Cryptogamie,Bryologie,2009,30 (1):185-197 ©2009Adac.Tous droits réservés

Distribution patternsof Leucodon speciesin Macaronesia, withspecialreferencetothe

JuanaMaríaGONZÁLEZ-MANCEBOa*,JairoPATIÑOa ,OlafWERNERb , RosalinaMariade AlmeidaGABRIELc &RosaMaríaROSb

a DepartamentodeBiologíaVegetal(Botánica),UniversidaddeLa Laguna, C/AstrofísicoFranciscoSánchezs/n,38071-La Laguna, ,IslasCanarias, ,[email protected]; [email protected]

b DepartamentodeBiologíaVegetal(Botánica),UniversidaddeMurcia, Campus de Espinardo,30100-Murcia, Spain,[email protected]; [email protected]

c CITAA -DepartamentodeCienciasAgrárias,Universidade dosAzores, P-9701-851 TerraChã-Angrado Heroísmo,,,[email protected]

(Received 10July2008,accepted 10November2008)

Abstract –The genus Leucodon isrepresented in Macaronesiabythree species, L.sciuroides , L.canariensis and L.treleasei,the lattertwobeing endemictothisregion. An analysisof distribution,frequencyand forall three speciesin thisregion shows singularpatternsforeachspecies,mainlyrelated tohabitatconservation and type of . Leucodon canariensis isthe most restricted speciesasregardshabitatconditions,witha confirmed presenceonlyon Madeiraand the Canary Islands,although moreabundantin the latter. Leucodon treleasei exhibits the widest habitatamplitude,especiallyon , and itispresentin all three northernarchipelagos. Leucodon sciuroides isthe most tolerant speciestoaridity and ismainlyfound on Madeiraand the Canary Islands,although its occurrencewasconfirmed in all the Macaronesianarchipelagos.

Leucodon /Leucodon sciuroides / Leucodon canariensis / Leucodon treleasei /Macaronesia /biogeography/conservation /habitatrequirements

INTRODUCTION

According toseveralauthors (e.g. Hansen &Sunding,1993),the MacaronesianRegion includesfour archipelagos,the Azores,Madeira, Canary Islandsand Islands.Nevertheless,the conceptof Macaronesiathat best appliestobryophytesmightbedifferent,atleast in the caseofmosses,since the Cape Verde Islandsshowhigheraffinitieswithtropicalmoss flora (Vanderpoorten etal .,2007; González-Mancebo etal .,2008b). Eitherin awider orstrictersense,Macaronesia, isone of the 25world biodiversity hotspots (Myers etal .,2000),and within the EuropeanMediterraneanregion,itisone of the most importantfloristicareas(Médail &Quézel,1997; Vanderpoorten &Long,2006).

*Correspondenceand reprints :[email protected] 186J.M.González-Mancebo,J.Patiño,O.Werner,R.M.deA.Gabriel &R.M.Ros

