a Departamento de Biologia Animal, Biologia Vegetal y Ecologia, Facultad de ... host Macaronesian species (Gil & Guerra, 1981; Guerra et al., 2003). .... (Phytogeography), Index of Ecological Significance (IES) values, and ...... AGUILO ALONSO M., ARAMBURU M.P., BLANCO A., CALATAYUD T., CARRASCO R.M.,.
Clyptogamie, Btyologie, 2016, 37 (!) . 53-85 © 20 16 Adac. To us droits reserves
Epiphytic bryophyte communities of Prunus lusitanica Iberian forests: biogeographic islands shaped by regional climates Juan Antonio CALLEJA a,b*, Lidia MINGORANCE a & Francisco LARA c a Departamento de Biologia Animal, Biologia Vegetal y Ecologia, Facultad de Biociencias, Universidad Aut6noma de Barcelona, E-08193, Barcelona, Spain b CREAF, Universidad Aut6noma de Barcelona, E-08193, Barcelona, Spain c
Departamento de Biologia, Facultad de Ciencias, Universidad Aut6noma de Madrid, Calle Darwin 2, E-28049, Madrid, Spain
Abstract - Epiphytic communities of Iberian forests remain partly unknown and most studies have focused on the dominant oak forests. We provide a comprehensive analysis and interpretation of the epiphytic bryophyte communities of forests dominated by the Tertiary relict evergreen cherry Prunus lusitanica. This type of forest, scattered in the western and northern half of the Iberian Peninsula, harbours a noticeable richness of epiphytic bryophytes, including an outstanding number of liverwort species. Their floristic composition varies markedly across the Peninsula yet is driven by the main climate patterns prevailing in the area. Multivariate analyses (TWINSPAN, CCA) render two main groups of epiphytic communities with their respective indicator species. Both groups share a high proportion of non-Mediterranean species, a circumstance that is most remarkable in the forests that fall within the Mediterranean Region, which could be considered as ecological refuges or biogeographic islands . Bryoflora I biogeographic elements I distribution I biodiversity I epiphytes I Iberian Peninsula I Iiverworts I mosses I species richness
INTRODUCTION The Iberian Peninsula harbours an outstanding diversity of forests with a large variety of vascular floristic assemblages extensively described (Peinado Lorca & Rivas-Martfnez, 1987; Rivas-Martfnez, 1987a, 2006, 2007, 2011 a, 2011 b; CostaTenorio et al. , 1997; Sainz Ollero & Sanchez de Dios, 2011 ). In recent decades, the epiphytic bryophyte communities of Iberian forests have also been studied but these investigations have focused mainly on oak (Quercus sp. pi.) forests (Gil & Guerra, 1981 , 1985; Burgaz et al. , 1994a, 1994b; Lara & Mazimpaka, 1994, 1998; Mazimpaka & Lara, 1995; Albertos et al., 2005 ; Garcia et al. , 2004, 2005 ; Marques et al., 2005 ; Garcia, 2006; Mazimpaka et al. , 2009; Medina et al. , 20 15). To a lesser extent, other singular forests that have been studied include those dominated by Juniperus thurifera L. (Medina et al. , 20 I 0), Olea europaea L. (Sim-Sim et al., 1995), Rhododendron ponticum subsp. baeticum (Boiss. & Reut.) Hand. -Mazz. (Gil & • Corresponding author: JuanAntonio.Call eja@ uab.cat doi/ 10. 7872/cry b/v37.iss 1.201 6.53
54
J.A . Calleja et al.
