Genetic mechanisms of local adaptation in a spruce hybrid zone
Populations will be locally adapted if they contain the appropriate genetic composition to survive and reproduce under current and local conditions. But environmental conditions do not remain constant, thus the appropriate genetic composition to survive and reproduce will change through time as environments change. If populations have increased genetic variation they have reduced risk of extinction in the face of future environmental stochasticity. Increased genetic diversity due to hybridization may result in a further capacity to adapt to changing environments. In this study we assessed the evolutionary mechanisms of gene flow and selection in characterizing the genetic structure of a Sitka-white spruce (Picea sitchensis x P. glauca) hybrid zone.
The broad goal was to identify the genetic consequences of introgression and the degree to which local adaptation in traits of economic value or those involved in adaptation to climate are exhibited across the hybrid zone using a variety of approaches; including molecular and quantitative trait analysis. While substantial genetic gains in growth and quality have been achieved using traditional methods, natural hybrid zones offer another valuable tool from which important genetic variation may be explored for future gains. The factors that drive natural selection and local adaptation in tree hybrid zones have broad ecological, conservation, and economic implications as both forest genetics and silviculture depend on understanding and managing genetic diversity in tree populations.
This hybrid zone has been analyzed using chloroplast, mitochondrial and nuclear microsatellite markers (Hamilton and Aitken, in press) as well as phenotypic traits (Hamilton et al. 2013) and single nucleotide markers (Hamilton et al. 2013). This range of marker types as well as phenotypic data from a common garden experiment, allowed for the inference of population history, sequence of species colonization, and effects of selection on adaptive loci within the hybrid zone.