Macaronesiaisalsowell-knownforexhibiting ahigh degree of endemism, especiallyasfarasvascularplants areconcerned (e.g. Kim etal .,2008;Reyes- Betancort etal .,2008). Asregardsbryophytes,a10%rateofendemicity isnot high compared withotherisland groups.However,within the EuroAsiatic- MediterraneanRegion,Macaronesiaisespeciallyrichinendemicbryophytes (Bischler,2004),although endemicity isquitelowamong the Azoreanbryophytes (only2.05%,Gabriel etal .,2005). The genus Leucodon includes38species(Crosby etal .,1999) with analmost worldwide distribution in temperateand warmregions.Inthe Macaronesianregion,thisgenus includesthree species: Leucodon sciuroides (Hedw.) Schwägr., L.canariensis (Brid.) Schwägr.,and L.treleasei (Cardot)Paris, the last twobeing Macaronesianendemics. Leucodon sciuroides isawidespread speciesof the Palaearcticregion. InEurope,itrangesfrom Iceland and northern Scandinavia(Nyholm,1954-1960; Pippo,1982)tothe Mediterraneanregion, whereitisadominantepiphyteonthe coastalplains(Preston,1994). Ithasalso been recorded in NorthernAfrica (Ros etal .,1999) and East (O’Shea, 2006)and in all the Macaronesianarchipelagos(Hedenäs,1992; Patiño Llorente &GonzálezMancebo,2005). Fordecades,identification problemsprevented toknowthe real distribution of thesethree species. Leucodon treleasei waseven considered asa synonymof L.canariensis byseveralauthors in the past (Corley etal .,1981; Dirkse etal .,1993). Thistaxonomicdifficulty wasovercome byHedenäs(1992), who clearlyestablished the morphologicaldifferencesbetween the twoendemic speciesand L.sciuroides .Thisauthorindicated thatthe occurrenceof L.canariensis in the Azoresisuncertain,and described the habitat,distribution and frequencyof thesespecieson the island of Madeira.However,these characteristicshavenotbeen studied in otherMacaronesianarchipelagos. The presentworkincludesadetailed revision of thesespecies,based on herbariumand freshmaterialfrom all the Macaronesianarchipelagos.Differences in habitat,distribution and frequencyof Leucodon specieswereanalysed in the Canary Islands,Madeira, the Azoresand the Cape Verde Islands,withspecial focus on the first archipelago,wherethe three speciesoccur.Afrequencyanalysis wasalsoperformed,in ordertogeneratehypothesesabout the centreofthe dispersalrange foreachofthe endemicspecies,taking intoconsideration that theyoccur most abundantlyin the centreoftheirrange and thattheirabundance graduallydeclinestowardstheirgeographicallimits (e.g. Söderström,1989).

MATERIAL AND METHODS

Bibliographyreferences The recordsof Leucodon speciesfrom the four Macaronesian archipelagoshavebeen thoroughlycompiled foreachofthe four archipelagos. Forthe Azoresthe following referenceshavebeen used:Russel (1862),Cardot (1897,1905),Trelease(1897),Geheeb&Herzog (1910),Allorge &Allorge (1945, 1948,1952),Schwab (1981),Eggers (1982),Hübschmann (1974),Sjögren (1990, 1996,1997,2001,2003,2005),Fontinha&Sérgio (1995). ForMadeira: Eggers (1982),Hedenäs(1992),Sérgio etal .(1992),Sjögren (2001) and Kürschner etal . (2007a, b). Forthe Canary Islands:Pitard&Negri(1907),Bryhn (1908),Bines Leucodon in Macaronesia187

(1965),Düll (1980),During (1981),Losada-Lima etal .(1984),Schwab &Haustein (1984),Koppe &Düll (1986),Malme (1988),Zippel (1998),González-Mancebo et al. (1989,1996,2004,2008a). Forthe Cape Verde Islands:Potierde laVarde (1946),Frahm etal .(1996),Patiño Llorente&GonzálezMancebo(2005),O’Shea (2006). Withthesedata, apreliminary approachwasmade toestimatethe occurrenceand frequencyof the specieson eachisland. Onlyislandsmeasuring morethan50km2 wereconsidered,withthe single exception of Corvo(15 km2 , the Azores),duetoits high altitude (718 ma.s.l.). Thus,Selvagens,Deserta (Madeira),and the islets of Graciosa, Alegranzaand MontañaClara(Canary Islands)werenotconsidered.

Plantmaterial The characters considered byHedenäs(1992)wereusefulfor establishing morphologicaldifferencesamong thesethree species,especiallyas regardscapsule shape and the sizeofthe middle-leafcellsin the secondary stems, aswell asthe cell shape of the cellssituated between the baseand middle leafat the leafmargin. DNA data(manuscriptin preparation) confirmed thatthe morphologicalcharacters used byHedenäsreliablyidentifythe three species. Plantmaterialfrom most of the areasreferred tointhe abovebibliographywas studied. Forthis,all classicallocalitieswerevisited,including thosewherethe recordsof the specieswereuncertain,eitherduetothe erroneous identification of herbariaspecimensorbecauseofdoubtconcerning habitataccording tothe main distribution signsof the species.Atotalof500 freshand 50herbarium specimensfrom the differentarchipelagoswereidentified,whichallowed to correcting the first bibliographicapproachonthe distribution and frequencyof the species.

