Pedunculate oak (Quercus robur L.) is one of the economically most valuable European forest tree species. It is the keystone climax species of forests which harbour high biodiversity and consequently has priceless ecological and social value. Survival of the specie’s populations in southern and southeastern Europe is endangered by predicted climate extremes such as prolonged drought. These populations are the “rear edge” of the species distribution range and their phenotypic response and adaptive capacity to climate change have not been well studied. Suggested spatial variability of climate change impacts in Europe implies that widespread species like pedunculate oak may face different levels of climatic risks in different parts of their ranges. Consequently, peripheral populations at southern range margins may face an increased risk of extinction and decrease of the overall within-species genetic diversity which may in return jeopardize the long-term adaptive potential and survival of the species in whole. Thus, the response of species to changing environments is likely to be largely determined by population responses at range margins. In contrast to the expanding edge, the low-latitude (rear) edge of species distribution remains understudied, and the critical importance of rear edge populations as long-term stores of species’ unique genetic diversity and foci of speciation has been little acknowledged.
Our research will be carried out on progenies and plant samples derived from the nine European populations sampled along a latitudinal environmental gradient. The focus of the research will be placed on populations from the southern and southeastern part of the specie’s distribution range (Croatia and Italy). We aim to compare adaptability, epigenetic and phenotypic responses to drought stress of southernmost populations with the populations from the central and northern part of the specie’s distribution range.
The main scientific objectives of the proposed project are to determine: 1) neutral genetic diversity and structure of selected pedunculate oak populations along a latitudinal gradient; 2) their epigenetic diversity and structure; 3) their epigenetic response to long-term drought stress; 4) their physiological, phenological, morphological, biochemical and growth (i.e. phenotypic) response to drought stress; 5) their adaptive genetic variability, differentiation and phenotypic plasticity; 6) current ecological niche preferences and main environmental variables driving its distribution 7) its future distribution under climate change scenarios based on ecological niche modelling and which parts of the contemporary distribution will suffer from decreased habitat suitability induced by climate change; 8) levels of adaptability of the studied populations by comparing their genetic and epigenetic variability and phenotypic plasticity.
Results of the proposed interdisciplinary project would put insights into current adaptive capacity of Q. robur populations from the wider latitudinal gradient to grow under different environments and drought stress regimes and their phenotypic, genetic, and epigenetic response after exposure to experimentally altered environmental conditions (i. e. drought stress).
Results would also enable identification of inherent genetic/epigenetic variation and phenotypic plasticity within and among natural populations across environmental gradient, interrelations between genetic, epigenetic, phenotypic and environmental variation and local adaptedness of the sampled populations. Moreover, as one of the main aspects of active adaptation to climate change, results would enable identification of the source populations best suited and adaptive to less favourable growth conditions and more frequent climatic extremes – particularly long term drought stress (i.e. higher genetic/phenotypic and epigenetic variation should enhance stress hardiness of populations). Such populations may provide genetic material for long term survival and growth of Quercus robur in an uncertain future.
Evaluation of the rear edge (i.e. low latitude) populations performance and viability under stress is of outmost importance for successful conservation of intra- and interspecific biodiversity under anticipated global change. The project results would enable to identify populations with particular conservation value (considering their unique alleles, amount of genetic diversity and phenotypic plasticity, genetic differentiation as well as considering habitats which may become unfavourable in the future) and to provide guidelines for the movement of the pedunculate oak reproductive material.