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ERC

TREEPEACE Report Summary

Project ID: 339728
Funded under: FP7-IDEAS-ERC
Country: France

Mid-Term Report Summary - TREEPEACE (From Holocene to Anthropocene: the pace of microevolution in trees)

Treepeace aims at assessing evolutionary changes in European oaks as a result of past environmental changes at two different time frames (holocene and anthropocene). The project explores different experimental settings in ancient and extant oak landscapes that are suitable for detecting evolutionary changes in time and space. Whenever technically feasible changes are tracked at both genomic and phenotypic levels. Treepeace is based on the rationale that the very high level of genetic diversity of oak species enhances evolutionary potential.
We experimentally demonstrated that authentic ancient oak DNA can be extracted from subfossil and archaeological wood remains, and that chloroplast DNA is rather abundant and can be sequenced, while the recovery rate of nuclear DNA is lower and sequencing will require more efforts. During our search for woody remains with the help of archaeologists, we discovered an enormous “hidden” resource that will ultimately allow to study entire ancient oak populations just as we study modern populations. This resource consists of pile dwellings recently classified as Unesco World Heritage, enabling also the observation of wood anatomical features. Thousands are present in many central European lakes.
In parallel, by comparing extant oak populations stemming from different present climates, we found genomic footprints of population divergence, some of which can be assigned to natural selection induced by temperature gradients. These footprints are currently cataloged on a genome wide basis and will be compared to changes of adaptive traits of the same populations. Ultimately, the molecular hot spots of divergence between extant populations of different climates will be explored in later comparisons of ancient and modern DNA.
On a much shorter time span, we investigated whether the “natural” warming following the little ice age in Europe has triggered evolutionary changes. To do so, we took advantage of the existence of oak stands that were born under the little ice age (more than 350 years ago). With the help of the French Forest Service, we identified three forests where ancient oak stands were still present and we installed a common garden experiment where progenies of four age structured cohorts (360 years, 180 years, 50 years and 10 years) are compared at the phenotypic and genomic levels. Our first results show that progenies of old oak populations flush later than progenies of younger oak populations suggesting recent evolution.
We performed a similar analysis by comparing populations artificially transplanted three centuries ago in Europe with their source populations. Here the spatial transfer mimics the temporal climatic changes. These investigations were conducted in Quercus rubra, a species native of North America, that has been widely introduced in Europe. Our results show significant divergence between both gene pools for growth, phenology and reproduction, again suggesting adaptive evolution over few generations.
Our last contribution is at the theoretical level. We use analytical models derived from quantitative genetics assumptions to make predictions about evolutionary change. Such predictions are nowadays feasible thanks to the possibility of deep genotyping that allows to reconstruct genetic relatedness between trees in natura. So far, we have estimated reproductive success and selection gradients after genotyping 2,500 saplings in a natural oak stand. These results will be complemented by heritability estimates next year, which are necessary for the prediction of evolutionary change. Finally theoretical investigations include the development of a simulation platform where major evolutionary processes are implemented to monitor in silico genetic changes under different climatic scenario. During the first two years, we have developed and upgraded the platform by introducing new functionalities that are needed for the focus of Treepeace.

Contact

Fabienne SCHNEIDER, (External partnership department)
Tel.: +33 557122688
E-mail
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