Hedw.) Hornsch. (Musci,Bruchiaceae

Discovery of anaturalhybrid between Bruchiavogesiaca Schwägr.and Trematodon ambiguus (Hedw.) Hornsch. (Musci,Bruchiaceae)

Jan-PeterFRAHM* &Boon-ChuanHO

Nees-Institut für BiodiversitätderPflanzen,Rheinische Friedrich-Wilhelms- UniversitätBonn,MeckenheimerAllee 170,53115 Bonn,Germany

(Received 11 November2008,accepted 25March2009)

Abstract —Anewlydiscovered naturalhybrid & Bruchiavogesiaca × ( Trematodon ambiguus isreported here. The sporophytichybrid plants wererecentlyfound from a locality in the VosgesMountains,France,growing togetherin amixed stand withboth sporophyticparentspecies.Thishybrid represents the second knownreport of ahybrid within the Bruchiaceae.

Bruchiaceae/ Bruchia / Trematodon /hybrid /VosgesMountains

INTRODUCTION

Trematodon ambiguus (Hedw.) Hornsch. and Bruchiavogesiaca Schwägr.areamong the rarest mossesof the VosgesMountains,easternFrance. Although aratherwidelydistributed Northerntemperatemoss,in the Vosges T.ambiguus wasfound onlythree timesbythe ancientbryologists Blind,Boulay and Mougeotin the 19th century and twicebyRenauld atthe begin of the 20th century (Frahm,2002). Itwasthen rediscovered in one locality in the vicinity whereRenauld found itahundred years earlier(Frahm,2003b, 2005a). Bruchia vogesiaca wasdescribed from acollection made byMougeotin 1822 in the Vosges and thereforenamed “ vogesiaca”,although the specieslaterturned out tooccur mostlyin SW-Europe aswell astwolocalitiesin NorthAmerica (NewHampshire and NewYork) and one in China(Fujian). The specieswasobserved tooccur at the type locality (Ammeltalquelle Sof the Hohnecksummit)until 1964(Frahm, 2002). In1983,itwasdiscovered atanewlocality in the VosgesMountainsby Lecointeand Pierrot(Rastetter,1985) and observed atthisplaceuntil 1992 (Frahm,2002,2005b). During the next years, B.vogesiaca wasfound in several othersitesin the surrounding of the latterlocality byFrahm and Vadam(Frahm, 2005b)aswell asin one location atLa Montagne northofthe previous records (Frahm,2003a, 2005b)atthe edge of afishpond. Since B.vogesiaca isaspecies of the BernConvention,the latterlocality wasannounced tothe authoritieswith the resultthatthe ownerof the fishpond destroyed the habitatwithabulldozer.

*Correspondenceand reprints :[email protected] 96J.-P.Frahm &B.-C.Ho

Fig. 1. Mixed stand of Trematodon ambiguus (left)with Bruchiavogesiaca and theirhybrid (right).

MATERIAL

Interestingly,bothspecieswerefound growing togetherin another locality in the Vosgesatthe PlateaudesMillesEtangsin 2006 (Frahm,unpubl.), the region wheretheywerefound before. The twospeciesgrewtogetheron a humid open pathatthe Etang desCuvesalong the routedesForts between Col de Montde Fourche and Coil de Croix.The presenceofthe twospeciesatthis newlydiscovered locality wasconfirmed in 2007.During arecentfieldtrip with students of the University of Bonn,the abovesitewasrevisited on September12, 2008. When bothspeciesweredemonstrated tothe students and itwasexplained that Bruchia hasinoperculatecapsules,the second authorrealized thattherewere capsuleswithadistinctmouth. Acloserexamination revealed thattherewasa mixtureof(1) typicalsporophytesof T.ambiguus withlong lightyellowishbrown setae,eachending withalong neckand along curved capsule,aswell as(2)few typicalsporophytesof B.vogesiaca withvery short setae,eachending in ashort darkbrown,erectcleistocarpous capsule and (3)numerous sporophyteswithsetae of intermediatelengthand slightlylargeroperculatecapsules.Thisobservation led tothe suspicion thatthe latterplants could behybridsbetween the formertwo species.The patchofplants wasabout 20 cmwide and covered by T.ambiguus at one end and B.vogesiaca atthe other(Fig. 1). The intermediatesgrewin the middle in the stand of Trematodon and Bruchia . Anaturalhybrid between Bruchiavosgesiaca and Trematodon ambiguus 97

Table 1. Comparison of sporophytemorphologyof Trematodon ambiguus, Bruchiavogesiaca and theirhybrid.

