See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/279302169

Comparative analyses of plastid and AFLP data suggest different colonization history and asymmetric hybridization between Betula pubescens and B. nana

Article in Molecular Ecology · June 2015 DOI: 10.1111/mec.13289 · Source: PubMed

CITATIONS READS 9 282

3 authors, including:

Pernille Bronken Eidesen Inger Greve Alsos University Centre in Svalbard (UNIS) UiT The Arctic University of Norway

48 PUBLICATIONS 2,123 CITATIONS 161 PUBLICATIONS 2,721 CITATIONS

SEE PROFILE SEE PROFILE

Some of the authors of this publication are also working on these related projects:

Norwegian Barcode of Life Network (NorBOL) View project

CHASE - Climate History along the Arctic Seaboard of Eurasia View project

All content following this page was uploaded by Inger Greve Alsos on 04 January 2018.

The user has requested enhancement of the downloaded file. Accepted Article Tlf: 790233 43 +47 Norway Longyearbyen, NO-9171 Box 156, PO Svalbard, in Centre University The Eidesen Bronken Pernille Correspondence: This hasThis article been accepted for publication andundergone peer full review butnot has 3 2 1 Pernille Bronken Eidesen hybridisation between different colonization historyand asymmetric and AFLP plastid of data suggest analyses Comparative Title: Article :Original type Article Accepted :18-Jun-2015Date : 17-Jun-2015 Date Revised Received: 16-Mar-2015 Date This This article is protected by copyright.reserved. Allrights as doi: 10.1111/mec.13289 lead todifferences between this versionand th through the been copyediting, paginationtypesetting, process, proofreading and which may Natural History Museum,University Oslo,PO1172of Blindern, Box Oslo, NO-0318 Norway Tromsø University Museum, Tromsø,NO-9037 Norway The University inCentre Svalbard,PO Box156, NO-9171 Longyearbyen, Norway

1 ,Inger Greve Alsos Betula 2 , Christian Brochmann , Christian

e Version of Record. Please this Version citee ofRecord. article pubescens 3

and and B. nana . Accepted Article contrast, contrast, In sheets. ice European oftheNorth east one of and south one Eurasia, in refugia twomajor least AFLP and pDNA results corroborated the former pDNA-based hypothesis that it expanded from at and species cold-adapted and widespread two the in processes range-shift from hybridisation distinguish to aimed We migration. postglacial Birches ( Abstract Keywords: of colonization Postglacial head: running Short [email protected] E-mail: Fax: 79 023301 +47 This This article is protected by copyright.reserved. Allrights pubescens increa but significant aweak identified between shared largely was expected as variation pDNA the Whereas regions. pDNA two for sequenced also was plants of64 subset a AFLPs); polymorphisms; length fragment (amplified markers high-resolution mainly nuclear using plants 901individual analysed hybrids. We other of five samples reference included and ranges their throughout (pDNA). DNA plastid in variation east-west-structured similarly B. pubescens B.

Betula B. pubescens B. with increasing latitude, suggesting hybridisation has been most frequent at the atthe frequent beenmost has hybridisation suggesting latitude, increasing with AFLP, plastid DNA, introgression, glacial refugia, migration, phylogeography phylogeography migration, refugia, glacial introgression, DNA, plastid AFLP, spp.) hybridise readily, confounding genetic signatures of refugial isolation and and isolation of refugial signatures genetic confounding readily, hybridise spp.) , the two species were distinctly differentiated at AFLP loci. In In loci. AFLP at differentiated distinctly were species thetwo , showed a striking lack of geographic structuring of its variation AFLP its of structuring geographic of lack striking a showed B. nana B. se in nuclear (AFLP) gene flow from from flow gene (AFLP) nuclear in se and Betula Betula B. pubescens B.

We sampled the two species , previously shown to share a a share to shown , previously Betula B. nana species and putative B. nana B. into , both the the , both B. B. nana . We

Accepted Article (AFLPs) have also been used to infer phylogenetic relationships in in relationships phylogenetic infer to beenused havealso (AFLPs) nuclear DNA sequence variation (Järvinen and plastid between incongruence shown have analyses phylogenetic and 2013), McAllister al. nana B. similar relationships nuclear as DNA sequences, but suggested that the two cold-tolerant species ThórssonKarlsson 2000; & (Jonsell hybridisation tofrequent due partly difficult, is notoriously genus the of taxonomy in sharing haplotype for explanation main the as introgression and hybridisation supports strongly evidence theavailable sorting, lineage incomplete among et al. (Palmé patterns phylogeographic and boundaries Birches ( Introduction of front expansion postglacial This This article is protected by copyright.reserved. Allrights circumpolar the and Siberian and European eastern the shrubs, diploid are Two other. with each Incongruence between pDNA and AFLP variation in in variation andAFLP pDNA between Incongruence tolerant species. from capture plastid and hybridisation leading-edge with combined refugium large single a from expansion 2008). 2008). 2014; Thomson Betula and Four species of Betula Betula B. pubescens pubescens B. B. nanaB. species. Although shared haplotypes resultmay from recurring mutations or L.) provide excellent examples of how hybridisation may confound both species species both confound may hybridisation of how excellent examples L.) provide B. et al. during colonization of new territory newterritory of colonization during

nana Betula et al. et are more closely related than inferred from former studies (Schenk studies from former inferred related than closely more are 2015). Plastid DNA (pDNA) haplotypes are typically extensively shared shared extensively typically are haplotypes (pDNA) DNA Plastid 2015). L., while trees, L., thediploid Eurasian are two 2001;Järvinen are usually recognised in Europe, and are capable of hybridising hybridising of capable are and Europe, in recognised usually are B. pubescens B. et al. et and that hybrids mainly backcrossed to backcrossed mainly thathybrids and et al. et 2004). Amplified Fragment Length Polymorphisms et al. 2004; Schenk 2004; B. pubescens B. 2004;Anamthawat-Jónsson Wang 2012; already occupied by this more cold- more this by occupied already Betula et al. et can be explained by efficient efficient by explained be can Betula (Palmé 2008; Ashburner & & Ashburner 2008; . These markers. These revealed B.

pendula B. et al.

humilis 2004). The 2004). B. pubescens B. Roth and the and Roth Schrank. Schrank. et et

. Accepted Article pattern in British inpattern occurs almost exclusively from alocal to an invading species (Currat increasing inthestudy with increased latitude pubescens pubescens them (Wang them speciesthree to clearlydistinguished be with only lowlevels of introgression evident between nana Rieseberg introgress without significant nuclear gene (i.e.chloroplast flow capture; Rieseberg &Soltis 1991; mislead interpretation of species-specifictheir phylogeographies (Jadwiszczak 2012). hybridisation, in particular among Jadwiszczak However, 2012). the extensive pDNA haplotype sharing inferred tobedue to 2003; latitudes, (Palmé from directions different recolonization; frombut both intermediate in western eastern one Europe in Europe.and pattern suggests This two wavesmain of postglacial et al. et al. Palmé 2003; (Palmé markers pDNA on based analyses phylogeographic to been subjected earlier pendula Betula regions; in contrast,regions; in with co-occurs lati athigh birches shrub with coexists southern range-contraction of of range-contraction southern tetraploid This This article is protected by copyright.reserved. Allrights 2014). Two major haplotypeswere found throug 2004; Maliouchenko in the British in Isles nuclearused microsatellites instead of markers pDNA showed and the Plastid DNA introgresses more frequently and faster than nuclear genes, and it can can it and genes, nuclear than faster and more frequently introgresses DNA Plastid et al. B. into areas already occupied by the more cold-adapted cold-adapted themore by occupied already areas into etal.

pubescens and and B. nana B. 1996). postglacialA recent of study the history of B. pubescens B. 2014). Nuclear 2014). introgression was detected from B. pubescens B. B.

, which is the hardiest of the European birches and common in low- arctic arctic low- in common and birches theEuropean of hardiest the is , which humilis Ehrh. (Tutin 1964;Atkinson 1992; DeGroot et et al. does not reach the Arctic (Elven Arctic the reach not does most likely results from past northwards range expansion of expansion range northwards past from results most likely B. nana nana B. 2007;Thórsson are nearly sympatric, but sympatric, nearly are B.

pendula tudes and altitudes. At high latitudes, latitudes, Athigh altitudes. and tudes is likely to have further reduced introgression at lower lower at introgression reduced further likely have to is , B. area. As simulations As suggest introgressionarea. that et al. et

pubescens 2010; Jadwiszczak hout Europe in all species, one dominating dominating one species, all in Europe hout B. pubescensB. , and etal. B. B. nana B. B.

etal. B. nana

et al. et 2011). All four2011). species have pendula

nana nana et al. et is more cold-tolerant is more and (Palmé 1997; 1997; Palmé . In addition, the . 2008), the introgression into B. pubescens B. , 2012;Jadwiszczak B.

B. et al. pubescens

pubescens et al. 2004), may 2004), typically , and , and 2004). 2004). B. B. , and B.

Accepted Article haplotypes in in haplotypes plastid shared for explanations as sorting lineage incomplete or mutations recurrent discard evidence pDNA studies,which theextensive former on patterns. plastid Based DNA-based from published previously the with results AFLP and plastid- our compared and DNA, nuclear represent plastid DNA analysis with analysis of genomicAFLPsDNA by (Vos so the as tohelp in identification of introgression (Rieseberg &Soltis 1991). Wecomplemented hybrids, putative some and species birch other of four samples available included also and 1), (Fig. hybridisation. Wesampled hardiest birches in Europe, Europe, in birches hardiest in phylogeographies species’ explore further et marker ifhistorical hybridisation has occurred Shaw (e.g. 2002;Eidesen errone that demonstrate markers nuclear and DNA organelle both on based plants and animals of Studies area. its into expanding when other the of have similar phylogeographic histories and to what degree one of them has acquired the plastids sorting. lineage incomplete than rather introgression number of shared closeralleles current to location the of conver than introgression supported rather sharing lineage so incomplete convergent mutations and Wang latitudes. This This article is protected by copyright.reserved. Allrights

al . (2004) and. (2004) Anamthawat-Jónsson (2012) have called for analyses of nuclear markers to In the present study, we aimed to disentangle the glacial and postglacial history of the of history postglacial and theglacial disentangle to we aimed study, present the In species thesetwobirch degree what to remainsunclear it geographical scale, At a larger Betula et al (e.g. Palmé (e.g. . (2014)argued. that alternative explanations introgression,to such as B. B.

nana nana et al. et and and 2004; Thomson B. B.

