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Ecology, diversity and conservationof relict laurel—leaved mesophyticscrublands in mainland PortugalJoão Honrado a b , Paulo Alves a , Ângela Lomba a , João Torresa & Francisco Barreto Caldas a ba CIBIO—Centro de investigação em biodiversidade e recursosgenéticos , Universidade do Porto , Rua do Campo Alegre,1191, P-4150-181 , Porto E-mail:b Faculdade de Ciências , Universidade do Porto , Rua doCampo Alegre 1191, P-4150-181 , PortoPublished online: 26 Apr 2013.

To cite this article: João Honrado , Paulo Alves , Ângela Lomba , João Torres & FranciscoBarreto Caldas (2007) Ecology, diversity and conservation of relict laurel—leaved mesophyticscrublands in mainland Portugal, Acta Botanica Gallica: Botany Letters, 154:1, 63-77, DOI:10.1080/12538078.2007.10516045

To link to this article: http://dx.doi.org/10.1080/12538078.2007.10516045

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Acta Bot. Gallica, 2007, 154 (1), 63-77.

Ecology, diversity and conservation of relict laurel-leaved mesophyticscrublands in mainland Portugal

by João Honrado(1,2), Paulo Alves(1), Ângela Lomba(1), João Torres(1) and FranciscoBarreto Caldas(1,2)

(1) CIBIO - Centro de investigação em biodiversidade e recursos genéticos, Universidade do Porto

Rua do Campo Alegre, 1191, P-4150-181 Porto ; jhonrado@fc.up.pt

(2) Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 1191, P-4150-181 Porto

Abstract.- Phylogeographic studies have repeatedly identified the southernEuropean peninsulas (Iberian, Italian and Balkanic) as major refuges for the floraduring Pleistocene glacial events. Due to the succession of cold and warm per-iods, a large number of frost-sensitive species became extinct or confined to iso-lated positions in the southern peninsulas, where specific physical conditionsworking at a local scale enabled the persistence of those frost-sensitive, relictspecies. The global purpose of this paper is to address the ecology and diversi-ty of relict laurel-leaved scrublands in mainland Portugal (Southwest Europe),where geographic segregation gave rise to a floristic diversification of communi-ty types. These biogeographically isolated scrublands configure seven distinctassociations, which are recognisable from both classical and numerical phyto-sociological approaches. The conservation of relict laurel-leaved scrublands inthe territory is also assessed in the framework of the EEC “Habitats” Directive.

Key words : conservation - diversity - phytosociology - Portugal - relict vegeta-tion.

Résumé.- Des études phylogéographiques ont souvent identifié les péninsuleseuropéenes du Sud (ibérique, italienne et balkanique) comme d’importantsrefuges pour la flore pendant les épisodes glacièrs du Pléistocène. À cause decette succession de périodes chaudes et froides, un grand nombre d’espècessensibles au froid extrême se sont éteintes ou confinées à des sites isolés dansces péninsules méridionales, où les conditions physiques particulières ont per-mis la persistence de ces espèces relictuelles. L´objectif de ce travail est la des-cription de l’écologie et la diversité des formations arbustives laurifoliéesrelictuelles au Portugal continental (sud-ouest de l’Europe), où l’isolement géo-graphique des populations a donné lieu à une diversification floristique des typesde communautés. Ces groupes de populations biogéographiquement séparéesdéfinissent sept associations végétales, reconnues par des analyses phytoso-ciologiques classiques et numériques. La conservation de ces formations arbus-tives relictuelles dans le territoire est aussi discutée dans le contexte de laDirective “Habitats”.

Mots clés : conservation - diversité - phytosociologie - Portugal - végétationrelictuelle.

arrivé le 30 novembre 2005, accepté le 14 avril 2006

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I. INTRODUCTION

Climate (both past and current) is generally considered the main factor determining thedistribution of plant species and communities, so that, in the absence of significant anthro-pic disturbance, vegetation in a given biogeographical context mainly depends on climateconditions, even in areas where substrate properties induce local variations (Comes &Kadereit, 1998; Honrado et al., 2001).

