A new status for the Western European taxa of the Cladonia cervicornis group

Abstract

Within Cladonia cervicornis, currently three taxa are accepted in western Europe, viz. ssp. cervicornis, ssp. verticillata and ssp. pulvinata. Co-occurrences of two or even all three taxa are quite frequent and have been observed by the authors in the field in numerous localities in the Netherlands as well as other European countries. We tested the hypothesis that all three taxa can be recognized at species level. Even in mosaics, single thalli of ssp. cervicornis and ssp. verticillata could be determined with certainty especially by colour, incision and orientation of the basal squamules. Ssp. pulvinata deviates from both ssp. cervicornis and verticillata in its persistently slender podetia with only few proliferations as well as the presence of psoromic acid instead of fumarprotocetraric acid. We propose to accept the three taxa of the Cladonia cervicornis-group as species, viz. C. cervicornis s.str., C. verticillata (Hoffm.) Schaerer and Cladonia pulvinata comb. et stat. nova, which has not been raised to specific level before.

Full text

Lichenological Contríbutions in Honour of G.B. Feige
M. Jensen (ed.): Bibliotheca Lichenologica 86: 193-203.
J. Cramer in der Gebriider Borntraeger VerlagsbuchhandlwtgBerlin' Stuttgart, 2003
A new status
for the Western European taxa of the
Cladoniu cervicornis group
C. M. vaNHpm' & A. Aprnoor'
I Lichenologisch Onderzoekbureau Nederland, Goudvink 47, NL-3766 WK Soest,
The Netherlands
2
Centraalbureau voor Schimmelcultures, P.O. Box 85167, NL-3508 AD Utrecht,
The Netherlands
Abstract: Within Cladonia cervicornis, currently three taxa are accepted in western Europe, viz.
ssp.
cer"vicornis, ssp. verticillatct and ssp.
ptilvinala. Co-occurrences oftwo or even al1 three taxa
are quite flequent and have been observed by the authors il the field in numerous localities in
the Netherlands as well as other European countries. We tested the hypothesis that all three taxa
can be recognized at species level. Even in mosaics, single thalli of ssp. cervicornzs and ssp.
verticillata could be determined with certainty especially by colour, incision and orientation of
the basal squamules. Ssp.
pulvinata deviates from both ssp. cervicornis and vertícillata in its
persistently slender podetia with only few proliferations as well as the presence
ofpsoromic acid
instead of fumarprotocetraric acid. We propose io accept the three taxa of the Cladonia
cervicornis-group as species, viz. C. cervicotzr^r s.str., C. verticillata (Hoffm.) Schaerer and
Cladonia pulvinata comb. et stat.
nova, which has not been raised to specific level before.
Introduction
The Cladonia species from heathlands and acid sand dunes in westem Europe are
among the best studied lichens in the world. The taxonomy of some species
complexes
is however not yet fully settled.
Although there is little disagreement
about
the delimitation
of the respective taxa, there is still much disagreement as
to
the level at which cedain taxa are recognized. A much-debated
example
is the
Cladonia
pyxidata-group
in the widest sense, where some authors accept all chemical
strains as different species, while others only accept the morphologically
recognizeable taxa as species or even only accept one species for the whole group.
Sti1l a morphologically
distinct
nerv
species was recognized in this group
recently,
viz. Cladonia
monomorpha
(APrRoor, SIPMAN & vAN
HERK 2001).
Within Cladonia cervicornis (Ach.) Flotow, currently three taxa occurring in
westem
Europe
are accepted at the level of subspecies according
to Aun (1980,
1983), viz. the nominal ssp. cetnicot"tlr, the
chemically
identical
but
morphologically
somewhat different ssp.
verticillata
(Hoffm.)
Ahti, and the mainly chemically deviant
ssp. pulvinata (Sandst.)
Ahti (Figs. 1-3). Ssp. verticillata is so far mainly
characterized by its few and small basal squamules with white undersides,
whereas
ssp. cervicornls has well-developed tufts of basal squamules, which are in part
tinged
193