Habitatcharacteristics Forthe analysisof speciesdistribution,severalhabitatcharacteristics wereconsidered:altitudinalrange,type of habitatand habitatamplitude. Fivetypesof habitathavebeen distinguished:1. sun-exposed habitats (including cultivated and disturbed areasand alsonon-forestry natural vegetation);2.sheltered habitats outside the forest; 3. (evergreen subtropicalforest);4. cloudlaurel forest (laurel forest withthe highest fog influence,mainlysituated along the mountain ridges);5. pine forest. Fivedifferentclassesof habitatamplitude havebeen considered: 1. unknown(old reports without precision);2.very restricted (presenceonlyin one ortwolocalities; maximumtwosquaresof 1km 2 );3.restricted disperse (restricted toone habitatwhereitisnotcommon);4. restricted locallyabundant (restricted toone habitatwherethe speciescancolonizedifferentmicrohabitats and reachahigh frequencyand/orbiomass);5. common (widelydistributed in severalhabitats and wide altitudinalrange).

Dataanalysis Detrended correspondenceanalyses(DCA;Hill &Gauch,1980)have been used tostudyisland and speciescomposition forall the Macaronesian islands.Thesewereperformed withthe CANOCO package (TerBraak& 188 J.M.González-Mancebo,J.Patiño,O.Werner,R.M.deA.Gabriel &R.M.Ros

Smilauer,2002),entering datacorresponding tofrequencyof the specieson each island. The frequencyforeachspecieson eachisland wasestimated counting the numberof 1km 2 cellswherethe specieshadbeen found,taking intoaccountour owncollectionsand alsoconfirmed recordsof otherauthors.

RESULTS

Dataof distribution,habitatand frequencyof Leucodon speciesin the MacaronesianRegion arepresented byeacharchipelago (Table 1).

The Azores

Leucodon canariensis hasbeen reported from SãoMiguel byTrelease (1897),Geheeb(1910),Allorge &Allorge (1945),and Hübschmann (1974). During our field workinthisarchipelago,only L.treleasei wasfound in the areas wherethe specieshadbeen recorded. The specimensreported bySchwab (1981) from Faialand SãoMiguel werelaterre-examined bythisauthorand re-identified as L.treleasei (Frahm, personalcommunication). The recordofSjögren (1990) from Graciosarefers to L.treleasei asitwasconsidered asynonymof L.canariensis .Consequently,the presenceofthisspeciesin the Azoresshould be considered uncertain,aswasalsopointed out byHedenäs(1992);forthisreason ithasbeen omitted in Table 1. Leucodon treleasei canbeconsidered frequentin thisarchipelago,since itisknownfrom all the islands.Itoccurs atanaltitudinalrange of 20-300 ma.s.l., mainlyon rocksbut alsoonseveralintroduced phorophytes( Labill., Pittosporumundulatum Vent.or Populus alba L.) and presents habitat amplitude valuesof 3-4,depending on the island,and alowerrelativefrequency compared withMadeira. Leucodon sciuroides hasbeen reported in the literatureforFaial (Russel,1862),SãoMiguel (Hedenäsunpublished:www.nrm.se/download/ 18.bb3f71108335b4bcd80002696/madeira.txt)and Terceira(Fontinha&Sérgio, 1995),but our owncollectionshaveconfirmed its presenceonlyon SãoMiguel and haveadded ittothe list of Graciosa.The specieswasfound growing atan altitudinalrange of 30-100 ma.s.l.,on rocks.According toour habitatamplitude classification,itbehavesasarestricted,dispersespecies.The absoluteand relative frequencyvaluesof thesespeciesarelowerin the AzoresthanonMadeiraand the Canary Islands.

