The grade of early-diverging eudicots includes five major lineages: Ranunculales, Trochodendrales, Buxales, Proteales and Sabiaceae. To examine the evolution of plastome structure in early-diverging eudicots, we determined the complete plastome sequences of eight previously unsequenced early-diverging eudicot taxa, Pachysandra terminalis (Buxaceae), Meliosma aff. cuneifolia (Sabiaceae), Sabia yunnanensis (Sabiaceae), Epimedium sagittatum (Berberidaceae), Euptelea pleiosperma (Eupteleaceae), Akebia trifoliata (Lardizabalaceae), Stephania japonica (Menispermaceae) and Papaver somniferum (Papaveraceae), and compared them to previously published plastomes of the early-diverging eudicots Buxus, Tetracentron, Trochodendron, Nelumbo, Platanus, Nandina, Megaleranthis, Ranunculus, Mahonia and Macadamia. All of the newly sequenced plastomes share the same 79 protein-coding genes, 4 rRNA genes, and 30 tRNA genes, except for that of Epimedium, in which infA is pseudogenized and clpP is highly divergent and possibly a pseudogene. The boundaries of the plastid Inverted Repeat (IR) were found to vary significantly across early-diverging eudicots; IRs ranged from 24.3 to 36.4kb in length and contained from 18 to 33 genes. Based on gene content, the IR was classified into six types, with shifts among types characterized by high levels of homoplasy. Reconstruction of ancestral IR gene content suggested that 18 genes were likely present in the IR region of the ancestor of eudicots. Maximum likelihood phylogenetic analysis of a 79-gene, 97-taxon data set that included all available early-diverging eudicots and representative sampling of remaining angiosperm diversity largely agreed with previous estimates of early-diverging eudicot relationships, but resolved Trochodendrales rather than Buxales as sister to Gunneridae, albeit with relatively weak bootstrap support, conflicting with what has been found for these three clades in most previous analyses. In addition, Proteales was resolved as sister to Sabiaceae with the highest support (bootstrap >90%) yet observed in plastome-scale phylogenetic analyses.

Aim A phylogeographical study of the widespread but phylogenetically isolated East Asian endemic tree species Tetracentron sinense (Trochodendraceae) was performed to evaluate whether and how Pleistocene and pre‐Pleistocene climate changes helped to influence current phylogeographical patterns, and to describe the current patterns of genetic diversity and their implications for conservation. Location Southwestern and central subtropical China. Methods Sequences of four chloroplast spacer regions were obtained from 157 individuals of T. sinense. A haplotype network was constructed using tcs. Genetic diversity and differentiation, spatial analysis of molecular variance (SAMOVA) and analysis of molecular variance (AMOVA) were used to test for genetic structure. beast was used to estimate the divergence times between haplotypes. Historical demographic expansion was tested using pairwise mismatch distribution analysis. Results Of the 21 recovered haplotypes, three were widely distributed, but most were restricted to particular regions. Populations with high haplotype diversity were located in western Hubei, southern Sichuan and southern Chongqing. The two earliest‐diverging haplotypes were found in southwestern China. The haplotype distribution of T. sinense demonstrated significant phylogeographical structure (NST > GST; P < 0.05). The best partitioning of genetic diversity by SAMOVA (K = 5) produced groups that matched the main tcs‐derived clades. Two independent range expansions within SAMOVA‐derived groups 2 and 3 were dated to approximately 399 and 311 ka, respectively. The time to the most recent common ancestor of all haplotypes was 9.6 (95% highest posterior density: 27.0–2.2) Ma, but most of the haplotype diversity appeared during the Quaternary. Main conclusions The extant distribution of T. sinense is likely to have been shaped by both pre‐Quaternary and Pleistocene climate changes. Southwestern China may have served as an important refugium for T. sinense throughout the Neogene, while the species also occupied multiple refugia during the late Pleistocene glacial periods. Populations of T. sinense were resolved into five allopatric groups, between which there is apparently no seed movement.

BackgroundAmong the 13 families of early-diverging eudicots, only Circaeasteraceae (Ranunculales), which consists of the two monotypic genera Circaeaster and Kingdonia, lacks a published complete plastome sequence. In addition, the phylogenetic position of Circaeasteraceae as sister to Lardizabalaceae has only been weakly or moderately supported in previous studies using smaller data sets. Moreover, previous plastome studies have documented a number of novel structural rearrangements among early-divergent eudicots. Hence it is important to sequence plastomes from Circaeasteraceae to better understand plastome evolution in early-diverging eudicots and to further investigate the phylogenetic position of Circaeasteraceae.ResultsUsing an Illumina HiSeq 2000, complete plastomes were sequenced from both living members of Circaeasteraceae: Circaeaster agrestis and Kingdonia uniflora. Plastome structure and gene content were compared between these two plastomes, and with those of other early-diverging eudicot plastomes. Phylogenetic analysis of a 79-gene, 99-taxon data set including exemplars of all families of early-diverging eudicots was conducted to resolve the phylogenetic position of Circaeasteraceae.Both plastomes possess the typical quadripartite structure of land plant plastomes. However, a large ~49 kb inversion and a small ~3.5 kb inversion were found in the large single-copy regions of both plastomes, while Circaeaster possesses a number of other rearrangements, particularly in the Inverted Repeat. In addition, infA was found to be a pseudogene and accD was found to be absent within Circaeaster, whereas all ndh genes, except for ndhE and ndhJ, were found to be either pseudogenized (ΨndhA, ΨndhB, ΨndhD, ΨndhH and ΨndhK) or absent (ndhC, ndhF, ndhI and ndhG) in Kingdonia. Circaeasteraceae was strongly supported as sister to Lardizabalaceae in phylogenetic analyses.ConclusionThe first plastome sequencing of Circaeasteraceae resulted in the discovery of several unusual rearrangements and the loss of ndh genes, and confirms the sister relationship between Circaeasteraceae and Lardizabalaceae. This research provides new insight to characterize plastome structural evolution in early-diverging eudicots and to better understand relationships within Ranunculales.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3956-3) contains supplementary material, which is available to authorized users.

Potentilleae, one of 10 tribes of the Rosaceae, are mainly distributed in alpine regions of the Northern Hemisphere. The taxonomy of Potentilleae has been challenging due to extensive hybridization, polyploidization, and/or apomixis characterizing several genera of Potentilleae, such as Alchemilla, Argentina, and Potentilla. To help clarify relationships within Potentilleae, a phylogenetic analysis of the tribe with an emphasis on the polyphyletic genus Sibbaldia was carried out using nuclear ribosomal internal and external transcribed spacer regions and the plastid trnL‐F and trnS‐G spacer regions. In agreement with previous phylogenetic analyses, three major clades were identified in the present study: the subtribe Fragariinae, the genera Argentina, and Potentilla. The 15 species of Sibbaldia were recovered in five distinct clades: three in subtribe Fragariinae, one in Argentina, and the last in Potentilla. The recently established genus Chamaecallis, comprising a single species formerly treated in Sibbaldia that has intermediate floral character states with respect to Fragariinae and Potentilla, was recovered as sister to Drymocallis. Morphological character state reconstruction indicated that a reduction in the number of stamens (≤10) is a derived character state that has arisen multiple times in Potentilleae. Molecular dating analyses agreed with previously published estimates and suggested that crown group Potentilleae arose in the Middle to Late Eocene, with most generic‐level divergences occurring in the Oligocene and Miocene.