No abstract

The grass subfamily Pooideae was studied using DNA sequence information from the chloroplast (cp) matK gene–3′trnK exon and the nuclear ribosomal (nr) ITS1–5.8S gene–ITS2 in a sample of 67 taxa covering all of its tribes. Branches with strong bootstrap support are consistently resolved in both datasets, whereas discrepancy is confined to low‐support or unsupported nodes in one of the datasets. The results do not reveal a significant role of past hybridisation, plastid lineage sorting or reticulation in the evolutionary diversification of the major lineages of the subfamily. The combined analysis of the plastid and nuclear datasets results in a largely well‐supported pattern of divergence for the major lineages of the subfamily. Some re‐alignments of tribes and subtribes are proposed and discussed with reference to relevant morphological and structural characters. We propose the recognition of broader tribes Nardeae with subtribes Nardinae and Lygeinae, Meliceae with subtribes Brylkiniinae and Melicinae, Stipeae with subtribes Ampelodesminae and Stipinae, and Triticeae with subtribes Littledaleinae, Brominae and Hordeinae. For the tribe complex of Aveneae and Poeae, the clear‐cut split into two major clades and further resolution into some high‐support lineages depicted by cpDNA is not contradicted by nuclear ITS and their taxonomic treatment as separate tribes or a single tribe remains an unanswered question.

Aim Geologically dynamic areas often harbour remarkable levels of biodiversity. Among other factors, mountain building is assumed to be a precondition for species radiation, and yet, the potential role of immigration as a source of biodiversity prior to radiation is often neglected. Here, we studied the biogeographical history of the large genus Saxifraga to unravel the role played by the Qinghai-Tibet Plateau (QTP) for the diversification of this genus and to understand factors that have led to the establishment of high biodiversity in and around this region.Location QTP and surrounding mountain ranges and worldwide distribution range of Saxifraga.Methods Using a total of 420 taxa (321 ingroup taxa) comprising more than 60% of extant Saxifraga species, we studied the evolutionary history of Saxifraga by performing phylogenetic analyses (maximum likelihood and Bayesian inference on nuclear ITS and plastid trnL-trnF, matK sequences), divergence time estimation (using uncorrelated log-normal clock models and four fossil constraints in beast) and ancestral range estimation (using BioGeoBEARS).Results Saxifraga originated in North America around 74 (64-83) Ma, dispersed to South America and northern Asia during its early diversification and colonized Europe and the QTP region by the Late Eocene. The QTP region was colonized several times independently, followed in some lineages by rapid radiations, temporally coinciding with recent uplifts of the Hengduan Mountains at the southeastern fringe of the QTP. Subsequently, several lineages dispersed out of Tibet.Main conclusions Immigration, recent rapid radiation and lineage persistence were all important processes for the establishment of a rich species stock of Saxifraga in the QTP region. Because floristic exchanges between the neighbouring areas and the QTP region were bi-directional, the spatio-temporal evolution of Saxifraga contrasts with the 'out of QTP' pattern, which has often been assumed for northern temperate plants.

Saxifraga, the most species‐rich and taxonomically complex genus of Saxifragaceae, is a characteristic component of temperate to polar climatic zones and of montane to alpine vegetation belts in mountain ranges of the Northern Hemisphere. The genus encompasses more than 440 species, which display notable diversity in growth form, vegetative and reproductive characters, as well as in micromorphology of pollen grains and seeds. Using a large taxon set including representatives attributed to nearly all recognised subgenera, sections and subsections of Saxifraga (altogether 254 species), as well as a broad coverage of outgroup taxa, we inferred evolutionary relationships within Saxifraga, explored the reasons of the striking inconsistencies between previous taxonomic treatments of Saxifraga, estimated the degree of homoplasy in characters frequently employed for classification, assessed the role of hybridisation in the evolution of the genus and, finally, provided a phylogeny‐based framework upon which to revise its taxonomy. The phylogenetic trees based on nuclear ribosomal internal transcribed spacer (ITS) and plastid trnL‐trnF DNA markers, including more than 460 newly generated sequences, were generally highly congruent, except within a single clade (sect. Saxifraga), in which incomplete lineage sorting and presumably allopolyploid speciation plays an important evolutionary role. Major lineages of Saxifraga are concordantly resolved by the DNA markers from both organelles with mostly strong node support. Our molecular phylogenetic results support the recognition of at least 13 sections and 9 subsections within Saxifraga. A part of these lineages agrees well with previously recognised infrageneric groupings, whereas others are differently delineated. Some of the groups identified by molecular phylogenetics are characterised only by the combination of different morphological characters. Frequently, micromorphological characters support the clades in the phylogenetic tree comparatively well. We here provide new ranks for three infrageneric epithets, namely for sect. Saxifragasubsect. Androsaceae and subsect. Arachnoideae and sect. Porphyrion subsect. Squarrosae. Finally, our study identifies remaining taxonomic uncertainties within Saxifraga.

To investigate the evolutionary diversification and morphological evolution of grass supertribe Poodae (subfam. Pooideae, Poaceae) we conducted a comprehensive molecular phylogenetic analysis including representatives from most of its accepted genera. We focused on generating a DNA sequence dataset of plastid matK gene-3′trnK exon and trnL-trnF regions and nuclear ribosomal (nr) ITS1-5.8S gene-ITS2 and ETS that was taxonomically overlapping as completely as possible (altogether 257 species). The idea was to infer whether phylogenetic trees or certain clades based on plastid and nrDNA data correspond with each other or discord, revealing signatures of past hybridization. The datasets were analysed separately, in combination, by excluding taxa with discordant placements in the individual gene trees and with duplication of these taxa in a way that each duplicate has only one data partition (plastid or nrDNA). We used maximum likelihood, maximum parsimony and Bayesian approaches. Instances of severe conflicts between the phylogenetic trees derived from both datasets, some of which have been noted earlier, point to hybrid origin of several lineages such as the ABCV clade encompassing several subtribes and subordinate clades,