Madeira

Leucodon canariensis canbeconsidered ararespeciesin Madeira, aswas pointed out byKürschner etal .(2007a). Asfarasweknow,itwasonlyreported from twolocationsin the mountains,whereitoccurs between 1250-1500 ma.s.l. in cloudlaurel forest habitats,on treesand shrubs,and alsounderornear periodicallydripping water(Hedenäs,1992). Itpresents ahabitatamplitude value of 3.The absolutefrequencyismuchlowerthanthatobtained in the Canary Islands; however,its relativefrequencyissimilar. Leucodon in Macaronesia189

Table 1. Main characteristicsof distribution,habitatand frequencyof Leucodon speciesin the Macaronesianarchipelagos.The estimated frequency,includesabsolutefrequency(numberof km2 )and relativefrequency(included between brackets),calculated withrespecttothe total surface(numberof km2 )ateacharchipelago according withour data.

Confirmed Altitudinal Estimated Habitat Habitat islandsnumber range frequency:absolute amplitude type (%) (m a.s.l.) (relative) L.canariensis Azores–––– – Madeira1(50)1250-1500 3Cloudforest 8(1.00) Canary Islands6(86)750-1370 2-4 Cloudforest, 74(0.96) sun-exposed habitats L.treleasei Azores9(100)20-300 3-4 Sheltered habitats 79(3.37) Madeira2(100)50-1500 3-5 Laurel forest,sun- 66 (8.28) exposed and sheltered habitats,cloudforest Canary Islands2(28) 400-1100 1-4 Laurel forest,sun- 31(0.40) exposed and sheltered habitats,cloudforest L.sciuroides Azores2(22)30-100 3Sheltered habitats 9(0.38) Madeira1(50)900-1800 2-4 Sun-exposed habitats 12(1.51) Canary Islands7(100)600-1600 2-5 Sun-exposed and 79(1.03) sheltered habitats, humid pine forest Cape Verde Islands2(25) 1200-12502Sun-exposed habitats 2(0.05)

Leucodon treleasei isthe most widespreadspeciesof the genus on Madeirawhereitcanbeclassified asacommon species,aswasmentioned by Hedenäs(1992)and Kürschner etal .(2007a). Ithasalsobeen reported from Porto Santo,whereitisnotsofrequent.Itgrows on tree barkand on rocksorboulders, atanaltitudinalrange of 50-1500 ma.s.l. in severalexposed and forested habitats in boththe northernand southernzonesof the island (habitatamplitude values, 3-5). InMadeira L.treleasei hasthe highest relativefrequencyof all Macaronesian islands. Leucodon sciuroides hasbeen found onlyin the largest island of the Madeiraarchipelago. Itwasfound on rocksand soil,mainlyon the highest mountainsbetween 1400-1800 ma.s.l. (Hedenäs,1992). Itpresents wide habitat amplitude values(2-4),and its absolutefrequencyvalueislowerthaninthe Canary Islands.

Canary Islands (Fig. 1)

Leucodon canariensis hasbeen reported from all islandsin the Canaries.In the courseofour investigations,severalrecordshavenotbeen confirmed,suchas thosegiven byMalme (1988) from the driest island of Lanzarote,whereweonly 190J.M.González-Mancebo,J.Patiño,O.Werner,R.M.deA.Gabriel &R.M.Ros