Many studies concerning Quaternary palaeoecology in Europe have established theoccurrence of southward contractions of distribution ranges of plant species duringPleistocene cold periods (« glaciations »), followed by rapid northward expansions at theend of each cold period (Bennet et al., 1991; Ferris et al., 1993, 1995, 1998; Axelrod,1996; Dumolin-Lapègue et al., 1997). This succession of cold and warm periods caused asignificant redistribution of the flora (Muñoz et al., 1996; Ramil-Rego et al., 1996). A largenumber of mesophilic and thermophilic species became extinct or confined, withinEurope, to rather isolated positions in southern territories (mostly the currentMediterranean Region). Plant families that were diverse and widespread (e.g. Palmaceae,Lauraceae, Myrtaceae) became represented in Europe by few, narrowly distributed taxa(sometimes only one taxon). Phylogeographic studies using both palinological and mole-cular data (e.g. Bennet et al., 1991; Ferris et al., 1993, 1995, 1998; Dumolin-Lapègue etal., 1997) have repeatedly identified the southern peninsulas (Iberian, Italian and Balkanic)as major refuges for the flora during glacial periods.

Depending on their rapidity and intensity, climate changes can give rise to events thatrange from genetic bottlenecks to local, regional or global extinction of taxa. However,specific physical conditions working at a local scale, such as those that can be found inrocky cliffs, along water courses or on special types of rock, can enable the persistence ofspecies in territories where macro-mesoclimate conditions are no longer appropriate fortheir occurrence. If these species are common extant taxa elsewhere, they are called cli-matic disjunctions (Pielou, 1992), but if their distribution is nowadays very restricted, theyare known as climatic relicts (Cox & Moore, 1993; Honrado et al., 2001). The same clas-sification can obviously be applied to vegetation types.

Within this context, the global purpose of this paper is to address the ecology and diver-sity of relict laurel-leaved scrublands in mainland Portugal (Western Iberian Peninsula,Southwest Europe). Only relict vegetation types were addressed since, as will be descri-bed, they raise specific questions regarding their persistence in the territory. A classicalphytosociological approach is complemented with numerical analyses of 56 relevés.Moreover, two new, still unreported, endemic vegetation types are described, and theconservation of relict laurel-leaved scrublands in the territory is assessed in the frameworkof the EEC « Habitats » Directive.

II. METHODS

A. Study area

The study area (mainland Portugal) includes the westernmost areas of the IberianPeninsula, in Southwest Europe (Fig. 1).

Previous studies have shown that climate and lithology play a major role in the distri-bution of vegetation types in Mainland Portugal (e.g. Costa et al., 1998), so the major cli-matic and lithologic features of the country are indicated in Figure 2. It is a climatically

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oceanic territory, with mild temperatures both in summer and in winter, increasingly war-mer southwards; winter frost is rare, except in interior mountains. In the north-western partof the territory, where many of the mountain areas are located, there is heavy rainfall anda small dry period in summer, so the climate is generally of the Temperate type (Rivas-Martínez et al., 2002). In Central-western and South-western Portugal, there is less rain-fall and the dry summer period ranges from three to five months (Mediterranean climate).Lithology ranges from acid rocks (granites and schist) in the Northwest and most of theinterior areas to limestone and sedimentary substrates in the central-western and south-western parts of the country.

B. Phytosociology and phytogeography

Vegetation types were studied according to the concepts and methods of Braun-Blanquet’s phytosociology (Géhu & Rivas-Martínez, 1981; Rivas-Martínez, 2002). Inshort, phytosociological relevés were performed in representative formations with widelyrepeatable (i.e. stable) physiognomy, ecology and floristic composition. Relevés were latersurveyed for similarity and classified within the syntaxonomic scheme of Rivas-Martínezet al. (2001).

Phytosociological data regarding relict laurel-leaved scrublands in mainland Portugal(56 relevés) were collected from the following sources: Capelo & Mesquita (1998) forMyrico fayae-Arbutetum unedonis (6 relevés), Costa et al. (2000) for Frangulo alni-Prunetum lusitanicae (19) and Vinco difformis-Lauretum nobilis (10), Honrado (2003) for

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Fig. 1. The study area (mainland Portugal) within an European context.Fig. 1.- L’aire d’étude (Portugal continental) dans le contexte européen.

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a b

c d

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Luzulo henriquesii-Prunetum lusitanicae (5) and Pruno lusitanicae-Arbutetum unedonis(4) and Honrado et al. (2004) for Omphalodo nitidae-Lauretum nobilis (6). From the sixrelevés of Calluno vulgaris-Rhododendretum baetici, two were collected from Braun-Blanquet et al. (1956) and the other four are original relevés reported here for the first time.

