agaricus species (cf. Callac et al
1993). To underscore this point we also considered
partial RPB2 gene sequence from RWK 1899 and
from RWK 1800 (A. devoniensis subsp. devoniensis
from California) obtained for a separate study
(Kerrigan and Xu unpubl; GenBank EU285571–72).
We found 1.5% sequence divergence between the two
sequences, whereas for this gene segment A. subrufescens
Peck from California and Spain diverged by
0.6%, two A. placomyces Peck sequences differed by
0.3%, and two A. depauperatus (F. H. Møller) Pilát
sequences differed by 0.4% (Kerrigan and Xu
unpubl).
Morphologically subsp. bridghamii tends to have a
more compact shape, with a stipe length/width ratio
of 1.2–3.0 (vs. (2.4–)3.4–8.3 in subsp. devoniensis, per
auct.), and shorter cheilocystidia (for subsp. devoniensis,
36–50 mm, per Møller (1952), although LAP
notes that the terminal elements in the type are often
only 15–26 3 9–14 mm (we also note that subsp.
devoniensis collection RWK 1800 from California
lacked cheilocystidia).
The habitat and range differences (sand dunes and
Cupressus macrocarpa groves near sea level for subsp.
devoniensis, vs. montane Picea forests above 1300 m
for subsp. bridghamii) are of uncertain value in
delimiting the taxa; however, the physiological
divergence implied by the differing abilities of
cultures of the two subspecies to use mushroom
compost (RWK 1899 and RWK 1900 grow poorly and
ultimately unsuccessfully on commercial Agaricus
mushroom compost, while Californian, French and
Greek subsp. devoniensis grow and fruit well on it) is
distinctive. In a contrasting example individuals from
all populations of A. bisporus, including those from
coastal cypress and montane spruce forests, use
compost approximately equally well (Kerrigan and
Callac unpubl). Considering the degree of sequence
divergence, and the morphological, cultural, and
ecological attributes of the Rocky Mountain organism,
subspecific rank within A. devoniensis appears to
be most appropriate for this entity. Only certain other
isolates of subsp. devoniensis show clear mating
reactions, so the negative results of mating confrontations
attempted by Callac between the subspecies
are ambiguous at this time (Callac et al 2006).
Sordid discolorations on pilei of A. devoniensis
subsp. bridghamii also were reported for A. litoralis
(Wakef. & A. Pearson) Pilát, a species sometimes
linked with A. devoniensis (;Psalliota arenicola
Wakef. & A. Pearson; Cappelli (1984) provides a
good summary and discussion of variation reported
for European A. devoniensis and its purported relative
A. litoralis) but now considered to be a synonym of A.

890 MYCOLOGIA
spissicaulis F.H. Møller, which is the type of section
Spissicaules (Heinem.) Kerrigan (Nauta 2001; Parra
2005, 2008). Stains have not been noted otherwise on
A. devoniensis proper.
The variation RWK has observed in spore length/
width ratios for the two Colorado collections strengthens
our sense that members of the ‘‘devoniensis
clade’’ may be morphologically plastic and correspondingly
difficult to delimit and/or identify. The
entire ‘‘A. devoniensis clade’’ remains challenging, as
discussed below.
Since 2003 we also have also studied additional material
of A. devoniensis not noted above. Collection data on this
material is: CA 504 (5A. fragilivolvatus holotype): Italy,
Sardegna, prov. Cagliari, Serramanna, under Eucalyptus
camalduensis, 23 Oct 1992, leg. M. Contu and P. Dessi, coll.
