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20 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 21
There is a signicant number of bryo-
phytes that are most often found in
articial habitats. In the 20th cen-
tury, rapid urbanization and exploita-
tion of natural resources throughout
Western Europe have profoundly altered the
natural habitats of mosses and liverworts.
Recording of bryophytes in cities and articial
habitats has increased dramatically in the last
few decades, and has signicantly improved our
knowledge of the articial ecology of bryophytes.
Tortula muralis is ubiquitous and abundant
on concrete, mortared walls and roof tiles but
is often present in only modest quantity on
calcareous rock outcrops in France or other
parts of Europe. Riccia crystallina is found on
compacted, ne-textured substrates in gardens,
but also in the inundation zone of natural ponds.
In cities, Syntrichia papillosa is observed growing
on concrete, but it is a typical epiphyte of Quercus
in natural Mediterranean areas. Pseudocalliergon
lycopodioides is often found in oligotrophic
fens, but also in China clay quarries in France.
Leptodictyum riparium is found growing at the
base of deciduous shrubs in alluvial forests and
also in greenhouses and on sloping tarmac roads.
For such species, it is not dicult to explain
occurrences in articial habitats as chance
colonization of secondary ecological niches.
On the other hand, some species have articial
habitats as their primary niches. Grimmia
crinita is almost always found on mortared
walls in churchyards in southern France. Many
bryophytes are adapted to arable land and some
particular species are dicult to spot outside this
anthropogenic habitat (for example Dicranella
staphylina and Didymodon tomaculosus). In
southern France, Leptophascum leptophyllum is
only observed along heavily disturbed paths in
or near urban areas, whilst its British occurrences
are in arable elds in the south. Rhynchostegium
rotundifolium is a specialist of castle walls and
is never found in natural biotopes in France,
whereas its two British populations are both
adjacent to lanes. In these cases, the original and
natural habitat can be rather dicult to trace.
It is not dicult to see G. crinita as a typical
inhabitant of calcareous outcrops, but it is in
fact almost never observed in such a situation
(Greven 2011). One could wonder where
Rhynchostegium rotundifolium was growing
before human settlement.
e study of the original habitats of
synanthropic bryophytes (ecologically associ-
ated with humans) can be a stimulating research
area. A population growing in an articial
habitat cannot be considered precisely equivalent
with a natural one, and it is a well-established
fact that populations are liable to genetic
modication following colonization events.
From a management perspective, a good under-
standing of natural habitats may be crucial for an
accurate conservation action plan.
Ephemerum cohaerens (Hedw.) Hampe is
typically linked with articial reservoirs in France
and in the UK, so its natural habitat is somewhat
obscure. We focused on this species because of its
rarity worldwide and because it could be a useful
tool in a conservation context.
e distribution of E. cohaerens
Following the recent taxonomic revision of
Holyoak (2010), six species of the genus
Ephemerum are known to occur in Europe.
E. cohaerens is one of the rarest species and
is included in the Red Data List of European
Bryophytes with the status ‘Vulnerable’ (ECCB
1995). It is also listed in the British Red Data
Books mosses and liverworts (Church et al., 2001),
on the revised UK Red List (Hodgetts, 2011)
and in other countries’ Red Data Books. is
species has a wide but discontinuous range in the
Holarctic, being mentioned in Eastern North
America (Bryan & Anderson 1957; Crum &
Anderson 1981; Bryan 2005), in Asia (China
and Japan; Bryan 2005) and Europe, where it
extends from Spain to e Netherlands, and
from the United Kingdom to Poland. A recent
French distribution map showed a great scarcity
of the species in France (Hugonnot et al., 2005).
e inundation zone of reservoirs as a habitat
for E. cohaerens
e inundation zone of reservoirs provides
important habitats for mosses (Atherton et al.,
2010). Alternative ooding and exposure are
characteristic of the margins of water bodies
(Ellenberg, 1988; Rodwell, 2000), whilst
open and moist, ne-textured substrates are
most characteristic. E. cohaerens shows special
adaptations to this peculiar habitat, such as
rhizoidal tubers (Pressel et al., 2005), fast
growth and abundant production of large
spores (50–90 µm) that enable it to cope with
specic seasonal constraints (alternating cycles
of waterlogging and drying). As it has been
demonstrated that the spore bank is of utmost
relevance in the strategy of Physcomitrium
sphaericum (Furness & Hall, 1981), it is likely
to play a major role in the case of E. cohaerens
Article
Ephemerum cohaerens,
an exquisite survivor of
functional alluvial habitats
Many bryophytes are now so familiar to
us in man-made habitats that it is often
difcult to understand what their natural
habitat would be without human
intervention. Vincent Hugonnot and
colleagues takes a look at one such
species, Ephemerum cohaerens,
familiar (although rare) to French and
British bryologists from the inundation
zone of articial reservoirs.
v E. cohaerens.
