Range expansion and adaptation of Sitka spruce
Sitka spruce (Picea sitchensis) has a long and narrow distribution that spans the Pacific coast of North America from California to Alaska. In spite of a quick post-glacial colonization and a young and still expanding northern population, this species shows pronounced clinal variation in climate-related traits along its entire range. Moreover, there is strong evidence for both local adaptation and phenotypic plasticity for these adaptive traits across the range. The paradox between recent colonization history and apparently high level of adaptation raises several interesting questions about the processes that potentially influence adaptation in Sitka spruce. My research will hopefully lead to a better understanding of the mechanisms and extent of adaptation to climate in natural populations through addressing some of the following topics.
First, the mode and history of colonization may have an influence on the adaptive potential of the species. To address this issue, a study of the population genetic structure using molecular markers can be used to infer long-term processes of range expansion. This approach can be coupled with a more localized study of populations at the current edges of the range to infer short-term processes of range expansion.
It has been shown in other spruce species that rapid adaptation of recently established populations can be enhanced by a mechanism of epigenetic memory during embryogenesis. Testing this hypothesis in Sitka spruce could help deciphering the genetic and epigenetic contribution to adaptation, and can strongly influence predictions about the potential and speed of adaptation in a climate change context.
Another key factor influencing adaptation in natural populations is migration, and more generally the level of gene flow. It is possible to study the effect of gene flow by comparing the levels of adaptation in isolated and continuous populations.
Funding: NSERC Discovery Grant, UBC Strategic Recruitment Fellowship