M. Contu 92/60 (CAG) (GenBank EU363035); CA 445
(originally determined as A. fragilivolvatus): Italy, Sardegna,
prov. Sassari, Golfo Araui, La Marinella, under
Eucalyptus sp., 24 Nov 2004, leg. & det. M. Contu (without
collection number, private herbarium) (EU363036);
CA457: Spain, La Rioja, Calahorra, under Pinus halepensis,
28 Nov 1997, leg. & det. Agustín Caballero, coll. AC2160
(private herbarium) (EU363034); CA 568 (5Dv9; GenBank
EU258677): Greece, Papakosta (close to Agiokampos),
Thessalie, under C. sempervirens on the coast, 17 Oct
2000, leg. & det. I. Theochari, P. Callac, & R. Kerrigan
(CGAB); CA 117 (5Dv7; GenBank AF432895): Greece,
Feres, Velestino, under C. sempervirens, 13 Jan 1999, leg. I.
Theochari, det. P. Callac (CGAB).
DISCUSSION
It is fair to say that section Bivelares encompasses a
number of rarely seen species, some of which remain
undescribed. Collecting and describing ultrarare
species of agarics present special challenges. We
realize that we presently can provide only partial
information on the ranges and variation of some of
the taxa described here. Some conjecture remains,
for example about the relationship of the two known
collections of A. subsubensis. Particularly with the
advent of molecular data, especially DNA sequences,
it is possible to provide robust markers for biological
novelty even when material for study is limited. We
think it is important to place such data in the public
record. Our intent is to document such species as well
as possible at present, in aid of encouraging and
improving the recognition, preservation and reporting
of future collections.
Cultures of JB-101, FS-22, and RWK 1789 date from
1990–1992. As far as we know these species have not
been encountered otherwise in nature. Their novelty
has long been evident from RFLP and other
molecular data. Unfortunately the latter two collections
were made under conditions that precluded
voucher preservation; only a culture or viable spores
were obtained. Both A. subsubensis and A. cupressophilus
have now been cultivated successfully from original
cultures, which have been deposited at ATCC. The
French CA103 (INRA), sequenced by Callac from a
culture (available at MYCSA) from mushrooms obtained
by J. Guinberteau under cypress on Oléron
Island, France, is also a unique entity that, lacking an
extant voucher, is in need of recollection. A. agrinferus
is uncommon in the Monterey cypress habitat of
coastal California, the only place it is known to occur in
North America, where it has perhaps one-tenth the
abundance of A. bisporus (Kerrigan 1982). Agaricus
tlaxcalensis is presently known only from scattered sites
planted with C. benthamii in Tlaxcala, Mexico.
The A. devoniensis clade is challenging not only
due to rarity but also due to apparently recent
speciation processes, which in the case of subsp.
devoniensis in Europe might include re-integration of
diverged populations (cf. Callac et al 2006 and
unpubl). On one hand, because we have observed
no differences in the types of both species, Agaricus
fragilivolvatus Contu is considered here a synonym of
A. devoniensis. The type of A. devoniensis has spores
6–7 3 5–5.5 mm and clavate cheilocystidia 16–26 3 9–
14 mm, while from the type of A. fragilivolvatus we
measured spores and cheilocystidia respectively as 6–7
3 (4.5–)4.8–5.5 mm and 17–34 3 8–13 mm. The
cheilocystidia in the A. fragilivolvatus type were
clavate to pyriform and not vesiculose as described
by Contu. Compare also GenBank sequences
AF432892, –93, –94, –96, –97 and EU363034 with
EU363035–36) (FIGS. 1, 2).
On the other hand, some real heterogeneity exists.
A. devoniensis subsp. bridghamii has been found twice
in Colorado and once in Alberta. Its range is
therefore considerable; however in our experience it
is rare or at least uncommon. Another member of the
clade, known only from two collections (see CA 117,
CA 568) from Greece has distinctly divergent ITS1+2
sequences and might deserve taxonomic recognition
after further study (see GenBank AF432895 and
EU258677).
Two additional members of this clade (see Gen-
Bank AF432889, AF059225) in need of further study
have been reported from New Zealand by Mitchell
and Bresinsky (1999), indicating a broad geographical
scope for this phylogenetic radiation. We discussed
in 2003 our sequence data from material
determined by Mitchell and Bresinsky as A. subperonatus
but which instead is closely related to A.
devoniensis (Challen et al 2003). Based on our review
and in comparison with European material, the ITS2
sequence deposited by Mitchell and Bresinski (1999)
as A. devoniensis from New Zealand also appears to

elong to a related but distinct entity in the ‘‘A.
devoniensis complex’’ (the unresolved phylogenetic
clade encompassing A. devoniensis and any variants
and closely related putative species) (FIG. 2).