Norbert Schnyder (Institut
für Systematische Botanik,
Universität Zürich)
22 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 23
Ephemerum cohaerens habitat Ephemerum cohaerens habitat
status of the habitats although they are reputedly
naturally quite eutrophic (Rodwell, 2000).
e example of Rhône river valley (France)
Ongoing bryological surveys in south-eastern
France surprisingly revealed that E. cohaerens
is rather frequent in articial gravel pits in the
Rhône valley, while totally absent at the margins
of the uctuating Rhône channel or connected
lateral arms of the river. is led the authors to
search for explaining factors. E. cohaerens appears
strictly located within the Rhône ood plain,
between the main channel and adjacent hill
slopes (Figs 1 & 2). Our repeated attempts to
nd the species in the river channel bed failed,
even though apparently suitable microhabitats of
bare and moist substrates are very frequent.
Seven E. cohaerens populations have been
discovered recently. In view of the scarcity
of abandoned and unforested gravel pits in
the Rhône river valley we are condent that
these gures reect the genuine abundance of
the species. Only one population is not in an
articial reservoir. With regard to bryophyte
assemblages, it is worth noting the occurrence
of other ephemeral species as Aphanorrhegma
patens, Bryum klinggraei and several liver-
worts (Aneura pinguis, Riccia cavernosa) that
are typical inhabitants of water-body margins
(Table 1). e distance between the populations
and the main channel is very variable, from more
than 1 km to 100 m (Table 1). Notwithstanding
too. In Europe, this species is mostly recorded
as growing on the margins of articial water
bodies (Hill et al., 1994; ECCB, 1995; Ahrens
in Nebel & Philippi, 2000; Dierssen, 2001;
Infante & Heras, 2005). Rarely the species grows
in stubble elds (Delarze et al., 1998) and except-
ionally in a Schoenus nigricans mire (Rogeon,
1975). Very little is known regarding the nutrient
, Fig. 2. Photographs of the localities of E. cohaerens.
1, Ain conuence; 2, Miribel-Jonage; 3, Tournon sur
Rhône; 4, Canal de Montélimar.
, Fig. 1. Location (red dots) of E. cohaerens populations
in the Rhône valley. 1, Ain conuence; 2, Miribel-
Jonage; 3, Tournon sur Rhône; 4, Canal de Montélimar.
1 1
3 3
2 2
4 4
24 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 25
Ephemerum cohaerens habitat Ephemerum cohaerens habitat
their distance from the main channel, all popu-
lations have developed on alluvial deposits left by
the past meanderings of this large, mature river.
Natural versus artificial stations
E. cohaerens populations were encountered
in two distinct ecological situations. e vast
majority of them (6 out of 7) are located at the
margins of water bodies located in abandoned
gravel pits. ese articial reservoirs have a very
low connectivity to the Rhône and are only fed
by aquifers that provide nutrient-poor waters.
e population located around the dynamic
conuence of the Ain and Rhône is the only one
in a natural situation. However, it is remote from
the main channel, dominated by groundwater
seepage and rainfall inputs, and is only connected
during major ood events.
Signicantly, in the Rhône valley, Hippuris
vulgaris and Nitella hyalina are two common and
typical oligotrophic associates. For charologists,
it is a well-known fact that some species of Chara
or Nitella are restricted to localities with clear
water and very low nutrient content (Krause,
1981; Simon & Nat, 1996).
From a general point of view, in a naturally
functioning river valley, channel dynamics lead
to dramatic changes in stability and create bare
habitats when meanders are cut o to form
oxbow lakes. e water quality in the active
channel is very dierent from the underground
water inltrating from the river or from the
ground (phreatic) water table of abandoned
channels. In the Rhône river valley mesotrophic
communities are replaced by oligotrophic ones
towards the margin of the oodplain (Bornette &
Amoros, 1991). In strongly man-inuenced river
valleys, such as the Rhône, large-scale connectivity
does not allow oligotrophic vegetation to
develop. Instead, hydrological isolation provides
optimal conditions for oligotrophic amphibious
bryophyte communities to grow. In a sense, E.
cohaerens could well be considered as a powerful
indicator of hydrological isolation from ooding
by water from the main river channel. Here,
phreatic articial reservoirs are ecological refugia
for E. cohaerens.
e distribution of E. cohaerens in Baden-
Württembergs (Ahrens in Nebel & Philippi,
2000; Meinunger & Schröder, 2007) and older
mentions of the species (Limpricht, 1890) closely
reect the dependence towards large functional
hydrosystems, another example being the Rhine
in Vanderpoorten et al. (1995). A recent survey
in south-western France suggests that E. cohaerens
could be more widespread than previously
realized in reservoirs of the Garonne valley where
a frequent associate is Riccia cavernosa (Celle et
al., 2010). is is at odds with observations in
the UK, however, where records come from ve
reservoirs and an articial lake in England, none
of which is associated with a large river. It is also
at odds with the nine Irish populations, most
of which come from the margins of uctuating
natural loughs.
Lessons for site management
Regarding site management, oligotrophic waters
are essential for the maintenance and expansion
of E. cohaerens, so nutrient enrichment should
be controlled. e aggregated eects of chem-
ical inputs (human sources of nitrogen, phos-
phorus and other pollutants) and the prevailing
transport of ne sediment in river channels have
greatly contributed to water quality deterior-
ation. e improvement of overall water quality
is usually only conceivable at a catchment scale
and is therefore beyond the reach of most site
managers. However, the observations from France
emphasize the need to maintain oligotrophic
conditions at the British and Irish sites, and raise
concerns for the Sussex population, which is a
very popular site for feeding ducks and swans.
