Primulaweiliei (Primulaceae), a new species from Hubei, Central China.

In this study, we describe and illustrate a new species, Primulaweiliei L.S.Yang, Z.K.Wu & G.W.Hu, from the Shennongjia Forestry District, Hubei Province in Central China. It is morphologically assigned to Primulasect.Aleuritia based on its dwarf and hairless habit, long petiole, fruits longer than calyx and covered by farina on the scape. This new species is similar to P.gemmifera and P.munroisubsp.yargongensis in the same section, but it can be distinguished by its smaller calyxes, homostylous flowers, corolla tube throat without annular appendage and only 1-2 flowers in each inflorescence. Based on the assessment conducted according to the IUCN Red List criteria, we propose that P.weiliei be classified as a Critically Endangered (CR) species.

Phylogenomics and divergence pattern of Polygonatum (Asparagaceae: Polygonateae) in the north temperate region.

Polygonatum is the largest genus of tribe Polygonateae (Asparagaceae) and is widely distributed in the temperate Northern Hemisphere, especially well diversified in southwestern China to northeastern Asia. Phylogenetic relationships of many species are still controversial. Hence it is necessary to clarify their phylogenetic relationships and infer possible reticulate relationships for the genus. In this study, genome-wide data of 43 species from Polygonatum and its closely related taxa were obtained by Hyb-Seq sequencing. The phylogenetic trees constructed from genome-wide nuclear and chloroplast sequences strongly supported the monophyly of Polygonatum with division into three major clades. A high level of incongruence was detected between nuclear and chloroplast trees as well as among gene trees within the genus, but all occurred within each major clade. However, introgression tests and reticulate evolution analyses revealed low level of gene flow and weak introgression events in the genus, suggesting hybridization and introgression were not dominant during the evolutionary diversification of Polygonatum in the Northern Hemisphere. This study provides important insights into reconstructing evolutionary relationships and speciation pattern of taxa from the north temperate flora.

Plastid phylogenomic analyses of the Selaginella sanguinolenta group (Selaginellaceae) reveal conflict signatures resulting from sequence types, outlier genes, and pervasive RNA editing.

Different from the generally conserved plastomes (plastid genomes) of most land plants, the Selaginellaceae plastomes exhibit dynamic structure, high GC content and high substitution rates. Previous plastome analyses identified strong conflict on several clades in Selaginella, however the factors causing the conflictions and the impact on the phylogenetic inference have not been sufficiently investigated. Here, we dissect the distribution of phylogenetic signals and conflicts in Selaginella sanguinolenta group, the plastome of which is DR (direct repeats) structure and with genome-wide RNA editing. We analyzed the data sets including 22 plastomes representing all species of the S. sanguinolenta group, covering the entire geographical distribution from the Himalayas to Siberia and the Russian Far East regions. We recovered four different topologies by applying multispecies coalescent (ASTRAL) and concatenation methods (IQ-TREE and RAxML) on four data sets of PC (protein-coding genes), NC (non-coding sequences), PCN (the concatenated PC and NC), and RC (predicted RNA editing sites "C" were corrected by "T"), respectively. Six monophyletic clades, S. nummularifolia clade, S. rossii clade, S. sajanensis clade, S. sanguinolenta I clade, S. sanguinolenta II clade, and S. sanguinolenta III clade, were consistently resolved and supported by the characteristics of GC content, RNA editing frequency, and gene content. However, the relationships among these clades varied across the four topologies. To explore the underlying causes of the uncertainty, we compared the phylogenetic signals of the four topologies. We identified that the sequence types (coding versus non-coding), outlier genes (genes with extremely high |ΔGLS| values), and C-to-U RNA editing frequency in the protein-coding genes were responsible for the unstable phylogenomic relationship. We further revealed a significant positive correlation between the |ΔGLS| values and the variation coefficient of the RNA editing number. Our results demonstrated that the coalescent method performed better than the concatenation method in overcoming the problems caused by outlier genes and extreme RNA editing events. Our study particularly focused on the importance of exploring the plastid phylogenomic conflicts and suggested conducting concatenated analyses cautiously when adopting organelle genome data.

Selaginelladianzhongensis (Selaginellaceae), a new spikemoss from China.

A new species of spikemoss from Yunnan Province of China, Selaginelladianzhongensis, is described and illustrated based on evidence from gross morphology, micromorphology and molecular phylogeny. S.dianzhongensis is most similar to S.amblyphylla in its habit of creeping stem, leaf size, and obviously dimorphic sporophylls, but is distinct by its ventral leaves ovate-oblong, subcordate at base, basiscopic base entire, axillary leaves ovate and decurrent at base. Molecular phylogeny analysis of three chloroplast gene regions (rbcL, atpI, psbA) shows that S.dianzhongensis forms an independent branch with strong support which is distantly related to S.amblyphlla and S.kurzii, but sister to S.bodinieri which is quite different in habitat of erect or ascending stem and rhizophores restricted to the lower part, and slightly dimorphic sporophyllus.