pubescens pubescens Betula rting, were unlikely. The asymmetric allele unlikely. Theasymmetric were rting, ous conclusions can be be can conclusions ous gent mutations, and the gradual increase in in increase gradual the and mutations, gent . throughout most of their geographic ranges ranges geographic their of most throughout , in terms of refugial refugial termsof , in et et al. B. nana B. 2015), we here assume 2015), here we that plastid et al. et populations supported supported populations 1995),which mainly etal. isolation, migration and and migration isolation, drawn from a single from single drawn a 2007a), and Palmé Accepted Article to as interpretation by interpretation Elven ssp. recognised: usually are subspecies allopatric largely Two 1986). Fries eastern Asia (Hultén &Fries 1986; Elven ssp. and Asia, western and Europe Greenland, (DeGroot sites nutrient-poor and acidic, moist, in occurs typically It 1). (Fig. distribution circumpolar shrubs. and genus The species Study Material andMethods migration. postglacial bedirect cannot it that such events hybridisation by been influenced has variation of pattern plastid the that imply would this patterns, plastid Alternat patterns. congruent show to data plastid post-glacial and isolation by refugial influenced werealso variation of patterns plastid If events. thanhybridisation rather history migration structuringofvariation AFLP within species will largely reflect refugial isolation and postglacial should data AFLP that expect we Thus, markers. will AFLPs that hypothesise wefurther 2014), British in variation microsatellite of analysis nuclear therecent of results the on based Moreover, events. hybridisation from result species among shared haplotypes This This article is protected by copyright.reserved. Allrights B. glandulosa B.

et al. et Betula Betula nana Betula 1997), and at southern latitudes is usually is latitudes at southern and 1997), (Betulaceae) consists of monoecious, wind-pollinated, and wind-dispersed trees trees wind-dispersed and wind-pollinated, monoecious, of consists (Betulaceae) according to the latest classification tothe according of et al (2 n . (2011), but it should be noted that =2 x =28) is a dwarf shrub native to arctic and boreal regions with a et al. et 2011). In thiswehave study followed the be less influenced by introgression than pDNA pDNA than introgression by influenced less be exilis migration history, we would expect AFLP and and AFLP expect would we history, migration distinguish the species and that geographical geographical that and species the distinguish ly interpreted inly interpreted terms refugialof isolation and ively, if there is a discrepancy between AFLP and and AFLP between discrepancy a is there if ively, (Suk.) Hult. in North America and central and and central and America North in Hult. (Suk.) found only in mountain areas (Hultén & & (Hultén areas mountain in only found Betula B (AshburnerMcAllister, & 2013). . nana ssp. exilis exilis ssp. nana Betula nana (Suk.) Hult. in (Wang is also referred referred is also et al. et

Accepted Article latitudes in Eurasia and belong to ssp. ssp. to belong and in Eurasia latitudes current study, most populations of of populations most study, current 28), and three North American species, species, American North and three 28), with 2013; Alsos2013; michauxii with overlapping and areas to upland restricted Nyman, (Ledeb.) analysed as part of several larger meta-studies (Alsos meta-studies larger several part of as analysed and generated initially were datasets These Information). Supporting S1, Table individuals; pubescens wide climatic tolerance (Atkinson 1992). In Europe, is usually it divided into two subspecies: ssp. classified as classified weinclude In addition, shrub). American North B. nana B. of populations containing mainly one datasets, AFLP available two re-analysed and re-scored We AFLP datasets intermediate forms where their ranges overlap 1;(Furlow (Fig. 1997). This This article is protected by copyright.reserved. Allrights glandulosa (DeGroot tolerant cold less is somewhat butit preferences, habitat similar cordifolia B.

nana s.l. (570 individuals), the other mainly containing populations of of populations containing other mainly the individuals), (570 s.l. For use as reference species, we included samples available of of available samples we species, useasreference included For Betula pubescens Betula (Ashburner McAllister, & 2013) shrub) Spach. dwarf (a south-east Canadian and , found in the lowlands with the same distribution as as distribution thesame with thelowlands in found , and and et al. B than with thelowland species . cf. B. 2015). The 2015).

nana minor are are known tohybridise, sometimes resulting continuum ain of (2 (2 n n = 4 B. pubescens B. =4 x x = 56), which = 56) is a Eurasian birch species (Fig. 1; Elven (Fig. species birch Eurasian a is = 56) B.

pubescens tortuosa B. pumila B. . Betula glandulosa . Betula dataset also, included populations of other other of populations included also, dataset B.

pendula ; thus, we consider hybridisation to be more likely morelikely be to hybridisation consider we ; thus, d from Greenland, ofwhathad samples been is regarded as hybrid between between hybrid as regarded is were sampled from upland areas or at high athigh or areas upland from sampled were L. (2 L. et al. . n = 4 = B. glandulosa B. 2007; Alsos 2007; x

is closely relatedto = 56; a North American shrub), shrub), American aNorth 56; = B. B.

pendula

nana

et al. et B. Michx. (2 B. pubescens B. pubescens

(Elven pendula , etal.

and ssp. 2012; Eidesen B. glandulosa glandulosa B. etal. et al. 1997). B. Roth (2 n

nana = 2 tortuosa 2011), with 2011), 2011). In the Betula (332 (332 x Betula andhas =28; a n =2 etal. x

B. B.

x =

Accepted Article and Neighbour Joining analyses (Figs. S2 and S3) were used to evaluate consistency among the among consistency to evaluate wereused andS3) S2 (Figs. analyses Joining Neighbour and Mantel dataset. of the thepower reduce potentially could which markers, fewer but datasets, original the than individuals more far contained dataset labelledcommon (6-FAM in combination primer had one datasets Both combinations). 40-53 testing (after combinations Information. Supporting theonline in provided are procedures rega Details present. autocorrelationbe might estimates less As 25mis ofthan shadow theseed of mapa 25 collected were species per plants 11 to up pendula was reduced, the new thenew reduced, was dataset re-scored the and datasets original two glandulosa with an error rate of 1.7% calcul of1.7% rate error with an of ranges “ range of 50–500base pairs were scored as or present (1) absent This (0). new dataset, called the thesize in fragments polymorphic Unambiguous, dataset. one them into combined and samples, datasets both from profiles AFLP original the species omitted from previously published analyses; i.e. i.e. analyses; published previously from omitted species This This article is protected by copyright.reserved. Allrights Betula spp. dataset”, included 901 samples from 117 populations, covering the entire geographic theentire samples populations,covering 901 fromincluded 117 spp. dataset”, Each ofEach two the original wasdatasets initially constructed using AFLP three primer from where scheme, leaves standardized a followed datasets collection these for Sample x B. pubescens pubescens , and ,

nana

B. and and

michauxii and B. Betula

pubescens B. Eco cf. cf. , spp. dataset revealed genetic patte genetic revealed dataset spp. R1-AGT/ and some putative hybrids as inferred from morphology ( nana ated from replicates (Bonin81 s. lat. (Fig. 1, Table S1). We scored 104 polymorphic markers, markers, polymorphic 104 scored We S1). Table 1, (Fig. lat. s. x Mse pubescens 1-CTC),for andthis primer combination, imported we into Genographer, version 1.6., re-scored all 1.6., re-scored version into Genographer, rding sampling schemes, DN schemes, rding sampling (Supporting Information). Although the power power the Although Information). (Supporting ). ). rt along a 250 m transect per sample location. mlocation. persample rt along a 250 transect tests, Principal Coordinate analyses (Fig. S1), Betula B. cf. , tospatial somebias due major etal. rns concordant with those of the the of those with concordant rns , 2004). The 2004). B.

pendula A extraction and AFLP A extraction and , Betula B. pumila spp. spp. B. cf. cf. , B.

Accepted Article correlated allele frequencies (Falush frequencies allele correlated and ancestry recent both assume and groups related closely handle should model theappropriate hybridise, to tend and wind, (Falush the 3) and combinations), primer the 2) combination), original two the from samples (all dataset spp. respectively. were2.0% rates Error Information). Supporting (Pritchard for this study as outlined above.Genetic groupswere inferred using STRUCTURE version 2.3.4 were pe analyses data otherwise, specified not If AFLP data analyses combinations). primer onthree based dataset our hybrids, our and samples reference species the excluding After combinations. primer three all with generated pubescens B. Information). (Supporting analyses further for reliable regarded was and datasets original two This This article is protected by copyright.reserved. Allrights B.

pubescens et al. Thus, further data analyses were based on three different AFLP matrices: 1) the the 1) matrices: AFLP threedifferent on werebased analyses data further Thus, resolution ensuremaximum withinTo et al. et B. 2007). As our 2007). focal species have wide distributions, are pollinated and dispersed by , we also analysed these species separately based on subsets of the original datasets datasets original the of subsets on based separately species these analysed also , we

nana 2000),where “0”was indicated as recessive the allele in the binary AFLP matrix dataset included 303 individuals 132polymorphic 303 included scored S1,for markers dataset (Table dataset included 528individuals scored polymorphic for 115 markers, and B. nana dataset (a subset of the original original the subsetof (a dataset current gene flow. Thus, we used the admixture model with with model theadmixture used we Thus, flow. current gene B. pubescens B. et al. 2003), 2003), andran the analyses with and without the datasets combined and re-scored for one forprimer one re-scored combined and datasets dataset (a subset of the original original of the subset (a dataset our focal species in the present study, presentstudy, our focal in the species (51 replicates) and 0.6% (30 replicates), replicates), (30 0.6% and replicates) (51 rformed on all three AFLP datasets constructed constructed datasets AFLP three all rformed on B. nana B. dataset based on three three on based dataset B. pubescens B. B. nana B. Betula

and

Accepted Article Curtis, and bootstrap resampling was done with 1000 replicates. replicates. 1000 with done was resampling bootstrap and Curtis, 2006), (Ehrich AFLPdat frequenc Marker analysis. this from omitted were individuals three than less with Populations species. between and within similarity examines and individuals, many comprising datasets of complexity the reduces approach clustering this manner, variables(Eidesen marker as the fit. residual improve to geneti for allow to effect random a as modelled model v. R (lme)in 3.1.0 (R Core Team 2014), with slope as afixed effect, and population pubescens relationship between levelof admixture (STRUCTURE values) between species ( (Corander 6.0 Version BAPS in run algorithm clustering STRUCT by inferred Genetic groups 2012). vonHoldt, & (Earl HARVESTER STRUCTURE software online bythe visualised were output of Summaries each run for were replicates Ten iterations. was done according to recommendations given by Pritchard byPritchard given recommendations to according done was of weak groups (Hubisz groups weak of LOCPRIOR option, which utilizes the sampling locationfor clustering, canand enhance structuring This This article is protected by copyright.reserved. Allrights Betula A Neighbour joining analysis (NJ) PAST in v. 3.0(Hammer Spatial distribution of genetic groups was inspected visually in ArcGIS 10, and the the and 10, ArcGIS in visually inspected was groups genetic of distribution Spatial spp. dataset, using populations as OTUs and the population frequencies of each AFLP ) and latitude was tested as described in in Wang described as tested was latitude and ) Betula pumila et al. et etal. 2009). A burn-in 2009). period of 2×10 2007b). Although populations do not evolve in a bi-furcating was used as outgroup, similarity index was set toBray- set was index similarity outgroup, as used was K from 1to 10, and evaluation of number of groups c drift. STRUCTURE valuesdrift. c logit-transformed were STRUCTURE ies were calculated using the R-script package package R-script the using calculated were ies URE, were also verified by another Bayesian Bayesian another by verified were also URE, et al. et al. et 2003). 2003). et al 5 iterations was used followed by 10 by followed used was iterations (2014), using (2014), amixed effects etal. . (2000) and and Evanno (2000) . 2001) was conducted on on conducted was 2001) B. nana B. et al. et and and (2005). B. B. 6