pink to bluish gray below; its podetia
are reported to be more poorly developed
(AHrt 1980). Ssp.
pulvinata is mainly recognized by the presence
of psoromic
acid
instead of fumarprotocetraric
acid, and slightly
more slender
podetia
(AHrI 1983).
This concept
is followed in most recent floras and checklists
(e.g.
Wrnru 1995,
DIEDERICH & SEnusmi,x
2000, ScHoLZ 2000). Some
morphs oÏ ssp.
verÍícillata and
ssp. cer'vicornzs,
however, are notoriously difficult to separate and putitive
intermediate specimens
are
reported
(PAUS 1997). In distribution
maps, all three taxa
are often taken together
(e.g. Henr.l 2000). Punrts et al. (1992) go as far as to
recognize
ssp.
pulvinata only as a chemotype.
It is obvious
that the distributions
of the three
taxa overlap, with ssp.
pulvinata
restricted to westem Europe (North to Norway, West to Great Britain, South to
Portugal and
East to Poland)
and the two other
taxa reported
from all over the world.
We adhere
to the currently
wide-accepted
view that species are
not to be defined but
have to be detected,
whatever the nature
of their characters
is. An important tool in
this approach
is the presence
or absence
of co-occurrences
of different
taxa on the
same
substrata
in one
single
habitat.
When
Ahti introduced the subspecific
level
for the three westem
European taxa of
rhe Cladonia cervicornis-group,
he noted the co-occurring
Dutch populations.
Material of ssp.
pulvinata was earlier ascribed
to Cladonia rappii A.W. Evans
(ScHADE
1960) described
from Florida; this opinion was followed in several
local
treatments
(e.g. HnvxwwN & StpvaN 1978). It was argued
by AHrt (1980),
however,
that C. rappii deviates in having very poorly developed
squamules and a
more greyish
colour,
leading
to the widely accepted opinion thaï C. rappii does
not
occur in Europe
(Punvrs eï. al. 1992). As far as we know, no valid name at species
level is available
lor ssp.
pulvinata, which is rather rare in most of its range. The
inland acid
dunes and heathlands
of the Netherlands
form the largest
refugium still in
existence.
Methods
Extensive
field work was caÍried out by the authors
in the Netherlands,
mainly
during 1995-2001.
More than 250 localities with coastal
and inland sand
dune
vegetation,
heathlands,
moors and mine spoil heaps
were searched for members of
Íhe C. cervicornii group;
nearly all known populations
were visited and
numerous
new localities
detected.
Approximately 300 collections
were made
(hb.
van Herk,
ABL); a1l
three currently
recognized taxa were found to be equally common,
and
studied
under field conditions
and
in the laboratory. Selected
localities were also
visited in Austria, Belgium, Denmark, France, Germany, Great Britain, Italy,
Luxembourg, Sweden
and Switzerland,
and about f,rfty herbarium specimens
(in
ABL) from other countries
were studied as
well.
We tested
the hypothesis that all three taxa can be recognized
at species level.
We tried to soÍt out 'hard' characters from environmental modifrcations,
particularly by searching
for co-occurrences of apparent different taxa. Special
emphasis was
given
to find close-contact
situations
(thalli
of two different
taxa
+
touching each other) to trace taxa behaving
as different species.
Photographs of
separate
species, as
well as thalli in close contact
were taken
in the field (Fig. 1:
the Netherlands, Utrecht, Soest, Stompert;
Figs. 2-7'. the Netherlands, Utrecht,
between Overberg and Amerongen, see Tab. 3). All photographs
were taken
194

under fresh and moist conditions. After taking the pictures, the samples were
collected
(hb. van Herk) and chemically
tested.
Results
Examination
of available herbarium
collections
confirmed that our westem
Eurooean
specimens all belong to one of the three taxa.
Co-occurrences
(within approx. 10b
m2
uniform terrain) of two or even all three taxa were quite frequent and have been
observed by the authors in the field in numerous localities
in the Netherlands.
Co-
occwïences
of ssp.
pulvínata and
ssp.
verticillata
have
also been observed
by us in
Belgium (Limburg, Hamont, Beverbeekse
Heide), France
(Ardennes,
Fépin) and
Germany
(Berlin, Doppelt);
co-occurrences
of ssp. cervicornis
and ssp. verticillata
also in France
(Fépin).
Close contact
occunences were found
rather frequent
as well
(Figs.
3-7). Close contacts of all three taxa
together were also found (Fig. 6). The
taxa are mainly characterized
by the shape of the basal squamules and their
chemistrg see Tabs. 1
& 2 for a comparison
between the taxa.
Fig, l: Cladonia
pulvinata with mature
podetia
which remain
slender when old (bar- 5 mm
in all fieures).
195

Fig.2: Cladonia
yerticillata
u'ith mature
podetia $ hich become
rypical1y
stout
s hen
old.
Fig,3: Cladonia
cervic'ornis
(a1l
except one
thallus in the
centre) shorving
its dceplv
incisecl
basal
squamules
r.r'ith rounded
axils. and C. vefiicilluta (on1y
in the centre)
sith shallol 11
lobed squamules.
196

Fig. 4: C puh,inaro
(leÍt) *'ith smaller. upnght squamules
s'ith a dor'vncun'ed margin, and C
yerticillata (right) u ith larger
procumbent.
douncun ed scluamules. C.
pubinoÍa shou.s three
aberant,
gall-like, pulvinate
nrÍts.
Fig. 5: C cervicornis
(left) *'ith distinctlv incised
squamules. and C. puh'inattt (right) u'ith
shallou'lv
lobed
squamules.
ï97