Guerra, 1981 ; Guerra et al., 2003), Abies pinsapo Boiss. (Guerra, 1982) and Prunus lusitanica L. (Aibertos et al., 1997; Calleja et al., 2001 ). The richness and composition variability of the epiphytic bryoftora of the Iberian forests have been analysed throughout altitudinal gradients, tree microhabitats and trunk dimensions (Mazimpaka & Lara, 1995 ; Lara & Mazimpaka, 1998; Mazimpaka et al. , 2009; Medina et al., 2014), across bioclimatic boundaries (Aibertos et al., 2005; Medina et al., 2014) and at large geographic scales (Burgaz et al. , 1994a, 1994b; Lara, 1993 ; Fuertes et al. , 1996; Medina et al., 20 I 0) . Both regional and local factors shape the variability of epiphytic bryophyte assemblages (Burgaz et al., 1994a; Mazimpaka & Lara, 1995; Fuertes et al., 1996; Lara & Mazimpaka, 1998 ; Mazimpaka et al. , 2009; Medina et al., 2010; Medina et al., 2014). At the regional scale, climate seems to be the main driver of the diversity and composition of epiphytic bryophyte communities (Garcia, 2006; Medina et al., 2010; Medina et al., 2014). At a local scale, microclimatic conditions plus historical factors may also favour unexpected epiphytic bryophytes that reveal singular biogeographic islands within forests inhabiting Mediterranean environments. Thus, the Iberian relict forests of Rhododendron ponticum, close to the Strait of Gibraltar, host Macaronesian species (Gil & Guerra, 1981 ; Guerra et al., 2003). Likewise, forests of Quercus ilex subsp. ballota (Desf.) Samp. in SierraAihamilla, a southeastern Iberian mountain nestled in the driest zone of E urope (Mazimpaka et al., 2009), support rich communities with an unpredicted proportion of mesic species. Among the Iberian forests, those dominated by Prunus lusitanica stand out, as it is a relict evergreen broad leaved cherry tree related to the Tertiary flora (Pignatti , 1978; Barr6n et al., 201 0). Prunus lusitanica groves occur in the western and northern halves ofthe Iberian Peninsula (Calleja & Sainz, 2009), within two very different biogeographical and climatic regions: the Mediterranean and Eurosiberian Regions (Rivas-Martinez, 1987a; Costa-Tenorio et al., 1997; Sainz Ollero & Sanchez de Dios, 2011 ). They usually colonise exceptionally wet sites, mainly on riverbanks and around springs in deep gullies and valleys, situated at middle altitudes in mountainous regions (Calleja et al., 2009; Garilleti et al., 20 12). The very specific environmental preferences of P. lusitanica might be expected to promote homogeneous epiphytic bryophyte communities irrespective of the regional climates, since these organisms are very sensitive to microclimates (Barkman, 1958; Vanderpoorten et al. , 2004; Raabe et al. , 201 0). Furthermore, the microclimatic conditions preferred by this subtropical relic species may also favour the presence of Macaronesian epiphytic bryophytes, as registered in Rhododendron ponticum stands (Gil & Guerra, 1981 ; Guerra et al., 2003). Results of a preliminary study based on a limited number of forests surveyed (Calleja et al., 2001) do not fully support these hypotheses. However, several local studies of the bryoftora inhabiting Iberian P.lusitanica forests remark the occurrence of singular bryophytes within the Mediterranean Region (Aibertos et al., 1997; Casas et al., 1999; Sergio et al., 2001). To date, we have a fragmentary knowledge of the ftoristic richness and composition variability of the epiphytic bryoftora of P. lusitanica forests across the Iberian Peninsula, and we ignore the enviromnental drivers of composition changes in these communities. The present study focus on epiphytic bryophytes inhabiting the trunks (excluding tree bases and branches) of Prunus lusitanica forests and our major aims are to i) provide a comprehensive perspective on the richness and variability of these communities throughout the Iberian Peninsula; ii) confirm whether these forests act as biogeographic islands, hosting unexpected species in different geographical and regional climate contexts; and iii) evaluate the potential relationship between regional climates and the ftoristic variability of the epiphytic bryophyte communities of this type of forests.
