Gailing, O. | Search bioRxiv

bioRxiv2019

Assignment of frost tolerant coast redwood trees of unknown origin to populations within their natural range using nuclear and chloroplast microsatellite genetic markers

Considering climate change and expected changes in temperature and precipitation, some introduced timber species are prospective for growing in Germany or Europe to produce valuable wood products and support sustainable forestry. The Californian tree, coast redwood (Sequoia sempervirens [D. Don] Endl.) is one of such species due to its excellent wood properties and high growth rate. It is sensitive to the freezing temperatures, but several trees of unknown origin introduced to Germany decades ago demonstrated high frost tolerance, and their propagated cuttings were planted all over German botanic gardens and arboreta. The knowledge of their origin within the natural distribution range could help us identify the potential genetic resources of frost resistant coast redwood genotypes. Therefore, both trees of unknown origin in Germany (G) and two reference data sets representing the \"Kuser provenance test\" established in 1990 in France (F) and samples collected in California (C) with known origin were genotyped using 18 microsatellite markers including 12 nuclear and six chloroplast simple sequence repeat (cpSSR) markers. The number of haplotypes found in the data sets based on six cpSSR markers was surprisingly very high. These markers were used to assign the German frost resistant trees (G) to the two reference data sets (F and C). The genetic structure among California samples (C) based on nSSR and cpSSR markers was very weak and mainly due to northern and southern clusters separated by the San Francisco Bay as a geographic barrier between coast redwood populations confirming previously published data. It was impossible to confidently assign frost tolerant trees (G) to single native populations, but rather to either the northern or southern cluster. However, the existing frost tolerant genotypes can already be used to establish commercial coast redwood plantation for future German forestry.

genetics↗

bioRxiv2019

Genomic landscape of the global oak phylogeny

O_LIThe tree of life is highly reticulate, with the history of population divergence buried amongst phylogenies deriving from introgression and lineage sorting. In this study, we test the hypothesis that there are regions of the oak (Quercus, Fagaceae) genome that are broadly informative about phylogeny and investigate global patterns of oak diversity.\nC_LIO_LIWe utilize fossil data and restriction-site associated DNA sequencing (RAD-seq) for 632 individuals representing ca. 250 oak species to infer a time-calibrated phylogeny of the worlds oaks. We use reversible-jump MCMC to reconstruct shifts in lineage diversification rates, accounting for among-clade sampling biases. We then map the > 20,000 RAD-seq loci back to a recently published oak genome and investigate genomic distribution of introgression and phylogenetic support across the phylogeny.\nC_LIO_LIOak lineages have diversified among geographic regions, followed by ecological divergence within regions, in the Americas and Eurasia. Roughly 60% of oak diversity traces back to four clades that experienced increases in net diversification due to climatic transitions or ecological opportunity.\nC_LIO_LIThe support we find for the phylogeny contrasts with high genomic heterogeneity in phylogenetic signal and introgression. Oaks are phylogenomic mosaics, and their diversity may in fact depend on the gene flow that shapes the oak genome.\nC_LI

evolutionary biology↗