Accepted Article the distribution range) were investigated by investigated were range) distribution the throughout west to east from variable positive continuous a as to vary (adjusted longitude and/or and latitude species within rarity and/or diversity genetic between relationships Possible 10. patterns of diversity and rarity were inspectedvisually by plottingvalues geographically in ArcGIS variance were performed PAST,(ANOVA) followe in from the results the on patterns rarity of analyses our based we species, within patterns phylogeographical when inferring processes historical emphasise to and hybridization, from resulting AF in provided byR-scripts calculated were 2006) measure of the amount rare markers of in each population (Schönswetter &Tribsch 2005; Ehrich matching) were run inARLEQUIN v. 3.5.1.3(Excoffier& Lischer, 2010). Excoffier (AMOVA; variance molecular of analyses used to visualize pairwise similarity among the AFLP multilocus phenotypes. phenotypes. multilocus AFLP the among similarity pairwise visualize to used This This article is protected by copyright.reserved. Allrights were treated as haplotypes to create a phenotypic (band-based) distance matrix. Pairwise F Pairwise matrix. distance (band-based) phenotypic a create to haplotypes as treated were To compare means of diversity and rarity among species and genetic groups, analyses of of analyses groups, genetic and species among rarity and diversity of means compare To

Calculation of intra-population diversity (Nei 1987; Kosman 2003), and a rarity index (a index (a (Nei1987; rarity diversity anda Kosman intra-population 2003), Calculation of To estimate differentiation between populati between estimate differentiation To executed (PCO) analyses coordinates Principal Betula spp. dataset only. only. dataset spp. multiple linear regression analyses in PAST. PAST. in analyses regression linear multiple LPdat. To reduce the influence of rare markers markers of rare influence the reduce To LPdat. et al. et d by Tukey’s pairwise post-hoc tests. Spatial Spatial tests. post-hoc pairwise by Tukey’s d ons and groups, AFLP multilocus phenotypes inPAST with Jaccard similarity index were 1992) based on1992) pairwisedistances (Simple st and Accepted Article Arbor, Michigan, USA). Sequences have been been have Sequences USA). Michigan, Arbor, Ann (Genecodes, 4.1.4 Sequencher in aligned and edited were sequences DNA Analyzer. Genetic Biosciences)wasused toremove unincorporated Applied Biosystems using BigDye directions both in sequenced and Biosciences), (Amersham Kit ExoSAP-IT using purified were products PCR procedures standard following template (Alsos GTTACG 3`) 2003). SamplesTTT TGC were amplified by using PCR 10x diluted DNA unordered, multi-state characters when gaps and gaps when characters multi-state unordered, or indels) and (substitutions characters binary as sites variable scored We indels. nested KR779549 - KR779606 and KR779607 - KR779658. Most variation was due toindels, including the exchanging by avoided and and al. 1999), rpoB- eight universal pDNA primer pairs: c-f (Taberlet c-f pairs: primer pDNA universal eight screened initially We Information). Supporting S1, (Table analyses theAFLP by revealed structure genetic on the based sequencing for chosen was populations 59 from individuals 64 of A subset DNA plastid of analyses and Sequencing against the corresponding pairwise F pairwise corresponding the against tested and (Ersts), 1.2.3 v. Generator Matrix Distance Geographic using coordinates geographical from recalculated were populations between distances geographical dataset, each For PAST. and This This article is protected by copyright.reserved. Allrights 2007).Based on amplification efficiency and levelof variation,pDNA two regions, trn B. pubescens B. S- Correlations betweengenetic geograph and trn G, were chosen for further sequencing. A large indel area in in area indel Alarge sequencing. further for chosen were G, trn C, datasets. Isolation by distance was tested by Mantel tests (Mantel 1967) in in 1967) (Mantel tests by Mantel tested was distance by Isolation datasets. trn C-ycf6_R, ycf6_F- C-ycf6_R, trn G primer with another reverse primer, anotherreverse with G primer st values retrieved from ARLEQUIN. from ARLEQUIN. retrieved values trn and amplification parameters from Shaw D (Shaw Terminator v.1.1 Kit. Sephadex G-50 (Amersham (Amersham G-50 Sephadex Kit. v.1.1 Terminator deposited in GenBank GenBank in deposited etal. et al. et dye terminators prior to analysis on an ABI 3100 ABI3100 an on to analysis prior terminators dye substitutions were found in the same position. position. same the in werefound substitutions ical distances were computed for the the for computed were distances ical 1991), psbA- 1991), 2005), rpl32- 2005), trn under accession nos. nos. accession under trn H, trn L and trn BW (5`TTAG AGA TTG TTG AGA (5`TTAG BW trn S- S- trn trn trn G (Hamilton G pDNA was was G pDNA Q- rsp16 (Shaw rsp16 Q- etal. trn (2007). Q- B. nana rps 16 et

Accepted Article (two-tailed). exacttest Fisher's on based values p with PAST, in tables contingency by investigated were groups, genetic and variation. pDNA on based distances genetic and geographical among correlations possible test to used also were tests Mantel distance. Hamming were tested against the corresponding genetic distances among pDNA haplotypes based on PAST, where genetic distances among AFLP multilo settings. default using run and data, mixed as entered was matrix The included. tobe data multi-state allows which 1999), (Bandelt v. 4.6.1.2 NETWORK thesoftware using network median-joining a constructing were by also haplotypes assessed relationships pDNA 2001), among the &Crandall (Posada replicates. Asphylogenetic metho distance, Hamming using PAST 10. ArcGIS in visually inspected were haplotypes of distributions Geographical regions. sequenced thetwo from information Plas omitted. were regions poly-T Ambiguous This This article is protected by copyright.reserved. Allrights Associations among haplotype haplotype among Associations AFLPpDNA datase and Correlations betweenthe in analysis joining Neighbour using wereassessed haplotypes pDNA among Relationships B. pumila ds reveal limitedmay resolution at the intraspecific level frequencies and species, and among haplotype frequencies frequencies haplotype among and species, and frequencies as outgroup, and bootstrap resampling with 1000 1000 with resampling bootstrap and outgroup, as tid haplotypes were defined by combining combining by defined were haplotypes tid cus phenotypes based on Jaccard Jaccard on similarity cus based phenotypes ts were computed using Mantel tests in in tests Mantel using computed were ts etal.

Accepted Article to the American/East Siberian ssp. ssp. Siberian theAmerican/East to “ distributions: geographical respective their and studied species/subspecies dominant four the well to corresponded groups four These Information). Supporting S4a, Fig. 2a; (Fig. peaked clearly K delta and plateaued, grou genetic Four arepresented. information on Thus, included. information locality without and with both run analyses, and STRUCTURE BAPS- on based inferred were partitions main Similar The Results This This article is protected by copyright.reserved. Allrights reflected in the NJ tree, but with low with intheNJtree,but (F reflected support two subspecies overlap (Figs. 1 and 2a). The sameclustering into species and subspecies were nana ssp. Siberian Atlantic/West clusters in the NJ tree (Fig. S3, Supporting Information). Information). Supporting S3, (Fig. tree theNJ in clusters but Information), Supporting S2, (Table STRUCTURE not were population byone represented only B. glandulosa B. between differences to due was variation total ofthe 22.3% that showed population asingle only nana B. combining after conducted analysis AMOVA hierarchical and Information), Supporting S5e-f, Fig. Mean population diversity was similar in these three groups (0.084, SD ± 0.044, 0.088 0.019,± and versus 0.096±0.040 and 0.111 ±0.050). ± 0.016,0.085 respectively), while raritywasconsiderably higher in Betula groups showed high levels of admixture, particularly in West Siberia where the ranges of the the of the ranges where Siberia West in particularly ofadmixture, levels high showed groups samples into one group and excluding hybrids and reference species represented by a by a represented species reference and hybrids excluding and one group into samples The spp. AFLP dataset dataset AFLP spp. B. glandulosa , B. pubescens B. group was the most divergent of the four groups (PCO and heat map; map; heat and (PCO groups four the of divergent most the was group nana and and B. glandulosa B. B. nana B. ) (Fig. 1; Fig. S5a-d, Table S2, Supporting Information). The two two The Information). Supporting S2, Table S5a-d, Fig. 1; (Fig. ) exilis ),“ and and 13% resulted from differences among populations. populations. among differences from resulted 13% and ” , “ B. pubescens B. ps were inferred based on where lnP(Data) lnP(Data) where on based inferred were ps recognized as separate genetic groups by by groups genetic separate as recognized ly data from STRUCTURE analyses with locality with locality analyses from STRUCTURE data ly B. nana B. ig. S3, Supporting Information). Reference species species Reference Information). Supporting S3, ig. were placed however outside the four main main thefour outside placed however were West” (largely corresponding to the the to corresponding (largely West” ” , “ B. nana B. B. glandulosa B. East” (largely corresponding corresponding (largely East” (0.227 ±0.093 (0.227 B. Accepted Article Beringia - East Siberia, 2) Svalbard, 3) West Siberia, 4) Europe, and 5) the Atlantic area (Fig. 4 a). a). 4 (Fig. area Atlantic the 5) and Europe, 4) Siberia, West 3) Svalbard, 2) Siberia, -East Beringia 1) pattern: geographical east-west clear a showed groups Thefive STRUCTURE. by indicated was that partition same the with groups five for likelihood highest the showed BAPS peak, nana in present tobe inferred were groups genetic Five Overall population differentiation (F differentiation population Overall Information). Supporting S2, Table population; each for value assignment average on based affinity (group groups within populations among found was 10.0% and groups thefive among found was variation total ofthe 13.0% AMOVA, hierarchical the In Information). Supporting S6. Fig. variation, the %of 1(8.2 along axis pattern geographical similar a showed east-west PCO compared tothe compared 0.001). 0.479, withtest, p< r= geographical distances were correlated (Mantel positive linear correlation with latitude (Fig. 3a; withcorrelation 3a; positive latitude(Fig. linear th and Information), Supporting S2, Table 2, Fig. pubescens B. into occurred tohave inferred was admixture much as twice average, On species. and populations The in 0.752, meanThe 0.001). p < intrapopulationdiversities inthe five genetic groupswere populations 0.138, ±0.025), but values the the from two datasets were stronglycorrelated (r= This This article is protected by copyright.reserved. Allrights B. nana nana B. Betula dataset (Fig. 2 b; Fig. S4b, Supplementary Information). Although Delta K showed no clear clear no showed K Delta Although Information). Supplementary S4b, Fig. b; 2 (Fig. dataset Because of the increased number of polymorphic markers for markersfor polymorphic of number theincreased of Because The level of admixture between our focal species was lowwas level species our focal overall, amongThe between varied admixture of but (Fig. 3b;p=0.999).