Epiphytic bryophytes of Prunus lusitanica forests
55
MATERIALS AND METHODS We studied the epiphytic bryoflora growing on the trunks of 14 forests dominated or eo-dominated by Prunus lusitanica, which encompass all the main nuclei of distribution of this type of forest in the Iberian Peninsula. Sampled forests were selected based on their optimal structure and representativeness (Calleja & Sainz, 2009) and severely disturbed forests or those with less than 25 individuals were discarded. In those areas where P lusitanica becomes fairly common (Calleja et al., 2009), two well preserved forests have been selected. Study sites are located m nine geographic areas within two different biogeographical regions, the Mediterranean and Eurosiberian (Tables 1, 2 and 3, Fig. 1). The boundaries and definition of both biogeographical regions follow the climatic and floristic criteria described by several authors (Rivas-Martinez, 1987a, 1987b; Moreno et al. , 1990; Table I. Geographical information of studied Prunus lusitanica forests. Country: PT = Portugal and SP =SPA IN ; Provinces: AV= Avila, BB= Beira Baixa, BL = Beira Litoral, BU = Burgos, CC = Caceres, CR = Ciudad Real, GE = Gerona, LE = Le6n, MH = Minho, NA = Navarra, and TO = Toledo; No. of trees = number of trees sampled N Pop!1/at 1·on Geographical Count1y Province · region
Locality
Coordinates (WGS84)
No. of trees
MTol
Mantes de Toledo
SP
CR
Arroyo del 04° 31 ' 21.99" W 39° 25 ' 26.91 " N Robledillo
25
2
MTo2
Mantes de Toledo
SP
TO
Garganta 04°53 ' 20.2I " W 39°34' 25.96" N Las Lanchas
22
3
LVil
Las Villuercas
SP
La Trucha 05° 14' 57.41 " W 39° 32' 52.03 " N
23
4
LVi2
Las Villuercas
SP
cc cc
Apretura rio 05° 27' 26.27 " W 39° 36' 29.98 " N VleJas
24
5
Grel
Sierra de Gredos
SP
AV
Rio Muelas 05° 11 ' 24.17" W 40° I 0' 40.03 " N
22
6
Gre2
Sierra de Gredos
SP
AV
Garganta_ 05° 13 ' 57 .53 " W 40° 11 ' 59.08 " N Santa Mana
18
PT
BB
PT
BL
Sierras de
7
A~or
Sierras de
8
A~or
Rio Ce ira
07° 51 ' 09.90" W 40° 10' 37.74 " N
25
Mata da
07° 55 ' 10.07 " W 40° 12 ' 56.83 " N
20
Margara~a
9
Monl
MontsenyGuilleries
SP
GE
Sot de l"Escala
10
Mon2
MontsenyGuilleries
SP
GE
San! Pere Despla
02° 28 ' 43.85 " E 41° 50 ' 38.69" N
25
11
An ea
Sierra de An cares
SP
LE
Fres~~odelo
06o 37' 39.64 " W 42° 48 ' 56.8 " N
20
12
Gere
Sierra de Geres
PT
MH
Rio Home 08° 08 ' 57.49 " W 41° 47' 22.38 " N
18
13
CC an
Sierra de Ordunte
SP
BU
Arroyo del 03° 18 ' 26.61 " W 43 ° 09 ' 40.4" N Lloral
25
14
PO cc
Pirineo Occidental
SP
NA
Rio Urrizate 01° 23 ' 29.95" W 43° 15 ' 12.85 " N
18
02° 29 ' 48.5 " E
41° 46 ' 30.8" N
25
J.A. Calleja el al.