The nomenclature of plant taxa is mostly according to standard Iberian floras(Castroviejo et al. (1986-2003) for published volumes, Franco (1971, 1984) and Franco &Afonso (1994, 1998, 2003) for other groups). Bioclimatic indices and typologies and phy-togeographic units are those of Rivas-Martínez et al. (2002).

C. Numerical analyses

In order to perform statistical analyses (cluster analysis and ordination), a global datamatrix was constructed from the 56 available relevés.

Cluster analysis consists in grouping the vegetation samples into classes, based on theirattributes (Kent & Coker, 1992). Hierarchical cluster analysis has been referred as a sui-table approach in the analysis of plant communities, allowing the grouping of phytosocio-logical relevés based on their floristic composition (Capelo, 2003). In this research ahierarchical cluster analysis was performed with the Community Analysis Package 3.1®

(Pisces Conservation) software. Relevés were grouped according to Ward’s method usingEuclidean distance.

Ordination techniques are considered to be complementary to cluster analysis.Specifically, indirect ordination techniques consist in the arrangement of vegetationsamples according to their similarity in terms of floristic composition (Kent & Coker,1992). Ordination analyses were performed with Canoco 4.5® for Windows (Ter Braak &Smilauer, 2002). A detrended correspondence analysis (DCA) was first performed to deter-mine the length of the gradient within the dataset. Given the length of the gradient, a uni-modal response was assumed and therefore a correspondence analysis (CA) (Ter Braak &Smilauer, 2002; Van Den Brink et al., 2003) was performed.

III. RESULTS AND DISCUSSION

A. Relict laurel-leaved mesophytic species in mainland Portugal

In mainland Portugal, two major floristic elements come together. The territory is thesouth-westernmost area for many eurosiberian temperate species, which predominate inmountain areas and in lowland areas of the Northwest with high annual rainfall. The

Fig. 2.- Main climatic (a-c) and lithologic (d) features of mainland Portugal. Maps a to c wereobtained by kriging interpolation of the following bioclimatic indices: a, thermicity index: It= 10(T+M+m), where T is the mean annual temperature, and M and m are, respectively,the mean maximum and mean minimum temperatures of the coldest month of the year;b, continentality index: Ic = Tmax-Tmin, where Tmax and Tmin are the mean temperaturesof the hottest and coldest months, respectively; c, annual ombrothermic index: Io =Pp/Tp, where Pp and Tp are the sums of, respectively, the total rainfall and the mean tem-perature of all months with positive mean temperature. Map d is a simplification of thelithologic map of mainland Portugal available at the site of the Portuguese Institute ofEnvironment (www.iambiente.pt/).

Fig. 2.- Données climatiques (a-c) et lithologiques (d) pour le Portugal continental.

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Mediterranean element predominates in the central, southern and north-eastern parts of thecountry and in lowland areas of the Northwest with at least two dry months in summer.

The vast majority of tropical and subtropical Tertiary vegetation was eliminated fromthe territory by Pleistocene glaciations (Honrado et al., 2001). However, several kinds ofevidence suggest that some forest remains could have survived Pleistocene glaciations intopographically sheltered valleys of Western Iberian Peninsula (Coudé-Gaussen, 1981).The presence of these woodland environments would have provided shelter for Tertiary(sub)tropical flora, allowing the persistence of the isolated populations we can nowadaysfind in the flora of mainland Portugal.

The mild temperatures and abundant (though seasonal) rainfall that characterise the cur-rent climate of North and Central Portugal favour the regular occurrence of those relict(sub)tropical taxa. Among the climatic relicts that can be found in the territory, three are tobe highlighted since they are usually dominant elements in relict laurel-leaved scrublands:the Common-laurel (Laurus nobilis), the Portuguese-laurel (Prunus lusitanica subsp. lusi-tanica) and the west-mediterranean subspecies of Pontic-rhododendron (Rhododendronponticum subsp. baeticum). There are, however, several other relict mesophytic taxa thatregularly occur in these laurel-leaved formations, like Dryopteris guanchica, Smilax aspe-ra, Woodwardia radicans, etc. There is still another group of laurel-leaved taxa whichbecame adapted to (sub)mediterranean climate conditions and cannot, therefore, be consi-dered true relicts: Arbutus unedo, Myrtus communis, Phillyrea latifolia, Rubia peregrinasubsp. longifolia, Viburnum tinus subsp. tinus, Vinca difformis and others.

