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Additional file 1: SuppInfo Frederick et al. BAA-870 genome. Table S1. All sequenced Rhodococcus strains (353) according to the NCBI database (accessed 13/03/2019). Table S2. All complete sequenced Rhodococcus species ranked by release date according to the NCBI Genome database (accessed 11/03/2019). Table S3. Whole genome distance statistics between Rhodococcus rhodochrous ATCC BAA-870 and two closely matched strains. Table S4. Rhodococcus rhodochrous ATCC BAA-870 protein function breakdown based on BASys annotation COG classifications.

Additional file 1: SuppInfo Frederick et al. BAA-870 genome. Table S1. All sequenced Rhodococcus strains (353) according to the NCBI database (accessed 13/03/2019). Table S2. All complete sequenced Rhodococcus species ranked by release date according to the NCBI Genome database (accessed 11/03/2019). Table S3. Whole genome distance statistics between Rhodococcus rhodochrous ATCC BAA-870 and two closely matched strains. Table S4. Rhodococcus rhodochrous ATCC BAA-870 protein function breakdown based on BASys annotation COG classifications.

Presentation by Charles Hefer at Galaxy Africa 2018 (Cape Town, South Africa)

Natural hybrid zones in forest trees provide systems to study the transfer of adaptive genetic variation by introgression. Previous landscape genomic studies in Populus trichocarpa, a keystone tree species, indicated genomic footprints of admixture with its sister species P. balsamifera and identified candidate genes for local adaptation. Here, we explored patterns of introgression and signals of local adaptation in P. trichocarpa and P. balsamifera, employing genome resequencing data from three chromosomes in pure species and admixed individuals from wild populations. Local ancestry analysis in admixed P. trichocarpa revealed a telomeric region in chromosome 15 with P. balsamifera ancestry, containing several candidate genes for local adaptation. Genomic analyses revealed signals of selection in certain genes in this region (e.g. PRR5, COMT1), and functional analyses based on gene expression variation and correlations with adaptive phenotypes suggest distinct functions of the introgressed alleles. In contrast, a block of genes in chromosome 12 paralogous to the introgressed region showed no signs of introgression or signatures of selection. We hypothesize that the introgressed region in chromosome 15 has introduced modular, or cassette-like variation into P. trichocarpa. These linked adaptive mutations are associated with a block of genes in chromosome 15 that appear to have undergone neo- or sub-functionalization relative to paralogs in a duplicated region on chromosome 12 that show no signatures of adaptive variation. The association between P. balsamifera introgressed alleles with the expression of adaptive traits in P. trichocarpa supports the hypothesis that this is a case of adaptive introgression in an ecologically important foundation species.

• Introgression can be an important source of adaptive phenotypes, although conversely it can have deleterious effects. Evidence for adaptive introgression is accumulating but information on the genetic architecture of introgressed traits lags behind. • Here we determine trait architecture in Populus trichocarpa under introgression from P. balsamifera using admixture mapping and phenotypic analyses. • Our results reveal that admixture is a key driver of clinal adaptation and suggest that the northern range extension of P. trichocarpa depends, at least in part, on introgression from P. balsamifera. However, admixture with P. balsamifera can lead to potentially maladaptive early phenology and a reduction in growth and disease resistance in P. trichocarpa. Strikingly, an introgressed chromosome 9 haplotype block from P. balsamifera restores the late phenology and high growth parental phenotype in admixed P. trichocarpa. This epistatic restorer block may be strongly advantageous in maximizing carbon assimilation and disease resistance in the southernmost populations where admixture has been detected. We also confirm a previously demonstrated case of adaptive introgression in chromosome 15 and show that introgression generates a transgressive chlorophyll–content phenotype. • We provide strong support that introgression provides a reservoir of genetic variation associated with adaptive characters that allows improved survival in new environments.

Presention for the Galaxy Africa workshop in Cape Town, April 2018

This is the open peer reviewers comments and recommendations regarding the submitted GigaScience article and/or dataset.

This is the open peer reviewers comments and recommendations regarding the submitted GigaScience article and/or dataset.