56
Table 2. B iogeograp hi cal regions, climatic characterisation and brief vegetation description of studied sites. A lt. = A ltitude; C lim atic characteri sation fo llowing Font Tu llot ( 1983); Biogeog. region = Biogeograph ical region: Med = Med iterranean, Eur = Eurosiberian, Med I Eur = transitional between both regions; Dom inant vegetation, Z = Zonal vegetation, Az = Azonal vegetation Population
All (m)
Climatic characterization
Biogeog region
Dominant vegetation
MTol
700
Mediterranean and continental
Med
Z: forests of Quercus jaginea subsp. broteroi, Q. i/ex subsp. ballota and Q suber; Az: dense patches of Prunus lusitanica mixed with Betula pendula, Fraxinus angustifolia and Salix atrocinerea
MTo2
900
Mediterranean and continental
Med
Z: forests of Quercus pyrenaica; Az: small forest of Prunus lusitanica with Betula pendu/a and Taxus baccata
LVi l
620
Mediterranean and continental
Med
Z: forests of Quercus pyrenaica; Az: forests of Alnus glutinosa and Prunus lusitanica
LVi2
500
Mediterranean an d continental
Med
Z: forests of Que reus jaginea subsp . broteroi and Q suber; Az: forests of Alnus glutinosa and Prunus lusitanica
Grel
660
Mediterranean and atten uated continental
Med
Z: forests of Quercus pyrenaica; Az: forests of A In us g/utinosa and a dense patch of Prunus lusitanica
Gre2
630
Mediterranean and attenuated continental
Med
Z: forests of Quercus pyrenaica. Az: dense patch of Prunus lusitanica
600
Mediterranean and Atlantic
Med
Z: burned forests of Arbutus unedo and Pinus pinaster and Quercus sp. pi. ; Az: dense patches of Prunus lusitanica
625
Mediterranean and Atlantic
Med
Z: mixed forests of Castanea saliva and Quercus robur; Az: mixed forest of Corylus ave/lana, Prunus lusitanica and Salix atrocinerea
Mon l
760
Northeastern Mediterranean
Med I Eur Z: forests of Fagus sylvatica and Quercus ilex subsp. i/ex; Az: mixed forests of C01ylus avel/ana, Fagus sylvatica, flex aquifolium, Prunus lusitanica and Sa/ix atrocinerea
Mon2
550
Northeastern Mediterranean
Med I Eur Z: forests of Quercus suber; Az: mixed forests of Alnus glutinosa, Cory/us avellana, Fraxinus excelsior and Prunus lusitanica
Anca
740
Western and semimaritime European
Gere
720
Western and maritime European
Eur
Z: forests of Quercus robur; Az: ripari an forests of Alnus glutinosa and patches of Prunus lusitanica
CC an
500
Western and maritime Eu ropean
Eur
Z: forests of Fagus sylvatica, Quercus pyrenaica and Q. robur, Az: mixed forests of C01ylus avellana, Frangula alnus and Prunus lusitamca
PO cc
175
Western and sem imaritime European
Eu r
Z: forests of Fagus sylvatica; Az: riparian forest of Corylus avel/ana, Fraxinus exce/sior and Prunus lusitanica
Med I Eur Z: forests of Que reus pyrenaica and Q. robur; Az: forests of A In us glutinosa and dense patches of Prunus /usitanica
Table 3. Epiphytic bryophytes collected on trunks of 14 Prunus lusitanica forests. Species abbreviations (Abbrev.), phytogeographical characterisation (Phytogeography), Index of Ecological Significance (IES) valu es, and number of locali ties (No. loc.) are shown for each spec ies. Species abbrev iations combine the first three letters of the generic name and the first two of the specific name. Phytogeographical e lements abbreviations: Eur = Eurosiberian, Eur-Oce = Eurosiberian and Oceanic, Ind = Indifferent, Med = Mediterranean, Med-Oce = Mediterranean and Oceanic, Oce = Oceanic Species
Abbrev.
Phyla geography
JES values MTol
MTo2
LVil
LVi2
Grel
8.3
6.8
-
-
-
Alleniella complanata
ALL CO
Eur-Oce
-
-
Antitrichia californica
ANT CA
Med
-
6.5
Antitrichia curtipendula
ANTCU
Eur
-
-
Brachytheciastrum dieckei
BRAD!