Laurus nobilis, Prunus lusitanica subsp. lusitanica and Rhododendron ponticum subsp.baeticum are usually dominant in permanent relict formations, occupying either shadedsites on steep slopes or biotopes with seasonal disturbance by running water, generally insheltered positions in valleys. The Strawberry-tree (Arbutus unedo) is a frequent dominantin mesophytic low scrublands that replace disturbed climactic woodlands under (sub)medi-terranean climate; these formations are not includable in the concept of « relict vegeta-tion » used here, since they are at an equilibrium with current mesoclimatic conditions.However, in the Gerês mountain range, a heavily rainy territory in Northwestern Portugal,there are highly resilient arborescent scrublands dominated by Arbutus unedo and withregular occurrence of Prunus lusitanica subsp. lusitanica (Honrado, 2003) that were inclu-ded in this study; arborescent Arbutus scrublands which are considered a relict climax oncentral-western palaeodunes (Capelo & Mesquita, 1998) were also included.

B. Laurel-leaved vegetation types in mainland Portugal

1. Classical and numerical syntaxonomySeven phytosociological associations of relict laurel-leaved scrublands are recognised

in mainland Portugal from a classical phytosociological approach (see Syntaxonomicalchecklist), two of which (Luzulo henriquesii-Prunetum lusitanicae and Calluno vulgaris-Rhododendretum baetici) are reported here for the first time. All seven associations areincluded in alliance Arbuto unedonis-Laurion nobilis (Rivas-Martínez et al., 2001).

According to the predominant species, four groups of scrubland types are recognisable(see description below): i) Laurus nobilis scrublands (in Portuguese: louriçais):Omphalodo nitidae-Lauretum nobilis and Vinco difformis-Lauretum nobilis; ii) Prunuslusitanica galleries (azerais): Frangulo alni-Prunetum lusitanicae and Luzulo henriquesii-Prunetum lusitanicae; iii) Arbutus unedo arborescent scrublands (medronhais): Prunolusitanicae-Arbutetum unedonis and Myrico fayae-Arbutetum unedonis; and iv)

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Rhododendron ponticum subsp. baeticum galleries (adelfeirais): Calluno vulgaris-Rhododendretum baetici.

Numerical analyses (both ordination and cluster analysis) of the total set of relevés wereperformed to assess the validity of both new and previously reported associations (Fig. 3and 4).

The CA ordination diagram (Fig. 3) discriminates three major groups of relevés: i) thesix species-poor Calluno vulgaris-Rhododendretum baetici relevés; ii) the 16 relevés of thecentral-western basophilous Laurus nobilis (Vinco difformis-Lauretum nobilis) andArbutus unedo (Myrico fayae-Arbutetum unedonis) scrublands, with the latter in an inter-mediate position regarding the third group; and iii) the relevés of the four species-rich aci-dophilous associations (Frangulo alni-Prunetum lusitanicae, Luzulohenriquesii-Prunetum lusitanicae, Omphalodo nitidae-Lauretum nobilis and Pruno lusita-nicae-Arbutetum unedonis). Within this group, relevés of each of the four associations tendto form discrete (though closely related) groups.

In the dendrogram of Figure 4, the relevés of the seven associations are clearly discri-minated, demonstrating the statistical validity of results from the classical phytosociologi-cal approach at the association level. At the first dichotomy, cluster analysis segregates thecentral-western basophilous Myrico fayae-Arbutetum unedonis and Vinco difformis-Lauretum nobilis from the five acidophilous associations. Within this group, relevés of thespecies-poor Calluno vulgaris-Rhododendretum baetici are separated from a group com-posed of the species-rich acidophilous scrublands dominated by Laurus nobilis, Arbutusunedo and Prunus lusitanica subsp. lusitanica. Mediterranean Prunus lusitanica subsp.lusitanica formations (Frangulo alni-Arbutetum unedonis) are then segregated from the

Fig. 3.- CA ordination dia-gram for the total set ofrelevés. (CALROD =Calluno vulgaris-Rhododendretum baetici,FRAPRU = Frangulo alni-Prunetum lusitanicae,LUZPRU = Luzulo henri-quesii-Prunetum lusitani-cae, MYRARB = Myricofayae-Arbutetum unedo-nis, OMPLAU =Omphalodo nitidae-Lauretum nobilis,PRUARB = Pruno lusitani-cae-Arbutetum unedonis,VINLAU = Vinco unedo-nis-Lauretum nobilis).

Fig. 3.- Diagramme CA pourl’ensemble des relevés.

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three temperate associations of the Northwest. Finally, thermotemperate Laurus nobilisscrublands are separated from mesotemperate formations with Prunus lusitanica subsp.lusitanica (both Arbutus and Prunus-dominated scrublands).