During this study we have evaluated some sequences
present in GenBank. We note that ‘‘A. padanus
HAI 0312’’ (GenBank AJ884647) recorded by Didukh
(2004) and sequenced by Didukh et al (2005) is a very
close match for A. bitorquis. We also have sequenced
the type of A. padanus, and it has a distinct sequence
similar to those of section Sanguinolenti (unpubl). We
therefore regard GenBank AJ884647 to be of A.
bitorquis.
Some comments on our earlier report with M.
Challen on Duploannulati (5Bivelares) (Challen et al
2003) are in order. Nomenclature of A. subfloccosus
s.l. and A. vaporarius are discussed above, as is the
challenge presented by Agaricus devoniensis and its
associates. The possibility of the existence of a
distinct, rare A. subperonatus elicits a range of
opinions but cannot be fully resolved at present.
M.M. Nauta (pers comm) has noted that our
statement concerning the lack of rufescence in A.
bitorquis (Quél.) Sacc. is at least an overgeneralization.
We are inclined to agree, in view of our
emerging belief that A. bitorquis var. validus (F.H.
Møller) Bon & Cappelli is most likely to be a
phylogenetically irrelevant name applied to occasional
individuals of A. bitorquis exhibiting discernible
rufescence, a trait hypothetically (for example) due to
a single gene change resulting in over-expression of
tyrosinase enzyme activity (see van Leeuwen and
Wichers 1999). We sequenced the ITS1+2 region of
one such individual (LAPAG 517: duplicate from P.
Arrillaga, garden, Zarauz, Guipúzcoa, Spain, 8 Apr
1996 [coll. 501-8/4/96 deposited in Arrillaga’s private
herbarium] Arrillaga 2004) (GenBank EU257804)
and found no differences from var. bitorquis sequences
other than one heteromorphism. We also have
added new A. bitorquis sequences to GenBank from
CLO 4465 (Clarke Ovrebo, Oklahoma [OKL];
EU258675) and JWS-1 ( John Sparks, New Mexico
[SFSU]; EU258674) for comparison. According to
Nauta the rufescent phenotype is not uncommon in
Europe, but in our own experience it is not common
and less so in North America. At best the rufescence
of typical A. bitorquis is limited to an indistinct sordid
discoloration of the stipe and of pileus context near
the lamellae, primarily in mature specimens.
There are now 10 named species and several
infraspecific taxa formally placed in section Bivelares.
Two subsections are recognized. Entities needing
names, after adequate further study, are known from
France, Greece and New Zealand. Additional discoveries
would not be surprising.
KERRIGAN ET AL: NEW TAXA IN AGARICUS SECTION BIVELARES 891
ACKNOWLEDGMENTS
We thank D. Arora, P. Arrillaga, P. Boisselet, A. Caballero, K.
Chadwick, M. Contu, J. Guinberteau, G. Maddalena, G.
Mata, A.D. Mitchell, M. Moinard, D. Murietta, A. Mua, C.
Ovrebo, K. Peterson, G. Pickett, S. Rextoueix, M. Shaw, J.
Sparks, F. Stevens and A. Tancrède, and the Colorado
Mycological Society, for specimens, cultures and/or collecting
assistance. J. Guinberteau provided FIG. 3 and other
assistance. Advice on Latin and translations were provided
by G. Heuclin, R. Halling and J. Santos. Some sequences
were kindly provided by M. Challen and J.-P. Xu. P. Callac
acknowledges ECOS-Nord and ANUIES (M06A01 Franco-
Mexican program) and the BRG (Bureau des Ressources
Génétiques, program No. 51, 2007/2008) for financial
support.
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