Supplementary online material
A new scenario for the Quaternary history of European beech populations:
palaeobotanical evidence and genetic consequences
D. Magri, G.G. Vendramin, B. Comps, I. Dupanloup, Th. Geburek, D. Gömöry, M. Latałowa,
Th. Litt, L. Paule, J.M. Roure, I. Tantau, W.O.van der Knaap, R.J.Petit and J.-L. de Beaulieu
Item S1
State-of-the-art of the postglacial history of beech in Europe
As a result of a long tradition of palynological studies in Europe, a considerable
number of pollen diagrams documenting the postglacial history of beech have been gathered.
In recent times, particular efforts have been made to improve the quality and the
chronological control of the diagrams, so that for most of Europe a rather satisfactory
reconstruction of the postglacial expansion of beech populations can be outlined. However,
there is still the need for more complete information for times older than the Holocene,
particularly for the last glacial period, known by a relatively small number of continuous
pollen records, in spite of the importance of detecting the existence, location and duration of
refugia for temperate trees. In this context, the study of plant macrofossils is of special value,
as it can enhance the information in regions where trees are very sparse, providing detailed
and unequivocal records of the local arboreal vegetation during the last glacial (Jackson et al.
1997; Birks & Birks, 2000; Willis et al., 2000).
Following the ever-increasing number of fossil data, several regional reviews of the
postglacial spread of European beech have been published over the years, including the
reconstructions by Birks (1989) for the British Isles, Björkman (1997) for southwestern
Sweden, Ralska-Jasiewiczowa (1983) and Latałowa et al., (2004) for Poland, Ralska-
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Jasiewiczowa et al., (2003) for northern lowlands of central Europe, Rybníčková and
Rybníček (1988) for the former Czechoslovakia, de Beaulieu et al., (1994) for the French
Alps and the Jura, van der Knaap et al., (2005) for the Alps, Schneider (1978) for the southern
border of the Alps, Magri (1998) for the Italian peninsula, Ramil-Rego et al., (2000) for the
NW Iberian peninsula, and Filipova-Marinova (1995) for Bulgaria.
A few surveys have also been published at the European scale, mainly aimed to
reconstruct the location of the glacial refugia for beech and its postglacial colonization routes.
Huntley and Birks (1983) locate the main areas of glacial refuge on the mountains of former
Yugoslavia and Bulgaria, Italy and the southern Carpathians, without excluding the
possibility of southern France. During the early Holocene beech would have expanded
principally along the main European mountain chains, although it was missing in the southern
Alps and southern Balkans. Huntley (1988) distinguishes three main features in the
postglacial history of European beech: a relatively slow initial expansion during the early
Holocene, starting from the Dinaric Alps and the southern Carpathians, an expansion only in
the Alpine region of central and eastern Europe during the mid-Holocene, and a late-Holocene
expansion into and across both lowland northern Europe and western Europe. Lang (1992,
1994) advances the hypothesis that Fagus followed two main paths of invasion: an eastern
route from the western Balkan peninsula to the eastern Alps, the Carpathians, northern
Germany, Poland and southern Sweden, and a western route from Italy to the western Alps,
France and southern England. According to Pott (1997, 2000) Fagus sylvatica spread from
various Pleistocene refugia in the Mediterranean region northward to its present-day range of
distribution in northern and central Europe following at least two different routes: an easterly
route from the Balkan peninsula through the Dinaric Alps to the eastern Alps, the Danube
valley and the Bohemian central highlands to the northern German and Polish lowlands and
then over the Baltic Sea to southern Sweden, and a western route from southern Apennines to
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western Alps and a separate branch from northern Portugal and Galicia into the Pyrenees, the
French Massif Central, northward to southern England. Brewer (2002) identifies two areas
where Fagus survived during the glacial maximum: southern Italy and southwestern Balkans.
While the Italian populations would have expanded slowly towards the Alps, the Balkan
populations would have spread rapidly northward through Germany and Poland towards
Scandinavia and westward into France, Spain and England.
In addition to these papers describing the timing and the mode of the postglacial
spread of Fagus populations across Europe, many papers presenting pollen analytical data
from sites with early immigration of beech discuss the question of the location of its glacial
refugia. Important contributions in this sense have been recently published from the Pirin
Mountains in Bulgaria (Tonkov, 2003), Romania (Bodnariuc et al., 2002; Björkman et al.,
2003; Tantau et al., 2003), the Czech Republic (Svobodová et al., 2001), NW Spain (GómezOrellana Rodríguez, 2002), the Central Mountain Range of the Iberian peninsula (Franco
Múgica et al., 2001), and Sicily (Sadori & Narcisi, 2001). While the reconstructions of beech
at a European scale (Huntley & Birks, 1983; Lang, 1994; Pott, 1997; Brewer, 2002) generally
support the idea that Italian and Balkan peninsulas were the main refuge areas for Fagus
sylvatica during the glacial period, as happened to most trees which today extend to northern
Europe (Bennett et al., 1991), these data from sites with early immigration of beech provide a
more diversified picture which needs to be explored in detail.
A further matter of discussion concerning the past distribution of beech has been the
primary factor controlling its Holocene migration patterns. According to Huntley et al.
(1989) the spread of beech would be related to changes in climatic conditions, which became
cooler and wetter in the second half of the Holocene. Several papers provide abundant
evidence for rapid migration capacity, climatic control and pacing of the migrations of beech
and other tree taxa also in eastern North America (e.g. Woods & Davis, 1989; Prentice et al.,
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1991; Jackson & Booth, 2002). Another possible explanation for the European beech
expansion could be a response to farming and other human activities, which may have
significantly contributed in opening the natural forest vegetation established at the beginning
of the postglacial, hence favouring colonization by beech (Andersen, 1984; Aaby, 1986;
Latałowa, 1992; Reille & Andrieu, 1994; Björkman, 1997; Küster, 1997). Gardner and Willis
(1999) suggest that other ecological factors may have been important in determining the
expansion of beech from the refuge areas into central Europe. Under this view, the expansion
would be an entirely natural phenomenon, whose timing, often coincident with anthropogenic
interference, would be the result of slow migration and establishment rates, typical of the
internal dynamics of beech forests. As shown for the Holocene spread of F. grandifolia across
North America (Bennett, 1988), low intrinsic rates of population increase coupled with slow
rates of spread and long distance from refugia, could explain the late arrival of beech in
central-northern Europe.
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