Fig. 6: All three species in close contact:
C. cen'icorrtis
(top 1eft), C. t,erlicillata
(down left)
and
C.
pulvinata (rightl.
Fig. 7: Enlarged 1eÍt part of fig. 6 s ith incised squamules
of C. cen'icornls (left) and
shallorvly
lobed squamules of C. verticillctta
(right). Young thalli of C. verlicillata are \ery
sirnilar
to C.
pulvinatu (cor-npare n'ith Fig. 5, right), horr'ever. chentistry and
mature
podetia
(Figs.
1 & 2) are distinct.
198

The taxa are most easy recognized
in moist and fiesh condition, when the
differences
between the colours
are more
pronounced.
Even in mosaics,
single thalli
of ssp. cervicornis and ssp. verticillata could be determined
with certainty.
Appropriate characters,
viz. colour,
incision
and orientation
ofthe basal
squamules
appear distinct
(Figs.
3 &7). No constant
differences
between ssp. cervicornis
and
ssp.
verticillata
were found
in their
podetia.
As a consequence, herbarium
specimens
collected
without basal squamules are difficult to identifu, and the only useful
characters in such material
is to be found
in the
shape of the
podetial
squamules.
Ssp.
pulvinata has
basal squamules
very similar to spp. verticillata,but in close-
contact
situations their size, colour and orientation
usually appear
slightly different
(Fig. a). Podetia of ssp.
pulvinata aÍe, however,
distinct from both ssp. cervicornis
and verticillata in their persistently
slender
appearance
(compare
Figs. 1 & 2) and
their few proliferations
(Tabs.
1 & 2). Collections
of ssp. verticillaía
without mature
podetia
are diÍficult to distinguish lrom ssp.
pezlvinata
only
by morphology (compare
Fig. 5 (right)
with Fig. 7 (right));
the
chemistry, however,
is always
distinct.
Surprisingly, the maximum
number
of tiers of the
podetia
is not a useful character
to take ssp. cet'vicornis and, verticillata apart, in contrast with the current opinion.
The vast majority
of the specimens
(or even
populations)
develop few (l-4) tiers;
the
frequencies
of the number
of tiers is the same in both taxa
(statistics
not given
here).
Ssp.
cervicornrr"r
has more
often a well developed thallus,
even reminiscent
of a small
Cladoniafoliacea.
The three taxa each show a slight preference
for a certain habitat, and have as a
consequence somewhat
different distributions in Europe and even within the
Netherlands (Figs. 8-10). Subspecies ceryicornis has the widest ecological
amplitude; it occurs in warm slightly calcareous
grasslands,
both calcareous coastal
and acid inland sand
dunes, sandy
patches
in heathlands,
and on humus
and
peat.
Subspecies verticillata
has a more restricted
occuÍrence: species-rich
acid
sand dune
vegetation and Calluna-heath
with a wind-blown sand cover are favoured;
occasionally it can be found at mine spoil heaps
associated with pollution of healy
metals
(HnmEL
2000).
Subspeciespzlvinata
is mostly restricted
to species-rich wind
blown-acid
sand dunes, rarely on acidified
coastal machair.
Examples
of the lichen
vegetation
at localities
where
all three taxa
occur
on the same few square meters
are
given
in Tab.
3. Often
primary
squamules
of various
Cladonia species
dominate,
and
each species is characterized
by the combination
of a certain colour and lobe
configuration.
Within Europe,
ssp.
pulvinata
is restricted
to sub-atlantic
regions;
ssp. cervicornis
is widespread,
but most abundant in the mediterranean
and warm regions
of central
Europe; ssp. verticillala is widespread
but more boreo-montane,
and is in the
mediterranean restricted
to the mountains.
We have not studied
specimens from
outside Eurasia
that are convincingly attributable
to any of these
three taxa. An
exception might be ssp. verticillata,
which is probably
a circumpolar taxon.
In other
regions,
e.g. in tropical America,
the species
may be replaced
by vicariants (AHrr
2000).
It is concluded that the three taxa of fhe Cladonia cewicornis-group
are
recognizeable
both in the field and in the herbarium. They behave
as sy,rnpatric
species,
just like the other Cladonia
species
occurring
in the same
region in these
habitats. we therefore propose
to accept
the three
taxa of the cladonia ceruicornis-
group as species,
viz. Cladonia cer.vicomis
s.str.,
Cladonia verticillata (Hoffm.)
199