nana nana from from AFLP dataset Betula B. nana B. spp. dataset, it showed higher intrapopulation diversity (mean over all over (mean diversity intrapopulation higher showed it dataset, spp. than viceversa (0.053 ±0.055versus 0.026 ±0.037; t-test; 0.01; p <

st ) was 0.205, and pairwise was) F and 0.205, e level of admixture showed a significant and and significant a showed admixture of e level p < 0.001). There was no trend related to latitude to latitude related trend no was There <0.001). p B. nana B. from STRUCTURE the analyses of the st values between populations populations between values B. nana B. in this dataset this in dataset B. B. Accepted Article regression analyses (results not shown). shown). not (results analyses regression by determined as longitude or latitude with relationships or linear structure, geographical clear no showed Information) Supporting S7b, (Fig. andrarity (Fig. 5) Intrapopulation diversity 0.001). basedonthe thevalues with strongly they were correlated but Information), Supporting S2, Table ±0.025; 0.157, populations all over (mean levels diversity correlated (Mantel test, 0.242, 0.001). p r= < Addingmore markers increased intrapopulation the Even with the higher number of markers in this dataset compared to the compared tothe dataset markers in ofthis number higher Even with the The Information). Supporting S2, Table S7a, Fig. 0.08; p = (ANOVA; 0.043), Atlantic ±0.037) (0.087 and Svalbard ±0.030), (0.086 the differencewere not significant - East Siberia group ± 0.034), (0.127 followed Siberia by West (0.114 ±0.032), Europe (0.088± Beringia unglaciated mainly the in found was rarity average highest Although notshown). (results showed opposite the trend (slope: -0.0062, intercept:0.5513; r= -0.548, 0.05; p = Fig. 4a). European group (slope: 0.0021, intercept: 0.015;r=0.672, p <0.001), whereas the Atlanticgroup latitu between strong positive linearrelationship ±0.020,0.142 WestSiberia: Wefound 0.151±0.018, a ± 0.014). –EastSiberia: 0.146 Beringia and 0.015;± Tukey’s pairwise post-hoc comparedtests) tothe others (Atlantic: 0.127 ± 0.039, Europe: (0.106 group theSvalbard in diversity low the of because 0.05) < p (ANOVA; different significantly This This article is protected by copyright.reserved. Allrights differentiated as inferred from F 4b) (Fig. thedataset of partition any suggested analyses in structure genetic of absence a striking was there Betula No linearNo relationshipswith latitude lo or

pubescens pubescens AFLP dataset st (0.058), and genetic and geographical distances were weakly weakly were distances and geographical genetic and (0.058),

de and diversity for populations assigned tothe assigned populations for diversity de and ngitude were found by regression analyses analyses regression by found were ngitude B. pubescens. B. . The populations were only weakly weakly only were populations The Betula Neither BAPS nor STRUCTURE STRUCTURE nor BAPS Neither spp. dataset (r = 0.856, < p =0.856, (r dataset spp. Betula spp. dataset, dataset, spp. Accepted Article (Figs 4c, dand 6). This haplotypewas shared among hapl the of widespread andgeographically frequent two pDNA regions, of which most were length variations (13 indels, 2 substitutions, and 3 sites sites 3 and substitutions, 2 indels, (13 variations length were most which of regions, pDNA two in the identified were sites variable and ten Eight alignment. and trimming after length bpin 502 nana restrict geographically were more haplotypes other The Europe. in frequent also was but area, Siberian East - Beringian the in dominated frequent with the haplotypes species,reference the had the member of theCanadian in found were haplotypes These Information). Supporting S8, Fig. 6; (Fig. rest the from differentiated strongly were Gg) Gh, G (Ge, variant identi were haplotypes pDNA 14 and samples, 48 for amplified successfully were regions Both position). thesame in substitution and with gaps highest haplotype diversity was found in Europe, Europe, in found was diversity haplotype highest where Greenland in found only was Ab Europe. Central The alignment. trimming and The dataset DNA plastid The This This article is protected by copyright.reserved. Allrights British Isles d). (Fig. 4c, trn and Q- In the haplotype network and NJ analysis, the pDNA haplotypes with the the with haplotypes pDNA the analysis, NJ and network haplotype the In trn rps B. pubescens B. S- 16 region was successfully amplified for 54 samples and was 640 bp in length after lengthbpin 640 successfully was samplesand was 54 region amplifiedfor 16 trn B. pubescens B. G variant G, but was not successfully analysed for for analysed not successfully was but G, Gvariant B. pubescens B. B. pendula and dominated in West Siberia – Eastern Europe and alsooccurred in aggregate, aggregate, (not successfully analysed for trn trn is not present.is our In focal species, -S- -S- trn trn B. nana B. G region was successfully amplified for 58 samples and was was and samples 58 for amplified successfully was region G G variant A were found (Table 1). Haplotype Aa was most most was Aa Haplotype 1). (Table found were A G variant B. cf. minor (Table 1). The Canadian TheCanadian 1). (Table minor cf. , and completely dominated Atlantic areas like like areas Atlantic dominated completely , and ed. Haplotype Cc and Ca were shared between between wereshared Ca and Cc Haplotype ed. fied (Table S3, Supporting Information). Information). Supporting S3, (Table fied and three haplotypes we otypes and placed as central in the network thenetwork in central as placed and otypes B. glandulosa trn B. pumila B. Q- rps trn , B. nana B. B. nana B. 16) and and 16) Q- and in the Greenlandic Greenlandic the in and rps re restricted to the the re restrictedto and and 16. In the two other and Betula michauxii Betula B. glandulosa B. B. pubescens B. B. pubescens B. trn -S- trn G , only , the , the B. also also . It . It Accepted Article Ab was left out of the analyses, the differences were no longer significant. In In significant. longer wereno differences the theanalyses, of out left Ab was nana between haplotypes pDNA of distribution in difference asignificant showed tables contingency of test The haplotypes. pDNA the between distances and genetic geographical the between common. most was Aa haplotype ancient assumed the but present, were haplotypes all Europe, haplotype while Cc, the Atlantic completely wasgroup dominated haplotype the tip by Ab. In thetip by weredominated groups Svalbard and Siberia West Aa, the haplotype ancient assumed 0.001); theBeringia–East exact testp< (Fisher's groups AFLP different with associated was haplotypes pDNA different of distribution geographic In this study, we were able to disentangle the glacial and postglacial history of of history postglacial and glacial the disentangle to were able we study, this In Discussion This This article is protected by copyright.reserved. Allrights striking incongruence between pDNA and AFLP variation in in variation AFLP and pDNA between incongruence striking is a there that demonstrated have We markers. DNA nuclear and of plastid combination a and pubescens found in nuclear admixture from from admixture nuclear in found twothese species results from postglacial hybridisation between the them,increase that and we in variation pDNA theshared of structuring geographic theparallel that histories, phylogeographic different have species thetwo that here argue We DNA. plastid their extentin same the to not but loci variation.nuclear at nuclear Furthermore, clearly differentiated thetwo are species relative cold-tolerant more already occupied by the more cold-tolerant cold-tolerant themore by occupied already hybridisation has facilitated northwards a postglacial expansion of and There was no correlation between genetic distances based on AFLP and pDNA, or or pDNA, and AFLP on based distances genetic between correlation no was There B. in terms of refugial isolation, migration migration isolation, refugial of terms in

pubescens (Fisher'sexact testp 0.01), < butif the B. nana B. nana B. shows congruent geographic structuring of its organellar and and organellar its of structuring geographic congruent shows into B. nana B. B. pubescens B. Siberia group was completely dominated by the bythe dominated completely was group Siberia and hybridisation by using range-wide sampling sampling range-wide byusing hybridisation and . with increasing lati B. pubescens B. B. nana B. pubescens specific Atlantic haplotype haplotype Atlantic specific whereas its close, but B. nana B. tude suggests that that suggests tude B. into territory into territory

nana , the and and B.

B.

Accepted Article This This article is protected by copyright.reserved. Allrights among closely related can result species from lineageincomplete sorting of ancestral distributions in geographical similar showed haplotypes these and species among were shared haplotypes of species different among led to plastid capture in the absence of extensive nuclear introgression. Simulations have also also have Simulations introgression. nuclear extensive of absence the in capture plastid to led nana between clear differentiation the someadmixture, weAlthough identified (Wang marker theAFLP Thus, Information). Supporting S3, Fig. 2; (Fig subspecies and species to corresponding groups genetic suggested data AFLP nuclear et al. ( oaks European several of analyses broad in beendemonstrated have (Palmé pDNA shared reason for main the as sorting linage incomplete than rather hybridisation suggests in distribution geographical asimilar has which hand, other the on Cc, as such haplotypes tip Common variation. ancient shared, represent also foundin commo and widespread was Aa haplotype Our 2004). in sharing haplotype extensive the for explanation likely a as discarded been have mutations parallel slowly, evolves DNA plastid As mutations. parallel from or polymorphisms composition of haplotype pDNA thatthe demonstrated been earlier has It sorting. lineage incomplete from 1997; Petit at AFLP loci, but not in plastid DNA, implies that hybridisation between them typically has has them typically between hybridisation that implies DNA, plastid in not but loci, AFLP at etal. etal. Our data confirm former reports of pDNA ha pDNA of reports confirm former data Our

In contrast, the Bayesian and NJ clustering of our ofour clustering and the NJ contrast, In Bayesian 2014), seem to be little influenced by introgression compared with plastid markers. compared with little introgression influenced by seem 2014), be to 2004). Similar 2004). extensive hybridisation and introgression among sympatric species B. glandulosa B. B. nana B. B et al. et . pubescens 2002). and and , which was clearly divergent based on AFLPs. Thus, this haplotype may may haplotype this Thus, AFLPs. on based divergent clearly was which , Betula B. pubescens pubescens B. changes according to the species occurring in sympatry, which which sympatry, in speciesoccurring the to according changes (JadwiszczakThomson 2012; B. nana B. (Fig. 4 c, d; Table 1). Besides hybridisation, shared pDNA pDNA shared hybridisation, Besides 1). Table c, d; 4 (Fig. and and s, as also found for for as also found s, plotype sharing and extensive hybridisation hybridisation extensive and sharing plotype B. pubescens B. n, inferred as central in the network, and and network, the in central as n, inferred Betula etal. ssp. dataset based on mainly mainly on based dataset ssp. , are much less likely to result 2015). Three common Three pDNA 2015). Quercus nuclear microsatellites nuclear B. pubescens Betula ; Dumolin-Lapegue (Palmé and and etal. B.

