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Different angles to trees in a changing climate

Datum: 2014.02.03

Text: Tor Myking and Kjersti Bakkebø Fjellstad/NordGen Forest

Mari Mette Tollefsrud, Yousry El-Kassaby, Outi Savolainen and Antoine Kremer all highlighted different aspects of adaptation in a changing climate at the Lillehammer conference. Photo: Kjersti Bakkebø Fjellstad/NordGen Forest

The conference Genetic resources for food and agriculture in a changing climate at Lillehammer on 27-29 January, organised by NordGen, included three keynote presentations specifically on forest trees.

Antoine Kremer (INRA, France) commenced with a presentation on adaptability and evolutionary history of forest trees and highlighted the fact that several tree species became extinct in Europe during the numerous glaciation – warming cycles over the last 2 million years. Using oaks as a study case, Kremer commented that rapid migration, extensive gene flow and hybridisation were crucial for tracking climatic warming. Simulations have shown that spread of acorns by jays and long-distance dispersal events together can maintain a very high migration level of about 400 m per year.

Kremer continued by explaining that hybridisation between related oak species (e.g. Quercus petrea x Q. robur) is another way in which genes can hitchhike to more preferable climates. In addition to spread, adaptation to local climates is decisive. One important component is assortative mating, trees flowering at the same time tend to mate and produce offspring with phenology similar to their parents. Trees located at the timberline will in this manner be modestly influenced by pollen of trees located at the valley bottom. This contributes to maintain clinal variation in e.g. budburst and bud-set along environmental gradients.

The glacial history and genetic structure was also an important point in Mari Mette Tollefsrud’s (Norwegian Forest and Landscape Institute) presentation, confined to Norway spruce and Siberian spruce, two closely related species with wide and overlapping distributions. By means of different molecular data she showed that the overlapping distribution zone, running north-south along the Ob River in Siberia, is rather narrow and suggests independent glacial histories. Norway spruce consists of a northern (Scandinavia, Russia, Belarus, Baltic states) and southern distribution (Central Europe), and the separation for several thousand generations has left a clear genetic signatures. The southern domain was further split in three refugia during the last glaciation, whereas the northern domain consists essentially of one large group. Interestingly, there is a mitochondrial haplotype endemic to Scandinavia, which is also found in lake sediments in Trøndelag, mid-Norway, suggesting a glacial refugium for Norway spruce on the coast of Norway. This is really surprising considering the general view on glacial history of Norway spruce!

The following presentation on forest tree breeding in face of climate change by Yousry El-Kassaby (UBC, Canada) was challenging. Traditional tree breeding programmes are long-term and very resource dependent. The programs are designed to meet the planting demands of the breeding zones, and climate adaptation can take place by south to north movement of plants within the breeding zone. However, this method is limited by the breeding zones. Could there be other options? El-Kassaby suggests an in situ breeding method to take advantage of the present populations’ verifiable ability to cope with harsh climates, and to avoid changing photoperiodic regimes associated with latitudinal translocation. Genetic evaluation of individuals could be based on DNA markers distributed throughout the genome, combined with quantitative genetic approaches. The question is whether such in situ selection would be lagging behind the climatic changes, and the presentation initiated a discussion about El-Kassaby’s approach versus active use of southern plant material, assumed to be adapted to the future climate.

Means of local adaptation was the essence of the presentation given by Outi Savolainen (Univ of Oulu, Finland). Proper synchronisation of flowering, budburst and budset with the climate is of utmost importance for vitality, reproduction and survival, also for trees. Identifying loci related to such adaptive traits is an important research task, and may be approached in various ways. Savolainen showed a number of examples, particularly connected to Arabidopsis. Because of a small genome and short generation time Arabidopsis is an important model species.

123 participants from four continents and 19 countries attained the conference at Lillehammer, which really succeeded to highlight the challenges of genetic resources in agriculture and forestry in the face of climate change.