To better understand the responses of arid-adapted, alpine plants to Quaternary climatic oscillations, we investigated the genetic variation and phylogeographic history of Orinus, an endemic genus of Poaceae comprising three species from the dry grasslands of the Qinghai-Tibet Plateau (QTP) in China. We measured the genetic variation of 476 individuals from 88 populations using three maternally inherited plastid DNA markers (matK, rbcL and psbA-trnH), the biparentally inherited nuclear ribosomal internal transcribed spacer (nrITS) and amplified fragment length polymorphisms (AFLPs). We found that the plastid DNA, nrITS and AFLPs show considerable, recent differentiation among the species. We detected 14 plastid haplotypes (H1–H14), of which only three were shared among all species, and 30 nrITS ribotypes (S1–S30), of which one (S10) was shared between two species, O. kokonoricus and O. intermedius, but absent in O. thoroldii. The nrITS types formed clades that were inconsistent with species boundaries. Based on these data, we propose and illustrate a complex hypothesis for the evolutionary history of Orinus involving lineage sorting and introgression, the latter of which may explain the shared S10 nrITS type. The AFLP results showed clades corresponding to current species delineation and suggest that lineage sorting in the genus is probably complete. We estimated the crown age of Orinus to be 2.85 (95% highest posterior density: 0.58–12.45) Mya (late Pliocene), and subsequent divergence occurred in the Quaternary. Early divergences were allopatric. More recently, Orinus probably underwent regional expansions corresponding to Quaternary climatic changes, especially glaciation, which is consistent with our divergence time estimates. These climatic changes could have facilitated the S10 event and other hybridization events. Our data also suggest that species of this small genus of grasses survived the Quaternary glacial period in the extremely adverse habitats of the QTP.

Melaphidina aphids (Rhus-gall aphids; Eriosomatinae: Fordini) comprise five genera from eastern Asia and one monotypic genus from eastern North America. Melaphidina are unique in feeding on plant species of Rhus subgenus Rhus (Anacardiaceae), on which they form galls during the summer. The phylogenetic relationships among some species of Melaphidina aphids remain controversial. In this study, we sought to resolve the backbone phylogeny of Melaphidina aphids by sampling 15 accessions representing all six genera, all species, and all subspecies except Meitanaphis microgallis using 20 gene regions: five nuclear genes as well as 13 protein-coding genes and two rRNA genes of the mitochondrial genome. Phylogenetic analyses included Bayesian and maximum likelihood methods. Independent analyses of nuclear and mitochondrial genes returned congruent topologies, and analyses of all gene regions combined showed well-supported relationships among Melaphidina species. In particular, these were: (1) Nurudea (excluding N. ibofushi) is sister to a clade composed of the five remaining genera; (2) the monotypic North American genus Melaphis is sister to a clade comprising the four remaining genera; and (3) (Schlechtendalia + N. ibofushi) is sister to the clade (Floraphis (Meitanaphis + Kaburagia). Our results support the transfer of Meitanaphis flavogallis to Kaburagia as an additional subspecies or species, and the recognition of Floraphis as a distinct genus. This study provides important molecular resources for subsequent evolutionary studies using more nuclear genes on the Melaphidina aphids and their close allies.

