Abstract
BackgroundDiversity among phenology-related genes is predicted to be a contributing factor in local adaptations seen in widely distributed plant species that grow in climatically variable geographic areas, such as forest trees. European beech (Fagus sylvatica L.) is widespread, and is one of the most important broadleaved tree species in Europe; however, its potential for adaptation to climate change is a matter of uncertainty, and little is known about the molecular basis of climate change-relevant traits like bud burst.ResultsWe explored single nucleotide polymorphisms (SNP) at candidate genes related to bud burst in beech individuals sampled across 47 populations from Europe. SNP diversity was monitored for 380 candidate genes using a sequence capture approach, providing 2909 unlinked SNP loci. We used two complementary analytical methods to find loci significantly associated with geographic variables, climatic variables (expressed as principal components), or phenotypic variables (spring and autumn phenology, height, survival). Redundancy analysis (RDA) was used to detect candidate markers across two spatial scales (entire study area and within subregions). We revealed 201 candidate SNPs at the broadest scale, 53.2% of which were associated with phenotypic variables. Additive polygenic scores, which provide a measure of the cumulative signal across significant candidate SNPs, were correlated with a climate variable (first principal component, PC1) related to temperature and precipitation availability, and spring phenology. However, different genotype-environment associations were identified within Southeastern Europe as compared to the entire geographic range of European beech.ConclusionsEnvironmental conditions play important roles as drivers of genetic diversity of phenology-related genes that could influence local adaptation in European beech. Selection in beech favors genotypes with earlier bud burst under warmer and wetter habitats within its range; however, selection pressures may differ across spatial scales.
Highlights
Diversity among phenology-related genes is predicted to be a contributing factor in local adaptations seen in widely distributed plant species that grow in climatically variable geographic areas, such as forest trees
Local adaptation has been considered an important factor in maintaining genetic variation within species, but environmental heterogeneity favors the evolution of adaptive phenotypic plasticity [1]
We observed that the individual heterozygosity estimated on the basis of significant single nucleotide polymorphisms (SNP) increased with latitude, longitude, and altitude and earlier phenology, indicating the importance of relevant genes in local adaptation
Summary
Diversity among phenology-related genes is predicted to be a contributing factor in local adaptations seen in widely distributed plant species that grow in climatically variable geographic areas, such as forest trees. Local adaptation is one of the most important evolutionary mechanisms allowing species to thrive across heterogeneous environments [1]. Knowledge about the extent of local adaptation and its underlying mechanisms in natural populations provides the basis for predicting responses to environmental fluctuations, including those associated with global climate change. The genetic underpinnings of local adaptation, though, are poorly understood. Local adaptation would be expected to change allelic frequencies of genes affecting fitness in particular environments. Local adaptation has been considered an important factor in maintaining genetic variation within species, but environmental heterogeneity favors the evolution of adaptive phenotypic plasticity [1]. Because phenotypic plasticity does not necessarily have to be adaptive [5], its interplay with adaptive traits confounds the ability to find genetic determinants of adaptation
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