Med-Oce
Brachytheciastrum velutinum
BRA YE
Oce
-
Co/olejeunea minutissima
COLM I
Oce
-
Gre2
Ar;:ol
Ar;:o2
13.0
102 .5
Monl
Mon2
An ea
Gere
CCan
48. 1 240.0
7.5
16.7
72.0
POcc
No. /oc. 9
rn
I
-a·
I
'< n
-o
-
-
-
-
16.7 -
6.5
I
::r ~
er ...,
'< 0
6.5
6.3
15.0
102.0
7.5
38.0
6
-o ::r
'< (ti C/l
-
-
-
-
38.9
-
-
11.1
30.6
-
-
3
0 ....,
I
:s
4
"'i2"
"l:l ..., ~
-
Cololejeunea rossettiana COL RO
Oce
Cryphaea heteromal/a
CRY HE
Oce
Dicranel/a heteromalla
DIC HE
Eur-Oce
-
-
Dicranoweisia cirrata
DIC Cl
Oce
-
-
Dicranum scoparium
me se
Eur
-
-
-
-
Eurhynchium sp.
EUR
Fabronia pusilla
FAB PU
Med-Oce
Frullania dilatata
FRU Dl
Oce
Frul/ania fragi lifolia
FRU FR
Eur-Oce
-
Frul/ania microphy l/a
FRU Ml
Eur-Oce
-
Frullania oakesiana
FRU OA
Oce
-
56.0 95.5
-
-
7.4
10.0
-
-
-
-
8.0
-
-
-
-
6.0
~.
s-
7.5
-
I
15 .0
-
I
1:)
2
b' ...,
7.5 -
~
19.4
(1)
-
-
:s ;:;·
-
I
~
"'
25.0 384.0
245.5
282.6
295.8
150.0
80.6
357.4 252.5 -
-
-
-
-
-
440.7
100.0
-
95.0
61 I
262.0 238.9
62.5
126.0
11 .1
17.5
-
44.4
-
14.0
14
V\ --..)
Table 3. Epiphytic bryophytes collected on trunks of 14 Prunus lusitanica forests. Species abbreviations (Abbrev.), phytogeographical characterisation (Phytogeography), Index of Ecological Significance (IES) values, and number of localities (No. loc.) are shown for each spec ies. Species abbreviations combine the first three letters of the generic name and the first two of the specific name. Phytogeographical elements abbreviat ions : Eur = Eurosiberian, Eur-Oce = Eurosiberian and Oceanic, Ind = Indifferent, Med = Mediterranean, Med-Oce = Mediterranean and Oceanic, Oce = Ocean ic. (continued) Species
Abbrev.
Phyto geography
IES values MTol
MTo2
Frullania tamarisci
FRU TA
Eur-Oce
Grimmia trichophylla
GRJ TR
Med-Oce
8.0
Habrodon perpusillus
HAB PE
Med-Oce
12.0
Harpalejeunea molleri
HARMO
Eur-Oce
-
-
Homalothecium sericeum
HOM SE
lnd
16.0
-
Hypnum andoi
HYPAN
Eur-Oce
-
Hypnum cupressiforme
HYPCU
1nd
. 32.0
Isothecium alopecuroides
1SOAL
Eur
lsothecium myosuroides
1SOMY
197.7
-
197.7
-
LVil
LVi2
Grel
Gre2
-
-
-
-
58.7
127.1
113 .6 261. 1
45.7
86.4
-
15 .2 39.1 -
-
333 -
122.7
91.7
13.6
A9o2
Man!
22.2
Mon2
630 -
Gere
CCan
PO cc
fo e.
40.0 3333
252.0
38.9
7
Anca
10.0
70.4 -
-
-
-
70.0
-
20.0
8 125 .0
-
1463
00
No.