These results stress the importance of both climate and lithology in determining the flo-ristic composition of relict laurel-leaved scrublands in the territory. In fact, laurel-leavedvegetation tends to occur in areas with (highly) oceanic and moderate to heavily rainy cli-mate in the north-western and central-western areas of Portugal, on soils derived fromlimestone, sand or acid rocks (Fig. 2 and 5).

2. Description of vegetation types (associations)Laurus nobilis scrublands

Tall scrublands dominated by the Common-laurel, typical of the north-western and cen-tral-western parts of the territory. They usually occupy sheltered positions in the edge ofboth Quercus robur or Q. faginea subsp. broteroi forests. Two associations are recognisedin the territory:

- Omphalodo nitidae-Lauretum nobilis, silicicolous laurel-thickets rich in temperate taxa(Hedera hibernica, Omphalodes nitida, Saxifraga spathularis) occurring along rockymargins of seasonal rivulets within forest landscapes dominated by Quercus robur(Honrado et al., 2004);- Vinco difformis-Lauretum nobilis, calcicolous laurel-thickets with abundant thermo-philous taxa (Viburnum tinus subsp. tinus, Pistacia lentiscus, Rosa sempervirens,

Fig. 4.- Cluster diagram for the total set of relevés (see Fig. 3 for abbreviations).Fig. 4.- Dendrogramme sur l’ensemble des relevés.

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Lonicera etrusca), colonising moist lime-rich soils with seasonally flowing waterswithin forest landscapes dominated byQuercus faginea subsp. broteroi (Costa etal., 2000).

Prunus lusitanica subsp. lusitanica scru-blands

Tall scrublands dominated by Prunuslusitanica subsp. lusitanica, occurring insmall areas in the north-western and centralparts of the territory, always on siliceoussoils. These formations occupy shelteredpositions in the bottom of deep valleys near-by seasonally running water within forestlandscapes dominated by Quercus robur.Two associations are recognised in the terri-tory:

- Frangulo alni-Prunetum lusitanicae,silicicolous mediterranean Prunus lusita-nica subsp. lusitanica galleries with abun-dant thermophilous laurel-leaved shrubs(e.g. Viburnum tinus subsp. tinus) andvines (e.g. Rubia peregrina), colonisingriver beds with seasonally flowing waters(Costa et al., 2000);- Luzulo henriquesii-Prunetum lusitani-cae ass. nova hoc loco (syntype: Table I,relevé n. 4), silicicolous temperate Prunuslusitanica subsp. lusitanica galleries, rich in temperate nemoral taxa (Ilex aquifolium,Saxifraga spathularis, Luzula sylvatica subsp. henriquesii) typical of rocky river bedswith seasonally flowing waters (Honrado, 2003).

Arbutus unedo arborescent scrublandsDense arborescent scrublands dominated by the Strawberry-tree, occurring in small

areas of the north-western and central-western parts of the territory, on either siliceoussoils or palaeodunes. Two associations are recognised in the territory:

- Pruno lusitanicae-Arbutetum unedonis, relict silicicolous Strawberry-tree formations,occurring in the north-western areas of the territory (Costa et al., 2000; Honrado, 2003);these formations are very stable in time and are dominated by arborescent specimens ofArbutus unedo, colonising shaded slopes in deep valleys with frequent mist, withinforest landscapes dominated by Quercus robur;- Myrico fayae-Arbutetum unedonis, relict arborescent Strawberry-tree formations,occurring on litter-rich soils of palaeodunes in the coastal areas of the central-westernpart of the territory; they are usually dominated by Arbutus unedo, Myrica faya andLaurus nobilis (Capelo & Mesquita 1998).

Fig. 5.- Geographic location of the siteswhere the 56 relevés were collected (com-pare with the climatic and lithologic mapsof Fig. 2).

Fig. 5.- Localisation géographique des sitesoù les 56 relevés furent effectués.

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Rhododendron ponticum subsp. baeticum mesophytic scrublandsCalluno vulgaris-Rhododendretum baetici ass. nova hoc loco (syntype: Table II, relevé

n. 6), temperate silicicolous low scrublands, absolutely dominated by Rhododendron pon-

ticum subsp. baeticum, occurring in a very restricted area of Northwest Portugal and colo-nising the heads of small river beds with seasonally flowing waters. This is the mostnarrowly distributed of all seven associations, with most formations located within theCambarinho botanical Reserve (Vouzela, Northwest Portugal). Both climatic changes andhuman disturbance history are believed to be responsible for this narrow distribution.