Fig. 1. Distribution of Leucodon treleasei, L.canariensis and L.sciuroides in the Canary Islands. Notconfirmed recordsarerepresented withempty circles. Leucodon in Macaronesia191 found L.sciuroides .Onthe contrary,the recordofFuerteventura(Sunding,1971) wasconfirmed,and the specieswasfound on rocksand barkonasmall endemic shrub( Asteriscus sericeus (L.f.) DC.),togetherwith L.sciuroides .OnGranCanaria itiscurrentlyvery rare,and its occurrencehasbeen onlyconfirmed in one of the fiveareaswherethe specieshadbeen reported in the past.Onthe island of La Palma, itwasonlyfound at1250-1370 ma.s.l.,growing on some tree species( Erica arborea L.and novocanariensis Rivas-Mart. etal .) in small areasof cloud laurel forest.OnElHierroalsoitpresents arestricted distribution while in Tenerife and La Gomera, thisspeciescurrentlyhasthe highest frequencyand abundance values.Its distribution on theseislandsisrestricted towell preservelaurel forest areas,especiallyin the summitareasof cloudlaurel forest from 700-1300 ma.s.l. Although in laurel forests of theseislandsitrepresents one of the mosseswiththe highest biomass,ithasnotbeen found in the centraland north-westernlaurel forest areasof Tenerife in our field work. The speciesmainlygrows asanepiphyteon severalphorophytes,showing the highest coveron Ilexcanariensis Poir.However, on La Gomera, itcanoccur outside the laurel forest,even on isolated cultivated trees(e.g. Castaneasativa Mill.) oron rocks.Ithashabitatamplitude valuesof 2-4, and its absolutefrequencyin the Canary Islandsisthe highest of Macaronesia. Leucodon treleasei wasfirst reported from La Palmaand GranCanaria byPitard&Negri(1907),and laterfrom Tenerife byHedenäs(unpublished: op. cit .) and Losada-Lima etal .(2001,2004). The citationsfrom La Palmaand Tenerife havebeen confirmed in thiswork,but notthosefrom GranCanaria, whereonly L.sciuroides hasbeen found. OnTenerife itisavery rarespecies, sinceitonlyhasbeen found in twolaurel forest localities,growing on indica (L.) Spreng. InLa Palmaitoccurs in easternareasand mayeven belocally abundant,growing from 400-900(1100)ma.s.l.,mainlyin laurel forest,in the canopyof severalwell-developed tree speciessuchas Ilexcanariensis , Laurus novocanariensis,Ocoteafoetens (Aiton) Baill. and P.indica.Itwasalsofound on thisisland growing on Castaneasativa in cultivated areas.Its habitatamplitude valuesin the archipelago are1-4,and its frequencyvalues(absoluteand relative) arethe lowest of Macaronesia. Leucodon sciuroides hasbeen found on all the islandsand most of the recordshavebeen confirmed in thiswork. However,its distribution in La Palma ismorereduced thaninitiallythought,becauseonlythe recordspublished byGonzález-Mancebo etal .(2004) havebeen confirmed during thiswork;the recordbyZippel (1998) waserroneous and correspondsto L.treleasei. Leucodon sciuroides reachesits highest frequencyand abundanceonGranCanaria, especiallyin cultivated areasin formerlaurel forest,whereitmainlygrows asan epiphyteonseveralphorophytes( Castaneasativa, Cupressus macrocarpa Hartw. exGordon, Juglansregia L.,etc.) and alsoonrocks.Itgrows in the Canariesat analtitudinalrange of (600)700-1200(1600)ma.s.l.. Although its abundanceand frequencyvary highlydepending on the island,theseincreasefrom west toeast (habitatamplitude values2-5 and the highest absolutefrequencyof Macaronesia).

Cape Verde Leucodon sciuroides isthe onlyspeciesof the genus recorded in the Cape Verde Islands,whereithasbeen reported from SantoAntãoand SãoNicolau,two of the north-westernislands,whichhavethe highest altitudes.Its presenceis restricted toanarrowaltitudinalrange,1200-1250ma.s.l.,and tothe most favourable areas.Itoccurs on rocksand on barkofseveralshrubs( Euphorbiatuckeyana Steud. and Globulariaamygdalifolia Webb),and trees(e.g. Dracaenadraco (L.) L.and 192J.M.González-Mancebo,J.Patiño,O.Werner,R.M.deA.Gabriel &R.M.Ros

Ficus sycomorus L.). Undertheseconditions,the speciesmayreachhigh covervalues and include short pendulous growth-forms.Ithasahabitatamplitude valueof2and the lowest frequency(relativeand absolute) of Macaronesia.

