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Range Wide Genotypic And Phenotypic Variation And Climate Change Adaptation In Red Spruce (picea Rubens Sarg.)
Prakash, Anoob
Prakash, Anoob
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Abstract
Species distributions are shaped by a combination of historical and contemporary processes, including past range expansions, migration, and patterns of adaptation to diverse environmental conditions across their ranges. Today, global climate change is a major driver of new changes in species distributions. Warming temperatures, shifting precipitation patterns, and more frequent climate extremes have led to widespread responses like altered phenology, range shifts, and physiological changes observed across many taxa. Long-lived, sessile organisms like trees are especially vulnerable because their migration and adaptation rates cannot keep pace with rapid climate changes. In this dissertation, I used multidisciplinary approaches to understand the genotypic and phenotypic variations and climate change adaptation present in red spruce (Picea rubens Sarg.), a climate sensitive conifer species found in eastern North America. Red spruce populations has declined over the past century due to logging, acid rain, climate stress, and exhibit low genetic diversity, particularly in the fragmented southern part of its range. To assess genetic and environmental influences on key traits like phenology and growth, I planted seeds from across the species range in three common gardens (Vermont, Maryland, and North Carolina) and performed whole-genome exome capture of mother trees. Genetic analysis revealed moderate heritability and regional differentiation for phenology and growth, alongside high plasticity. Importantly, northern red spruce populations showed extensive introgression from black spruce (Picea mariana), which contributes adaptive genetic diversity for key traits such as biomass and height. These advanced-generation hybrids may play a key role in climate adaptation and evolutionary rescue for red spruce populations in a changing environment. Genotype-phenotype based genomic offset models to forecast climate-driven maladaptation in red spruce revealed strong concordance with genotype-environment association based predictions. Further, our results underscore that forecasts based solely on present patterns of genotype-environment associations may underestimate future adaptive potential or risk due to the high frequency of loci whose effects on relative fitness are context dependent across environments. This work advances our understanding of climate adaptation in red spruce and highlights the importance of introgression as a source of adaptive genetic diversity for vulnerable forest tree species.
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2026
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Plant Biology