Available via license: CC BY 4.0
Content may be subject to copyright.
Citation: Puglisi, M.; Sciandrello, S.
Bryophyte Diversity and Distribution
Patterns along Elevation Gradients of
the Mount Etna (Sicily), the Highest
Active Volcano in Europea. Plants
2023,12, 2655. https://doi.org/
10.3390/plants12142655
Academic Editor: Koji Mikami
Received: 26 June 2023
Revised: 7 July 2023
Accepted: 8 July 2023
Published: 15 July 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
plants
Article
Bryophyte Diversity and Distribution Patterns along Elevation
Gradients of the Mount Etna (Sicily), the Highest Active
Volcano in Europea
Marta Puglisi * and Saverio Sciandrello
Department of Biological, Geological and Environmental Sciences, University of Catania, Via A. Longo 19,
95125 Catania, Italy; s.sciandrello@unict.it
*Correspondence: mpuglisi@unict.it
Abstract:
Mt Etna in Sicily hosts a bryophyte floristic richness of 306 taxa, corresponding to
259 mosses, 43 liverworts, and 4 hornworts. Species richness shows a hump-shaped relationship with
the elevation, with a peak at 1200–1700 m a.s.l. Chorotype patterns clearly change along an altitudinal
gradient, from the Mediterranean, located at 0–300 m a.s.l., to Arctic-montane and boreo-Arctic mon-
tane at 1800–2700 m a.s.l., showing a correlation with the bioclimatic belts identified for the Mt Etna.
In regard to the life form pattern, the turf species are the most represented in each elevation gradient,
except at 2300–2700 m a.s.l. where the tuft species are prevalent. The life strategy pattern shows the
colonists as the prevailing species, featured by an increasing trend up to 2200 m of elevation; above
this limit, they are exceeded by the perennial stayers. Furthermore, taking into consideration the
red-listed species (at the European and/or Italian level), as well as the species of phytogeographical
interest, it was possible to identify the high bryophyte conservation priority areas; these areas are
located in thermo-Mediterranean and oro-Mediterranean bioclimatic belts, the latter corresponding
to the oldest substrates of the volcano where some of the most interesting bryophyte glacial relicts
find refuge.
Keywords:
bryophyte flora; chorotypes; conservation; diversity; elevation gradients; life forms; life
strategies; hotspot areas
1. Introduction
Bryophytes are the most diverse group of land plants after the flowering plants. They
are significant contributors to diversity in many temperate ecosystems and play a crucial
role in ecosystem functioning [
1
]. Bryophytes are poikilohydric and lack roots and, in
most cases, an outer waxy cuticle; they take up water and nutrients directly through
their surface [2]. Unlike tracheophytes, they are particularly sensitive to the microclimate,
mainly moisture, because they lack control over water loss which they compensate for
with different strategies, using physiological mechanisms [
3
] and colony architecture [
4
] to
increase desiccation tolerance. They are more sensitive to environmental changes because
of their simple anatomy (absence of roots and an efficient vascular system) and because they
absorb water and nutrients from their entire surface; therefore, global warming and climate
change have significant impacts on them. One of the effects on bryophytes is the alteration
of their distribution patterns [
5
], with shift to higher elevations or latitudes in search
of suitable habitats. As they have a high sensitivity to climatic conditions, widespread
distribution, and are found from the tropics to the polar regions, from sea level to above
the tree line, they have been advanced as useful organisms to be used in latitudinal and
altitudinal studies [
6
]. In particular, elevation gradients are among the most suitable
model templates for testing species diversity distribution–climate relationships, reflecting
the adaptive traits or life strategies of species found at different elevations. In mountain
areas, the elevation gradient causes changes in moisture, temperature, precipitation, and
Plants 2023,12, 2655. https://doi.org/10.3390/plants12142655 https://www.mdpi.com/journal/plants
Plants 2023,12, 2655 2 of 19
solar radiation. Thus, the knowledge of richness, abundance, and distribution of species
and their assemblage along the altitudinal gradients provide us with data to study the
relationships between species diversity and climate change [
7
–
9
] and improve conservation
strategies [
10
]. The many studies to date have focused on relatively few taxonomic groups,
in particular vascular plants, invertebrates, and vertebrates [
11
]. Research on bryophyte
diversity along elevation gradients is mainly focused on large mountains in various parts
of the world, including tropical zones, Alps, and central Apennines [
8
,
11
–
15
]., while the
Mediterranean islands have received no attention.
Sicily, the largest Mediterranean island, is considered one of the main biodiver-
sity hotspots in the Mediterranean region [
16
–
19
], with about 3250 native and natural-
ized taxa of vascular plants [
20
] and 600 bryophytes (117 liverworts, 4 hornworts, and
479 mosses) [
21
]. Mt Etna, as a geologically recent volcano (Late Quaternary), located in
eastern Sicily, is very interesting for the study of plant colonization processes and speci-
ation mechanisms, both of which are favored by its important altitudinal development
(highest peak at 3328 m a.s.l.), geographic isolation (i.e., insular mountain system causing a
“double insularity”), geo-lithological isolation, and the incessant volcanic activity leading
to a continuous creation of new, bare land. This high Mediterranean mountain hosts a set
of phytogeographically interesting bryophytes (artic-montane, boreo-Arctic montane, and
boreal-montane species) that find on the Mt Etna their southernmost distribution limit.
2. Results
Based on the collected data, the bryophyte flora of Mt Etna accounts for 306 taxa
(259 mosses, 43 liverworts, and 4 hornworts), together belonging to 56 families. The most
represented are Pottiaceae (71 taxa, 23.2%), Brachytheciaceae (28 taxa, 9.2%), Grimmiaceae
(26 taxa, 8.5%), Bryaceae (17 taxa, 5.6%), and Mniaceae (15 taxa, 4.9%). The life form
spectrum of the bryophyte flora indicates prevalence of turf species (40.7%), followed by
mat (21.8%), cushion (11.3%), tuft (10.5%), and weft (8.0%) (Figure 1). The life strategy
spectrum shows the higher incidence of colonist (42.2%) and perennial stayer (31.3%)
species (Figure 2).
Plants2023,12,xFORPEERREVIEW2of21
climaterelationships,reflectingtheadaptivetraitsorlifestrategiesofspeciesfoundat
differentelevations.Inmountainareas,theelevationgradientcauseschangesinmois‐
ture,temperature,precipitation,andsolarradiation.Thus,theknowledgeofrichness,
abundance,anddistributionofspeciesandtheirassemblagealongthealtitudinalgra‐
dientsprovideuswithdatatostudytherelationshipsbetweenspeciesdiversityand
climatechange[7–9]andimproveconservationstrategies[10].Themanystudiestodate
havefocusedonrelativelyfewtaxonomicgroups,inparticularvascularplants,inverte‐
brates,andvertebrates[11].Researchonbryophytediversityalongelevationgradientsis
mainlyfocusedonlargemountainsinvariouspartsoftheworld,includingtropical
zones,Alps,andcentralApennines[8,11–15].,whiletheMediterraneanislandshavere‐
ceivednoaention.
Sicily,thelargestMediterraneanisland,isconsideredoneofthemainbiodiversity
hotspotsintheMediterraneanregion[16–19],withabout3250nativeandnaturalized
taxaofvascularplants[20]and600bryophytes(117liverworts,4hornworts,and479
mosses)[21].MtEtna,asageologicallyrecentvolcano(LateQuaternary),locatedin
easternSicily,isveryinterestingforthestudyofplantcolonizationprocessesandspeci‐
ationmechanisms,bothofwhicharefavoredbyitsimportantaltitudinaldevelopment
(highestpeakat3328ma.s.l.),geographicisolation(i.e.,insularmountainsystemcausing
a“doubleinsularity”),geo‐lithologicalisolation,andtheincessantvolcanicactivity
leadingtoacontinuouscreationofnew,bareland.ThishighMediterraneanmountain
hostsasetofphytogeographicallyinterestingbryophytes(artic‐montane,boreo‐Arctic
montane,andboreal‐montanespecies)thatfindontheMtEtnatheirsouthernmostdis‐
tributionlimit.
2.Results
Basedonthecollecteddata,thebryophytefloraofMtEtnaaccountsfor306taxa(259
mosses,43liverworts,and4hornworts),togetherbelongingto56families.Themost
representedarePoiaceae(71taxa,23.2%),Brachytheciaceae(28taxa,9.2%),Grimmi‐
aceae(26taxa,8.5%),Bryaceae(17taxa,5.6%),andMniaceae(15taxa,4.9%).Thelifeform
spectrumofthebryophytefloraindicatesprevalenceofturfspecies(40.7%),followedby
mat(21.8%),cushion(11.3%),tuft(10.5%),andweft(8.0%)(Figure1).Thelifestrategy
spectrumshowsthehigherincidenceofcolonist(42.2%)andperennialstayer(31.3%)
species(Figure2).
0%
10%
20%
30%
40%
50% 43.2%
10.3%
21.4%
8.2% 9.5%
3.6% 1.6% 1% 0.6% 0.6%
Figure 1. Life form spectrum of the Mt Etna bryophyte flora.
Plants 2023,12, 2655 3 of 19
Plants2023,12,xFORPEERREVIEW3of21
Figure1.LifeformspectrumoftheMtEtnabryophyteflora.
Figure2.LifestrategyspectrumoftheMtEtnabryophyteflora.
2.1.ElevationalGradientofSpeciesRichness
Overall,withincreasingelevation,theareaforeachaltitudinalbeltdeclinesalmost
constantly(Figure3).Thebryophyterichnessdistribution,inrelationtothebeltareaex‐
pressedinpercentage(Figure4),showsaparabolic,unimodal(hump‐shaped)relation‐
shipwiththeelevation,showingapeakofrichnessat1200–1700ma.s.l.;then,from1700
to2700ma.s.l.,agrowingreductioninspeciesrichnessoccurs.
Figure3.ElevationalgradientofeachbeltonMtEtna.
