National Research Council of Italy

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IBBR publication #760

Forests at the limit: evolutionary genetic consequences of environmental changes at the receding (xeric) edge of distribution. Report from a research workshop

Mátýas C, Vendramin GG, Fady B

Annals of Forest Science 66 (8): 800-800. (2009)
doi: 10.1051/forest/2009081
URL: http://www.springerlink.com/content/dm832440x074v048/fulltext.pdf

In view of expected climatic changes, the adaptive potential of forest ecosystems and the future risks of diversity loss and extinction have received much attention. The behaviour of a species or of a population under changing conditions depends on its adaptive potential (genetic diversity, persistence, plasticity). In ecology, judging of adaptability is based on the concept that the presence of a species (its distribution pattern) depends - among other factors - on the limits of its physiological tolerance to climatic effects. This concept has to be extended, however, by the assertion that physiological tolerance is unquestionably determined by genetics. Limits of tolerance are therefore genetically set and will determine the presence or absence of a given species in a given environment. Thus, adaptive responses to environmental stress are to a large extent governed by genetic diversity, especially at the limits of distribution where strong shifts are expected. Publications on shifts of vegetation triggered by climate change in the temperate belt are abundant. However, studies and analyses deal mostly with the shift of the "upper" or "front" thermal limits of distribution. Migration at the front or forward colonisation is the most visible and illustrative response to climate change. On the other hand, the retreat at the rear and xeric limit is insufficiently studied in spite of its ecological importance. Xeric species-margins may be defined as low altitude and low latitude limits of species distribution along a moisture balance gradient. In the northern hemisphere, xeric distribution limits of forests and forest tree species extend across the woodland ecotones of the Mediterranean, Southeast Europe, South Siberia and North America. The forest cover in these densely populated regions bears high ecological and social values; it is therefore an imperative to evaluate how available knowledge could help mitigate effects triggered by rapidly changing climate. At the xeric limit, selection pressure may narrow genetic variation and the increase in frequency of extreme events may result in growth decline and mortality. What makes the problem of climatic selection at the xeric margin so special? Patterns and processes there are fuzzy, more difficult to follow than at the front limits. Human effects are omnipresent and ecological as well as socioeconomic consequences serious. Additional efforts are necessary to properly understand the heritable component of ecosystem responses to change, to mobilise the relevant research communities, and to make results understandable for stakeholders. With the support of the European Network of Excellence "EVOLTREE", a research workshop was organised in Sopron (Hungary) by Prof. Csaba Mátyás (University of West Hungary) to provide a forum for discussions and the emergence of new concepts. The aim of the meeting was to present the state of knowledge and to identify future research needs with the objective of providing means to mitigate the effects of climatic selection pressure at the receding edge of forest tree species distribution. The intention of the organizer was to broaden both the geographic and disciplinary scopes of the topic to a global scale so as to raise awareness on the issue of receding, xeric limits of forests. The meeting was held in Sopron because it is located at the receding (xeric) edge of closed-canopy stand-forming temperate European forests. Discussions covered three thematic areas: 1. Ecological, demographic and evolutionary perspectives of marginal and receding edge populations; 2. Genetic implications of extreme selection events: genomics of adaptation, genetic background of tolerance and plasticity; 3. Experiences from field trials, tasks for human intervention and research gaps at the receding edge of ranges

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