These traits include morphological, physiological, and phenological characteristics such as growth, foliar characteristics, timing of bud break and bud set, water use efficiency, photosynthetic capacity, and survival (Bussotti et al. Genecological studies allow us to (1) identify adaptive traits and selective drivers, (2) infer species’ adaptive strategies, and (3) assess evolutionary potentials.Īdaptive traits are characterized by strong population differentiation and associations with environmental gradients. Genecology, the study of genetic variation in relation to the environment, is often used to investigate adaptation in forest trees (Aitken 2004, St.Clair and Howe 2007).
New mutations are expected to contribute little to the adaptive potential of tree populations in the short-run (Petit and Hampe 2006). Finally, evolutionary adaptation (or simply “adaptation”) may improve or maintain population fitness through local changes in allele frequencies via within-population natural selection or the introduction of new alleles from other populations (Kremer et al. 2014), the mere existence of population-level genetic variation highlights the limits of phenotypic plasticity. Furthermore, although phenotypic plasticity can contribute to forest resilience in the short term (Alfaro et al. For most tree species, however, migration rates are not expected to keep pace with future climatic changes (Davis and Shaw 2001). Affected species may cope with these changes via migration (i.e., colonization of new areas), phenotypic plasticity, or evolutionary adaptation (including gene flow among populations Aitken et al. This study demonstrates that co-occurring tree species can develop very different adaptive strategies under identical environmental conditions, and suggests that Norway spruce might be more vulnerable to future maladaptation due to rapid climate change than silver fir.Įuropean forests are expected to be impacted by changes in temperature and water regimes and associated increases in natural disturbances (Lindner et al. In contrast, because silver fir has a more conservative growth habit, it has evolved to become an adaptive generalist.
We conclude that Norway spruce has become an adaptive specialist because trade-offs between rapid juvenile growth and frost avoidance have subjected it to strong diversifying natural selection based on temperature.
Soil characteristics explained little population variation in both species. In silver fir, height growth was more weakly associated with temperature and elevation, but also associated with water availability. In Norway spruce, height growth and second flushing were strongly associated with temperature and elevation, with seedlings from the lowlands being taller and more prone to second flush than seedlings from the Alps. Population differentiation and associations between seedling traits and environmental variables were much stronger for Norway spruce than for silver fir, and stronger for seedling height growth than for bud phenology. For each species, we collected seed from more than 90 populations across Switzerland, established a seedling common-garden test, and developed genecological models that associate population variation in seedling growth and phenology to climate, soil properties, and site water balance. We studied the genecology of Norway spruce ( Picea abies) and silver fir ( Abies alba), two co-occurring but ecologically distinct European conifers in Central Europe. adaptive generalists, large-scale studies comparing different species in the same experiment are rare.
Which species are most vulnerable to climate change? Which are the most important adaptive traits and environmental drivers of natural selection? Even though species have been classified as adaptive specialists vs. Although common genecological patterns have emerged, species-specific details are also important.
Understanding the genecology of forest trees is critical for gene conservation, for predicting the effects of climate change and climate change adaptation, and for successful reforestation.