Accepted Article In of history The ssp. nana exilis identified. are discrepancies Betula organism possesses (Currat agiven that genes of majority of the history the with be incongruent to likely are pDNA, as such introgression, of levels high with markers on based reconstructions thatphylogenetic shown This This article is protected by copyright.reserved. Allrights species c; (Fig. Palmé4 AFLP groups, and largelycongruent with the limited pDNA data previously reported for this introgression mark two arepDNA betweenthe than AFLP data do not support the latest classification by Ashburner & McAllister (2013), where where (2013), McAllister & Ashburner by classification latest the not support do data AFLP seen intheother patterns geneticon the influence pubescens B. Table 1). 1). Table 6; Aa(Fig. haplotype pDNA widespread ancient, assumed the was shared haplotype pDNA only relative close species-specificreflect In patterns. study this in sampling range-wide the and included able to include all relevant werenot We influence. an had have may margins range their or at sympatrically found species B. nana B. should be drawn on the basis of nuclear variation rather than pDNA variation when when variation pDNA than rather variation nuclear of basis the on drawn be should for data AFLP our Although Betula glandulosa Betula , the geographic distribution of different pDNA halotypes was associated with different different with associated was halotypes pDNA different of distribution geographic , the , suggesting that potential hybridisation with with hybridisation potential that , suggesting B. glandulosa B. is referred to as as to is referred

nana

et al. Betula also showed distinctly higher levels of genetic rarity genetic of levels higher distinctly showed also , but these species were strongly differentiated at AFLP loci, and the the atAFLP loci, and differentiated strongly species were , butthese et al. 2004; Maliouchenko B. glandulosa 2008). Thus, 2008). we suggest that phylogeographic in inference species our in analyses B. nana,B. B. nana and and we initially expected to detect someinfluence its from . B. pubescens B. et al. et we are confident that our AFLP data mainly mainly data AFLP thatour confident we are two species. It is also worth noting that the the that noting worth also is It species. two ers, there is still a possibility that other other that possibility a still is there ers, 2007; Thórsson 2007; , but based on the reference samples samples reference the on based but B . glandulosa seem to be less influenced toby belessinfluenced seem etal. has not made any major major any made not has 2010). This 2010).

than B. nana B. B Betula . and

Accepted Article areas furthest east, i.e. Beringia, remained unglaciated throughout the Pleistocene, and were not were Pleistocene, not and the throughout east, i.e. remained furthest Beringia, unglaciated areas Binney Europe WestSiberia and and the extremely glacial dry conditions in Siberia East (Astakhov 2008; Pleistocene of the gl onset the distribution before Beringia may explain the eastern eastern the mayexplain Beringia as dry as East & Brigham-GretteSiberia (Elias 2013). Persistence over several glaciations in records from Russia (Andreev c). 4 (Fig. structure genetic hierarchical a supports also (Europe), andwest Siberia) East – (Beringia east the in centres Aa, with haplotype ancient assumed di postglacial; to (late-glacial processes recent whil process, differentiation older an represent within as subgroups) alongtheeast-west identi pattern, this refined markers more contained the of Theanalyses 2a). (Fig. subspecies allopatric partly thetwo to referred to as main groups) in in groups) main toas referred this species. in patterns genetic observed the behind drivers major the are history migration postglacial and in ongenetic structure influence had has little hybridisation thatinterspecific suggests S3), (Fig pattern thephylogenetic with combination in congruence, This This article is protected by copyright.reserved. Allrights et al. et B. nana B. Pliocene macrofossils from e.g. North Greenland (Bennike & Böcher 1990) andpollen 1990) (Bennike &Böcher Greenland e.g. North macrofossils Pliocene from The analysesThe of the 2009) 2009) must repeatedly have fragmented the Eurasian distribution of . The main east-west genetic pattern that also recognized east-west genetic taxonomically Themain that is pattern seems. to Betula et al. B. nana B. nana B. spp. AFLP dataset identified identified dataset AFLP spp. gradient. This pattern suggests a hierarchical genetic structure structure genetic hierarchical a suggests pattern This gradient. 2014) suggest 2014) that , “ B. nana B. main group, and the Beringia-East Siberia subgroup may may subgroup Siberia theBeringia-East and group, main scussed below). The disjunct distribution of the the of distribution disjunct The below). scussed e the substructuring probably represents more represents probably substructuring e the East” and “ East” aciations. The recurrent ice-sheet formation in ice-sheet recurrent The aciations. fying five genetic groups (hereafter referred to referred (hereafter groups genetic five fying B. nana B. B. nana B. nana B. had a widespread, continuous continuous widespread, a had two groups genetic (hereafter West”, largely corresponding corresponding West”, largely B. nana B. , and that refugial isolation isolation refugial that , and dataset that that dataset B. nana B. . The Accepted Article north. the in diversity genetic higher explain may also which linages, postglacial expanding of mixture some indicating subgroup, Siberian West the like subgroups, other to belonging individuals with Petit 2005; Wang diversity andgenetic habitat suitable lost probably cold-adapted the conditions, northw increased diversity genetic that found (Ibrahim expectations to contrary However, represents probably subgroup theEuropean and large,more or lessconnected glacial refugium al Thus, today. mountains European southern and (Tralausheet 1963; Hultén& Fries1986; Binney reco been have macrofossils late-glacial Many expande recurrently which population(s), western assign Individuals glaciated. repeatedly was which rarity the Beringian in region (Fig. SupportingS7a, Information). genetic elevated significant, not although indicated, the with line also in is Persistence 2003). recordsof presence show well-documented refugium for many arctic-alpine plants (Abbott &Brochmann 2003), and pollen postglac and populations persistent both represent This This article is protected by copyright.reserved. Allrights range, distribution the of part theAtlantic-European dominates group main western The etal. 2014). In addition, several populations in Northeast Europe were mixed weremixed Europe Northeast in populations several In addition, 2014). B. nana B. nana B. prior toand during LGM the (Goetcheus &Birks 2001; Ager has most of its suitable habitat in the north, and it has has and it north, the in habitat suitable its of most has et al. et ards in Europe. Under the current climate climate current the Under Europe. in ards rded in the areas south of the Scandinavian ice ice Scandinavian of the south areas the in rded etal. B. nana ong the southern to southeastern glacial margin, margin, glacial southeastern to southern the ong postglacial descendants from this refugium. refugium. this from descendants postglacial 1996; Hewitt 2000; Excoffier ed to this group are probably descendants from from descendants probably are group tothis ed d and contracted throughout the Pleistocene. Pleistocene. the throughout contracted d and at the rear-edge of its current range (Hampe & & (Hampe range current ofits rear-edge the at ial expansionial from this refugium. Beringia is a 2009), and may have survived glacial periods in a a in periods glacial survived have may B. nana B. isstill in present central etal. 2009), we Accepted Article 2003; Alsos2003; northward from periglacial populations in the we the in populations periglacial from northward expanded probably group this of ancestors the deglaciation, of phase early an During Greenland. Siberia. West and Europe East dominated in Svalbard found haplotype pDNA the and Information), Supporting S6, Fig. (PCO, subgroup Siberian theWest of those to similar most genetically were group Svalbard the that suggesting analyses earlier with in line are results Our further. diversity theintrapopulation reduce later population sizereduction in response tothe late Holocenecooling (Birks 1991), would al. al. This This article is protected by copyright.reserved. Allrights isolation Western Siberia in c). (Fig.Evidence 4a, during for WestSiberia refugia in the last only haplotype pDNA a of presence The populations. admixed of these differentiation current the explain can glaciation last the during isolation Refugial a, b). 2 (Fig. groups western and main eastern the between populations admixed isolation in these heavily glaciated areas. Sv areas. glaciated heavily these in isolation during bottlenecking and effects founder from result et al. (Skrede e.g. species plant arctic other several for been found has glaciation 1998), 1998), andonly theknown ice-free area couldsustain not growth of in studies pDNA previous of findings with the line in andis 2007a), 2004; Maliouchenko The Atlantic subgroup is present in Europe, common in Iceland, and dominant in in dominant and Iceland, in common Europe, in present is subgroup Atlantic The Individuals belonging to the West Siberian Siberian West the to Individuals belonging The Svalbard and the Atlantic subgroups contained less genetic diversity, and most likely likely most and diversity, genetic less contained subgroups theAtlantic and Svalbard The etal. B. nana B. 2007). Svalbard was probably colonised during the Holocene warm period, and and warmperiod, Holocene duringthe colonised Svalbard probably was 2007). colonised Svalbard from Russia (Alsos et et al. 2007). albard was heavily glaciated during LGM (Landvik LGM during glaciated heavily was albard sternmost part of the European refugium and up up and refugium European of the part sternmost subgroup seem to be descendants from initial initial from descendants to be seem subgroup found in this region (Ca), supports refugial postglacial colonisation rather than refugial than refugial rather colonisation postglacial et al. et 2007). Individuals assigned to to assigned Individuals 2007). Betula B. nana B. etal. (Palmé 2003; Palmé 2003; (Palmé (Landvik 2006; Eidesen 2006; etal. et et

et et

Accepted Article subgroup, also supports such a scenario. Periglacial areas were not suitable for for werenotsuitable areas Periglacial a scenario. such supports also subgroup, to this exclusive was that Ab haplotype pDNA specific species and derived the Further, cooling. range-co with combination in possibly expansion, increasi with diversity genetic intrapopulation effects and bottlenecking along way the 2000). (Hewitt The significant reduction in funder successive through differentiation to lead can expansion leading-edge Such Greenland. and Iceland to Atlantic North the across dispersal by followed coast, Norwegian the along This This article is protected by copyright.reserved. Allrights with previously published pDNA data (Palmé data pDNA published with previously from Iceland of Recolonisation press). al. in et (Alsos evidence floristic and genetic on based species numerous for beeninferred and has 1991), (Fredskild records fossil dated of thesuccession with agreement isin Greenland Icelandand to for hybridisation and plastid capture into for nana of front attheexpanding westwards and north moved have may haplotype This LGM. during macrofossils and pollen influx values for where evidence, paleobotanical with line in is This ice-margin. the to close rather located refugia cons possibly or refugium, European main single a of efficient suggest recolonization data broad-fronted, AFLP nuclear mainly our Thus, areas. glaciated previously in reduction no showed and high was differe weak only and distance, by isolation weak In contrast to of history The B. nana B. , and diminished at the rear end. The current distribution of the Atlantic subgroup inferred inferred subgroup Atlantic the of distribution current The rearend. the at diminished and ,

barely overlaps with the current distribution of of distribution current the with overlaps barely B. nana B. B.

pubescens , we found no geographical structuring of the AFLP variation in in variation theAFLP of structuring geographical no found we ,

B. B. B. pubescens B. cf. et al. et pubescens ng latitude supports such recent northward northward recent such supports ng latitude a refugium in Western Europe is also concordant concordant also is Europe Western in refugium a ntiation among populations. Population diversity diversity Population populations. among ntiation ntractions in response to the late Holocene Holocene late the to response in ntractions isting of several smaller but partly connected connected partly but smaller several of isting 2004; Thórsson 2004; . Westward colonisation from NW Europe Europe NW from colonisation Westward . B. pubescens B. illustrate rapid postglacial spread B. pubescens B. etal. after the last glaciation from last the after 2010). 2010). , reducing possibilitiesthe B. pubescens B. B. pubescens

