Natural selection and climate change: Temperature-linked spatial and temporal trends in gene frequency in Fagus sylvatica

Jump A.S., Hunt J.M., Martínez-Izquierdo J.A., Peñuelas J. (2006) Natural selection and climate change: Temperature-linked spatial and temporal trends in gene frequency in Fagus sylvatica. Molecular Ecology. 15: 3469-3480.
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Doi: 10.1111/j.1365-294X.2006.03027.x

Resum:

Rapid increases in global temperature are likely to impose strong directional selection on many plant populations, which must therefore adapt if they are to survive. Within populations, microgeographic genetic differentiation of individuals with respect to climate suggests that some populations may adapt to changing temperatures in the short-term through rapid changes in gene frequency. We used a genome scan to identify temperature-related adaptive differentiation of individuals of the tree species Fagus sylvatica. By combining molecular marker and dendrochronological data we assessed spatial and temporal variation in gene frequency at the locus identified as being under selection. We show that gene frequency at this locus varies predictably with temperature. The probability of the presence of the dominant marker allele shows a declining trend over the latter half of the 20th century, in parallel with rising temperatures in the region. Our results show that F. sylvatica populations may show some capacity for an in situ adaptive response to climate change. However as reported ongoing distributional changes demonstrate, this response is not enough to allow all populations of this species to persist in all of their current locations. © 2006 The Authors.

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Rapid climate change-related growth decline at the southern range edge of Fagus sylvatica

Jump A.S., Hunt J.M., Pen̈uelas J. (2006) Rapid climate change-related growth decline at the southern range edge of Fagus sylvatica. Global Change Biology. 12: 2163-2174.
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Doi: 10.1111/j.1365-2486.2006.01250.x

Resum:

Studies on Fagus sylvatica show that growth in populations toward the southern limit of this species' distribution is limited strongly by drought. Warming temperatures in the Mediterranean region are expected to exacerbate drought where they are not accompanied by increases in precipitation. We studied levels of annual growth in mature F. sylvatica trees over the last half-century in the Montseny Mountains in Catalonia (northeast Spain). Our results show significantly lower growth of mature trees at the lower limit of this species' distribution when compared with trees at higher altitudes. Growth at the lower Fagus limit is characterized by a rapid recent decline starting in approximately 1975. By 2003, growth of mature trees had fallen by 49% when compared with predecline levels. This is not an age-related phenomenon, nor is it seen in comparable populations at higher altitudes. Analysis of climate-growth relationships suggests that the observed decline in growth is a result of warming temperatures and that, as precipitation in the region has not increased, precipitation is now insufficient to ameliorate the negative effects of increased temperatures on tree growth. As the climate-response of the studied forest is comparable with that of F. sylvatica forests in other southern European regions, it is possible that this growth decline is a more widespread phenomenon. Warming temperatures may lead to a rapid decline in the growth of range-edge populations and a consequent retreat of the species distribution in southern Europe. Assessment of long-term growth trends across the southern range edge of F. sylvatica therefore merits further attention. © 2006 Blackwell Publishing Ltd.

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