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
43.8%
12.4%
5.5% 7.8%
30.2%
0.3%
Figure 2. Life strategy spectrum of the Mt Etna bryophyte flora.
2.1. Elevational Gradient of Species Richness
Overall, with increasing elevation, the area for each altitudinal belt declines almost
constantly (Figure 3). The bryophyte richness distribution, in relation to the belt area ex-
pressed in percentage (Figure 4), shows a parabolic, unimodal (hump-shaped) relationship
with the elevation, showing a peak of richness at 1200–1700 m a.s.l.; then, from 1700 to
2700 m a.s.l., a growing reduction in species richness occurs.
Plants2023,12,xFORPEERREVIEW3of21
Figure1.LifeformspectrumoftheMtEtnabryophyteflora.
Figure2.LifestrategyspectrumoftheMtEtnabryophyteflora.
2.1.ElevationalGradientofSpeciesRichness
Overall,withincreasingelevation,theareaforeachaltitudinalbeltdeclinesalmost
constantly(Figure3).Thebryophyterichnessdistribution,inrelationtothebeltareaex‐
pressedinpercentage(Figure4),showsaparabolic,unimodal(hump‐shaped)relation‐
shipwiththeelevation,showingapeakofrichnessat1200–1700ma.s.l.;then,from1700
to2700ma.s.l.,agrowingreductioninspeciesrichnessoccurs.
Figure3.ElevationalgradientofeachbeltonMtEtna.
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
43.8%
12.4%
5.5% 7.8%
30.2%
0.3%
Figure 3. Elevational gradient of each belt on Mt Etna.
Plants 2023,12, 2655 4 of 19
Plants2023,12,xFORPEERREVIEW4of21
Figure4.ElevationgradientofMtEtnabryophytespeciesrichness.
2.2.ClusterAnalysis
Floristicsimilarityacrossthedifferentelevationalgradientswasexaminedusing
hierarchicalclusteranalysis(Figure5).Allfloraspeciesarejoinedinclusterscorre‐
spondingtothemountainrangesinwhichtheyoccur.
Theresultsoftheclusteranalysisshowtwomain,wellseparated,andnotcorrelated
floristicgroups:onewithspeciesrichnessongradientsoflowandmediumelevationto
1600a.s.l.(clusterA),andtheotherathighelevations,to2700m(ClusterB).ClusterAis
subdividedintwogroupsofclusters(A1andA2),thefirstonecomprisingthebryo‐
phytesofthebelts0–1000ma.s.l.,andthesecondonethebryophytesof1000–1600m
a.s.l.Inparticular,clusterA1comprisestheclustersA11(speciesoccurringat0–300m
a.s.l.)andA12(speciesoccurringat400‐,1000ma.s.l.).ClusterBincludesonlythecluster
B1,subdividedintoB11(speciesoccurringat1700–2200ma.s.l.)andB12(speciesoccur‐
ringat2300–2700ma.s.l.).Thehighestsimilarityisshownbythespeciesofthecluster
B12,representedbyafewspecies,occurringinafewrefugestations.
Figure5.ClusteranalysisoftheMtEtnabryophytesinrelationtothealtitudinalrange.
Figure 4. Elevation gradient of Mt Etna bryophyte species richness.
2.2. Cluster Analysis
Floristic similarity across the different elevational gradients was examined using
hierarchical cluster analysis (Figure 5). All flora species are joined in clusters corresponding
to the mountain ranges in which they occur.
Plants2023,12,xFORPEERREVIEW4of21
Figure4.ElevationgradientofMtEtnabryophytespeciesrichness.
2.2.ClusterAnalysis
Floristicsimilarityacrossthedifferentelevationalgradientswasexaminedusing
hierarchicalclusteranalysis(Figure5).Allfloraspeciesarejoinedinclusterscorre‐
spondingtothemountainrangesinwhichtheyoccur.
Theresultsoftheclusteranalysisshowtwomain,wellseparated,andnotcorrelated
floristicgroups:onewithspeciesrichnessongradientsoflowandmediumelevationto
1600a.s.l.(clusterA),andtheotherathighelevations,to2700m(ClusterB).ClusterAis
subdividedintwogroupsofclusters(A1andA2),thefirstonecomprisingthebryo‐
phytesofthebelts0–1000ma.s.l.,andthesecondonethebryophytesof1000–1600m
a.s.l.Inparticular,clusterA1comprisestheclustersA11(speciesoccurringat0–300m
a.s.l.)andA12(speciesoccurringat400‐,1000ma.s.l.).ClusterBincludesonlythecluster
B1,subdividedintoB11(speciesoccurringat1700–2200ma.s.l.)andB12(speciesoccur‐
ringat2300–2700ma.s.l.).Thehighestsimilarityisshownbythespeciesofthecluster
B12,representedbyafewspecies,occurringinafewrefugestations.
Figure5.ClusteranalysisoftheMtEtnabryophytesinrelationtothealtitudinalrange.
Figure 5. Cluster analysis of the Mt Etna bryophytes in relation to the altitudinal range.
The results of the cluster analysis show two main, well separated, and not corre-
lated floristic groups: one with species richness on gradients of low and medium ele-
vation to 1600 a.s.l. (cluster A), and the other at high elevations, to 2700 m (Cluster B).
Cluster A is subdivided in two groups of clusters (A1 and A2), the first one compris-
ing the bryophytes of the belts 0–1000 m a.s.l., and the second one the bryophytes of
1000–1600 m a.s.l. In particular, cluster A1 comprises the clusters A11 (species occurring at
0–300 m a.s.l.) and A12 (species occurring at 400-,1000 m a.s.l.). Cluster B includes only the
cluster B1, subdivided into B11 (species occurring at 1700–2200 m a.s.l.) and B12 (species
occurring at 2300–2700 m a.s.l.). The highest similarity is shown by the species of the cluster
B12, represented by a few species, occurring in a few refuge stations.
Plants 2023,12, 2655 5 of 19
2.3. Life form Distribution Patterns
Life form distribution patterns along the altitudinal gradient of the whole Etnean
flora are shown in Figure 6as percentage of each life form category per altitudinal interval
related to the area of each altitudinal belt. Turf species (including turf protonemal and
turf scattered) are the dominant life form, accounting for 40.7% of the whole bryoflora;
they tend to increase up to 1900 m a.s.l., the latter representing their peak, and then they
rapidly decrease up to 2700 m a.s.l. Cushion species, very scarcely present up to 700 m a.s.l.,
increase up to 2100 m a.s.l. and then abruptly decrease up to 2300 m a.s.l. Mat species show
a good presence at 100–300 m a.s.l. and at 1200–2000 m a.s.l., then decrease. Dendroid and
fan species, mostly represented on the Mt Etna by epiphytes, mainly occur between 1200 m
and 1800 m a.s.l. Tuft species, scarcely occurring at 0–900 m a.s.l., show an increasing trend,
and dominate at 2300–2700 m a.s.l.
Plants2023,12,xFORPEERREVIEW5of21
2.3.LifeformDistributionPaerns
LifeformdistributionpaernsalongthealtitudinalgradientofthewholeEtnean
floraareshowninFigure6aspercentageofeachlifeformcategoryperaltitudinalin‐
tervalrelatedtotheareaofeachaltitudinalbelt.Turfspecies(includingturfprotonemal
andturfscaered)arethedominantlifeform,accountingfor40.7%ofthewholebry‐
oflora;theytendtoincreaseupto1900ma.s.l.,thelaerrepresentingtheirpeak,and
thentheyrapidlydecreaseupto2700ma.s.l.Cushionspecies,veryscarcelypresentupto
700ma.s.l.,increaseupto2100ma.s.l.andthenabruptlydecreaseupto2300ma.s.l.Mat
speciesshowagoodpresenceat100–300ma.s.l.andat1200–2000ma.s.l.,thendecrease.
Dendroidandfanspecies,mostlyrepresentedontheMtEtnabyepiphytes,mainlyoccur
between1200mand1800ma.s.l.Tuftspecies,scarcelyoccurringat0–900ma.s.l.,show
anincreasingtrend,anddominateat2300–2700ma.s.l.
Overall,thelowerelevations(<500m)arecharacterizedbyanabundanceofturf
speciesandexclusivepresenceofsolitarythalloid(especiallyRicciaspp.)andsolitary
creepingspecies(Fossombroniaspp.);moreover,alotofmatthalloidspeciesoccurtoo.
Theelevationsfrom600mto1200ma.s.l.arecharacterizedbyadominanceofweftspe‐
cies;turfsandmatsarerepresentedwithlowerpercentages.Above1300ma.s.l.,turf,
cushions,andmatsaredominating.
Figure6.LifeformsoftheMtEtnabryophyteflorainrelationtoelevation.
2.4.LifeStrategyDistributionPaerns
Colonistspecies,amountingto42.2%ofthetotal,arethedominantlifeformand
tendtoincreaseupto2000ma.s.l.,andthentheydecrease(Figure7).Perennialstayer
species,accountingforanaverageof31.3%,behavesimilarlytocolonisttaxa,alsopeak‐
ingat2000ma.s.l..Thelong‐livedshulestrategy,accountingfor8.2%,showanin‐
creasingtrendupto2400ma.s.l.Short‐livedshulespecies(6.1%)graduallydecrease
withincreasingelevationupto700ma.s.l.,increasingupto1200ma.s.l.andthende‐
Figure 6. Life forms of the Mt Etna bryophyte flora in relation to elevation.
Overall, the lower elevations (<500 m) are characterized by an abundance of turf
species and exclusive presence of solitary thalloid (especially Riccia spp.) and solitary
creeping species (Fossombronia spp.); moreover, a lot of mat thalloid species occur too. The
elevations from 600 m to 1200 m a.s.l. are characterized by a dominance of weft species;
turfs and mats are represented with lower percentages. Above 1300 m a.s.l., turf, cushions,
and mats are dominating.