24. 1 167.5
A9ol
lJl
327.5 51.9
106.0
220.0 -
4
-
119.4 11.1
16.0
4
202.0
14
244.4
-
2
'-
>
n e:.. 5. !>:> ~
I:> ,._
-
Eur-Oce
Lejeunea cavifolia
LEJ CA
Eur
Leptodon smithii
LEPSM
Med-Oce
Leucodon sciuroides
LEU SC
Ind
Metzgeria }itrcata
MET FU
Oce
-
8.7
-
6.5 222.7 30.0
15 .9
110.0 445.5
Microlejeunea ulicina
MIC UL
Eur-Oce
Neckera pum ila
NEC PU
Eur-Oce
Nogopterium gracile
NOG GR
Oce
12.0
Orthotrichum scanicwn
ORT SC
Med
-
Orthotrichum acuminatwn
ORTAC
Med
136.0
26.1
193.8
-
60.4
534.8 4 12.5
118.2
444.4 36.1
522.7
140.9
255.6 -
72.7
-
22.7
32.6
-
-
-
-
24.1
6.8
14.8
-
37.0
52.0
-
-
314.8
322.0 12.0
137.5
180.6
-
30.6
-
-
-
-
112.5
-
5.6
-
41.7
6.0
8.3
7 5 9 4
280.0
191.7
14
-
146.0
86.1
3
48.0
461.1
105 .6
14.8
84.0
83.3
115 .0 416.7
88 .9 297.5
-
20.8
-
17.5
27.8 474.1 240.0
-
-
14.8 440.0
-
8 4
6.0
-
6
Table 3. Ep iphytic bryophytes collected on trunks of 14 Prunus lusitanica forests. Species abbreviations (Abbrev.), phytogeographical characterisation (Phytogeography), Index of Eco logical Sign ificance (IES) values, and number of loca lities (No. loc.) are shown for each species. Species abbreviations combine the first three letters of the generic name and the first two of the specific name. Phytogeographical elements abbreviations: Eur = Eurosiberian, Eur-Oce = Eurosiberian and Oceanic, Ind = Indifferent, Med = Mediterranean, Med-Oce = Mediterranean and Oceanic, Oce = Oceanic. (continued) Species
Abbrev.
IES values
Phyto geography
MTol 48.0
MTo2
LVil
LVi2
Gre/
Gre2
-
-
-
-
Orthotrichum affine
ORT AF
Ind
Orthotrichum ibericum
ORT IB
Med-Oce
Orthotrichum lyellii
ORT LY
Oce
184.0
Orthotrichum pal/ens
ORT PA
Eur
-
Orthotrichum pumilum
ORT PU
Med
-
Orthotrichwn rupestre
ORT RU
Med
Orthotrichum speciosum
ORT SP
Eur
8.0
Orthotrichum striatum
ORT ST
Oce
42.0
15.9
30.4
Orthotrichum tene/lum
ORTTE
Med-Oce
150.0
38.6
543
Pore/la obtusata
POROB
Oce
-
1023
PTE Fl
Eur
-
-
Radula complanata
RADCO
Eur
Rhynchostegium confertum
RHYCO
lnd
Syntrichia laevipila
SYN LA
Med-Oce
U/ota bruchii
ULO BR
Eur
-
Ulota crispa
ULO CR
Eur
-
Ulota crispula
ULO CL
Eur
Pterigynandrum filiforme
Zygodon rupestris
115.9
130.4
29.2
93.2
Ar;ol
Ar;o2
-
-
5.6
138.9
83.3
No.
Mon2
5.6
8.0
-
-
-
-
-
12.0
-
40.0
5.6
-
-
-
-
-
22 .7
-
31.8
56.8
22.9
6.8
14.6
15.9
13.0
27.8
11.1
-
-
-
-
-
14.0
-
-
-
-
38 .9
-
-
7.5
6.0
-
6.0
-
-
127.8
144.4
170.0
2463
298.0
-
-
-
-
-
12.0
6.5
-
79.5
83
-
38.9
72.9
333
-
83
111.4
An ea
Cere
CCan PO cc
M on/
152.8
7.5
11.1
15.0
125.0
-
158.0
-
55.6
loc.
3
tTl
I
-o ::r
13
"2.
-
'< ()
-
I
u .... '
1.5) were discarded and the significance of the resulting model was tested by a Monte Carlo test with permutations (Ter Braak & Smilauer, 2002). To complete the explanation of community variability, the IES values of the six above-mentioned phytogeographical elements per forest were projected as supplementary variables in the final model (without affecting its eigenvalues and statistical significance) (Ter Braak & Smilauer, 2002; Leps & Smilauer, 2003). Both environmental and phytogeographical data per forest are available in Appendix 3, and CCA data analysis are provided in Appendix 4. Taxon nomenclature follows Ros et al. (2007) for liverworts and Ros et al. (20 13) for mosses, except for the genus Ulota D.Mohr that follows Caparr6s et al. (2014). Flora Iberica (Castroviejo, 1986-2014) was used for vascular plants.
