Résumé des résultats (Abstract)
(Anglais)
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Problem to be solved When and how did forest trees have come to occupy their present range in Europe, after the last ice-age, when re-immigrating from their refugia? And what have been the consequences of these huge population movements on their levels of genetic diversity and their potential to cope to new climatic challenges? Since several decades, paleobotanists have attempted to understand the origin and migrations of our forest trees, using mostly fossil pollen remains. However, it is not always possible to distinguish the pollen of related tree species, and most of the migration routes inferred from these records remain hypothetical. Recently, the development of DNA techniques has shed new light on the re-immigration of trees. So far, these studies have been based on the sampling of existing tree populations only. But more direct historical evidence could be provided by molecular investigations of ancient tree remains excavated by the paleobotanists, provided that appropriate laboratory methods could be developed. Scientific objectives and approaches FOSSILVA aims at improving our understanding of the origin of the major European tree species. It associates geneticists and palaeoecologists in order to confront both approaches and to develop a new one, the palaeogenetic exploration of tree remains. Different types of plant remains (such as wood, macrofossils, pollen) are being tested for their ability to yield DNA suitable for genetic investigations. Fossil samples are studied in parallel with DNA isolated from living trees, to identify the relationships between modern tree populations and their putative ancestors, and check for possible human disturbances. The study area of the project is restricted to south western and western Europe, and focuses on six tree species. These include two broad-leaved species (beech and oaks) and four conifers (two species of pines, fir and spruce). These trees were selected for several reasons: their present day genetic diversity has already been explored, hypotheses on their history exist but need to be validated, and they are of major economical and ecological importance.
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