2.4. Life Strategy Distribution Patterns
Colonist species, amounting to 42.2% of the total, are the dominant life form and tend
to increase up to 2000 m a.s.l., and then they decrease (Figure 7). Perennial stayer species,
accounting for an average of 31.3%, behave similarly to colonist taxa, also peaking at
2000 m a.s.l.. The long-lived shuttle strategy, accounting for 8.2%, show an increasing trend
up to 2400 m a.s.l. Short-lived shuttle species (6.1%) gradually decrease with increasing
Plants 2023,12, 2655 6 of 19
elevation up to 700 m a.s.l., increasing up to 1200 m a.s.l. and then decreasing again up
to 1600 m a.s.l. Annual shuttle species (11.9%), mostly concentrated at 100–300 m a.s.l.,
decrease at a constant rate up to 1600 m a.s.l. The fugitive category is represented only by
the moss species Funaria hygrometrica Hedw. occurring at 100–1000 m a.s.l.
Plants2023,12,xFORPEERREVIEW6of21
creasingagainupto1600ma.s.l.Annualshulespecies(11.9%),mostlyconcentratedat
100–300ma.s.l.,decreaseataconstantrateupto1600ma.s.l.Thefugitivecategoryis
representedonlybythemossspeciesFunariahygrometricaHedw.occurringat100–1000
ma.s.l.
Overall,colonistandperennialspeciesarethemostrepresentativelifestrategiesin
almostallelevationranges,withcolonistsprevailingfrom1700ma.s.l.andrepresenting
theonlylifestrategy,togetherwiththelong‐livedshuleone,from2300mto2700m
a.s.l..Atlowelevations,upto300ma.s.l.,inadditiontocolonists,theannualshule
strategyprevails,mostlyrepresentedbyliverwortsandhornwortswithaMediterranean
distribution.
Figure7.LifestrategyoftheMtEtnabryophyteflorainrelationtoelevation.
2.5.ChorotypeDistributionPaerns
ChorotypedistributionpaernsalongthealtitudinalgradientareshowninFigure8.
Atlowelevations,upto300ma.s.l.,Mediterraneanspeciesdistinctlyprevailwithapeak
at100ma.s.l.,thenrapidlydecreaseupto800ma.s.l.TheSoutherntemperatespecies
mostlyoccurupto700ma.s.l.,withapeakat100ma.s.l.,decreasingupto1400ma.s.l.
Widetemperatespeciesarefairlyequallydistributedfrom300ma.s.lto1600ma.s.l.,
withlow‐altitudepeaksat100–200ma.s.l.andhigh‐altitudepeaksat1000–1200ma.s.l.
Temperatespeciesincreaseupto1200ma.s.l.,thelaerrepresentingthehighestpeak,
andthenrapidlydecreaseupto2000ma.s.l.Mediterraneanmontanespeciesappearat
700ma.s.l,withapeakat1500ma.s.l.,anddecreaseupto1700ma.s.l.Boreo‐temperate
andwideborealspeciesarescarcelypresentat300–1000ma.s.l.,thenincreaseupto2000
ma.s.l,withapeakat1600ma.s.l.Boreo‐temperate,scarcelyoccurringupto1100m
a.s.l.,increaseupto1600mandthendecreaseupto2000ma.s.l.Thewideborealspecies
behavesimilarlytotheboreo‐temperatetaxa,withapeakat1700ma.s.l.Theboreal
montanespecies,scarcelyoccurringat800–1000ma.s.l.,increaseupto2000ma.s.l.and
thenrapidlydecreaseupto2200ma.s.l.Finally,boreo‐ArcticmontaneandArc‐
tic‐montaneoccurat1700–2500ma.s.l.withapeakat2000–2100ma.s.l.
Figure 7. Life strategy of the Mt Etna bryophyte flora in relation to elevation.
Overall, colonist and perennial species are the most representative life strategies
in almost all elevation ranges, with colonists prevailing from 1700 m a.s.l. and rep-
resenting the only life strategy, together with the long-lived shuttle one, from 2300 m
to 2700 m a.s.l. At low elevations, up to 300 m a.s.l., in addition to colonists, the an-
nual shuttle strategy prevails, mostly represented by liverworts and hornworts with a
Mediterranean distribution.
2.5. Chorotype Distribution Patterns
Chorotype distribution patterns along the altitudinal gradient are shown in Figure 8.
At low elevations, up to 300 m a.s.l., Mediterranean species distinctly prevail with a peak
at 100 m a.s.l., then rapidly decrease up to 800 m a.s.l. The Southern temperate species
mostly occur up to 700 m a.s.l., with a peak at 100 m a.s.l., decreasing up to 1400 m a.s.l.
Wide temperate species are fairly equally distributed from 300 m a.s.l to 1600 m a.s.l.,
with low-altitude peaks at 100–200 m a.s.l. and high-altitude peaks at 1000–1200 m a.s.l.
Temperate species increase up to 1200 m a.s.l., the latter representing the highest peak,
and then rapidly decrease up to 2000 m a.s.l. Mediterranean montane species appear at
700 m a.s.l, with a peak at 1500 m a.s.l., and decrease up to 1700 m a.s.l. Boreo-temperate
and wide boreal species are scarcely present at 300–1000 m a.s.l., then increase up to
2000 m a.s.l, with a peak at 1600 m a.s.l. Boreo-temperate, scarcely occurring up to
1100 m a.s.l., increase up to 1600 m and then decrease up to 2000 m a.s.l. The wide boreal
species behave similarly to the boreo-temperate taxa, with a peak at 1700 m a.s.l. The boreal
montane species, scarcely occurring at 800–1000 m a.s.l., increase up to
2000 m a.s.l. and then rapidly decrease up to 2200 m a.s.l. Finally, boreo-Arctic mon-
tane and Arctic-montane occur at 1700–2500 m a.s.l. with a peak at 2000–2100 m a.s.l.
Plants 2023,12, 2655 7 of 19
Plants2023,12,xFORPEERREVIEW7of21
Figure8.ChorotypesoftheMtEtnabryophyteflorainrelationtoelevation.
ToinvestigatethecorrelationbetweenthechorotypesoftheEtneanbryophytesand
thebioclimaticbelts,aCCAordinationwasperformed.AsshowninFigure9,thether‐
mo‐Mediterraneanbelt,inthealtitudinalgradient0–500ma.s.l.,hostsMediterranean
andsoutherntemperatespecies.Inthemeso‐Mediterraneanbioclimaticbelt,at600–1000
ma.s.l.,thetemperateandwide‐temperatespeciesarefound,andinthesu‐
pra‐Mediterraneanbioclimaticbelt,at1000–1600ma.s.l.,theMediterraneanmontane,
boreo‐temperate,andwideborealspeciesoccur.Finally,intheoro‐Mediterranean(1600–
2400ma.s.l.)andcrioro‐Mediterranean(above2500ma.s.l.)bioclimaticbelts,onlybo‐
reo‐ArcticmontaneandArcticmontanespeciesoccur.
Figure 8. Chorotypes of the Mt Etna bryophyte flora in relation to elevation.
To investigate the correlation between the chorotypes of the Etnean bryophytes and
the bioclimatic belts, a CCA ordination was performed. As shown in Figure 9, the thermo-
Mediterranean belt, in the altitudinal gradient 0–500 m a.s.l., hosts Mediterranean and southern
temperate species. In the meso-Mediterraneanbioclimatic belt, at 600–1000 m a.s.l., the temperate
and wide-temperate species are found, and in the supra-Mediterranean bioclimatic belt, at
1000–1600 m a.s.l., the Mediterranean montane, boreo-temperate, and wide boreal species
occur. Finally, in the oro-Mediterranean (1600–2400 m a.s.l.) and crioro-Mediterranean (above
2500 ma.s.l.) bioclimatic belts, only boreo-Arctic montane and Arctic montane species occur.
Plants 2023,12, 2655 8 of 19
Plants2023,12,xFORPEERREVIEW8of21
Figure9.CanonicalCorrespondenceAnalysis(CCA).Totalvariance(inertia)inthespeciesdata:
5.75;Eigenvalues:axis1=0.86;axis2=0.73,Varianc einspeciesdata%ofvarianceexplained14.9
(axis1),12.8(axis2),Cumulative%explained14.9(axis1)and27.7(axis2).
3.Discussion
3.1.DegreeofSpeciesRichness
Distributionofspeciesrichnessalongelevationalgradients,relatedtotheareaof
eachaltitudinalbelt,showsahump‐shapedrelationshipwithelevation.Thispaern
recordedonMtEtnaisinaccordancewithotherstudiesonbryophytesalongelevational
gradientsonseveralislands,suchasLaRéunion[12],LaPalma(CanaryIslands)[13],
PicoIsland(AzoresIslands)[14],andinthecontinentaltransectsinColombia[12].Along
the27altitudinalintervalsoftheelevationtransectonMtEtna,manyspeciesofbryo‐
phytescanbeobserved.However,themaximumrichnesswasachievedatthemiddleof
thegradient,wherethegreaterconcentrationofbeechwoodsanddeciduousoakwoods
withQuercuscongestaC.PreslorQuercuscerrisL.providemoresuitablehabitatsforbry‐
ophytecolonization.Inthesesites,favorableclimaticconditions,mostlyrelatedtowater
availability(precipitationandrelativehumidityduethepresenceofwoods),aredecisive
fortheeffectivecolonizationofbryophytes.Theincreasinglyharsherecologicalcondi‐
tions,withlesspotentialareaforgrowth,towardgreaterelevationsleadstodecreasing
speciesrichness.Overall,theareaavailableforplantcolonization,onahighactivevol‐
canosuchasMtEtna,isnotconstantduetothesuddenfalloutoflavaflowsortephra
fallsthatmaysuddenlycoverhugesurfacesorduetocatastrophicnaturaleventsthat
mayreducetheavailableareabecauseofhugecollapses,asitoccurred15,000yearsago
onMtEtna.Inaddition,suchvariationsmaymainlyaffectareasathighelevationsand,
subsequently,causevariationsintotalplantspeciesrichnessanddegreeofisolation.
