Implementing the dynamic conservation of elm genetic resources in Europe: case studies and perspectives

Many European countries have undertaken the static preservation of native elm genotypes in clone collections maintained ex situ. Less development has been devoted to the dynamic conservation of elm populations in situ. Case studies of elm conservation in France are given here as an illustration of methods employed at country level. We also briefly review the process used by the European Forest Genetic Resources Programme (EUFORGEN) to monitor elm dynamic conservation in a pan-European perspective. Dynamic conservation methods were promoted by EUFORGEN through leaflets, strategies, Technical Guidelines and the geo-referenced database EUFGIS on Dynamic Conservation Units (DCUs). Because the network of DCUs needs to be representative of the partitioning of adaptive diversity across the species distribution range, a GIS-aided approach has been developed to position DCUs in environmental zones and identify conservation gaps. The two DCUs of European white elm (Ulmus laevis Pall.) selected in riparian forests of two different climatic zones of France show that management oriented toward habitat protection is compatible with dynamic conservation, and that the species can still be conserved in situ in spite of Dutch Elm Disease (DED). Collaboration with habitat conservationists enabled the monitoring of losses to DED and the assessment of within-population diversity for flowering phenology. Collaboration with forest geneticists revealed that the diversity of the Garonne population was low, but that it contained rare DNA variants and adaptive traits. Since 1987, experimental restoration of countryside hedges has been carried out, using field elm clones (Ulmus minor Mill.) selected from the French national collection and tested for lower susceptibility to the agent of DED in artificial inoculation tests. Such plantations can be viewed as a very dynamic form of conservation if they permit the local gene pool to be reinforced with trees able to reach sexual maturity and exchange pollen with elms in the neighborhood, hence contributing new genotypes that will be submitted to natural selection and provide fuel for ongoing adaptation processes. Initiatives assembling a large consortium of stakeholders, including habitat conservationists and hedge re-constructors, are needed to trigger new conservation projects.