| 1. |
- Cardoni, Simone, et al.
(författare)
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5S‐IGS rDNA in wind‐pollinated trees ( Fagus L.) encapsulates 55 million years of reticulate evolution and hybrid origins of modern species
- 2021
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 109:4, s. 909-926
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Tidskriftsartikel (refereegranskat)abstract
- Standard models of plant speciation assume strictly dichotomous genealogies in which a species, theancestor, is replaced by two offspring species. The reality in wind-pollinated trees with long evolutionaryhistories is more complex: species evolve from other species through isolation when genetic drift exceeds gene flow; lineage mixing can give rise to new species (hybrid taxa such as nothospecies and allopolyploids). The multi-copy, potentially multi-locus 5S rDNA is one of few gene regions conserving signal from dichotomous and reticulate evolutionary processes down to the level of intra-genomic recombination. Therefore, it can provide unique insights into the dynamic speciation processes of lineages that diversified tens of millions of years ago. Here, we provide the first high-throughput sequencing (HTS) of the 5S intergenic spacers (5S-IGS) for a lineage of wind-pollinated subtropical to temperate trees, the Fagus crenata – F.sylvatica s.l. lineage, and its distant relative F. japonica. The observed 4963 unique 5S-IGS variants reflect acomplex history of hybrid origins, lineage sorting, mixing via secondary gene flow, and intra-genomic competition between two or more paralogous-homoeologous 5S rDNA lineages. We show that modern species are genetic mosaics and represent a striking case of ongoing reticulate evolution during the past 55 million years.
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| 2. |
- Denk, Thomas, et al.
(författare)
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Comment on “Eocene Fagaceae from Patagonia and Gondwanan legacy in Asian rainforests”
- 2019
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Ingår i: Science. - USA : American Association for the advancement of Science. - 0036-8075 .- 1095-9203. ; 366:6467
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Tidskriftsartikel (refereegranskat)abstract
- Wilf et al. (Research Articles, 7 June 2019, eaaw5139) claim that Castanopsis evolved in the Southern Hemisphere from where it spread to its modern distribution in Southeast Asia. However, extensive paleobotanical records of Antarctica and Australia lack evidence of any Fagaceae, and molecular patterns indicate shared biogeographic histories of Castanopsis, Castanea, Lithocarpus, and Quercus subgenus Cerris, making the southern route unlikely.
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| 3. |
- Denk, Thomas, et al.
(författare)
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Genomic landscape of the global oak phylogeny
- 2019
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; , s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The tree of life is highly reticulate, with the history of population divergence emerging frompopulations of gene phylogenies that reflect histories of introgression, lineage sorting anddivergence. In this study, we investigate global patterns of oak diversity and test the hypothesisthat there are regions of the oak genome that are broadly informative about phylogeny. We utilize fossil data and restriction-site associated DNA sequencing (RAD-seq) for 632individuals representing nearly 250 Quercus species to infer a time-calibrated phylogeny ofthe world’s oaks. We use a reversible-jump Markov chain Monte Carlo method to reconstructshifts in lineage diversification rates, accounting for among-clade sampling biases. We thenmap the > 20 000 RAD-seq loci back to an annotated oak genome and investigate genomicdistribution of introgression and phylogenetic support across the phylogeny. Oak lineages have diversified among geographic regions, followed by ecological divergencewithin regions, in the Americas and Eurasia. Roughly 60% of oak diversity traces back to fourclades that experienced increases in net diversification, probably in response to climatic transitionsor ecological opportunity. The strong support for the phylogeny contrasts with high genomic heterogeneity in phylogeneticsignal and introgression. Oaks are phylogenomic mosaics, and their diversity may infact depend on the gene flow that shapes the oak genome.
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| 4. |
- Denk, Thomas, et al.
