Background and aims-The species of the 'Briza complex' (Pooideae, Poaceae) are distributed in South America and Eurasia. They are relatively well-studied morphologically and have a complex taxonomic history, but only a few phylogenetic studies have been conducted using molecular data. Monophyly of the complex, which is based on presence of 'brizoid' spikelets, has not been questioned and sampling strategies in previous studies have prevented assessments thereof. Methods-We investigate phylogeny and node ages in the Briza complex and test monophyly of the group using nuclear and chloroplast data. Extensive sampling from the Briza complex and putatively related species in the subfamily Pooideae is employed. Key results-Despite morphological similarity among species, the Briza complex is polyphyletic. Members were found in three different clades, showing the South American species, the Eurasian species and Briza humilis to be distinct groups. The South American and the Eurasian clades originated about 11 and 13 million years ago, respectively. Briza humilis diverged from Phleum (or a related genus) about 10 million years ago, whereas its crown clade is from the Pliocene-Pleistocene border. The almost simultaneous origins of these clades in the mid-Miocene coincide with temporal estimates of major diversification in grasses and formation of grassland habitats. Conclusions-Based on our results, we support the names Chascolytrum for the South American clade and Briza for the Eurasian clade. For the Briza humilis clade, we propose the name Brizochloa. The parallel evolution of (seemingly) similar 'brizoid' spikelets in the Pooideae is surprising; however, studies have shown that floral morphology can alter dramatically by one-step mutations, causing evolutionarily distantly related species to have similar appearance. Our findings may hopefully inspire new morphological investigations of the species of the former Briza complex, as well as other poorly studied and potentially polyphyletic genera, such as Deschampsia and Echinopogon.

The genus Potentilla (Rosaceae) has been subjected to several phylogenetic studies, but resolving its evolutionary history has proven challenging. Previous analyses recovered six, informally named, groups: the Argentea, Ivesioid, Fragarioides, Reptans, Alba and Anserina clades, but the relationships among some of these clades differ between data sets. The Reptans clade, which includes the type species of Potentilla, has been noticed to shift position between plastid and nuclear ribosomal data sets. We studied this incongruence by analysing four low-copy nuclear markers, in addition to chloroplast and nuclear ribosomal data, with a set of Bayesian phylogenetic and Multispecies Coalescent (MSC) analyses. A selective taxon removal strategy demonstrated that the included representatives from the Fragarioides clade, P. dickinsii and P. fragarioides, were the main sources of the instability seen in the trees. The Fragarioides species showed different relationships in each gene tree, and were only supported as a monophyletic group in a single marker when the Reptans clade was excluded from the analysis. The incongruences could not be explained by allopolyploidy, but rather by homoploid hybridization, incomplete lineage sorting or taxon sampling effects. When P. dickinsii and P. fragarioides were removed from the data set, a fully resolved, supported backbone phylogeny of Potentilla was obtained in the MSC analysis. Additionally, indications of autopolyploid origins of the Reptans and Ivesioid clades were discovered in the low-copy gene trees.

Background: Most cinquefoils (Potentilla L., Rosaceae) are polyploids, ranging from tetraploid (4x) to dodecaploid (12x), diploids being a rare exception. Previous studies based on ribosomal and chloroplast data indicated that Norwegian cinquefoil (P. norvegica L.) has genetic material from two separate clades within Potentilla; the Argentea and the Ivesioid cladesand thus a possible history of hybridization and polyploidization (allopolyploidy). In order to trace the putative allopolyploid origin of the species, sequence data from low-copy, biparentally inherited, nuclear markers were used. Specimens covering the circumpolar distribution of P. norvegica and its two subspecies were included, along with the morphologically similar P. intermedia. Potentilla species of low ploidy level known to belong to other relevant clades were also included. Results: Gene trees based on three low-copy nuclear markers, obtained by Bayesian Inference and Maximum Likelihood analyses, showed slightly different topologies. This is likely due to genomic reorganizations following genome duplication, but the gene trees were not in conflict with a species tree of presumably diploid taxa obtained by Multispecies Coalescent analysis. The results show that both P. norvegica and P. intermedia are allopolyploids with a shared evolutionary history involving at least four parental lineages, three from the Argentea clade and one from the Ivesioid clade. Conclusions: This is the first time that reticulate evolution has been proven in the genus Potentilla, and shows the importance of continuing working with low-copy markers in order to properly resolve its evolutionary history. Several hybridization events between the Argentea and Ivesioid clades may have given rise to the species of Wolf's grex Rivales. To better estimate when and where these hybridizations occurred, other Argentea, Ivesioid and Rivales species should be included in future studies.

Classification of Potentilla L. has varied considerably through time. Some authors have collapsed all of the Potentilleae tribe into a single genus, while others have divided it into more than 20 genera. All those classifications, except for the one that collapsed them all, have rendered the genus Potentilla polyphyletic. We discuss Potentilla from a phylogenetic perspective in order to achieve a reasonable classification in which Potentilla is based on a clade (monophyly). Other criteria are taken into account, namely: history, phylogenetic stability, gene flow, information content and ease of identification. All previously described genera in Potentillinae are briefly discussed and assigned to major clades. In order to do this, it was necessary to designate types for: Fraga Lapeyr., Trichothalamus Spreng., and Dactylophyllum Spenn. We discuss seven scenarios, representing the effects of classifying Potentilla at the seven major clades in Potentillinae, and conclude that the most supported and least disruptive is to classify Potentilla as the clade comprising all of Potentillinae excluding the Anserina clade.

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