Ordination analysis ADCA of all islandsand speciesseparatesthree groupsof islands (Fig. 2). The grouppositioned on the leftof the graph isformed byall islandsfrom the Azores,Madeira, PortoSantoand La Palma.Thesearethe islandswhere Leucodon treleasei ismorefrequentorthe onlyspeciespresent.The high frequencyof thisspeciestogetherwiththe lowpresenceof L.canariensis on La Palmaexplainsits exclusion from the Canariesgroup. Onthe top rightareaof the graph thereisagroupformed byislandswhere L.sciuroides isthe only speciesof the genus (the Cape Verde Islandsand Lanzarote) and GranCanaria (wherethisspeciesisextremelyfrequent). The thirdgroupisformed byall the westernCanary Islands(withthe exception of La Palma),in which L.canariensis shows its best representation. Axis1(withthe highest eigenvalue) ishighly correlated withthe frequencyof L.treleasei and L.canariensis ,while axis2seems tobecorrelated withthe relativefrequencyof L.sciuroides . 1.5 Santo Antao Sao Nicolao

L. sciuroides Lanzarote

Fuerteventura Sta.Maria Flores Sao Miguel 2 Sao Jorge Terceira

axis Corvo Graciosa Pico Faial Hierro Madeira Porto Santo La Palma Tenerife L. treleasei Gomera

L. canariensis –0.5 –0.5 axis 1 2.5

SPECIES SAMPLES Azores Madeira Canary Islands Cape Verde

Fig. 2.Detrended CorrespondenceAnalysis(DCA)ofall the MacaronesianIslandsand the studied three species.Dataforthe speciesrepresentthe absolutefrequencyateachisland (numberof estimated km2 ). Eigenvaluesforall the three speciesanalysed wereaxis1:0.714, axis2:0.018 and lengthsof gradientforthe first twoaxes:2.037 and 1.264. Islandsfrom the differentarchipelagosareindicated withdifferentsymbol. Leucodon in Macaronesia193