(författare)
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Niche evolution in a northern temperate tree lineage: biogeographical legacies in cork oaks (Quercus section Cerris)
- 2023
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Ingår i: Annals of Botany. - : Oxford University Press. - 0305-7364 .- 1095-8290. ; 238:6, s. 2668-2684
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims: Cork oaks (Quercus section Cerris) comprise 15 extant species in Eurasia. Despite being a small clade, they display a range of leaf morphologies comparable to the largest sections (>100 spp.) in Quercus. Their fossil record extends back to the Eocene. Here, we explore how cork oaks achieved their modern ranges and how legacy effects might explain niche evolution in modern species of section Cerris and its sister section Ilex, the holly oaks.Methods: We inferred a dated phylogeny for cork and holly oaks using a reduced-representation next-generation sequencing method, restriction site-associated DNA sequencing (RAD-seq), and used D-statistics to investigate gene flow hypotheses. We estimated divergence times using a fossilized birth–death model calibrated with 47 fossils. We used Köppen profiles, selected bioclimatic parameters and forest biomes occupied by modern species toinfer ancestral climatic and biotic niches.Key Results: East Asian and Western Eurasian cork oaks diverged initially in the Eocene. Subsequently, four Western Eurasian lineages (subsections) differentiated during the Oligocene and Miocene. Evolution of leaf size, form and texture was correlated, in part, with multiple transitions from ancestral humid temperate climates to mediterranean, arid and continental climates. Distantly related but ecologically similar species converged on similar leaf traits in the process.Conclusions: Originating in temperate (frost-free) biomes, Eocene to Oligocene ranges of the primarily deciduous cork oaks were restricted to higher latitudes (Siberia to north of Paratethys). Members of the evergreen holly oaks (section Ilex) also originated in temperate biomes but migrated southwards and south-westwards into then-(sub)tropical southern China and south-eastern Tibet during the Eocene, then westwards along existing pre-Himalayan mountain ranges. Divergent biogeographical histories and deep-time phylogenetic legacies (in cold and drought tolerance, nutrient storage and fire resistance) thus account for the modern species mosaic of Western Eurasian oak communities, which are composed of oaks belonging to four sections.
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| 5. |
- Piredda, Roberta, et al.
(författare)
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High-throughput sequencing of 5S-IGS in oaks – exploring intragenomic variation and algorithms to recognize target species in pure and mixed samples
- 2021
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Ingår i: Molecular Ecology Resources. - : Wiley-Blackwell. - 1755-098X .- 1755-0998. ; 21, s. 495-510
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Tidskriftsartikel (refereegranskat)abstract
- Measuring biological diversity is a crucial but difficult undertaking, as exemplified in oaks where complex patterns of morphological, ecological, biogeographical and genetic differentiation collide with traditional taxonomy, which measures biodiversity in number of species (or higher taxa). In this pilot study, we generated high-throughput sequencing amplicon data of the intergenic spacer of the 5S nuclear ribosomal DNA cistron (5S-IGS) in oaks, using six mock samples that differ in geographical origin, species composition and pool complexity. The potential of the marker for automated genotaxonomy applications was assessed using a reference data set of 1,770 5S-IGS cloned sequences, covering the entire taxonomic breadth and distribution range of western Eurasian Quercus, and applying similarity (blast) and evolutionary approaches (maximum-likelihood trees and Evolutionary Placement Algorithm). Both methods performed equally well, allowing correct identification of species in sections Ilex and Cerris in the pure and mixed samples, and main lineages shared by species of sect. Quercus. Application of different cut-off thresholds revealed that medium- to high-abundance (>10 or 25) sequences suffice for a net species identification of samples containing one or a few individuals. Lower thresholds identify phylogenetic correspondence with all target species in highly mixed samples (analogous to environmental bulk samples) and include rare variants pointing towards reticulation, incomplete lineage sorting, pseudogenic 5S units and in situ (natural) contamination. Our pipeline is highly promising for future assessments of intraspecific and interpopulation diversity, and of the genetic resources of natural ecosystems, which are fundamental to empower fast and solid biodiversity conservation programmes worldwide.
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