Phenotypic and Genomic Local Adaptation across Latitude and Altitude in Populus trichocarpa

Abstract

Local adaptation to climate allows plants to cope with temporally and spatially heterogeneous environments, and parallel phenotypic clines provide a natural experiment to uncover the genomic architecture of adaptation. Though extensive effort has been made to investigate the genomic basis of local adaptation to climate across the latitudinal range of tree species, less is known for altitudinal clines. We used exome capture to genotype 451 Populus trichocarpa genotypes across altitudinal and latitudinal gradients spanning the natural species range, and phenotyped these trees for a variety of adaptive traits in two common gardens. We observed clinal variation in phenotypic traits across the two transects, which indicates climate-driven selection, and coupled gene-based genotype–phenotype and genotype–environment association scans to identify imprints of climatic adaptation on the genome. Although many of the phenotype- and climate-associated genes were unique to one transect, we found evidence of parallelism between latitude and altitude, as well as significant convergence when we compared our outlier genes with those putatively involved in climatic adaptation in two gymnosperm species. These results suggest that not only genomic constraint during adaptation to similar environmental gradients in poplar but also different environmental contexts, spatial scale, and perhaps redundant function among potentially adaptive genes and polymorphisms lead to divergent adaptive architectures.

Dissecting the Polygenic Basis of Cold Adaptation Using Genome-Wide Association of Traits and Environmental Data in Douglas-fir

“…Both GWAS and GEA analyses suggested a polygenic basis of cold adaptation, with many genes associated with cold-related traits and climate adaptation. This is coincident with recent genome-wide analyses in widespread, outcrossing plant species with large population sizes such as Zea mays [ 64 ], Populus trichocarpa [ 65 ], Pinus contorta [ 66 ], and Pinus sylvestris [ 67 ]. Trait architecture in coastal Douglas-fir seems to be more complex than previously suggested, with traits (such as growth, emergence and phenology) controlled by both large and small effect genes, and others (cold hardiness) mainly controlled by large numbers of small effect genes.…”

The genetic basis of adaptation in phenology in an introduced population of Black Cottonwood (Populus trichocarpa, Torr. & Gray)

“…6a). These overlaps are similar in magnitude to previous comparisons (Zhang et al, 2019) and suggest that the genetic architecture of autumn phenology traits is shared across both native and novel environments. However, the relatively large numbers of study specific candidate genes also hint at the complexity of these traits under the variable natural conditions.…”

Ecological Factors Generally Not Altitude Related Played Main Roles in Driving Potential Adaptive Evolution at Elevational Range Margin Populations of Taiwan Incense Cedar (Calocedrus formosana)

“…The amount of genetic diversity, the strength of natural selection, and the extent of gene flow can all influence the probability of the occurrence of local adaptation ( Hoffmann and Sgrò, 2011 ). Local adaptation can occur in association with conditions in different parts of a species’ distribution range and adaptive potential at elevational edges is particularly important for species’ contraction and expansion following climate change ( Byars et al, 2007 ; Leimu and Fischer, 2008 ; Hereford, 2009 ; Chen et al, 2014 ; Rumpf et al, 2019 ; Zhang et al, 2019 ). However, central populations can also be vulnerable in the face of global climate change ( Bennett et al, 2015 ).…”