Despitethis,MtEtnahostsarichbryophytefloracorrespondingtomorethanahalfof
theSicilianflora[21].
Figure 9.
Canonical Correspondence Analysis (CCA). Total variance (inertia) in the species data: 5.75;
Eigenvalues: axis 1 = 0.86; axis 2 = 0.73, Variance in species data % of variance explained 14.9 (axis 1),
12.8 (axis 2), Cumulative % explained 14.9 (axis 1) and 27.7 (axis 2).
3. Discussion
3.1. Degree of Species Richness
Distribution of species richness along elevational gradients, related to the area of each
altitudinal belt, shows a hump-shaped relationship with elevation. This pattern recorded
on Mt Etna is in accordance with other studies on bryophytes along elevational gradients on
several islands, such as La Réunion [
12
], La Palma (Canary Islands) [
13
], Pico Island (Azores
Islands) [
14
], and in the continental transects in Colombia [
12
]. Along the 27 altitudinal
intervals of the elevation transect on Mt Etna, many species of bryophytes can be observed.
However, the maximum richness was achieved at the middle of the gradient, where the
greater concentration of beech woods and deciduous oak woods with Quercus congesta
C.Presl or Quercus cerris L. provide more suitable habitats for bryophyte colonization. In
these sites, favorable climatic conditions, mostly related to water availability (precipitation
and relative humidity due the presence of woods), are decisive for the effective colonization
of bryophytes. The increasingly harsher ecological conditions, with less potential area for
growth, toward greater elevations leads to decreasing species richness. Overall, the area
available for plant colonization, on a high active volcano such as Mt Etna, is not constant
due to the sudden fallout of lava flows or tephra falls that may suddenly cover huge
surfaces or due to catastrophic natural events that may reduce the available area because
of huge collapses, as it occurred 15,000 years ago on Mt Etna. In addition, such variations
may mainly affect areas at high elevations and, subsequently, cause variations in total plant
species richness and degree of isolation. Despite this, Mt Etna hosts a rich bryophyte flora
corresponding to more than a half of the Sicilian flora [21].
Plants 2023,12, 2655 9 of 19
3.2. Species of Conservation Interest
Our study revealed important data regarding the distribution pattern and preferential
habitats of some rare bryophytes [
22
] included in the Italian and European Red Book.
Overall, on the Mt Etna, 26 species are considered threatened or near threatened at the
European and/or Italian level (Table 1), corresponding for 8.5% of the whole Etnean flora.
Four species are categorized as Endangered (EN) in Europe, six as Vulnerable (VU), and six
as Near Threatened (NT); one additional species is classified as Data Deficient (DD). An
additional five species, considered Least Concern (LC) at the European level, are classified
as Vulnerable in Italy and other five species as Near Threatened. Although the species
under NT and DD classifications are not strictly considered threatened, as the term is
applied by the IUCN, these categories indicate that these species deserve special attention;
in particular, they can fall under a threat category when more information is acquired (DD),
or if their habitats change drastically (NT) [23].
Moreover, a set of phytogeographycally interesting species should be considered too.
They are species occurring in Sicily, only on Mt Etna, and rare in Italy. They mostly occur at
1700–2100 m a.s.l., and only one species reaches 2700 m a.s.l. Moreover, for some species,
the Mt Etna finding stations represent the only ones confirmed in Italy.
Overall, the areas with high concentrations of species of conservation interest corre-
spond to two different bioclimatic belts: the thermo-Mediterranean (0–400 m a.s.l.) and
the supra- and oro-Mediterranean (2400–2700 m a.s.l.). The first belt hosts a group of
threatened Mediterranean bryophytes that are very rare in Italy, such as Anthoceros agrestis
Paton, Exormotheca pustulosa Mitt., Riccia warstorfii Limpr. ex Warnst., Ephemerum serratum
(Hedw.) Hampe, Ephemerum crassinervium (Schwägr.) Hampe subsp. rutheanum (Schimp.)
Holyoak, and Funariella curviseta (Schwägr.) Sérgio, etc.
In correspondence with the supra-Mediterranean and oro-Mediterranean bioclimatic
belts, the areas with the highest values of rare species are characterized by mesophilous
forests dominated by Fagus sylvatica, usually occurring between 1600 m and 2000 m a.s.l.,
referring to the Directive 92/43/EEC priority Habitat 9210* “Apennine beech forests with
Taxus and Ilex” or by pine woodlands dominated by Pinus nigra subsp. calabrica and
Juniperus hemisphaerica, between 1400 and 1600 m a.s.l., referred to the priority Habitat 9530*
“sub-Mediterranean pine forests with endemic black pines”. Other extremely important
habitats for the conservation of bryophytes are natural caves, referred to by the Habitat
8320 as “fields of lava and natural excavations”, and to the orophilous pulvinate shrubby
with Astragalus siculus Biv. or Juniperus hemisphaerica Presl., referred to by the Habitat 4090
as “endemic oro-Mediterranean heaths with gorse”. Moreover, the oro-Mediterranean belt
corresponds to one of the most active areas of the volcano for the fallout of volcanic ash
and partly for volcanic eruptions, the belt corresponding to the oldest substrates of the
volcano. In a remarkable variety of natural rocky habitats, here some of the most interesting
species find refuge, such as Brachytheciastrum collinum (Schleich. ex Müll.Hal.) Ignatov &
Huttunen, Grimmia fuscolutea Hook., G. alpestris (F.Weber & D.Mohr) Schleich., G. donniana
Sm., G. torquata Drumm., Mielichhoferia elongata (Hoppe & Hornsch. ex Hook.) Hornsch.,
M. mielichhoferiana (Funck) Loeske, and Schistidium flaccidum (De Not.) Ochyra. At present,
they are the most interesting glacial relicts of the Sicilian bryophyte flora.
Plants 2023,12, 2655 10 of 19
Table 1. Bryophytes of conservation interest on the Mt Etna. * Priority Habitat.
Taxon Red-List
Europe
Red-List
Italy
Phytogeographical
Interest
Distribution on the Etna
Sites Altitude Range
(m a.s.l.)
Habitat
(Directive
92/43/EEC)
Amphidium
mougeotii (Schimp.)
Schimp.
LC LC Occurring in Sicily
only on the Etna.
Grotta dei Faggi; Grotta
delle Palombe; Mts
Silvestri; Mts Calcarazzi;
Mt Baracca; Mt
Pomiciaro; Grotta dei
Lamponi; Grotta dei
Ladri; Grotta di Casa
del Vescovo; Grotta di
Cassone; Grotta del
Coniglio; Rifugio Citelli;
Mt Palestra; Contrada
Germaniera; Grotta
Intraleo; Grotta
Corruccio.
1400–2100 8320, 4090
Anthoceros agrestis
Paton NT NT Rare in Italy.
Aci Castello; Piano delle
Immacolatelle; Catani;
Capo Mulini; Grotta
Immacolatella IV.
0–300 8320
Aschisma
carniolicum (F.Weber
& D.Mohr) Lindb.
EN VU
Rare in Italy;
occurring in Sicily
only on the Etna.
Capo Mulini. 0–100 -
Aulacomnium
androgynum (Hedw.)
Schwägr.
LC NE
Rare in Italy;
occurring in Sicily
only on the Etna.
Contrada Giarrita; M.
Rinatu. 1000–1700 9210 *
Brachytheciastrum
collinum (Schleich.
ex Müll.Hal.)
Ignatov &
Huttunen
LC VU
Rare in Italy;
occurring in Sicily
only on the Etna.
Mt Palestra; Mt Maletto;
Grotta dei Lamponi;
Contrada Germaniera;
Grotta del Gelo.
1700–2200 8320, 9530 *
Callicladium
imponens (Hedw.)
Hedenäs, Schlesak
& D.Quandt
NT NE
Rare in Italy;
occurring in Sicily
only on the Etna.
Valle S. Giacomo. 700–800 8320
Clevea spathysii
(Lindenb.)
Müll.Frib.
NT DD Very rare in Italy. Acireale; Aci Trezza. 0–100 -
Coscinodon cribrosus
(Hedw.) Spruce LC LC Occurring in Sicily
only on the Etna.
Grotta Cassone; Mts
Silvestri; Mt Palestra;
Rifugio Citelli; Mt
Baracca; I Dammusi;
Valle del Tripodo; Casa
del Vescovo; Etna
botanical garden
"Nuova Gussonea"; Mt
Baracca; Mt Pomiciaro;
rifugio di M.te Maletto;
Grotta dei Tre Livelli;
Contrada Giarrita;
Grotta di Casa del
Vescovo; Mt Arcimis; a
nord di Rifugio
Sapienza.
1400–2100 8320, 4090, 9210 *,
9530 *
Cynodontium
bruntonii (Sm.)
Bruch & Schimp.
LC NE Occurring in Sicily
only on the Etna.
Mt Spagnolo; I
Dammusi. 1000–1600 9210
Entosthodon
muhlenbergii
(Turner) Fife
NT NT Rare in Italy. Valle S. Giacomo; Mt
Minardo. 700–900 9210, 9340
Plants 2023,12, 2655 11 of 19
Table 1. Cont.
Taxon Red-List
Europe
Red-List
Italy
Phytogeographical
Interest
Distribution on the Etna
Sites Altitude Range
(m a.s.l.)
Habitat
(Directive
92/43/EEC)
Ephemerum serratum
(Hedw.) Hampe LC VU
Rare in Italy;
occurring in Sicily
only on the Etna.
Piano delle
Immacolatelle; Grotta
Immacolatella IV.
300–400 8320
Exormotheca
pustulosa Mitt. NT CR
The Etna locality is
the only one
confirmed in Italy.
Aci Castello. 0–100 -
Fossombronia
caespitiformis
(Raddi) De Not. ex
Rabenh. subsp.
multispira (Schiffn.)