Table I, Tableau I.- Luzulo henriquesii-Prunetumlusitanicae ass. nova.

Relevé n. 1 2 3 4 5Altitude (m) 620 650 710 630 570N. of taxa 16 19 25 29 37

Characteristic taxaPrunus lusitanica subsp. lusitanica 4 5 5 4 4Erica arborea 1 2 1 2Ruscus aculeatus 1 + 1 +Arbutus unedo 1 1Rubia peregrina 1

Differential taxa Dryopteris affinis subsp. borreri 1 1 1 1 1Ilex aquifolium 2 1 1 1 1Saxifraga spathularis 2 1 2 1 1Luzula sylvatica subsp. henriquesii 2 1 1Omphalodes nitida 1 1 +Pyrus cordata 1 1 1Vaccinium myrtillus 2 1 2Sanicula europaea + +Betula celtiberica 1Eryngium juresianum 1Taxus baccata +

Companion taxaBlechnum spicant 2 1 1 1 1Hedera hibernica 2 3 4 3 1Lonicera periclymenum 1 1 1 1 1Rubus sp. 1 2 2 2 2Teucrium scorodonia 1 1 1 1Brachypodium sylvaticum 1 1 1Frangula alnus 1 1 1Polypodium interjectum 1 1 1Viola palustris 1 1 1Aquilegia vulgaris subsp. dichroa + 1Athyrium filix-femina 2 1Brachypodium pinnatum subsp. rupestre 2 1Carex elata subsp. reuteriana 1 1Crepis lampsanoides 1 +Euphorbia dulcis 1 1Festuca elegans + 1Primula acaulis + +Osmunda regalis +Potentilla erecta 1Quercus robur 1 1Salix atrocinerea 1

Companion taxa present in one relevé: Rel. 2:1 Agrostis xfouilladei, + Angelica sylvestris,+ Veronica officinalis; Rel. 3: + Anemone tri-folia subsp. albida, + Hypericum androsae-mum, 1 Polystichum setiferum; Rel. 4: 1Carex remota, 1 Prunella grandiflora subsp.pyrenaica; Rel. 5: 1 Arenaria montana, 1Clinopodium vulgare, 1 Cytisus scoparius, 1Fraxinus angustifolia, 1 Galium broterianum,+ Hieracium vulgatum, + Laserpitium eliasiisubsp. thalictrifolium, + Linaria triornitho-phora, 1 Peucedanum gallicum, 1 Picris hie-racioides subsp. longifolia, + Vincetoxicumhirundinaria subsp. lusitanicum, 1 Viola rivi-niana.

Relevé sites1 - Terras de Bouro: Serra do Gerês, Near

Bouça da Mó, to Albergaria, 29TNG6926.2 - Terras de Bouro: Serra do Gerês,

Albergaria, Rio Maceira, 29TNG7127.3 - Terras de Bouro: Serra do Gerês, Ribeira

da Laja, 29TNG7023.4 - Terras de Bouro: Serra do Gerês, Rio

Gerês, near Curral da Laja, 29TNG7023.5 - Terras de Bouro: Serra do Gerês, Ribeira

da Figueira, 29TNG7022.

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Braun-Blanquet et al. (1956) had already reported two relevés of a « groupement àRhododendron ponticum ssp. baeticum », which were included in Table II and in the nume-rical analyses. Agrostis xfouilladei, Calluna vulgaris and Quercus robur are differentialtaxa regarding the southern-Spain mediterranean association Scrophulario laxiflorae-Rhododendretum baetici, which in turn is characterised by the occurrence of Frangulaalnus subsp. baetica, Scrophularia laxiflora, Viburnum tinus subsp. tinus and Quercuscanariensis (Pérez Latorre et al., 2000).

Table III synthesizes the most important biogeographical, bioclimatical and floristicalfeatures of the seven associations of laurel-leaved relict scrublands in mainland Portugal.

IV. CONCLUSIONS

A. The importance of phylogeographical data in phytosociology

The Quaternary succession of cold and warm periods caused a significant redistributionof the coenozoic flora, with a large number of frost-sensitive species becoming extinct orconfined to rather isolated positions in Southern Europe. Plant families once diverse andwidespread became represented only by few, narrowly distributed taxa.

