Epiphytic bryophyte communities of Prunus

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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

:t

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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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