J.R.Bray & Cargill
LC NT Rare in Italy. S. Maria La Stella; Capo
Mulini. 0–100 3170 *
Fossombronia
wondraczekii (Corda)
Dumort. ex Lindb.
LC NT Rare in Italy. Aci Castello; Grotta
Cantarella. 0–300 8320
Funariella curviseta
(Schwägr.) Sérgio VU VU? Rare in Italy. Aci Castello; Acireale 0–100 -
Grimmia alpestris
(F.Weber & D.Mohr)
Schleich.
LC NT
Rare in Italy;
occurring in Sicily
only on the Etna.
Etna botanical garden
"Nuova Gussonea". 2100–2200 9530 *
Grimmia crinita
Brid. VU VU Rare in Italy. Etna botanical garden
"Nuova Gussonea". 9530 *
Grimmia decipiens
(Schultz) Lindb. LC NE Rare in Italy.
Grotta Forcato; Grotta
delle Palombe; Ingresso
Demanio forestale; Mt
Spagnolo; Contrada
Tabbutazzo; Contrada
Timpazza; Mt Intraleo;
Mt Minardo; Fornazzo;
Mt Maletto; Mt
Guardiola.
1300–1500 8320, 9210 *, 9340
Grimmia donniana
Sm. LC NE
Rare in Italy;
occurring in Sicily
only on the Etna.
Mt Spagnolo; I
Dammusi; Etna
botanical garden
"Nuova Gussonea"; Mt
Minardo; Ingresso
Demanio forestale; Mt
Maletto; Mt Pomiciaro;
strada forestale tra Mt
Maletto e Mt Spagnolo.
1800–2200 8320, 9210, 9530
Grimmia fuscolutea
Hook. VU EN
Very rare in Italy;
occurring in Sicily
only on the Etna.
Mts Silvestri. 2000–2200 8320, 4090
Grimmia elatior
Bruch ex Bals.-Criv.
& De Not.
LC NE
Rare in Italy;
occurring in Sicily
only on the Etna.
Contrada Tabbutazzo;
Ingresso Demanio
forestale; Mt Minardo;
Mts Silvestri.
1700–1900 8320, 4090
Grimmia torquata
Drumm. LC VU
Rare in Italy;
occurring in Sicily
only on the Etna.
Grotta delle Palombe. 1800–1900 8320
Hydrogonium
bolleanum
(Müll.Hal.)
A.Jaeger
DD VU Rare in Italy. Fiume Fiumefreddo. 0–100 3280
Hymenoloma
crispulum (Hedw.)
Ochyra
LC LC Occurring in Sicily
only on the Etna. I Dammusi. 1900–2100 9210 *
Plants 2023,12, 2655 12 of 19
Table 1. Cont.
Taxon Red-List
Europe
Red-List
Italy
Phytogeographical
Interest
Distribution on the Etna
Sites Altitude Range
(m a.s.l.)
Habitat
(Directive
92/43/EEC)
Isopterygiopsis
pulchella (Hedw.)
Z.Iwats.
LC LC Occurring in Sicily
only on the Etna. Grotta delle Palombe. 1700–2000 8320
Mielichhoferia
elongata (Hoppe &
Hornsch. ex Hook.)
Hornsch.
VU VU
Rare in Italy;
occurring in Sicily
only on the Etna.
Mts Silvestri. 1900–2000 4090
Mielichhoferia
mielichhoferiana
(Funck) Loeske
NT VU
Rare in Italy;
occurring in Sicily
only on the Etna.
Mt Frumento; Mts
Silvestri. 1900–2100 4090
Physcomitrium
eurystomum Sendtn.
subsp. eurystomum
VU CR
The only recent report
for Italy.
Botanical garden of
Catania. 0–100 -
Pohlia proligera
(Kindb.) Lindb. ex
Broth.
LC NT
Rare in Italy;
occurring in Sicily
only on the Etna.
Grotta dei Lamponi;
Mts Silvestri. 1800–1900 8320, 4090
Pohlia wahlenbergii
(F.Weber &
D.Mohr)A.L.Andrews
var. calcarea
(Warnst.) E.F.Warb.
LC NT Rare in Italy. Aci Castello. 0–100 -
Ptychostomum
cernuum (Hedw.)
Hornsch.
EN EN
The Etna locality is
the only one
confirmed in Italy.
Grotta del Santo. 1200–1300 8320
Pyramidula tetragona
(Brid.) Brid. EN NE
Very rare in Italy;
occurring in Sicily
only on the Etna.
Aci Castello. 0–100 -
Rhabdoweisia fugax
(Hedw.) Bruch &
Schimp.
LC NE Rare in Italy. Grotta delle Palombe. 1700–1800 8320
Schistidium
flaccidum (De Not.)
Ochyra
VU NT
Rare in Italy;
occurring in Sicily
only on the Etna.
Mt Minardo; Ingresso
Demanio forestale; Casa
del Vescovo.
1700–1800 9340, 9530 *, 8320
Timmia bavarica
Hessl. LC LC Rare in Italy. Grotta dei Lamponi. 1700–1800 8320
Tortula bolanderi
(Lesq. & James)
M.Howe
EN EN Very rare in Italy. Grotta Forcato. 600–700 8320
Tortula hoppeana
(Schultz) Ochyra LC VU Rare in Italy. Mts Silvestri; nord di
Rifugio Sapienza. 2000–2500 4090
3.3. Life form Distribution Patterns
Life form is an ecological concept embracing structural characters, the aggregation
of individuals, and their relationships with environmental demands [
24
,
25
]. They are
expressions of morphological adaptations to special ecological niches and reflect habitats,
being especially related to moisture conditions [26].
Overall, the bryophyte flora of Mt Etna is characterized by the preponderance of
turf species, and lower occurrence of the weft and cushion, although cushion species
become important in the high mountain ranges. Along the altitudinal transects of Mt Etna,
mat thalloid, solitary creeping, and solitary thalloid are characteristic of lowland areas,
wefts, dendroid, and fans are typical of montane habitats, whereas higher elevations are
rich in cushion, turf, and mats. Moreover, the occurrence of tuft species is quite high at
1900–2700 m a.s.l., mostly represented by cryophytes of montane and high montane areas.
Plants 2023,12, 2655 13 of 19
As a general trend, mat-, weft-, tail-, or fan-forming bryophytes prefer shady and
humid sites (e.g., forest habitats), whereas cushion- and turf-forming bryophytes (mostly
acrocarpous mosses) increase in sun-exposed, xeric sites underlying drought stress [
25
];
cushions are particularly effective at storing water and are characteristic of habitats with
occasional desiccation [
27
]. Overall, turf and cushion, suitable for reduction of water loss
and protection against strong irradiation (drought stress), represent the more competitive
life forms at high elevations, because the species with this life form can survive to unsuitable
climatic and edaphic conditions like snow cover, strong insolation, and strong winds as
occurring on Mt Etna at high elevations. Many tuft-forming bryophytes are cryophytes of
montane and high montane areas.
3.4. Life Strategy Distribution Patterns
The life strategy system is based on characters such as life span (avoidance vs. tol-
erance strategy of the gametophyte), breeding system, main reproductive effort (sexual
vs. asexual reproduction), and dispersal strategies [numerous small spores (<25
µ
m) pro-
viding chance dispersal vs. few large spores (>25
µ
m), indicating decreasing long-range
dispersal and achory] [
28
]. Life strategies reflect the ecological site conditions [
25
] and can
be envisaged as a system of co-evolved adaptive traits [
29
]. On the Mt Etna, colonist and
perennial species prevail in almost all elevational ranges. In particular, colonist species
(characterized by a rather short life cycle and a high sexual or asexual reproductive effort)
are considered as pioneers colonizing harsh environments, where they usually reach very
high percentages, such as rocky surfaces, e.g., [
30
–
33
]. On the Mt Etna, many moss species
occur on lava surfaces, showing this typical life strategy. The perennial stayer life strategy,
characterized by a long life cycle and low reproductive effort, is frequent in late successional
stages or long lasting sites under roughly constant environmental conditions, e.g., [
33
];
many pleurocarpous mosses follow this life strategy. On the Mt Etna, these species are
mostly concentrated at 1200–2000 m a.s.l. in humid forests, such as beech woods. Shuttle
species are typical of unstable habitats, often underlying anthropogenic disturbance (annual
and short-lived shuttle species). The annual shuttle species can be observed in numerous
marchantioids of seasonally dry sites, xeric protosoils, amongst rock boulders and exfo-
liating knobs, underlying disturbance, e.g., [
34
]; on the Mt Etna, these species, together
with short-lived shuttle taxa, are mostly present at low elevations where anthropogenic
influence is higher. Long-lived shuttle species require more stable environments where
the end of habitat is predictable; many corticolous bryophytes show this life strategy on
the mountain areas of Mt Etna. In agreement with Lloret & González-Mancebo [
35
], who
analyzed elevation patterns of life strategy categories in the bryophytes in the Canary
Islands, perennial stayers and long-lived shuttle species become established in the upper
localities, while many annual shuttle species and colonists become established in the lowest
localities. Colonists also occupy the harsh summit in the highest islands.
3.5. Chorotype Distribution Patterns
Overall, at low elevations (0–500 m a.s.l.), the Mediterranean species clearly prevail,
followed by the southern temperate taxa, present to a lesser extent; also, a small number of
wide temperate and temperate species occur. Instead, at medium elevations the temperate
species prevail up to 1200 m a.s.l., together with boreo-temperate species up to 1700 m; in
the same altitudinal interval (700–1700 m a.s.l.), the Mediterranean montane species appear.
Above 1700 m a.s.l., the boreal montane, boreo-Arctic montane, and Arctic montane species
prevail; only the boreo-Arctic montane and Arctic montane reach 2700 m a.s.l., beyond
which no bryophytes were found.