Phylogeographic studies have repeatedly identified the southern peninsulas (Iberian,Italian and Balkanic) as major refuges for the flora during glacial periods. Local ecologi-cal conditions have enabled the persistence of species and vegetation types in territorieswhere mesoclimatical conditions are no longer appropriate for their occurrence. If those

Table II, Tableau II.- Calluno vulgaris-Rhododendretum baetici ass. nova.

Relevé nº 1 2 3 4 5 6Altitude (m) 500 500 500 538 498 517Nº of taxa 8 8 8 12 12 20

Characteristic taxaErica arborea + 1 + 1 + +Rhododendron ponticum subsp. baeticum 5 4 5 4 5 5

Differential taxa Quercus robur 1 1 + + 1 +Agrostis xfouilladei + + + 1Calluna vulgaris 1 + +

Companion taxaPteridium aquilinum 1 2 + 1 2 1Dactylis glomerata subsp. lusitanica + + + +Lonicera periclymenum + + + +Rubus sp. + 1 1 1Blechnum spicant + + +Salix atrocinerea + 2 1Teucrium scorodonia + +Cistus psilosepalus + +Digitalis purpurea + +Osmunda regalis +Potentilla erecta +Tamus communis + +Ulex minor + +

Companion taxa present in one relevé:Rel. 2: + Pterospartum tridentatumsubsp. cantabricum; Rel. 4: 1 Cytisusstriatus, + Ulex europaeus subsp. late-bracteatus; Rel. 5: 1 Quercus xandega-vensis; Rel. 6: + Carex ovalis, + Carexpilulifera, + Ranunculus repens.

Relevé sites:1 to 6 - Vouzela: Cambarinho,

29TNF6702 (relevés 2 and 3 fromBraun-Blanquet et al., 1956).

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species or vegetation types have a restricted distribution, they are known as climaticrelicts. The mild temperatures and abundant rainfall that characterise the current climate ofNorth and Central Portugal favour the occurrence of relict taxa, like the Common-laurel(Laurus nobilis), the Portuguese-laurel (Prunus lusitanica subsp. lusitanica) and the west-mediterranean subspecies of Pontic-rhododendron (Rhododendron ponticum subsp. baeti-

cum). These taxa are usually dominant in relict formations, occupying shaded sites onsteep slopes with either topographic or edaphic constraints, or then biotopes with seasonaldisturbance by running water, generally in sheltered positions in valleys or in sub-coastalareas.

The relict character of vegetation types dominated by these shrubs and small trees is lar-gely responsible for the fragmentary distribution pattern that can nowadays be observed.Biogeographical segregation gave rise to a floristic diversification of community types,with climate and lithology playing a central role in that discrimination. Therefore, biogeo-graphically isolated groups of scrublands configured distinct, narrowly distributed asso-ciations which are recognisable from both classical and numerical phytosociologicalapproaches.

B. Conservation issues and final remarks

Table III.- Synthesis of the biogeographical, bioclimatical and floristical features of the sevenrelict laurel-leaved scrubland associations in mainland Portugal.

Tableau III.- Synthèse des données biogéographiques, bioclimatiques et floristiques dessept associations arbustives laurifoliées relictuelles du Portugal continental.

Associations Biogeographical sectors Thermoclimates Ombroclimates Characteristic combination

Calluno vulgaris- Galician-Portuguese Meso-temperate Humid Rhododendron ponticum subsp. baetic.

Rhododendretum baetici Erica arborea

Pteridium aquilinum

Calluna vulgaris

Frangulo alni- Dividing-Portuguese Meso-mediterranean Sub-humid Prunus lusitanica subsp. lusitanica

Prunetum lusitanicae Estrelensean Humid Viburnum tinus subsp. tinus

Frangula alnus

Luzulo henriquesii- Juresian Meso-temperate Humid Prunus lusitanica subsp. lusitanica

Prunetum lusitanicae Hyper-humid Saxifraga spathularis

Luzula sylvatica subsp. henriquesii

Pruno lusitanicae- Juresian Meso-temperate Humid Prunus lusitanica subsp. lusitanica

