A GENETIC-STUDY OF FAGUS-SYLVATICA L VAR TORTUOSA PEPIN

A form of the European beech (Fagus sylvatica L) was described as 'Tor tillard' (var tortuosa Pepin) by Pepin (1861). We have named this form 'winding beech'. It exists at present in 3 European stands: in Verzy, near Reims (France, 49 degrees 14'N, 3 degrees 59'E, alt 288 m); in t he Suntel mountains, near Hanover (Germany, 52 degrees 12'N, 9 degrees 17' E, alt 170-250 m); and in Dalby-Soderskogs in southern Sweden (55 degrees 38'N, 13 degrees 19'E). These stands are located within the o ptimal European range of the beech (fig 1). In each stand, common beec h (F sylvatica L) and winding beech (F sylvatica L vartortuosa Pepin) coexist and, in spite of gene exchanges (surely limited) they keep the ir respective morphological characters and can be considered as 2 'sub populations: A genetic analysis of the 6 subpopulations was carried ou t using 12 polymorphic alloenzymatic markers. We also analysed: (i) in dividuals from populations of other beech species, using the same mark ers; and (ii) individuals from common beech populations located in the 3 regions where winding beeches are found. Interstand and intrastand allelic frequencies were compared. We also carried out: (i) a hierarch ical analysis including the 6 subpopulations, using Nei's genetic dist ances; and (ii) a discriminant analysis including the 6 subpopulations and the other sampled beech stands. We then compared (i) the heterozy gote numbers of the 2 subpopulations within each stand, at each locus and for all loci together; and (ii) the homozygote and heterozygote di stribution at 1, 2, 3,... 8 loci. Multilocus F(i)s values were also co mputed. All alloenzymes observed in common beech are present in windin g beech, whereas some were not observed in other beech species (table I). Moreover, in these other species new alloenzymes appear. Thus it i s possible to suppose that both forms of the European beech still have a common evolutive history and that their separation is rather recent and even incomplete. The comparison between the allelic frequencies o f the 2 subpopulations within each stand shows a very small number of significant deviations (table II). On the other hand, the interstand c omparison between winding beech subpopulations or between common beech subpopulations shows that most deviations are significant (table II). This result is confirmed by the dendrogram built from Nei's genetic d istances (fig 2). The discriminant analysis divides the 6 subpopulatio ns and the beech stands sampled within the 3 regions into 3 groups acc ording to their geographical location (fig 3). There is no difference of F(i)s values between the 2 subpopulations within each stand (fable III). The heterozygote number at each locus (table IV) and the distrib ution of homozygotes (0) and heterozygotes at 1,2,3... 8 loci (table V ) differ very little from one subpopulation to the other within each s tand. From all these results we can discuss some previous hypotheses: (i) a geographical common origin of both beech forms and material tran sports from one stand to another (ii) the preponderance of vegetative reproduction in winding beech; (iii) the degeneration of winding beech es caused by endogamy, genetic drift and vegetative reproduction; and (iv) a wider and more continual former geographical area. This study q uestions the transport of material from I station to another and the d egeneration of the winding beech and minimizes the influence of vegeta tive reproduction (table VI,, fig 4). it also leads to a discussion on the origin of the winding beech; our results do not provide enough ar guments in favour of either a wider former geographical area or a mult iple origin.