Drought-adaptation potential in Fagus sylvatica: linking moisture availability with genetic diversity and dendrochronology.

Han Y H Chen,Andrea R Pluess,Pascale Weber

doi:10.1371/journal.pone.0033636

Han Y H Chen, Andrea R Pluess + Show 1 more

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https://doi.org/10.1371/journal.pone.0033636

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Abstract

BackgroundMicroevolution is essential for species persistence especially under anticipated climate change scenarios. Species distribution projection models suggested that the dominant tree species of lowland forests in Switzerland, European beech (Fagus sylvatica L.), might disappear from most areas due to expected longer dry periods. However, if genotypes at the moisture boundary of the species climatic envelope are adapted to lower moisture availability, they can serve as seed source for the continuation of beech forests under changing climates.Methodology/Principal FindingsWith an AFLP genome scan approach, we studied neutral and potentially adaptive genetic variation in Fagus sylvatica in three regions containing a dry and a mesic site each (n ind. = 241, n markers = 517). We linked this dataset with dendrochronological growth measures and local moisture availabilities based on precipitation and soil characteristics. Genetic diversity decreased slightly at dry sites. Overall genetic differentiation was low (F st = 0.028) and Bayesian cluster analysis grouped all populations together suggesting high (historical) gene flow. The Bayesian outlier analyses indicated 13 markers with three markers differing between all dry and mesic sites and the others between the contrasting sites within individual regions. A total of 41 markers, including seven outlier loci, changed their frequency with local moisture availability. Tree height and median basal growth increments were reduced at dry sites, but marker presence/absence was not related to dendrochronological characteristics.Conclusion and Their SignificanceThe outlier alleles and the makers with changing frequencies in relation to moisture availability indicate microevolutionary processes occurring within short geographic distances. The general genetic similarity among sites suggests that ‘preadaptive’ genes can easily spread across the landscape. Yet, due to the long live span of trees, fostering saplings originating from dry sites and grown within mesic sites might increase resistance of beech forests during the anticipated longer dry periods.

Highlights

Climate change threatens to cause widespread modifications to forest composition and structure
Due to the long live span of trees, fostering saplings originating from dry sites and grown within mesic sites might increase resistance of beech forests during the anticipated longer dry periods
A geographically explicit modeling study for Switzerland indicated that the most common deciduous tree species, European beech (Fagus sylvatica L.), might be vulnerable to the combination of the expected climatic conditions: With increasing temperatures and dryer summers, areas nowadays covered by beech forests are expected to shrink tremendously while areas at higher altitudes are expected to become suitable for this species

Summary

Introduction

Climate change threatens to cause widespread modifications to forest composition and structure. The predicted distribution is even more constraint if biotic interactions with co-occurring tree species were included in the model [3]. Such models are restricted as they are calibrated by using a random sample of the populations studied [4] and thereby might undervalue the range limits. If individuals at the dry distribution limits are adapted to lower moisture availability, F. sylvatica might contain the genetic variation for the continuation of beech forests under climate change even in the areas which are predicted to be devoid. Species distribution projection models suggested that the dominant tree species of lowland forests in Switzerland, European beech (Fagus sylvatica L.), might disappear from most areas due to expected longer dry periods. If genotypes at the moisture boundary of the species climatic envelope are adapted to lower moisture availability, they can serve as seed source for the continuation of beech forests under changing climates

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