Arbutetum unedonis Arbutus unedo

Ilex aquifolium

Myrico fayae- Dividing-Portuguese Meso-mediterranean Sub-humid Arbutus unedo

Arbutetum unedonis Myrica faya

Laurus nobilis

Omphalodo nitidae- Galician-Portuguese Thermo-temperate Sub-humid Laurus nobilis

Lauretum nobilis Meso-temperate Humid Hedera hibernica

Meso-mediterranean Omphalodes nítida

Vinco difformis- Dividing-Portuguese Meso-mediterranean Sub-humid Laurus nobilis

Lauretum nobilis Vinca difformis

Smilax aspera

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The conservation of relict species and vegetation types is one of the most sensitive andurgent tasks in conservation biology, for three main reasons: i) their current distributionpatterns provide important insights on the recent environmental evolution of their territo-ries; ii) they are usually found at or near the limits of physiologic tolerance for one or moreecological factors; and iii) they exhibit poor recovering capacity after destruction by anykind of disturbance. Therefore relict vegetation types are usually rare (or even absent) inlandscape mosaics exhibiting moderate to intensive disturbance related to human activitiessuch as agriculture or forestry.

Relict mesophytic laurel-leaved scrublands occurring in mainland Portugal are classi-fied as a priority habitat for conservation by the 92/43/EEC Council Directive (« Habitats »Directive), namely within habitat 5230* (see the Directive’s Annex I). In a recent surveyof habitat types occurring in mainland Portugal, the Portuguese phytosociologicalAssociation provided a set of individual characterisation files for 98 habitat types, whichcan be found at the site of the National Institute for Nature Conservation (www.icn.pt).Within habitat 5230*, five subtypes were considered to occur in mainland Portugal, sho-wing a remarkable resemblance to the classification proposed in this paper (seeSyntaxonomical checklist and Table IV).

Many of the 56 relevés presented in this paper were collected within either EU Natura2000 sites and/or national protected areas, so most of the best representations of these nar-rowly endemic vegetation types are under some kind of formal protection. However, theirrelict character and their (palaeo)botanical peculiarity should justify the elaboration of spe-cific conservation plans in order to promote their long-term presence in the territory.

Table IV.- Comparison of the subtypes of habitat 5230* (Annex I of 92/43/EEC CouncilDirective) occurring in mainland Portugal with the seven associations presented in thispaper.

Tableau IV.- Comparaison entre les sous-types de l’habitat 5230* présents au Portugalcontinental et les sept associations décrites ici.

Subtype of habitat 5230 Associations

Laurus nobilis scrublands Omphalodo nitidae-Lauretum nobilis

Vinco difformis-Lauretum nobilis

Prunus lusitanica subsp. lusitanica scrublands Frangulo alni-Prunetum lusitanicae

Luzulo henriquesii-Prunetum lusitanicae

Arbutus unedo-Prunus lusitanica subsp. lusitanica scrublands Pruno lusitanicae-Arbutetum unedonis

Arbutus unedo-Myrica faya scrublands Myrico fayae-Arbutetum unedonis

Rhododendron ponticum subsp. baeticum scrublands Calluno vulgaris-Rhododendretum baetici

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Syntaxonomical checklist of relict laurel-leaved mesophytic scrublandsin Mainland Portugal

Class QUERCETEA ILICIS Br.-Bl. ex A. & O. Bolòs 1950Order Pistacio lentisci-Rhamnetalia alaterni Rivas-Martínez 1975

Alliance Arbuto unedonis-Laurion nobilis Rivas-Martínez, Fernández-González &Loidi 1999

Sub-alliance Arbuto unedonis-Laurenion nobilis Rivas-Martínez & Sánchez-Mata 2001Association Frangulo alni-Prunetum lusitanicae Lopes, J.C. Costa, Lousã &

Capelo in J.C. Costa, Lopes, Capelo & Lousã 2000Association Luzulo henriquesii-Prunetum lusitanicae J. Honrado, P. Alves, A.

Lomba, J. Torres & F. B. Caldas ass. novaAssociation Myrico fayae-Arbutetum unedonis Capelo & Mesquita 1998Association Omphalodo nitidae-Lauretum nobilis J. Honrado, P. Alves & F.B.

Caldas in J. Honrado, P. Alves, H.N. Alves & F.B. Caldas 2004Association Pruno lusitanicae-Arbutetum unedonis (Aguiar & Capelo 1995)

J.C. Costa, Capelo & Lousã in J.C. Costa, Lopes, Capelo & Lousã 2000Association Vinco difformis-Lauretum nobilis Capelo & J.C. Costa in J.C.

Costa, Lopes, Capelo & Lousã 2000Sub-alliance Rhododendrenion baetici Rivas-Martínez & Sánchez-Mata 2001

Association Calluno vulgaris-Rhododendretum baetici J. Honrado, P. Alves,A. Lomba, J. Torres & F. B. Caldas ass. nova

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