The role of forest genetic resources in responding to biotic and abiotic factors in the context of anthropogenic climate change

The current distribution of forest genetic resources on Earth is the result of a combination of natural processes and human actions. Over time, tree populations have become adapted to their habitats including the local ecological disturbances they face. As the planet enters a phase of human-induced climate change of unprecedented speed and magnitude, however, previously locally-adapted populations are rendered less suitable for new conditions, and ‘natural’ biotic and abiotic disturbances are taken outside their historic distribution, frequency and intensity ranges. Tree populations rely on phenotypic plasticity to survive in extant locations, on genetic adaptation to modify their local phenotypic optimum or on migration to new suitable environmental conditions. The rate of required change, however, may outpace the ability to respond, and tree species and populations may become locally extinct after specific, but as yet unknown and unquantified, tipping points are reached. Here, we review the importance of forest genetic resources as a source of evolutionary potential for adaptation to changes in climate and other ecological factors. We particularly consider climate-related responses in the context of linkages to disturbances such as pests, diseases and fire, and associated feedback loops. The importance of management strategies to conserve evolutionary potential is emphasised and recommendations for policy-makers are provided

Criteria and indicators for sustainability forest management: assessment and monitoring of genetic variation

The paper contains proposals for genetic criteria and indicators wich can form part of a more general set of, economic, environmental and social criteria and indicators for the monitoring of forest sustainability at the scale of forest management units. It proposes one criterion for conservation of forest genetic resources and four indicators related to processes that maintain genetic diversity. For each indicator, sets of verifiers are suggested which differ in the biologically relevant features they measure, in their precision, and in technical facilities they require. Finally, the need for rapid assessment and precision under difficult conditions requires research and development of efficient direct surrogate measures of the genetic resource. We therefore include recommendations for short- and medium term research that would improve the scientific value, cost effectiveness, ease of use, and further development of genetic criteria and indicators

Pedigree and mating system analyses in a western larch (Larix occidentalis Nutt.) experimental population

$\bullet$The mating pattern and gene flow in a western larch (Larix occidentalis Nutt.) experimental population was studied with the aid of microsatellite markers and a combination of paternity-mating system analysis. The commonly difficult to assess, male gametic contribution was determined with 95% confidence and its impact on genetic gain and diversity was determined. $\bullet$ Male fertility success rate ranged between 0 and 11%. Male reproductive output parental imbalance was observed with 50% of the pollen being produced by the top 5% of males while the lower 39% males only produced 10% of the pollen. $\bullet$ A significant difference was observed between male effective population size (genetic diversity) estimates from paternity assignment compared to those based on population's census number (21 vs. 41); however, this difference did not affect estimates of genetic gain. $\bullet$ A total of 221 full-fib families were identified (sample size range: 1–8) and were nested among the studied 14 seed-donors. $\bullet$ A combination of paternity-mating system analysis is recommended to provide a better insight into seed orchards' mating dynamics. While pollen flow tends to inflate mating system's outcrossing rate, the paternity analysis effectively determined the rate and magnitude of contamination across receptive females.Analyse de paternité et du mode de croisement dans une population expérimentale de mélèze occidental (Larix occidentalis Nutt.). $\bullet$ Les modes de croisement et les flux de gènes dans une population expérimentale de mélèze occidental (Larix occidentalis Nutt.) ont été étudiés à l'aide de marqueurs microsatellites et d'une analyse combinée de paternité et du système de reproduction. La contribution gamétique mâle – communément difficile à estimer – a été déterminée avec un seuil de confiance de 95 % et son impact sur le gain génétique et la diversité a été déterminé. $\bullet$ Le taux de succès reproductif mâle était compris entre 0 et 11 %. Un déséquilibre dans la contribution des parents mâles a été observé avec la production de 50 % du pollen par 5 % des pères alors que 39 % d'entre eux ne contribuaient que pour seulement 10 % du pollen. $\bullet$ Une différence significative a été observée entre la taille efficace de la population mâle (diversité génétique) estimée par la recherche de paternité et celle basée sur les effectifs recensés de la population (21 vs. 41) ; cependant, cette différence n'affecte pas l'estimation du gain génétique. $\bullet$ 221 familles de plein-frères ont été identifiées (effectifs entre 1 et 8), regroupées parmi les 14 arbres-mères étudiés. $\bullet$ La combinaison d'une analyse de paternité et du système de reproduction est recommandée pour étudier de manière approfondie la dynamique de croisement en vergers à graines. Tandis que les flux de pollen tendent à augmenter le taux d'inter-croisements, l'analyse de paternité détermine de manière effective le taux et l'amplitude de contamination des arbres-mères