RESULTS Richness and diversity The epiphyte bryoflora on trunks of the 14 sampled Prunus lusitanica forests comprises 53 species: 41 mosses and 12 liverworts (Table 3 and Fig. 2). The family Orthotrichaceae is especially well represented with 3 genera and 15 species. In addition, the families Brachytheciaceae, Frullaniaceae and Lejeuneaceae are represented by I to 5 genera with 5 species per family. Frullania Raddi among liverworts and Orthotrichum Hedw. among mosses are the most species-rich genera, with 5 and 11 species respectively (Table 3). Three liverworts: Frullania dilatata (L.) Dumort., Metzgeria .furcata (L.) Dumort., and Radula complanata (L.) Dumort. , and two mosses: Hypnum cupressiforme Hedw. and Orthotrichum lyellii Hook. & Taylor, occur in nearly all the sampled forests. In contrast, 29 species are found in fewer than three forests (Table 3). Richness per forest varies from 11 to 20 species (mean = 16.4 ± 3.2), the number of moss species per forest usually being greater than that of liverworts. Similar richness figures are found in Mediterranean and Eurosiberian forests (including those in transitional areas), 16.0 ± 3.3 and 17.0 ± 3.2, respectively. The number of liverworts is slightly higher in Eurosiberian and transitional forests (range = 6-8, mean = 6.7 ± 0.8) than in the Mediterranean ones (range = 2-6, mean = 4.0 ± 1.2) (Fig. 2), yet some liverworts (Frullania dilatata, Metzgeria .furcata and Radula complanata) show high IES values in the latter region (Table 3).
Epiphytic bryophytes of Prunus lusilanica forests
63
60
3,0
,--
so
• •
~
•
•
2,3
2,4
•
2,5
•
2,5
2,5 12
2,3
•
2,2
•
2,2
•
2,2
2, 1
•
40
•
~
2,0
•
•
2,0
2, 1
2,0
1-
2,0
c.
'15
•
ci ~ 30
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Fig. 2. Richness of mosses and liverworts and Shannon-Weaver diversity index (H) of the 14 Prunus lusitanica forests . Population abbreviations are shown in Table I. Superscript letters on forest abbreviations refer to the biogeographical region s: M = Mediterranean Region, E = Eurosiberian Region , M/E = transitional between both regions.
The Shannon-Weaver index (H') varies from 2 to 2.5 in most forests , forest M on 1 being the exception, with a value of only 1.7 (Fig. 2).
Phytogeographical spectra Heterogeneity in bryophyte composition affects not only the identity of the species involved but also the phytogeographical spectra of each forest. This is true even for groves located in the same biogeographical region and geographical area (Figs. I and 3). Despite this variability, some general trends arise. The Oceanic element shows high percentages in all the surveyed forests (21-40%). The Mediterranean element never dominates, even in forests located within the Mediterranean Region , where it can occasionally be absent. This Mediterranean element is also poorly represented or totally absent in most of the forests located in the Eurosiberian Region or in its boundaries. Likewise, the Mediterranean-Oceanic element shows low percentages in these forests. Instead, the Eurosiberian and Eurosiberian-Oceanic elements gain great relevance in the communities of forests growing in the Eurosiberian Region. This last result also applies, although with more modest values, in the westernmost (Estl and Est2) and northeastern (Mon1) communities of the Mediterranean Region.
Classification analysis TWINSPAN Certain indicator and preferential pseudospecies (species at different abundance levels) discriminate different epiphytic bryophyte communities growing on trunks of Prunus lusitanica forests , with eigenvalues raging from 0.29 to
J.A. Calleja et al.
64
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