B. B. , Accepted Article from the early coloniser and diploid diploid and coloniser early the from (Stebbins, 1971; Chapman& Abbott, 2010), introgression during postglacial expansion isexpected species (Currat pubescens with formation hybrid increased show Iceland Bergman Birks 1996; that Crossing experiments in after the last glaciation, and about 600 years were needed for wereneeded years 600 about and glaciation, last the after Betula parent is of lowploidy (Eriksson &Jonsson 1986; DeGroot nana B. pDNA andAFLP data for The congruent pDNA structure between as in (Truong andIceland Sweden e.g. from studies local with line in is which pollen, and seeds through both flow, gene current in diversity high overall and data AFLP on based structure (Birks beenquestioned resultshave although these evidence has suggested scattered refugia closeLGM tothe margin ice (Kullman 2002, 2008), (Birks mountains the into valleys the up and coast Norwegian (MacDonald This This article is protected by copyright.reserved. Allrights west pattern reported 4; earlier (Fig Palmé 2003; Palmé B. pubescens B. B. nana B. cf. The shared pDNA haplotypes (Aa, Ca, and Cc) showed a similar geographical distribution distribution geographical similar a showed Cc) and Ca, (Aa, haplotypes pDNA shared The into pubescens (Karlsdóttir etal. B. pubescens B. , and the overall pDNA pattern we observed in in observed we pattern pDNA overall the , and etal. was rapidly expanding into areas already occupied by by occupied already areas into expanding rapidly was 2000) 2000) from EuropeanCentral refugia (Willis was, for example, the first tree that that first tree was, the example, for 2008), and readilymore from diploids totetraploids than et al. etal. Betula B. pubescens during postglacial range expansion. Macrofossils and pollen data show show data pollen and Macrofossils expansion. range postglacial during 2005), and analysis of size distribution of of distribution of size analysis and 2005), 2014). As introgression2014). invading to the mainly thelocal occurs from etal. also suggest that hybridisation is hybridisation that suggest also 2007; Thórsson 2007; B. nana , suggest asymmetric hybridisation and plastid capture from from capture plastid and hybridisation asymmetric , suggest B. nana into the later coloniser later tetraploidinto the and B. nana and and et al. et et al. et B. pubescens during periods of expansion of of expansion of periods during 2010). 2010). etal. 2005). The total absence of large-scale colonized the Atlantic coast of Norway Norway of coast theAtlantic colonized et al. et B. pubescens B. B. pubescens B. 2004; Maliouchenko 2004; et al. et et al. Betula 1997). Thetetraploid more successful when the female when more thefemale successful , but clear discrepancy between between discrepancy clear but , 2005). Swedish megafossil 2000; Birks& Willis 2008). Betula to spread round the round tospread also suggest high levelsof B. nana B. was inline with aneast- pollen diameters from from diameters pollen vice versa vice (van Dinter (van Dinter & etal. B. pubescens B. B. B. B . 2007). 2007).

. Accepted Article in this and previous studies (Palmé studies previous and this in between pDNA haplotypes of sharing extensive the to contrast In Conclusions species, tree a As plants. colonising These hybrids. established already the through population the in genome species' invading the of presence extensive an by already will there withoutcolonization initialby seeds(Petit allowing some species in tosettle an area through initial extensive pollen flow and hybridisation pubescens B. than cold-tolerant less genetic variation and evolutionarynovelty (Ellstrand & Schierenbeck 2006). recolonization by with crosses between species. Our admixture data also supports asymmetric backcrossing of hybrids with backcross to tend hybrids As parent. maternal as successful more pubescens This This article is protected by copyright.reserved. Allrights be obtained. to inferences phylogeographical allowing loci, atAFLP differentiated clearly were species two the 1968; Wang1968; expansion through pollen swamping seems likely. likely. seems swamping pollen through expansion pollen donor (Eriksson &Jonsson and1986) the establishment of hybrids leading-edgeat the of dwarf-shrub the than disperser pollen B. pubescens B. The observed leading-edge hybridisation with with hybridisation leading-edge observed The

should therefore be more successful as pollen donor, and the diploid diploid the and donor, pollen as successful more be therefore should et al. et . In addition, colonization of new territories colonization new of addition, . In Betula 2014), 2014), B. pubescens , particularly at the leading edge of expansion. expansion. of edge leading the at , particularly

nana B. nana B. B. showed a clear east-west structure throughout Eurasia, and the the and Eurasia, throughout structure east-west clear a showed

pubescens , but hybrids between them are likely to be more cold-tolerant than than cold-tolerant be more to likely are them between hybrids but , . Hybrids may have better invasion ability because of increased of increased because ability invasion better have may Hybrids . et al. et B. pubescens will be inclined to accumulate plastids in interspecific interspecific in plastids to accumulate be inclined will B. nana B. 2004; Maliouchenko et al. et . Thus, hybrids represent potential mates for thelater for potential mates represent hybrids 2004). When seeds manage to establish later later on, establish Whenseeds to manage 2004). produces more pollen, and is a more efficient a producesis morepollen, and B. pubescens B. nana B. may be facilitated by “pollen swamping”, swamping”, “pollen by may befacilitated etal. may haverapid facilitated also the B. is probably a more successful more successful a probably is 2007; Thórsson

nana B. pubescens B. and Betula pubescens Betula B.

B. nana B. pubescens et al. (Elkington shouldbe 2010), shown is is Accepted Article nuclear (AFLP) gene flow from from flow gene (AFLP) nuclear plastid capturefrom with established were run at the Lifeportal,were run the at University of Oslo analyses STRUCTURE discussions. helpful for Carlsen Tor and themanuscript, of version early an on commenting for Petit J. Rémy and Ehrich Dorothee Skrede, Inger lab, the in assistance for I Supporting S1, Table (cf. collectors thankall We Acknowledgements seeds. through establish to managed thefirst for expansion further and reproduction facilitated by swamping) (pollen flow pollen extensive that suggest frequent most been has hybridisation pubescens in variation AFLP and pDNA between Theincongruence flow. gene current and with historical The lackof AFLP structure suggests efficient expansion from asingle large refugiumcombined pubescens Europe theNorth iceEuropean of sheets, east North were the These southof last species period. glacial this the for during existed refugial areas in structure AFLP The variation. AFLP the of structuring the with associated was haplotypes pDNA of distribution This This article is protected by copyright.reserved. Allrights Norway. of Council theResearch from Brochmann toChristian 146515/420 occupied by the more cold-tolerant cold-tolerant more the by occupied can be explained by asymmetrical hybridisation with with asymmetrical hybridisation by beexplained can similar of pattern pDNA tothat a showed B. pubescens B. B. nana B. B. nana indicates at least two (Europe and Beringia) and possibly three separate separate three possibly and Beringia) and (Europe two atleast indicates to as pollen donor, and backcrossed with with backcrossed and donor, pollen as B. nana B. pubescens B.

at the postglacial expansion front of of front expansion thepostglacial at into nana B. pubescens B. , created a zone of more cold-tolerant hybrids, which which hybrids, cold-tolerant more of zone a created , . The study. The was supported bygrants 150322/720 and . We . We identified a weakbut significant increase in an ice sheets, and in Beringia. In contrast, Beringia.In ice and sheets, an in nformation), Virginia Mirré and Gro H. Jacobsen Jacobsen H. Gro and Mirré Virginia nformation), B. nana B. with increasing latitude, suggesting suggesting latitude, increasing with B. pubescens B. B. pubescens B. , but nostructuringbased AFLPs.on B. nana B. B. pubescens B. into territories already already territories into , where hybrids mainly are mainly hybrids , where individuals that later B. pubescens. B. ,to leading B. We

B. B. Accepted Article Astakhov V (2008) Geographical extremes in th Andreev AA, Tarasov PE, Wennrich V Anamthawat-JónssonHybridisation, K (2012) Alsos IG,Eidesen PB, EhrichD Alsos IG, Ehrich D, Thuiller W Ager TA (2003) Late QuaternaryLate TA(2003) Ager vegetation andclimatethe history central of Bering land Atkinson MDAtkinson (1992) Ashburner K, McAllister HA (2013) Alsos IG (2003) Bennike O, Böcher J (1990) Forest-tundra ne Bandelt HJ, Forster P, Röhl A (1999) Median-j RJ,Abbott Brochmann(2003) Hist C References This This article is protected by copyright.reserved. Allrights Bergman J,Hammarlund Bergman D, HannonG, Barnekow L, Wohlfarth(2005) B Deglacial QUEEN considerations. Royal Botanic Gardens, Kew. El'gygytgyn pollen record. history vegetation of northeastern Russian Arctic inferred from theLake www.intechopen.com. terrestrial and aquatic systems In: Birch. Icelandic the changing Arctic. 2051. plants.northern University ofPhD thesis, Tromsø. Genetic Arctic: variation, recruitmentand phylogeographyin a changing climate bridge from St.bridge Michael Island,western Alaska. of Eric Hultén. phylogenies. phylogenies. ofEcology Journal Arctic KøbenhavnGreenland.the Kap fromPlio-Pleistocene North formation, remains vegetation vegetation succession and Holocene tree-limit dynamics in the Scandes Mountains,

43 , 331-338. Conservation biology of the most thermophilous plant species in the

Molecular Biology and Evolution and Biology Molecular Betula pendula Molecular Ecology Proceedings of the Royal Society B-Biological Sciences

80 Current topics inphylogenetics andphylogeography of Science , 837-870. , et al. , et , et al. , et Polar Research Polar Climate of the Past

316 Roth (B-Verrucosa Ehrh) and (B-Verrucosa Roth The genusThe Betula.revision Ataxonomic ofbirches oryandof evolution the arctic inflora: the footsteps (2012)Genetic consequences of climate change for (2007) plant long-distance Frequent colonization in (ed. Anamthawat-Jónsson K), pp. 117-144. InTech, , et al. , et , 1606-1609.

12 ighboring the north pole:plant and insect , 299-313. (2014) Late Pliocene andEarly Pleistocene introgression and phylogeography of oining for networks inferring intraspecific

e history glacial ofnorthernEurasia: post- 27 , 280-288.

10 16 Quaternary Research , 1017-1039. , 37-48. B pubescens

60

279 Ehrh. , 19-32. , 2042-

Accepted Article DeGroot WJ,Thomas introgression massive invasions: of side hidden The L (2008) Excoffier RJ, Petit M, Ruedi M, Currat This This article is protected by copyright.reserved. Allrights Chapman MA,ChapmanIntrogression AbbottRJ (2010) A,Bonin BellemainE, EidesenPB HJB,Birks Willis KJ (2008) Alpines, trees, and refugia in Europe. HH, Birks LarsenBirks E, HJB (2005)Did tree- HA,Binney Willis KJ, Edwards ME Dumolin-Lapegue S, Demesure S, Dumolin-Lapegue Fineschi B, S, Ehrich D (2006) aflpdat:Ehrich collection a ofr for functions convenientof handling AFLP data. D, vonHoldt,Earl, (2012) BM ASDyke (2004) AnNorth outline of Americ J,Corander P,Waldmann Sillanpaa MJ (2003)Bayesian analysis ofgenetic differentiation HHBirks (1991) Holocene vegetational history Eidesen PB,AlsosEidesen IG, PoppM by local genes. Journal ofEcology Journal inerrors population genetics studies. Diversity Kullman (2002). glaciation alongwest the Norway?coast of A reviewof the evidence, inlight of Quaternary Science Reviews woodytaxa innorthern Eurasia: evidence new afrom macrofossildatabase. Palaeobotanyof And Palynology west-centralSweden: stratigraphic data compared to megafossil evidence. structure of oaks whitestructure throughout European the continent. phytologistNew macrofossilsplant from anArctic Skardtjorna, lake. northern Canada.northern In: 1487. between populations. Molecular Ecology Notes Resources output andStructure implementing the Evanno method. Conservation Genetics J, Gibbard PL), pp. 373-424. Elsevier, Amsterdam.