Dracocephalum heterophyllum (Lamiaceae: tribe Mentheae) is an annual aromatic herb native to East Asia with a long record of human uses, including medicinal, alimentary, and ornamental values. However, no information is available about its molecular biology, and no genomic study has been performed on D. heterophyllum. Here, we report the complete chloroplast (cp) genome of D. heterophyllum and a series of comparative genomic analyses between this and closely related species of Lamiaceae. Results indicated that the cp genome has a typical circular structure of 150,869 bp in length, consisting of a long single-copy (LSC) region with 82,410 bp, a short single-copy (SSC) region with 17,098 bp, and two inverted repeat (IR) regions of 51,350 bp. A total of 133 genes were identified, including 37 tRNA genes, 8 rRNA genes and 88 protein-coding genes, with a GC content of 37.8%. The gene content, organization, and GC values observed here were similar to those of other Dracocephalum species. We detected 99 different simple sequence repeat loci, and the codon usage analysis revealed a preferential use of the Leu codon with an A/U ending. Comparative analysis of cp genome sequences revealed five highly variable regions with remarkably higher Pi values (>0.03). The mean Ka/Ks between D. heterophyllum and three other Dracocephalum species ranged from 0.01079 (psbB) to 1.0497 (ycf2). Two cp genes, ycf2 and rps11, were proven to have high ratios of Ka/Ks, implying that cp genes may had undergone positive selection in the evolutionary history. We performed multiple sequence alignments using the cp genome of 22 species and constructed maximum likelihood (ML) and Bayesian trees, and found that D. heterophyllum were more closely related to D. moldavica and D. palmatum. In addition, the phylogenetic relationships between Dracocephalum and other members of Lamiaceae were consistent with previous results. These results are valuable for further formulating effective strategies of conservation and management for species in Dracocephalum, as well as providing a foundation for future research on the genetic resources of Dracocephalum.

Psammochloa villosa is an ecologically important desert grass that occurs in the Inner Mongolian Plateau where it is frequently the dominant species and is involved in sand stabilization and wind breaking. We sought to generate a preliminary demographic framework for P. villosa to support the future studies of this species, its conservation, and sustainable utilization. To accomplish this, we characterized the genetic diversity and structure of 210 individuals from 43 natural populations of P. villosa using amplified fragment length polymorphism (AFLP) markers. We obtained 1,728 well‐defined amplified bands from eight pairs of primers, of which 1,654 bands (95.7%) were polymorphic. Results obtained from the AFLPs suggested effective alleles among populations of 1.32, a Nei's standard genetic distance value of 0.206, a Shannon index of 0.332, a coefficient of gene differentiation (G_ST) of 0.469, and a gene flow parameter (Nm) of 0.576. All these values indicate that there is abundant genetic diversity in P. villosa, but limited gene flow. An analysis of molecular variance (AMOVA) showed that genetic variation mainly exists within populations (64.2%), and we found that the most genetically similar populations were often not geographically adjacent. Thus, this suggests that the mechanisms of gene flow are surprisingly complex in this species and may occur over long distances. In addition, we predicted the distribution dynamics of P. villosa based on the spatial distribution modeling and found that its range has contracted continuously since the last interglacial period. We speculate that dry, cold climates have been critical in determining the geographic distribution of P. villosa during the Quaternary period. Our study provides new insights into the population genetics and evolutionary history of P. villosa in the Inner Mongolian Plateau and provides a resource that can be used to design in situ conservation actions and prioritize sustainable utilization.

Root rot is a very destructive soil-borne disease, which severely affects the quality and yield of Angelica sinensis in major planting areas of Gansu Province, China. Twelve Fusarium strains were identified from root rot tissue and infected soil in the field by comparing each isolate strain internal transcribed spacer, translation elongation factor 1-α sequence and RNA polymerase second largest subunit gene with the sequences of known fungal species in the NCBI database. Of these isolates, four were F. acuminatum, followed by three F. solani, two F. oxysporum, and one each of F. equiseti, F. redolens, and F. avenaceum. Under greenhouse conditions, pathogenicity testing experiment was carried out using five strains: two F. acuminatum, one F. solani, one F. oxysporum, and one F. equiseti. Among them, the incidence of F. acuminatum–induced root rot on A. sinensis was 100%; hence, it was the most aggressive. Liquid chromatography was used to show that F. acuminatum could produce neosolaniol (NEO), deoxynivalenol, and T-2 toxins. Of these, the level of NEO produced by F. acuminatum was high compared with the other two toxins. By isolating Fusarium spp. and characterizing their toxin-producing capacity, this work provides new information for effectively preventing and controlling A. sinensis root rot in the field as well as improving the quality of its medicinal materials.