3.6. Cluster Analysis
Overall, it is possible to identify a correlation between the clusters and the bioclimatic
belts of the Mt Etna. In particular, cluster A11 includes species of the thermo-Mediterranean
belt, with a clear dominance of Mediterranean mosses and liverworts, as well as occur-
Plants 2023,12, 2655 14 of 19
rence of a group of southern temperate and temperate species. Cluster A12 comprises
the species of the meso-Mediterranean belt, where the highest presence of southern tem-
perate, temperate, and wide temperate species is found; here, the Mediterranean species
disappear. Clusters A11 and A12 share the occurrence of some southern temperate and
temperate species with wider altitude ranges. Cluster A2 includes the species of the supra-
Mediterranean belt, characterized by the presence of wide boreal, boreo-temperate, and
some boreal montane species, nearly absent in the lower altitudinal belts; moreover, a
group of wide temperate and temperate species are also present. Occurrence of these last
species render cluster A2 somewhat similar to the previous A12 and A11. Cluster B11
includes species of the oro-Mediterranean belt, where the Arctic montane and boreo-Arctic
montane species are located, together with boreal montane and wide boreal species; only
some boreo-temperate species are still found, while the wide temperate and temperate ones
have vanished. Cluster B12 comprises species of the cryoro-Mediterranean belt; these are
only a few boreo-Arctic montane species that reach the record altitude of 2700 m a.s.l. The
presence of these species approaches the last two clusters (B11 and B12).
4. Material and Methods
4.1. Study Area
Mount Etna is a large stratovolcano of basaltic nature. Its height varies over time due
to its eruptions which cause it to rise or fall. It is a polygenic basaltic volcano covering
a surface of 1178 km
2
from the sea level, along the eastern coast of Sicily; it reaches an
altitude of 3328 m a.s.l., being the highest active volcano in Europe and one of the world’s
most active volcanoes. At the same time, it represents the highest mountain in Sicily and
the highest mountain in Italy south of the Alps. It is characterized by an almost continuous
eruptive activity from its summit craters and fairly frequent lava flows from lateral fissures.
Its origin is quite recent (late Quaternary), having formed 500 ka ago along a diverging zone
in the framework of the Africa–Europe plate convergence [
36
], with eruptions occurring
beneath the sea off the ancient coastline of Sicily. Four main eruptive phases can be
recognized, comprising different volcanic successions in which the eruptions occurred with
a similar eruptive style in the same geodynamic setting [
37
,
38
]. During each phase, several
volcanic centers formed, and remnants of these are still recognizable in the field [
38
]. In
particular, after an earlier phase of scattered and discontinuous volcanic activity occurring
about 500 ka and 330 ka ago, the volcanism in the Mt Etna region was concentrated along
the Ionian Sea coast between 220 and 121 ka ago [
38
,
39
]. According to [
40
], about 80% of the
volcanic products were erupted only in the past 110 ka due to the stabilization of the magma
source and, 15,000 years ago, the younger volcanics mantled most of the previous edifice
(88% of the area) with a widespread cover of lava flow fields and pyroclastic deposits [
41
].
This, joined to a general process of tectonic uplifting, sometimes broken by the subsidence
related to flank sliding of this volcanic edifice, contributes to our understanding of the
present structure of the Etna volcano but also to the highlighting of relevant constraints and
evolutionary chances for the plants colonizing this mountain in which soils are rejuvenated
quite frequently, especially at higher elevations, not only with lava flows, but above all
with the fall of volcanic ash and tephra.
As far as the climate is concerned, according to the bioclimatic classification pro-
posed by Rivas-Martinez [
42
] and Rivas-Martinez et al. [
43
], Mt Etna is characterized by a
Mediterranean pluviseasonal oceanic bioclimate, very diversified in relation to the altitude
and exposure. Thermotypes range from the low thermo-Mediterranean to the lower cryo-
Mediterranean, while ombrotypes range from the semiarid to the upper hyperhumid [
44
].
In Sicily, the lower cryo-Mediterranean and upper oro-Mediterranean belts exclusively
occur on Mt Etna.
4.2. Floristic Data Sources
This research is based on a complete checklist of the Etnean bryophyte flora resulting
from literature data, integrated with several field observations conducted in the last three
Plants 2023,12, 2655 15 of 19
decades all around the volcano by the first author of the paper. Currently, an updated
published bryophyte flora of Mt Etna does not exist and, therefore, it was necessary to
draw up a preliminary control list and provide accurate distribution data in order to
be able to establish the altitudinal range for each taxon. All reports regarding Mt Etna
were considered. The first important contribution was from Strobl [
45
], with the reports
of about fifty bryophytes. Some papers concern some restricted Etna territories [
46
–
50
].
Other sporadic information can be found in larger studies on the bryoflora of Sicily and
Italy [
51
–
74
]. Finally, a number of more recent published floristic and phytosociological
contributions were considered [
33
,
34
,
75
–
84
]. More than 700 phytosociological published
relevés were examined. As far as the floristic reports and phytosociological relevés are
concerned, without any explicit altitudinal indication but only the locality (i.e., toponym),
elevation was determined by consulting topographic maps at 1:25,000 or 1:50,000 provided
by the I.G.M. (Istituto Geografico Militare_Military Geographic Institute). Combining these
data, also checking the taxonomic and nomenclatural correspondences, it was possible to
establish a reliable distribution and altitudinal range for each species.
Mt Etna (0–3357 m), according to Trigas, Panitsa, and Tsiftasis [
85
] and Sciandrello
et al. [
86
], was divided into 33 belts 100 m wide and the bryophyte diversity of each
altitudinal belt was calculated as the total number of species per interval. All species
were considered to have a continuous distribution between their minimum and maximum
elevation limits. The area of each altitudinal belt was calculated using digital elevation
models in ArcGIS 10.3 (3D Analyst).
For each species chorotypes, ecological indices, life forms, and life strategy were
considered. The chorotypes follow Hill et al. [
87
], according to the classification of Hill
and Preston [
88
], where the species are assigned to biome categories corresponding to the
biomes in which they are found. The classification is as follows: Arctic-montane (with main
distribution in tundra or above tree-line in temperate mountains), boreo-Arctic montane (in
tundra and coniferous forest zones), wide-boreal (from temperate zone to tundra), boreal-
montane (main distribution in coniferous forest zone), boreo-temperate (in conifer and
broadleaf zones), wide temperate (from Mediterranean region to coniferous forest zone),
temperate (in broadleaf forest zone), southern-temperate (in the Mediterranean region and
broadleaf forest zones), Mediterranean (in the Mediterranean region).
Life forms were defined according to Hill et al. [
87
], and life strategies according to
Dier
β
en [
89
]. The Ellenberg indicator values (moisture, light, soil acidity) were obtained
from Hill et al. [87].
Simple scatter plots were used to show the life forms, life strategies, and corotypes
along the elevational gradient of Mt Etna. Simple regression analyses were used to correlate
total bryophyte flora to log-area of each elevational interval, both as number of species for
each altitudinal interval and as distribution of the floristic richness in relation to the real
surface of each belt expressed as a percentage. Regression analyses and generalized linear
models were performed using the statistical package Past Version 2.17. A multivariate
analysis (Linkage method: Ward’s, Distance measure: Correlation) and ordination (CCA)
were used to establish spatial patterns about the bioclimatic belts and corotypes. Cluster
analysis and ordination of the dataset were performed using PC-ORD 6 software [90].
In order to identify areas with high bryophyte conservation priority, occurrence on
the Mt Etna of species considered threatened or near threatened at the European and/or
Italian level [
23
,
91
], as well the occurrence of rare and very rare species (in Italy and/or in
Sicily, or occurring in Sicily only on the Mt Etna) was considered.
The nomenclature of the species and taxonomy follow Hodgetts et al. [92].
5. Conclusions
Species distribution models are widely utilized in conservation biogeography due to
their ability to estimate potential range shifts for species and communities in response to
climate change. Moreover, they have been successfully used to study the distribution of
bryophytes in a variety of ecosystems, including identifying areas of high conservation
Plants 2023,12, 2655 16 of 19
value [
93
,
94
]. Consequently, they represent a valuable tool for informing and guiding
conservation management planning.
Our contribution wanted to go one step further by using quantitative data on the
spatial distribution of the bryophyte species along the altitudinal gradient and highlight
areas with a high concentration of species of conservation interest. In particular, the peculiar
hump-shaped pattern of floristic richness at medium elevations (1200–1700 m a.s.l.) was
highlighted corresponding to the greater concentration of beech and deciduous oak woods
that provide more suitable habitats for bryophyte establishment; here, the boreo-temperate
species showing turf and mat life forms and colonist and perennial stayer life strategies
are prevalent.
The results of the analysis on the species of conservation interest (red-listed and/or
phytogeographically interesting) emphasize the fact that the high plant conservation prior-
ity areas are located in the oro-Mediterranean (1800–2400 ms.l.m.) bioclimatic belt, where
the oldest substrates of the volcano (110–15 ka), which functioned as refuge areas for high-
latitude species (Arctic montane, boreo-Arctic montane, and boreal montane), is found;
moreover, it should be noted that in the thermo-Mediterranean belt, some red-listed liver-
worts are found and, therefore, this should also be taken into consideration for conservation
actions. The worthy bryophyte diversity of the Mt Etna discussed in this paper confirmed
the floristic value of this volcano, as already highlighted by Sciandrello et al. [
85
] for the
vascular flora.
Author Contributions:
Conceptualization, M.P.; methodology, M.P. and S.S.; investigation, M.P.; data
curation, M.P.; writing—original draft preparation, M.P.; writing—review and editing, M.P. and S.S.
All authors have read and agreed to the published version of the manuscript.
Funding:
This research was financially supported by the research programme (PIA.CE.RI. 2020–2022
Line 2 cod. 22722132149) funded by the University of Catania and Line 3 Starting Grant Progetto
HAB-VEG cod. 22722132172) funded by the University of Catania.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
Kolari, P.; Pumpanen, J.; Kulmala, L.; Ilvesniemi, H.; Nikinmaa, E.; Grönholm, T.; Hari, P. Forest floor vegetation plays an
important role in photosynthetic production of boreal forests. For. Ecol. Manag. 2006,221, 241–248. [CrossRef]
2. Gignac, L.D. Bryophytes as indicators of climate change. Bryologist 2001,104, 410–420. [CrossRef]
3.