1 4 , 147-160. , 359-361 Evolution PA, WeinRW(1997)

186 Journal of Biogeography

85 , 63-71. Quaternary Glaciations:and Extent Chronology Genetics , 241-264.

62 Structure harvester: Structure a website visualizing program and for , et al. , et

, 1908-1920. 6 , 603-604. , et al. , et

, et al. , et 28 (2007a) Nuclearvs. plastiddata: complex

163 , 2445-2464.

134 (2004) How to trackand assess genotyping , 367-374. (2009) The distribution of late-Quaternary Molecular Ecology , 129-151. an deglaciation with emphasis on central and Betula nana Corre VL, PetitPhylogeographic RJ (1997) of fitnessgenes across a ploidy barrier. and climatic change inSpitsbergen west - Betula

32 , 1461-1471. , Pinus L. and L. and The Holocene The and

13 Betula glandulosa Picea Genetics Plant& Ecology , 3261-3273. survivethe last

1

, 209-218. 146 (eds. Ehlers Ehlers (eds. , 1475- Review Michx. Michx. The Accepted Article Excoffier L, Lischer L, HEExcoffier (2010)Arlequin suite 3.5: ver of aseries new programs to G, Evanno RegnautS, Goudet Detecting J (2005) ofthe number individualsclusters of PJ(Internet) Ersts Falush D,Falush Stephens M, JKPritchard (2003) Inference of population structure using Smouse L, Excoffier PE, QuattroAnalysis JM (1992) ofmolecular variance inferredfrom Foll L, Excoffier M, PetitRJ(2009) Genetic consequencesof range expansions. Eriksson G, Jonsson A (1986) A review of the genetics of Elven R, Murray DF, Razzhivin V, Yurtsev BA (2011) between hybridization (1968)Introgressive TT Elkington SA, Brigham-Grette JElias (2013)Glaciati Ellstrand NC,SchierenbeckEllstrand KA (2006)Hybridiz PB,CarlsenEidesenT, U,BrochmannMolau C (2007b)Repeatedlyout ofBeringia: This This article is protected by copyright.reserved. Allrights Eidesen PB,EidesenEhrich D, Bakkestuen V perform population geneticsperform underLinuxanalyses and Windows. using the software structure: a simulation study. http://biodiversityinformatics.amnh.org/open_source/gdmg Museum of Natural History, Center for Biodiversity and Conservation, Research Forest Ecology ResoursesEcology Oslo, http://nhm2.uio.no/paf/ plants, Vascular version. Draft (PAF): plants? in invasiveness Iceland. In North-West Ehrh Amsterdam. Elsevier, In: Beringia. 898–910. mulitilocus genotype data: linkedlocimulitilocus and allelecorrelated frequencies. DNA restriction data. distancesmetric among DNA haplotypes: Application to human mitochondrial Review of Ecology, Evolution, and Systematics dispersal highways,trafficdispersal and of barriers capitals diversity. Cassiope tetragona 3925. history ofaPleistocene 164 , 1567-1587. Geographic Distance Matrix Generator(version 1.2.3). Encyclopedia ofQuaternaryScience

1 , 421-434.

embraces the Arctic. 10 , 564-567. Genetics Euphytica circumpolar key species. New PhytologistNew , et al.

131

148 , 479-491. ons: LatePleistocene Glacial Events in (2013)Geneticroadmap ofthe Arctic:plant , 35-46. Natural HistoryUniversity Museum, of ation as ation a stimulusthe for of evolution Journal of Biogeography Journal of

67

40 Checklist ofthe PanarcticFlora Molecular Ecology Molecular , 109-118. Molecular Ecology Molecular , 481-501. (ed. Elias S), pp. 191-201. Betula Betula nana . Scandinavian Journal of New Phytologist L and Land Molecular

American 34

14

16 , 1559-1574. B Pubescens , 2611-2620. , 3902- Genetics Annual

200

,

Accepted Article Hamilton MBPrimer Note Hamilton (1999) Hammer Ø,HammerHarper DAT, Ryan(2001) PAST: PD Paleontological Statistics Software VG,Goetcheus BirksFull-glacial HH (2001) Ibrahim KM, NicholsIbrahim RA,Hewitt(1996) GM Spatial patternsof genetic variation Hultén E, Fries M (1986) A, Hampe PetitRJ(2005) Conserving under biodiversity climate change:therear edge JJ Furlow (1997) (1991) B Fredskild The genus D,Falush Stephens M, JKPritchard (2007) Inference of population structure using This This article is protected by copyright.reserved. Allrights Hubisz MJ,Hubisz D, Falush M, Pritc Stephens Hewitt G (2000) The genetic legacy of the Quaternary ice ages. JadwiszczakKA(2012) What can molecular markerstellabout us glacialthe and Jadwiszczak KA, Banaszek A, Jabło Jadwiszczak KA, Banaszek A, Chrzanowsk Jonsell B, Karlsson T(2000) intergenic regionsintergenic with intraspecific variation. Science Reviews intephra the Beringia National Park, Seward Peninsula, Alaska. Cancer Analysis. Data and Education for Package and Oxford. synecology. and generated bygenerated different forms ofdispersal duringrange expansion. Resources with thestructure assistance ofsample groupinformation. matters. Notes data:genotype dominantnull markersand alleles. multilocus 291. postglacial histories of European birches? variation of European central suture zone. Schrk.phylogenetic lineages thezone of eastern humilis follows Betula admixture Genomes

7 Koeltz Scientific Books, Königstein. , 574-578. Ecology Letters

8 Betula

9 , 1017-1030. , 1322-1332. Betula humilis

. In: Nordicof Journal Botany 20 Atlas ofAtlas NorthEuropean Vascular Plants NorthoftheTropic of , 135-147. Flora ofFlora North America NorthofMexico. Flora nordica Betula

8 , 461–467. s -s for Fourprimer pairs the Schrk. in Poland and Belarus. Belarus. and Poland in Schrk. ń in Greenland-Holocene history, present distribution skaSozinov E, Chloroplast OV(2012) DNA Plant Ecology & Plant Ecology Diversity hard JK (2009) Inferring weak population Bergius Foundation, Stockholm. a A, KłosowskiS, SozinovThe OV(2014) upland tundra vegetation preserved under Silva Fennica

Palaeontologia Electronica 11 , 393-412. Molecular Ecology amplification of chloroplast

Nature 46 , 1-7. , 1-7. Tree Genetics &Tree Genetics Molecular EcologyMolecular , 733–745. Molecular EcologyMolecular Vol. 3, New York

405 Quaternary

Heredity 8 , 521-523. , 907-913.

4 , 9.

77 , 282- Accepted Article Kullman L(2008) EarlyKullman postglacial appearance PetitRJ,Bodenes C, Ducousso A,Rousse Landvik Landvik JY, Brook EJ,Gualtieri L Landvik JY, Bondevik S,Elverhøi A Kullman L (2002) Boreal tree taxa in the Central Scandes during the Late-Glacial: Kosman E (2003) Nei's gene diversity and the index of average differences are identical L, Karlsdóttir Hallsdóttir EggertssonM, O, Thorsson K AET, Anamthawat-Jonsson (2014) L Morales Orlando A, P, Palmé Järvinen This This article is protected by copyright.reserved. Allrights MacDonald GM, Velichko AA, Kremenetski CV Palmé AE (2003) Nei M (1987) Mantel N (1967) The detection of disease clustering and a generalized regression Palmé AE, Su Q, Palsson S, Lascoux M (2004) Extensive sharing of chloroplast O,Maliouchenko Palmé AE, BuonamiciA, VendraminGG, Lascoux M (2007) review and perspective. 1124. American Journal ofBotany (Betulaceae)species basedon nuclear ADH and chloroplast matK sequences. mechanism of invasion of invasion in oaks. mechanism glaciation: Ice-free areas existed. Reviews theand SeaBarents Ice area: sheet extent configuration.and history. forest Late-Quaternary for Implications ofmeasures diversity within populations. AgriculturalIcelandic Sciences Birch hybridization in Thistilfjördur, approach. 1601-1610. and climate change across NorthernEurasia. hybridization Corylusgenera: Betula, Salix. Theand impact of colonizationpost-glacial and with particularwith focus on phylogeographyComparative population and of structure European B haplotypes among birchesEuropean indicates hybridization among . pubescens Molecular Evolutionary Genetics Molecular Evolutionary

17 Cancer Research Evolutionary history and chloroplast DNA variation in three plant , 43-75. and PhD thesis, Uppsala University. Uppsalathesis, PhD B . nana Quaternary Science Reviews B . . Molecular EcologyMolecular , et al. pendula

27

91 , et al. , et , 209-220. , 1834-1845. 27 New Phytologist , et al. , et (2003) Northwest Svalbard during the last Geology l G, Kremer A(2004)Hybridization as a , 95-109. and (1998)Thelast of glacial maximum Svalbard North-east Iceland during the Holocene. (2004) Phylogenetic relationships of B Columbia University Press, ColumbiaYork. New of tree species in northern Scandinavia: . , et al. , et Plant Pathology

31 pubescens Quaternary Research , 905-908.

13 (2000) Holocene treeline history Journal ofBiogeography

, 167-178. 161

, 151-164. . 27 Journal of Biogeography , 2467-2472.

52 Quaternary Science , 533-535.

53 Betula pendula Betula , 302-311.

29 species, , 1117- Betula

34 , ,

Accepted Article Petit RJ, Csaikl UM, Bordacs S This This article is protected by copyright.reserved. Allrights Posada D,Posada Crandall Intraspecific KA (2001) ge Schenk MF, Thienpont MF,Schenk Koopman C-N, WJM,Gilissen Smulders LJWJ, (2008) MJM LH,RiesebergWhitton J, Molecular LinderCRmarker (1996) incongruence in plant JK,Pritchard Stephens M, Donnelly P (2000) Shaw J,Shaw Lickey EB, BeckJT P,Schönswetter Tribsch(2005) Vicariance A and dispersalin thealpine perennial Rieseberg LH, Soltis DE (1991) Phylogenetic c (2014)TeamR Core R: Alanguageand environment statistical for computing. R Shaw J,Shaw EB, Lickey SchillingSmall EE, Shaw KLConflictShaw (2002) betweennuclear and mitochondrial DNAphylogenies of recenta Skrede I, EidesenSkrede PB, Brochmann RP, Portela (2006) Refugia,C differentiation and Svendsen J, Alexanderson H, Astakhovc VI, GL(1971)Stebbins populations. oaks:white Phylogeography and patterns of diversity based on data from over 2600 Trends in Ecologyand Evolution Journal ofBotany Journal chloroplastnoncoding DNA sequences for phylogenetic analysis. Genetics & Genomes Phylogenetic relationships in hybrid zones andphylogenetic trees. plants. genotype data. multilocus Bupleurum stellatum forFoundation Computing, StatisticalVienna angiosperms: the tortoise and the hare III. hare the and the tortoise angiosperms: genome sequences to choosenoncodingregions for phylogeneticstudies in 288. States ofStates America Hawaiian crickets. species radiation: What mtDNA reveals an ( postglacialmigration in Eurasia, arctic-alpineexemplified bythe mountain avens UK Dryas octopetala Dryas Evolutionary Trends InPlants Forest Ecology andManagement Chromosomal evolution in higher plants

L.). L.). 99 92 Proceedings of the National Academy of Sciences of the United , 16122-16127. L. (Apiaceae). , et al. , et , 142-166.