DISCUSSION AND CONCLUSIONS

The three speciesanalysed showed differentdistribution patterns,which maybeatleast partlyexplained bytheirecologicalrequirements.Habitatand frequencyforeachspeciesvaried among the differentarchipelagosand islands. Leucodon canariensis ismainlydistributed in the Canary Islands,where itoccurs on all islandswiththe exception of Lanzarote(the driest one,e.g. Marzol,2001). Its developmentisalmost restricted tolaurel forest areaswiththe highest frequencyof mist (cloudlaurel forest),and tothe most humid areaof the xericisland of Fuerteventura, wherethistype of forest iscurrentlyabsent.Asfar asweknow,therearenorecordsof L.canariensis in the Azores.InMadeira, the distribution of thisspeciesismorerestricted thaninthe Canaries,sinceit comprisesanarroweraltitudinalrange. Nevertheless,the relativefrequencyin botharchipelagosissimilar,whichisclearlyrelated tothe greatest surfaceofnon suitable habitats (drierhabitats)inthe Canary Islands. The distribution of L.canariensis in the Canary Islandsiscloselyrelated tothe island topographyand habitatconservation. Inwell developed cloudlaurel forests the speciesshows high coverand biomass asanepiphyte. From these areas,the speciescancolonizeless favourable habitats,suchasrocksin non- forested areasoreven isolated trees.However,thesehabitats do notseem tobe colonized bythe specieswhen thereisno spatialcontinuity withlaurel forest habitats,whichmayberelated toits type of dispersal(ashuttle species,with sporeslargerthan20 µm). The negativeeffects of reduction of habitatquality seem tobestrongerwhen thereisno association between the speciesand well- preserved areas.Thus,in islandswherenaturallaurel forest habitats havebeen destroyed,the occurrenceofthe speciesin open habitats isvery rare. According toSnäll etal .(2003),connectivity stronglyaffects the probability of atree becoming colonized byepiphyticmossesand lichens,becauseoftheirrestricted dispersalrange. The drasticreduction of the L.canariensis distribution in Gran Canaria(Fig. 1) isclearlyrelated tothe intensivelaurel forest destruction thathas occurred sincethe conquest (500 years ago) toour days,duetowhichonly0.5% of the originallaurel forest remains(Fernández,2001). Bryophytestypicallyhave broadgeographicaldistribution. However,according toLöbel etal. (2006),habitat insularity significantlyalters regionaldispersalprocessesin epiphytes,even those of assumed good dispersers. Leucodon treleasei isbetterrepresented on islandsfrom northern latitudes.Inthe Azoresitoccurs on various substratesin all islands,although in restricted altitudinalrange,whichcould explain its lowerrelativefrequencyin this archipelago thaninMadeira.Inthisarchipelago,itiscommon onlyon the larger island of Madeira, while drierconditionson PortoSantoseem torestrictits development.Inthe Canaries, L.treleasei onlyhasahigh frequencyon La Palma. Thisisland isthe north-westernmost in the Canariesand ischaracterized bythe highest meanprecipitation values(Afonso,1988),whichmightindicateahigher climaticsimilarity withnorthernarchipelagos.Taking intoaccountthe distribution of these Leucodon species,LaPalmaismoresimilartoMadeirathan tothe otherCanary Islands(Fig. 2). Habitats where L.treleasei occurs on La Palmaareoccupied by L.sciuroides on otherislands.The increasing aridity observed from westerntoeasternCanary Islands(Marzol,1988) seemstobe parallel tothe increasing frequencyof L.sciuroides from 700 mto1500 ma.s.l. The altitudinalrange wherethe relativeabundanceof Leucodon treleasei and L.sciuroides in the Canary Islandsreachesits highest valueissimilar.Both 194 J.M.González-Mancebo,J.Patiño,O.Werner,R.M.deA.Gabriel &R.M.Ros speciesmayoccur in similarhabitats,but on differentislands.However,the nearerthe conditionsresemble Mediterraneanaridity, L.sciuroides becomes morefrequent.Thus, Leucodon sciuroides replaces L.canariensis when natural conditionsaredestroyed,especiallyin easternislands.Inthissense,the origin of L.canariensis mightbemoreassociated toecologicalconditionsthanto geographicaldisjunction. Thisappears tobeawell illustrativeexample of the evolutionary importanceofthe Macaronesiancloudforest habitats in the Mediterraneanregion. The differencesin habitatamplitude and distribution patternsof both endemicspecies( L.canariensis and L.treleasei),even when bothspeciescan occur in the same type of habitatand locality,maysuggest differentorigins. Leucodon treleasei hasgreaterhabitatamplitude than L.canariensis .Some recentlyobtained results based on ananalysisof the Macaronesianvascularflora open newresearchlinesusing moleculardata.Forexample,Vargas(2007)found thatspeciesrarity and restriction tolaurel forest habitats mayberelated torelict lineagesand Terciary vascularflora.So,anolderorigin mightbehypothesized for L.canariensis compared to L.treleasei.Aquestion remains:howmaycurrent distribution patternsof Macaronesianendemicspeciesberelated totheirorigin? Climaticand habitatconditionsmayhavebeen dramaticallydifferentwhen the speciesfirst colonized the archipelagos,whichmightexplain restricted or fragmented distributions.Forinstance Leucodon canariensis seemstobearelict speciesin Macaronesia, especiallyon Fuerteventura.Onthe otherhand,inter- archipelago dispersalevents in Macaronesiaappeartobequiterecentformany generaof phanerogams(Kim etal .,2008). Ifinter-islandsand inter-archipelago dispersalevents arefrequentin mossesaswell,then otherfactors like habitat availability mightbemoreimportantin explaining the presentdistribution patterns. The Macaronesianspeciesof the genus Leucodon arecurrentlybeing studied withmoleculartechniquestoanalysethe relationship between them,in an attempttoexplain the differencesin theirdistribution patterns. Acknowledgments. Thispaperispart of the projects entitled “Biogeografíay procesosevolutivosen briófitos.Estudiosen lasIslasMacaronésicas”funded bythe SpanishMinisterio de Educación yCiencia(CGL2005-00028) and “ListaRojade los Briófitosde lasIslasCanarias”funded bythe Canary IslandsGovernment(P1042004-028), who alsofunded apredoctoralgranttoJP (TES2005/086). WearegratefultoKatiaCezón, Julio LealPérez,Angel Fernández-Lópezand SusanaFontinhafortheirdifferent assistancesin the field work. AlsoFranciscoRomagueraGarcíaforhishelp withthe revision of the speciesrecordsfrom all Macaronesianarchipelagos.Finallywearealso gratefultoJan-PeterFrahm and Alain Vanderpoorten forthe correction and constructive comments on anearlyversion of the manuscript.

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