Abstract Detail

Population Genetics/Genomics

Prakash, Anoob [1], Keller, Stephen [2].

Detecting signals of polygenic adaptation in the face of demographic history and population structure in red spruce (Picea rubens).

Geographic variation and clines in growth and phenology traits are commonly observed across the range of forest trees whose distributions often span broad environmental gradients of climate. However, oftentimes these gradients of climate and trait variation also coincide with expansion history and population genetic structure, making it difficult to know if trait variation is locally adaptive or the byproduct of demographic history and genetic drift. Traditional methods based on quantitative trait variation across variable environments fail to consider the complex relationships existing between populations. Furthermore, methods that control for neutral structure such as QST - FST comparisons rely on estimating the additive genetic variance (VA) for traits as well as being able to group samples into discrete populations – both of which present difficulties for forest trees that are long-lived and occur in continuous stands across the landscape.
An innovative approach to test for polygenic local adaptation in these situations is to use population genomics to derive molecular estimates of kinship between sampled individuals without grouping them into discrete popualtions. These kinship estimates can be combined with Principal Component Analysis (PCA) to derive components of trait variance that separate along major axes of population genetic structure as well as used to estimate VA, the ratio of which can be used to compute an index of polygenic local adaptation (QPC) and test its statistical significance. With this framework we can investigate the divergence of traits from neutral expectations and identify traits that are locally adapted even in the face of major axes of population genetic structure such as those that arise during species expansion history.
Here, we apply the QPC approach to red spruce (Picea rubens Sarg.) – a climate-sensitive coniferous tree species with an expansion history that left a highly fragmented distribution towards the warmer southern range edge and continuous distribution in the northern part of its range. We estimated molecular kinship based on exome capture SNPs and paired these with growth and phenology traits measured in common gardens located across the range along a latitudinal gradient. We reveal evidence for polygenic adaptation in trait means as well as their plasticity, and discuss how the adaptive standing genetic variation uncovered will be pivotal to tackling the selective pressures imposed by climate change.

1 - University of Vermont, Plant Biology, 111 Jeffords Hall, 63 Carrigan Drive, Burlington, VT, 05405, USA
2 - University Of Vermont, Department Of Plant Biology, 111 Jeffords Hall, 63 Carrigan Dr, Burlington, VT, 05405, United States

diversifying selection
population genetics
quantitative genetics

Presentation Type: Oral Paper
Number: PGG2003
Abstract ID:780
Candidate for Awards:None

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