It is not recommended to favour the creation
of new gravel pits because quarry owners do not
need our recommendations to severely exploit
available natural resources: new gravel pits will
continue to appear here and there in the Rhône
valley. Hence the best way to conserve dynamic
populations of E. cohaerens there is surely to
favour a return to a more natural functioning.
e subtle balance between re-energization of
the river and management of human pressures is
dicult to attain, and remains to a large extent
illusory. Experiments in Switzerland (Cosandey
& Rats, 2007) showed nevertheless that the
Table 1. Characteristics of the populations of E. cohaerens
Locality No. of
populations
Habitat Associated species Water input Distance from the
main channel (m)
1 – Ain conuence 1Oxbow lake Bryum pseudotriquetrum
Calliergonella cuspidata
Leptodictyum riparium
Groundwater +
rainfall inputs
750
2 – Miribel-Jonage 4Articial
reservoir:
gravel pit
Aneura pinguis
Bryum gemmiferum
Bryum pseudotriquetrum
Calliergon cuspidatum
Cratoneuron licinum
Drepanocladus aduncus
Leptodictyum riparium
Pellia endiviifolia
Philonotis calcarea
Pohlia melanodon
Groundwater +
rainfall inputs
1,100
3 – Tournon sur
Rhône
1Articial
reservoir:
gravel pit
Barbula unguiculata
Bryum argenteum
Bryum pseudotriquetrum
Hygroamblystegium varium
Leptobryum pyriforme
Leptodictyum riparium
Pellia endiviifolia
Groundwater +
rainfall inputs
150
4 – Canal de
Montélimar
1Articial
reservoir:
gravel pit
Aphanorrhegma patens
Bryum klinggraei
Dicranella schreberiana
Dicranella staphylina
Leptobryum pyriforme
Oxyrrhynchium hians
Riccia cavernosa
Groundwater +
rainfall inputs
100
26 FieldBryology No108 | Nov12
Ephemerum cohaerens habitat
FieldBryology No108 | Nov12 27
Ephemerum cohaerens habitat
Hampe and E. spinulosum Bruch & Schimp. (Ephemeraceae,
Bryopsida), new to the Iberian Peninsula. Cryptogamie.
Bryologie 26, 327–333.
Krause, W. (1981). Characeen als Bioindikatoren für den
Gewässer-zustand. Limnologica 13, 399–418.
Limpricht, K.G. (1890). Die Laubmoose Deustchlands,
Oesterreichs und der Schweiz. I. Leipzig: E. Kummer.
Meinunger, L. & Schröder, W. (2007). Verbreitungsatlas der
Mosse Deutschlands, Band 2. Regensburg: Herausgegeben
von O. Dürhammer für die Regensburgische Botanische
Gesellschaft.
Nebel, M. & Philippi, G. (2000). Die Moose Baden-
Württembergs, Band 1. Stuttgart: Verlag Eugen Ulmer.
Pressel, S., Matcham, H.W. & Duckett, J.G. (2005). Studies of
protonemal morphogenesis in mosses. X. Ephemeraceae; new
Erratum
Bosanquet, S. (2012). Vagrant epiphytic mosses
in England and Wales. Field Bryology 107, 3–17
On p. 13 of the above article, the photographs
were incorrectly labelled. e correct labelling of
these photographs is shown here.
e Editor and author apologize for this
error.
x Orthotrichum philibertii. Michael Lüth
x Orthotrichum rogeri. Michael Lüth
re-energization of riparian habitats was possible
at the local level, without an increase in exposed
alluvium.
E. cohaerens is unable to tolerate shade, so
encroachment by riverine shrubs and trees should
be kept at a minimal level and planting totally
precluded. Paradoxically, water eutrophication
and vegetation succession are only problematic in
articial hydrosystems: in natural hydrosystems,
the spontaneous rejuvenating eects of cyclic
ooding are regular phenomena. Today, in the
Rhône valley, recreation of regressive successions
in already existing gravel pits requires expensive
intervention.
Life traits of E. cohaerens (large quantities
of tubers and spores) seem advantageous in
a strongly man-inuenced valley. It is highly
probable that signicant numbers of spores are
carried from one articial pond to another by
migrating birds, and that is also likely to be the
case in the British reservoirs and Irish loughs.
Studies involving the life span of spores buried in
the sediment are urgently needed to determine
with accuracy the optimal frequency of seasonal
water uctuations of articial ponds.
Acknowledgments
Sam Bosanquet provided insightful comments that signicantly
improved an earlier version of this text.
Vincent Hugonnot, Jaoua Celle &
Thierry Vergne
Conservatoire Botanique National du Massif
Central, pôle bryophytes, le Bourg, 43 230
Chavaniac-Lafayette, France (e vincent.
hugonnot@cbnmc.fr
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