Proctor, M.C.F.; Tuba, Z. Poikilohydry and homoihydry: Antithesis or spectrum of possibilities? New Phytol.
2002
,156, 327–349.
[CrossRef]
4.
Spitale, D. Switch between competition and facilitation within a seasonal scale at colony level in bryophytes. Oecologia
2009
,
160, 471–482. [CrossRef] [PubMed]
5.
Zanatta, F.; Engler, R.; Collart, F.; Broennimann, O.; Mateo, R.G.; Papp, B.; Muñoz, J.; Baurain, D.; Guisan, A.; Vanderpoorten, A.
Bryophytes are predicted to lag behind future climate change despite their high dispersal capacities. Nat. Commun.
2020
,11, 5601.
[CrossRef] [PubMed]
6.
Andrew, N.; Rodgerson, L.; Dunlop, M. Variation in invertebrate-bryophyte community structure at different spatial scales along
altitudinal gradients. J. Biogeogr. 2003,30, 731–774. [CrossRef]
7.
McCain, C.M.; Grytnes, J.-A. Elevational gradients in species richness. In Encyclopedia of Life Sciences; John Wiley & Sons:
Chichester, UK, 2010.
8.
Nascimbene, J.; Spitale, D. Patterns of beta-diversity along elevational gradients inform epiphyte conservation in alpine forests
under a climate change scenario. Biol. Conserv. 2017,216, 26–32. [CrossRef]
9.
Mejia, A.; Castro, V.; Peralta, D.F.; Moncada, B. Altitudinal zonation of mosses in west of the Sierra Nevada of Cocuy, Boyacá,
Colombia. Hoehnea 2020,47, e162020. [CrossRef]
10.
Socolar, J.B.; Gilroy, J.J.; Kunin, W.E.; Edwards, D.P. How should beta-diversity inform biodiversity conservation? Trends Ecol.
Evol. 2016,31, 67–80. [CrossRef]
11.
Becker-Scarpitta, A.; Auberson-Lavoie, D.; Aussenac, R.; Vellend, M. Different temporal trends in vascular plant and bryophyte
communities along elevational gradients over four decades. Ecol. Evol. 2022,12, e9102. [CrossRef]
12.
Ah-Peng, C.; Wilding, N.; Kluge, J.; Descamps-Julien, B.; Bardat, J.; Chuah-Petiot, M.; Strasberg, D.; Hedderson, T.A.J. Bryophyte
diversity and range size distribution along two altitudinal gradients: Continent vs. Island. Acta Oecol.
2012
,42, 58–65. [CrossRef]
Plants 2023,12, 2655 17 of 19
13.
Hernández-Hernández, R.; Kluge, J.; Ah-Peng, C.; González-Mancebo, J.M. Natural and human-impacted diversity of bryophytes
along an elevational gradient on an oceanic island (La Palma, Canarias). PLoS ONE 2019,14, e0213823. [CrossRef] [PubMed]
14.
Coelho, M.C.M.; Gabriel, R.; Hespanhol, H.; Borges, P.A.V.; Ah-Peng, C. Bryophyte diversity along an elevational gradient on
Pico Island (Azores, Portugal). Diversity 2021,13, 162. [CrossRef]
15.
Di Nuzzo, L.; Vallese, C.; Benesperi, R.; Giordani, P.; Chiarucci, A.; Di Cecco, V.; Di Martino, L.; Di Musciano, M.; Gheza, G.; Lelli,
C.; et al. Contrasting multitaxon responses to climate change in Mediterranean mountains. Sci. Rep.
2021
,11, 4438. [CrossRef]
[PubMed]
16.
Médail, F.; Quézel, P. Hot-spots analysis for conservation of plant biodiversity in the Mediterranean Basin. Ann. Mo. Bot. Gard.
1997,84, 112–127. [CrossRef]
17.
Médail, F.; Quézel, P. Biodiversity hotspots in the Mediterranean Basin: Setting global conservation priorities. Conserv. Biol.
1999
,
13, 1510–1513. [CrossRef]
18.
Myers, N.; Mittermeier, R.A.; Mittermeier, C.G.; Da Fonseca, G.A.B.; Kents, J. Biodiversity hotspots for conservation priorities.
Nature 2000,403, 853–858. [CrossRef]
19.
Médail, F.; Diadema, K. Glacial refugia influence plant diversity patterns in the Mediterranean Basin. J. Biogeogr.
2009
,36,
1333–1345. [CrossRef]
20. Raimondo, F.M.; Domina, G.; Spadaro, V. Checklist of the vascular flora of Sicily. Quad. Bot. Amb. Appl. 2010,21, 189–252.
21. Aleffi, M.; Tacchi, R.; Poponessi, S. New checklist of the bryophytes of Italy. Cryptogam. Bryol. 2020,41, 147–195.
22.
Henriques, D.; Borges, P.A.V.; Ah-Peng, C.; Gabriel, R. Mosses and liverworts show contrasting elevational distribution patterns
in an oceanic island (Terceira, Azores): The influence of climate and space. J. Bryol. 2016,38, 183–194. [CrossRef]
23.
Puglisi, M.; Campisi, P.; Aleffi, M.; Bonini, I.; Cogoni, A.; Dia, M.G.; Miserere, L.; Privitera, M.; Tiburtini, M.; Poponessi, S. Red-list
of Italian bryophytes. 1. Liverworts and hornworts. Plant Biosyst. 2023. [CrossRef]
24.
Kürschner, H.; Stech, M.; Sim-Sim, M.; Fontinha, S.; Frey, W. Life form and life strategy analyses of the epiphytic bryophyte
communities of Madeira’s laurel and ericaceous forests. Bot. Jahrb. Syst. 2007,127, 151–164. [CrossRef]
25.
Kürschner, H.; Frey, W. Life strategies in bryophytes—A first example for the evolution of functional types. Nova Hedwig.
2013
,
96, 83–116. [CrossRef]
26.
Frahm, J.-P. Ecology of bryophytes along altitudinal and latitudinal gradients in Chile. Studies in austral temperate rain forest
bryophytes 16. Trop. Bryol. 2002,21, 67–79.
27.
Frahm, J.-P.; Pócs, T.; O’Shea, B.; Koponen, T.; Piippo, S.; Enroth, J.; Rao, P.; Fang, Y.-M. Manual of Tropical Bryology. Bryophyt.
Divers. Evol. 2003,23, 1. [CrossRef]
28. Kürschner, H. Life strategies and adaptations in bryophytes from the near and Middle East. Turk. J. Bot. 2004,28, 73–84.
29. During, H.J. Life strategies of bryophytes: A preliminary review. Lindbergia 1979,5, 2–18.
30.
Puglisi, M.; Kürschner, H.; Privitera, M. Saxicolous bryophyte communities of mountain areas of Greece—Phytosociology, ecology,
life forms and life strategies. Nova Hedwig. 2013,97, 159–178. [CrossRef]
31.
Puglisi, M.; Kürschner, H.; Privitera, M. The Schistidio atrofusci-Grimmietum pulvinatae, a new association of the class
Grimmietea anodontis on the Mediterranean mountains. Nova Hedwig. 2015,100, 205–214. [CrossRef]
32.
Puglisi, M.; Kürschner, H.; Privitera, M. The mountain and high-mountain bryophyte vegetation of the Pollino National Park
(Southern Italy): Syntaxonomy and ecology. Nova Hedwig. 2016,103, 385–413. [CrossRef]
33.
Puglisi, M.; Campisi, P.; Dia, M.G.; Privitera, M.; Spampinato, G. Bryophytes as ecological indicators in the beech woods of Sicily.
Nova Hedwig. 2019,108, 339–363. [CrossRef]
34.
Puglisi, M.; Privitera, M.; Minissale, P.; Costa, R. Diversity and ecology of the bryophytes in the cave environment: A study on
the volcanic and karstic caves of Sicily. Plant Biosyst. 2019,153, 134–146. [CrossRef]
35.
Lloret, F.; González-Mancebo, J.M. Altitudinal distribution patterns of bryophytes in the Canary Islands and vulnerability to
climate change. Flora 2011,206, 769–781. [CrossRef]
36.
Barreca, G.; Branca, S.; Corsaro, R.A.; Scarfì, L.; Cannavò, F.; Alois, M.; Monaco, C.; Faccenna, C. Slab Detachment, Mantle Flow,
and Crustal Collision in Eastern Sicily (Southern Italy): Implications on Mount Etna Volcanism. Tectonics
2020
,39, e2020TC006188.
[CrossRef]
37.
Branca, S.; Coltelli, M.; De Beni, E.; Wijbrans, J. Geological evolution of Mount Etna volcano (Italy) from earliest products until
the first central volcanism (between 500 and 100 ka ago) inferred from geochronological and stratigraphic data. Int. J. Earth Sci.
2008,97, 135–152. [CrossRef]
38.
Branca, S.; Coltelli, M.; Groppelli, G. Geological evolution of a complex basaltic stratovolcano: Mount Etna, Italy. Ital. J. Geosci.
2011,130, 306–317.
39.
De Beni, E.; Branca, S.; Coltelli, M.; Groppelli, G.; Wijbrans, J. 39Ar/40Ar isotopic dating of Etna volcanic succession. Ital. J. Geosci.
2011,130, 292–305.
40.
Branca, S.; Ferrara, V. The morphostructural setting of Mount Etna sedimentary basement (Italy): Implications for the geometry
and volume of the volcano and its flank instability. Tectonophysics 2013,586, 46–64. [CrossRef]
41.
