Chloroplast DNA haplotype variation and population differentiation in Sorbus aucuparia L. (Rosaceae : Maloideae)

Intra-specific chloroplast DNA (cpDNA) variation was studied in Sorbus aucu paria L., an entomophilous, mid-or early successional tree producing fleshy fruits. Eight PCR-amplified fragments of the chloroplast genome were scree ned for restriction fragment length polymorphisms, using one or two 4 bp-cu tter restriction endonucleases. cpDNA variation was investigated on two geo graphical scales: (1) among four regions in France and Belgium; and (2) wit hin the Belgian region. A total of 150 individuals from six populations wer e analysed. Fourteen polymorphisms were detected in six of the cpDNA fragme nts. All polymorphisms probably resulted from insertions or deletions, and allowed the identification of 12 haplotypes. The level of genetic different iation computed on the basis of haplotype frequencies was similar on the tw o geographical scales considered (G(STc) = 0.286 among regions, G(STc) = 0. 259 among populations within the Belgian region). These values are much low er than those obtained in nine previously studied temperate tree species, w hich are all wind-pollinated, late-successional species producing dry fruit s. These results might primarily be accounted for by the contrasting life h istory traits of S. aucuparia. In order to obtain insights into the relativ e contribution of pollen and seeds to gene flow G(STc) was also compared wi th previously obtained G(ST) estimates based on allozyme data.