Phylogenetic relationships among species of Quercus (oaks) from western Eurasia including the western part of the Himalayas are examined for the first time. Based on ITS and 5S–IGS data three major infrageneric groups are recognized for western Eurasia: the cerroid, iliciod, and roburoid oaks. While individuals of the cerroid and ilicoid groups cluster according to their species, particularly in the 5S–IGS analyses, individuals of species of roburoid oaks do not cluster with exception of Quercus pontica. The Cypriot endemic Quercus alnifolia belongs to the ilicoid oaks, in contrast to traditional views placing it within the cerroid oaks. Based on all ITS data available, the groups identified for western Eurasia can be integrated into a global infrageneric framework for Quercus. The Ilex group is resurrected as a well–defined group that comprises taxa traditionally placed into six subsections of Q. sects. Cerris and Lepidobalanus (white oaks) sensu Camus. Phylogenetic reconstructions suggest two major lineages within Quercus, each consisting of three infrageneric groups. Within the first lineage, the Quercus group (roburoid oaks in western Eurasia) and the Lobatae group evolved by “budding” as is reflected by incomplete lineage sorting, high variability within groups, and low differentiation among groups. The groups of the second lineage, including the Cyclobalanopsis, Cerris (cerroid oaks in western Eurasia), and Ilex (ilicoid oaks in western Eurasia) groups, evolved in a more tree–like fashion.

The tree of life is highly reticulate, with the history of population divergence emerging from populations of gene phylogenies that reflect histories of introgression, lineage sorting and divergence. In this study, we investigate global patterns of oak diversity and test the hypothesis that 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 632 individuals representing nearly 250 Quercus species to infer a time-calibrated phylogeny of the world's oaks. We use a reversible-jump Markov chain Monte Carlo method to reconstruct shifts in lineage diversification rates, accounting for among-clade sampling biases. We then map the > 20 000 RAD-seq loci back to an annotated oak genome and investigate genomic distribution of introgression and phylogenetic support across the phylogeny.Oak 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, probably in response to climatic transitions or ecological opportunity.The strong support 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.

Over the past 25 years the discovery and study of Cretaceous plant mesofossils has yielded diverse and exquisitely preserved fossil flowers that have revolutionized our knowledge of early angiosperms, but remains of other seed plants in the same mesofossil assemblages have so far received little attention. These fossils, typically only a few millimetres long, have often been charred in natural fires and preserve both three-dimensional morphology and cellular detail. Here we use phase-contrast-enhanced synchrotron-radiation X-ray tomographic microscopy to clarify the structure of small charcoalified gymnosperm seeds from the Early Cretaceous of Portugal and North America. The new information links these seeds to Gnetales (including Erdtmanithecales, a putatively closely related fossil group), and to Bennettitales--important extinct Mesozoic seed plants with cycad-like leaves and flower-like reproductive structures. The results suggest that the distinctive seed architecture of Gnetales, Erdtmanithecales and Bennettitales defines a clade containing these taxa. This has significant consequences for hypotheses of seed plant phylogeny by providing support for key elements of the controversial anthophyte hypothesis, which links angiosperms, Bennettitales and Gnetales.

No abstract

No abstract

No abstract

No abstract

No abstract