Barreca, G.; Branca, S.; Monaco, C. Three-Dimensional Modeling of Mount Etna Volcano: Volume Assessment, Trend of Eruption
Rates, and Geodynamic Significance. Tectonics 2018,37, 842–857. [CrossRef]
42. Rivas Martínez, S. Bases para una nueva clasificacion bioclimatica de la tierra. Folia Bot. Matritensis 1993,10, 1–23.
Plants 2023,12, 2655 18 of 19
43.
Rivas-Martinez, S. Bioclimatic Map of Europe: Bioclimates, Scale 1:16 Mill; Cartographic service; University of Léon: Léon, Spain,
2004.
44.
Bazan, G.; Marino, P.; Guarino, R.; Domina, G.; Schicchi, R. Bioclimatology and vegetation series in Sicily: A geostatistical
approach. Ann. Bot. Fenn. 2015,52, 1–18. [CrossRef]
45. Strobl, P.G. Flora des Aetna. Osterr. Bot. Z. 1880,38, 24, 26, 58–60, 95–96, 131. [CrossRef]
46. Zodda, G. Briofite sicule. IV. Malpighia 1911,24, 258–277.
47. Lo Giudice, R.; Privitera, M. La flora muscinale della Valle S. Giacomo (Etna). Rev. Bryol. Lichénol. 1979,45, 453–466.
48.
Lo Giudice, R.; Privitera, M. Contributo alla conoscenza della brioflora cavernicola dell’Etna. Arch. Bot. Biogeogr. Ital.
1981
,
57, 171–192.
49.
Lo Giudice, R.; Privitera, M. Sulla brioflora di alcune grotte etnee (Grotta Forcato, Grotta delle Palombe, Grotta dei ladri). Arch.
Bot. Biogeogr. Ital. 1983,59, 137–157.
50. Privitera, M.; Lo Giudice, R. La florula muscinale della lecceta di Monte Minardo (Etna). Webbia 1979,33, 457–469. [CrossRef]
51. Philippi, R.A. Über die Vegetation am Ätna. Flora 1832,7, 727–764.
52. De Notaris, G. Syllabus Muscorum in Italiae et Insulis Circumstantibus; Ex Typographia Canfari: Torino, Italy, 1838; pp. 1–331.
53. De Notaris, G. Musci Italici. Particula. I. Trichostomacei. Gen. Tortula; Ex Typographia Surdorum: Genova, Italy, 1862; pp. 1–69.
54. De Notaris, G. Epilogo Della Briologia Italiana; Co’ Tipi del R.I. de’ sordo-muti: Genova, Italy, 1869; pp. 1–781.
55. Lojacono Pojero, M. Primo elenco briologico di Sicilia. Nat. Sicil. 1883–1884,3, 62–66, 97–101.
56. Massalongo, C. Repertorio della Epaticologia Italica. Annu. R. Ist. Bot. Roma 1886,2, 87–155.
57. Brizi, U. Notizie. Addenda ad floram Italicam. Note di Briologia Italiana. Malpighia 1890,4, 262–282, 350–362.
58. Bottini, A. Appunti di Briologia Italiana. Nuovo Giorn. Bot. Ital. 1890,22, 259–266.
59. Bottini, A. Sulla Briologia delle isole italiane. Webbia 1907,2, 345–402. [CrossRef]
60. Zodda, G. Notizie sull’erbario del Prof. Alfio Fichera. Atti Rend. Accad. Dafnica Sci. Lett. Arti Acireale 1906,2, 1–7.
61. Zodda, G. Le Brofite del Messinese. II. Ann. Bot. 1907,6, 237–269.
62. Zodda, G. Le Briofite del Messinese. III. Ann. Bot. 1908,7, 449–487.
63. Zodda, G. Briofite sicule. III. Malpighia 1908,22, 506–521.
64. Zodda, G. Sulla Marchantia circumscissa di Bivona. Boll. Orto Bot. R. Univ. Napoli 1909,2, 251–253.
65. Zodda, G. Le Briofite del Messinese. IV. Ann. Bot. 1913,11, 253–280.
66. Zodda, G. Hepaticae. In Flora Italica Cryptogama; Soc. Bot. Ital., Rocca S.: Casciano, Italy, 1934.
67. Zodda, G. Schedule Briologiche. Nuovo Giorn. Bot. Ital. 1958,65, 860–861.
68. Barsali, E. Epatiche di Sicilia, Isole Eolie e Pelagie. Bull. Natur. 1908,28, 14–17, 29–32.
69. Roth, G. Neuere und noch weniger bekannte Europäische Laubmoose. Hedwigia 1913,53, 124–133.
70. Nicholson, W.E. Bryological notes from Sicily. Rev. Bryol. Lichénol. 1921,48, 38–43.
71.
Müller, K. Die Lebermoose. In Rabenhorst’s L., Kryptogamen Flora von Deutschland, Osterreich Und Scheweiz; Akademische
Verlagsgesellschaft: Leipzig, Germany, 1920; Volume 6, pp. 481–640.
72. Reimers, H. Beiträge zur Moosflora von Italien. Willdenowia 1956,1, 533–562.
73.
Lübenau, R.; Lübenau, K. Ein Beitrag zur Moosflora der Äolischen Inseln Lipari, Vulcano und Stromboli. Naturwiss. Mitt.
Kempten-Allg. 1968,13, 82–97.
74.
Lübenau, R.; Lübenau, K. Ein Beitrag zur Moosflora der Äolischen Inseln Lipari, Vulcano und Stromboli. Herzogia
1970
,2, 89–106.
[CrossRef]
75. Lo Giudice, R. Studio fitosociologico sulla briovegetazione epifitica della Sicilia. Arch. Bot. Ital. 1991,67, 76–98.
76. Privitera, M.; Puglisi, M. La vegetazione briofitica dell’Etna (Sicilia, Italia). Braun-Blanquetia 1996,19, 1–59.
77. Privitera, M.; Puglisi, M. Noteworty orophilous mosses from Mount Etna (Sicily). Bocconea 1997,5, 905–911.
78. Privitera, M.; Puglisi, M. Some interesting records for the Italian moss flora. Cryptogam. Bryol. 2002,23, 171–179.
79. Puglisi, M. New interesting records to the moss flora of Sicily (Italy). Cryptogam. Bryol. 2009,30, 395–398.
80. Puglisi, M.; Privitera, M. A synopsis of the Italian bryophyte vegetation. Cryptogam. Bryol. 2012,33, 357–382. [CrossRef]
81. Puglisi, M.; Privitera, M. New moss records for the Mediterranean islands. Cryptogam. Bryol. 2018,39, 177–183. [CrossRef]
82.
Puglisi, M.; Privitera, M. New and noteworthy records of mosses from Italian national and regional Parks. Plant Biosyst.
2018
,152,
604–607. [CrossRef]
83. Puglisi, M.; Minissale, P.; Sciandrello, S.; Privitera, M. The bryophyte vegetation of the Mediterranean temporary ponds in Italy.
Plant Sociol. 2015,52, 69–78.
84.
Puglisi, M.; Kürschner, H.; Privitera, M. Phytosociology and life syndromes of bryophyte communities from Sicilian caves, a clear
example of relationship between bryophytes and environment. Plant Sociol. 2018,55, 3–20.
85.
Trigas, P.; Panitsa, M.; Tsiftasis, S. Elevational gradient of vascular plant species richness and endemism in Crete—The effect of
post-isolation mountain uplift on a continental island system. PLoS ONE 2013,8, e59425. [CrossRef]
86.
Sciandrello, S.; Minissale, P.; Giusso del Galdo, G. Vascular plant species diversity of Mt. Etna (Sicily): Endemicity, insularity and
spatial patterns along the altitudinal gradient of the highest active volcano in Europe. PeerJ 2020,8, e9875. [CrossRef]
87.
Hill, M.O.; Preston, C.D.; Bosanquet, S.D.S.; Roy, D.B. BRYOATT Attributes of British and Irish Mosses, Liverworts and Hornworts;
Centre for Ecology and Hydrology: Huntingdon, UK, 2007; pp. 1–88.
88. Hill, M.O.; Preston, C.D. The geographical relationship of British and Irish bryophytes. J. Bryol. 1998,20, 127–226. [CrossRef]
Plants 2023,12, 2655 19 of 19
89.
Dierssen, K. Distribution, ecological amplitude and phytosociological characterization of European bryophytes. Bryophyt. Biblioth.
2001,56, 1–289.
90.
McCune, B.; Mefford, M.J. Multivariate Analysis of Ecological Data, Version 6; MjM Software PC-ORD: Gleneden Beach, OR, USA,
2011; pp. 1–34.
91.
Hodgetts, N.G.; Cálix, M.; Englefield, E.; Fettes, N.; García Criado, M.; Patin, L.; Nieto, A.; Bergamini, A.; Bisang, I.; Baisheva, E.;
et al. A Miniature world in Decline: European Red List of Mosses, Liverworts and Hornworts; International Union for Conservation of
Nature: Gland, Switzerland, 2019.
92.
Hodgetts, N.G.; Söderström, L.; Blockeel, T.L.; Caspari, S.; Ignatov, M.S.; Konstantinova, N.A.; Lockhart, N.; Papp, B.; Schröck, C.;
Sim-Sim, M.; et al. An annotated checklist of bryophytes of Europe, Macaronesia and Cyprus. J. Bryol.
2020
,42, 1–116. [CrossRef]
93.
Heikkinen, R.K.; Luoto, M.; Araújo, M.B.; Virkkala, R.; Thuiller, W.; Sykes, M.T. Methods and uncertainties in bioclimatic envelope
modelling under climate change. Prog. Phys. Geogr. 2006,30, 751–777. [CrossRef]
94.
ˇ
Cíhal, L. Bryophytes in a Changing World: Understanding Distribution Patterns, Risks, and Conservation. Diversity
2023
,15, 647.
[CrossRef]
Disclaimer/Publisher’s Note:
The statements, opinions and data contained in all publications are solely those of the individual
author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to
people or property resulting from any ideas, methods, instructions or products referred to in the content.