Character & Bruchiavogesiaca *hybrid ( Trematodon ambiguus

Seta1.5-3mm long 3-4 mm long Atleast 8mmlong Darkreddishbrown Darktolightbrown Lightyellowishbrown

NeckShorterthanurn, Ca.aslong asurn, Longerthanurn, long-tapering short-cylindric long-cylindric

UrnStraight Straight Inclined,curved Peristome &operculumnot operculate,peristome poorly Peristome &operculum differentiated differentiated well-differentaied

Calyptramitratemitratecucullate

SporeWarty (verrucose) Warty (verrucose) Papillose

*Fewhybrid sporophytesarewith6mm setaslightlyinclined and curved darkbrowncapsule but inoperculate

Sample materialwastaken backtothe NeesInstituteforBiodiversity of Plants,University of Bonn,formoredetailed studyunderthe microscopes.The dried herbariumsample isdeposited in the herbariumFrahm (BONN).

RESULTS

Although the gametophytesof the bothautoicous speciesborne peri- gonia, the sporophyteswithintermedi- atemorphologyonlysprout on the gametophytesof B.vogesiaca,indicat- ing thatfemale plants of Bruchiavoge- siaca werefertilized byspermatozoids of Trematodon ambiguous.Relatively fewsporophytesof true B.vogesiaca arefound. The characters of the sporo- phytesof both, Trematodon ambiguus, Bruchiavogesiaca and theirhybrid are compared in Tab.1. Afteracomparison of the sporo- phytes(Tab.1),itbecomesclearthatthe intermediatesporophyticplants areinter- generichybridswithmixed characters between the parentspecies.The hybrid could beeasilydistinguished bythe inter- mediatemorphologyof the sporophytic characters (setalength,neck,urn) of the Fig. 2.Single plants of Trematodon ambiguus parentspecies(Fig. 2). Onlythe shape of (left), Bruchiavogesiaca (right)and their the calyptraaswell asthe sporemorphol- hybrid (middle) (Scale:millimetregrid). ogyisshared with Bruchiavogesiaca. 98 J.-P.Frahm &B.-C.Ho

The peristomesof the hybrid plants arevery poorlydeveloped. Onlyfew teethareobserved,the majority part of the peristome exist asremnants withonly the basalpart developed. The hybrid capsulescontain asmanysporesasthe parentspeciesbut about half the numberof sporesarecollapsed and irregularin shape. The normal looking sporesareexpected tobeabortiveand non-viable. Sporesof all three are similarin size,falling in the range of 26–32 µm in diameter.

DISCUSSION

Naturallyoccurring hybridsamong bryophytes,especiallybetween differentgenera, haverarelybeen described in scattered publications.A compilation of thesecanbefound in the recentreviewpaperbyNatcheva& Cronberg(2004). The majority of the reported hybridsarefound tobeterrestrial, bisexual,short-lived moss speciesoccurring in disturbed open habitats,belonging tothe Funariaceae,Ditrichaceae,Pottiaceaeand Bryaceae(Natcheva& Cronberg,2004). Noteworthy,von Wettstein (1932)hasshownthathybridsin the Funariaceae,bothinterspecificand intergeneric, canbeartificiallyraised. This points tothe factthathybridscaneasilybeinduced in natureif“conditions”(such asphenology,habitatspecificity,distribution etc.) arejust rightbychance. The presentreport of the generation of ahybrid, & Bruchiavogesiaca × ( Trematodon ambiguus,wasmade possible byseveralpremises,similartomany previouslyreported hybrids.Although bothspeciesaregenerallyvery rare,they occur in the same region in the VosgesMountains(in anareaof 10 × 15 km2 )and alsoinsimilarhabitats (on very damp soil especiallynearwaterbodiesin opened places). Moreover,bothspeciesaresummerannualsand showupbetween end of June and beginning of September,thus havevery similarreproductivephenology. Interestingly,within the Bruchiaceae,thereisalreadyaknownnatural hybrid, Bruchiamicrospora Nog. × Trematodon longicollis Michx.,reported to occur in Japanand China(Rushing &Snider,1985;Gao etal.,1999). Hence,the presentreport represents the second knownbigenerichybrid between Bruchia and Trematodon but withanentirelydifferentspeciespair.

REFERENCES

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