1a
tb
Schaerer
and Cladonis
pulvinata (Sandst.)
van Herk & Aptroot
comb. et stat.
nova,
basionym: Cladoniaverticillataf.pulvinata Sandst., Cladon. Exsicc. No.233
(1918).
Type material
of C.
pulvinata has
been studied by us and
is in full agreement with
our perception
of the species.
It is illustrated
by SaNnsrEDE
(1931).
Although the
taxon was originally described for its aberrant morphology (pulvinate due to
increased branching of the squamules, see Fig. 4) rather than its chemistry, it seems
to be the only name available for the
psoromic-containing
species. Still, we prefer
to
use this basion)ryn at species
level (which is not mandatory) rather than describing
a
new taxon, because the name
pulvinatahas
been attached
to this taxon now for some
time. It has to our
knowledse not
been
raised
to species level before.
Tab. 1: Kev to the species.
Podetia with up to 7 tiers.
Cups up to 11
mm wide, always becoming stout when full-
grown (height-breadth
ratio 1-3). Fumarprotoceffaric acid
present (Pd+
red) .............2
Podetia with up to 2 tiers. Cups up to 4 mm wide, remaining slender when full-
grown (height-breadth
raïro 2.5-6), often stunted. Psoromic acid present (Pd+
yellow) ..C.
ptrlvinara
Basal squamules deeply incised (>50%) with lanceolate
lobes and rounded axils,
strongly curled when dry, showing conspicuously
their undersurfaces
(like C
foliacea), the apices pointing horizontally or downward. Upper surface colour
uniformly
yellow-green
when fresh, margin flat .....................................C cervicornis
Basal
squamules entire or only shallowly lobed, lobes rounded, never lanceolate, not
curled when dry, procumbent
or pointing
upright. The upper surface
colour is bluish
"::::"::*::o::::ï::::.:::l:T:::Ïiilllll-f
1':l*:'ti?ï:::,;;;;.
"Iab.2'. Chancters
of the westem European taxa
of the Cladonia cervicornis-srotp.
2a
2b
character
medullary chemistry
squamule direction (dry)
sqamule size
upper surface colour
lower surface colour
squamule dissection
squamule lobes
lobe margin (dry)
marginal black rhizines
mahlre cups
proliferations
^rJ hÍÁfêfêh^ê
distribution
C. cervicomis
fumarprotoceÍraric
strongly upcurled
up to 12 mm
yellow-green
purplish hue
deeply incised
lanceolate+rounded
axi ls
flat
occasionally present
stout
up to 7 tiers
acid and calcareous
mediÍerr.
& sub-atlantic
C. verticillaía C.
pulvinota
fumarprotocetraric psoromic
not curled slightly upcurled
upto6mm uptoTmm
bluishgreenbrownish brownishtinged
mostly whitish yellowish hue
not/shallou'lyincised shallowlyincised
rounded rounded
oftendowncurved usuallydowncurved
not observed not observed
stout slender
up to 7 tiers up to 2 tiers
acid
soils acid soils
boreo-montane atlantic
200

Tab. 3: Species
constitution
of some representative
locations
in the Netherlands
where all
three
taxa occur. 1: prov. Utrecht,
Leusden,
Den Treek,
Kelderbosch,
grid ref: 153.61456.g,
old Calluna
heath
with a wind-blown sand
cover,
c. l0 x I 0 m2,
24_3_2001:
2..
prov
. Drenthe.
casteren.
Gasterense
Duintjes.
grid reÊ 240.21562.6,wind-blor.rn
acid
sand
dune uith dense
cladonia cover and sparse grasses,
10 x I0 mt, lg-11-2001;3: prov. utrecht,
between
overberg and Amerongen,
Amerongsche
Bosch, grid ref: 163.4/44g.3,wind-blown
acrd
sand
depression
with dense
cladonia cover
surroundedby
callunaheath, 15
x 15
m2, 19-12-2001.
Cetraria aculeata
Cladina arbuscula
Cladina portentosa
Cladonia borealis
C. callosa
C. cervicornis
C. coccifera
C. críspata
C. floerkeana
C.
foliacea
C. furcata
C. glauca
C. gracilis
C. grayi (s.1.)
1,2,3
I,2,3
1,2,3
I,2,3
1a
1,2,3
1,2,3
I,2,3
t2
1a)
1,2,3
I,2,3
1.2,3
C. macilenta 1,2,3
C.
monomorpha 1,2
C.
pulrinata 1,2,3
C. ramulosa t,2,3
C. strepsilis 1,2
C. uncialis 2,3
C. verricillata 1,2,3
C. zopfii t.2,3
Diploschistes
muscotam 2
Micareo leprosula 2
Placynthiella trliginosa 2
Stereocauloncondensatum 3
Trapeliopsisgranulosa 1,2,3
Fig. 8: Distribution of
Cladonia pulvinata in the
Netherlands based on
herbarium
specimens.
201

Fig. 9: Distribution of
Clodonia venicillata in
the Netherlands
based
on
herbarium
specimens.
Fig. t0: Distribution of
Cladonia cervicornis in
the Netherlands based
on
herbarium
specimens.
202

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