4 Molecular Ecology , 911-924. , etal. Genetics (2005) Theutility oftortoise thehare (2005)II:relative 21 and Betula (2002) Chloroplast DNA variation in European

RL (2007) ComparisonRL (2007) ofwhole chloroplast 16

155 , 37-45. (Betulaceae) onAFLPbased markers. Taxon Acta Botanica Neerlandica

et al. Inference of population structure using 5 , 65-84. , 945-959. ne genealogies: trees grafting intonetworks. onsequences of cytoplasmic gene flow in

American Journal of Botany (2004) Late (2004) Quaternary sheet ice history

d conceals about modes of speciation inofspeciationd about modes conceals 15 54 , 1827-1840. , Austria. , http://www.R-project.org/. , 725-732.

156 , 5-26. . Edward Arnold, London,

45 American , 243-262.

94 , 275- Tree Tree Accepted Article Wang N,Wang BorrellJS, Bodles WJ HogersVos P, R, BleekerM ÆT,Thórsson Pálsson S, Lascoux M, Anamthawat-Jónsson K (2010) Introgression and KJ,Willis RudnerSumegiP (2000) E,The full-glacial forests of CentralSoutheastern and van Dinter M,H Birks(1996) Distinguishing fossil TG Tutin (1964) Truong C,PalmeAE,Felber FRecent (2007) ofinvasion the mountain birch Distribution H ofbor Tralau (1963) ÆT,Thórsson Salmela E, Anamthawat-Jónsson K (2001) Morphological, cytogenetic, and AM,DickThomson Dayanandan CW, S, Carine(2015) A M similar phylogeographical GiellyP,Taberlet L, Pautou G,Bouvet J This This article is protected by copyright.reserved. Allrights NJ in used matrices marker-frequency the tests, mantel for used matrices distance geographical originalmatrices, AFLPThe AFLPdata three the Accessibility Data fingerprinting. Norway. the vegetationalimplications historyfor oflate-glacial western fruits: wingless their Biogeography triploid hybrids in Iceland inferred from cpDNA haplotype variation. of phylogeography 339–350. thanintrogression by shared biogeographical history. of dwarf inof dwarf birch Britain. ecological studySweden.ecological innorthern pubescens 582. 404-408. in birch. hybridization introgressive evidence molecular for amongstructure sympatric NorthAmerican birches ( 1109. non-codingthree regionsof DNA. chloroplast of northern Eurasia. Europe. Europe. Quaternary Research Vegetation History and Archaeobotany Flora Europaea ssp.

37 Nucleic AcidsNucleicResearch tortuosa , 2098-2110. Betula nana Quaternary Science Reviews , et al. above the treelinetodue climate geneticchange: and , et al. , et Molecular EcologyMolecular Cambridge University Press, Cambridge. (1995) AFLP (1995) new- a technique DNAfor eal arcticand montane plants.

(2014) Molecular footprints of Holocenethe retreat 53 (diploid), , 203-213. (1991) Universal primers for amplification of matrixes used for the data presented the here, presented data matrixes usedfor the Journal of Evolutionary Biology

23 B. pubescens , 4407-4414. Betula nan

23 Plant Molecular Molecular Plant Biology , 2771-2782.

5

23 , 229-240. , 1229-1271. Betula Journal ofBiogeography a and a and (tetraploid) and their their and (tetraploid) Arkiv för Botanik för Arkiv ) is better explained by Journal ofHeredity B. pubescens Journal of Betula Betula

20

17 , 369-380. , 1105- using

5 , 533-

42

92 , , Accepted Article species. parental the of each to 0.5 as counted were these and Cc, and between hybrids Two indicated. denoted by lowercase letters; see Table S3, Supporting Information for details). details). for Information Supporting S3, Table see letters; lowercase by denoted and and B. nana B. Haplotype Aa Ab A variable of sites) Table 1. Tables writing. in andparticipated results the discussed funding, provided conceived theideas, Brochmann C. draft; on commented and results, the discussed sampling, and information ground back to contributed Alsos I.G. writing; the led and data the analysed work, thelab led sampling, to contributed idea, the developed Eidesen B. P. Author Contributions KR779658. data have depositedbeen GenBank in under accession nos. KR779549 - KR779606 and KR779607 - sequence and doi:10.5061/dryad.c3g80, Dryad in available are S3) (Table haplotypes generate to used alignments and analyses, STRUCTURE for matrices input populations, among analyses This This article is protected by copyright.reserved. Allrights B. B. B. michauxii B. glandulosa B. oa 1 0111111112 1 1 1 1 1 1 1 10 3 3 15 7 1 Total p p p cf. endula endula umila ubescens B. pendula B. minor Plastid DNA haplotypes observed in species of of species in observed haplotypes DNA Plastid

1 1 were not successfully analysed for for analysed successfully not were trn . . 2 1 6.5 1.5 9 7 1 1 1 1 1 1 1 3.5 1.5 1 1 3 5 S- trn G (variants denoted by uppercase letters) and and letters) uppercase by denoted (variants G f -B aC dE eG gG -H Ia Ha Ge GgGh G- Fe Ed Dd Cc Ca Be A- B. nana and B. pubescens trn Q- Betula rps were included, containing haplotype Ca haplotype containing were included, 16, but their 16, but based on combined sequences (18 (18 sequences combined on based trn trn Q- S- trn rps G variant are 16 (variants (variants 16 Betula michauxii

Accepted Article pDNAmarker systems. retrievedfromdifferent they are as areunknown, haplotypes among similarity the actual but studies, both in groups haplotype pubescens Fig. 5 charts (Maliouchenko charts Maliouchenko after redrawn previous studies, in identified groups haplotype plastid of distribution the show charts Pie 6). Fig. (cf. groups haplotype to according coding colour with Information), sequencing of the of the sequencing on based haplotypes plastid combined identify symbols Coloured variation. pDNA of distribution show d) c) and in charts pie and symbols Coloured phenotypes. AFLP multilocus of analyses pubescens B. Fig. 4 0.999). 0.016, 0.001), psuch < whileno trend was found in pubescens as modelled population and effect fixed a as slope Fig. 3 shown). markers in of polymorphic number the values for each population fitted by the mixed effects model given by Wang by model given effects mixed the by fitted population each for values represent diamonds Red individual. per values indicate circles Black phenotypes. AFLP multilocus pubescens for fit best species; in this were polymorphic that markers 115 and combinations fitfor (best complete basedonthe structure Fig. 2 et al. Svendsen and Dyke(2004) on based yr ago) 000 20 about (LGM, maximum glacial last the during (1986),Hultén &Fries Furlow (1997)andElven Fig. 1 Figure legends This This article is protected by copyright.reserved. Allrights (2004). (2004). Geographical distribution of intrapopulation genetic diversity in a) a) in diversity genetic intrapopulation of distribution Geographical Trend of admixture in relation to latitude a) from relationa) tolatitude in admixture of Trend a) Geographical distribution of distribution Geographical a) Geographical distribution of AFLP (a, b) and plastid DNA (c, d) variation in in variation d) (c, DNA plastid and b) (a, AFLP of distribution Geographical Genetic structure based on STRUCTURE analyses of multilocus AFLP phenotypes. a) Genetic Genetic a) phenotypes. AFLP multilocus of analyses on STRUCTURE based structure Genetic based on multilocus AFLP phenotypes generated with three primer combinations (D3; (D3; combinations primer three with generated phenotypes AFLP multilocus on based (a), levels of admixture significantly increase with latitude slope (n=303; 0.063, SE into K . Colours in a) and b) (cf. Fig. 2) identi 2) Fig. (cf. and b) a) in Colours . = 4). b) Genetic structure in in structure Genetic b) =4). et al. et B. nanaB. trn (2007). Resemblance of colours among haplotype groups presented pie in presented groups haplotype among colours of Resemblance (2007). S- et al. et , inferred from logit-transformed STRUCTURE admixture proportions of of proportions admixture STRUCTURE logit-transformed from inferred , trn G and , 2007) and our data indicate similar geographical distribution of distribution geographical similar indicate data andour 2007) , trn dataset with 901 withsamples dataset 901 of Q- Betula nana Betula rps B. pubescens B. 16 regions in this study (Table S3, Supporting Supporting S3, (Table study this in regions 16 B. nana B. et al. et , (528 samples based on three primer primer three on samplesbased (528 fy genetic groups inferred from STRUCTURE STRUCTURE from inferred groups fy genetic a random effect to allow for genetic drift. In In drift. genetic for allow to effect random a B. B. nana B. did not reveal any further substructure (not (not substructure any further reveal not did

(2011).. b) Approximate extent of glaciers of glaciers extent b)Approximate (2011).. glandulosa B. nana B. (n=531; slope (n=531; 0.018, SE 0.000, p = Betula into and B. pubescens B. scored for 104 AFLP104markers scored for B.

pubescens Betula nana Betula et al. et Betula nana Betula and b) and from K (2014), with with (2014), based on on based =5).Increasing and b) and B. B.

B. B. Accepted Article individuals.

and and regions, plastid oftwo sites) variable (18 combined sequences on based are Haplotypes branches. along indicated is haplotypes separating sites variable of Number data. missing pumila and and Fig. 6 Information). Supporting S2, Table This This article is protected by copyright.reserved. Allrights trn B. Plastid DNA haplotype network based on 47 samples mainly representing representing mainly samples on 47 based network haplotype DNA Plastid

pubescens pubescens and and Q- rps B 16 (Table S3, Supporting Information). Circle size is proportional to number of of number to proportional is size Circle Information). Supporting S3, (Table 16 . cf. minor (BP), but also North American reference individuals of of individuals reference American North also but (BP), . HaplotypeGh found in B . cf. minor was omitted from the network due to to due network the from omitted was B.

glandulosa glandulosa Betula (BG), (BG),

nana trn S- B. (BN) (BN) trn

G

Accepted Article

This This article is protected by copyright.reserved. Allrights

Accepted Article This This article is protected by copyright.reserved. Allrights

Accepted Article This This article is protected by copyright.reserved. Allrights

View publication stats Accepted Article This This article is protected by copyright.reserved. Allrights