Infodoc : Sciences, Techniques et Culture

Recolonization of Europe by forest tree species after the last glaciation is well documented in the fossil pollen recor. This spread may have been achieved at low densities by rare events of long-distance dispersal, rather than by a compact wawe of advance, generating a patchy genetic structure through founder effects. In long-lived oak species, this structure could still be discernible by using maternally transmitted genetic markers. To test this hypothesis, a finescale study chloroplast DNA (cpDNA) variability of two sympatric oak speices was carried out in western France. The distributions of six cpDNA length variants were analyzed at 188 localities over a 200 x 300 km area. A cpDNA map was obtained by applying geostatistics methods to the complete data set. Patches of several hu[...]

Recolonization of Europe by forest tree species after the last glaciation is well documented in the fossil pollen recor. This spread may have been achieved at low densities by rare events of long-distance dispersal, rather than by a compact wawe of advance, generating a patchy genetic structure through founder effects. In long-lived oak species, this structure could still be discernible by using maternally transmitted genetic markers. To test this hypothesis, a finescale study chloroplast DNA (cpDNA) variability of two sympatric oak speices was carried out in western France. The distributions of six cpDNA length variants were analyzed at 188 localities over a 200 x 300 km area. A cpDNA map was obtained by applying geostatistics methods to the complete data set. Patches of several hundred square kilometers exist which are virtually fixed for a single haplotype for both oak species. This local systematic interspecific sharing of the maternal genome strongly suggests that long-distance seed dispersal events followed by interspecific exchanges were involved at the time of colonization, about 10.000 years ago.