Boehmeria nivea var. strigosa (Urticaceae), a new variety from Southwest China

Boehmeria nivea var.strigosa Zeng Y.Wu&Y.Zhao,a new variety of B.nivea(Urticaceae)from Southwest China,is here described based on evidence from morphology and molecular phylogeny.This new variety is mainly characterized by its green abaxial leaf blade,partly connate stipules,and densely patent strigose hairs on stems and potioles.The phylogenetic analysis based on rbc L,nrDNA and rbc L+nrDNA datasets,revealed that all individuals of B.nivea var.strigosa formed a monophyletic group.The conservation status of B.nivea var.strigosa is assessed as“Near Threatened”(NT)according to IUCN evaluation criteria.The discovery of this new variety is not only crucial for the taxonomy of ramie,but also provides reference for the exploration and utilization of ramie.

Across two phylogeographic breaks: Quaternary evolutionary history of a mountain aspen (Populus rotundifolia) in the Hengduan Mountains

Biogeographical barriers to gene flow are central to plant phylogeography.In East Asia,plant distribution is greatly influenced by two phylogeographic breaks,the Mekong-Salween Divide and Tanaka-Kaiyong Line,however,few studies have investigated how these barriers affect the genetic diversity of species that are distributed across both.Here we used 14 microsatellite loci and four chloroplast DNA fragments to examine genetic diversity and distribution patterns of 49 populations of Populus rotundifolia,a species that spans both the Mekong-Salween Divide and the Tanaka-Kaiyong Line in southwestern China.Demographic and migration hypotheses were tested using coalescent-based approaches.Limited historical gene flow was observed between the western and eastern groups of P.rotundifolia,but substantial flow occurred across both the Mekong-Salween Divide and Tanaka-Kaiyong Line,manifesting in clear admixture and high genetic diversity in the central group.Wind-borne pollen and seeds may have facilitated the dispersal of P.rotundifolia following prevalent northwest winds in the spring.We also found that the Hengduan Mountains,where multiple genetic barriers were detected,acted on the whole as a barrier between the western and eastern groups of P.rotundifolia.Ecological niche modeling suggested that P.rotundifolia has undergone range expansion since the last glacial maximum,and demographic reconstruction indicated an earlier population expansion around 600 Ka.The phylogeographic pattern of P.rotundifolia reflects the interplay of biological traits,wind patterns,barriers,niche differentiation,and Quaternary climate history.This study emphasizes the need for multiple lines of evidence in understanding the Quaternary evolution of plants in topographically complex areas.

Effects of taxon sampling on molecular dating for within-genus divergence events,when deep fossils are used for calibration

A universal method of molecular dating that can be applied to all families and genera regardless of their fossil records, or lack thereof, is highly desirable. A possible method for eudicots is to use a large phylogeny calibrated using deep fossils including tricolpate pollen as a fixed （124 mya） calibration point. This method was used to calculate node ages within three species-poor disjunct basal eudicot genera, Caulophyllum, Podophyllum and Pachysandra, and sensitivity of these ages to effects such as taxon sampling were then quantified. By deleting from one to three accessions related to each genus in 112 different combinations, a confidence range describing variation due only to taxon sampling was generated. Ranges for Caulophyllum, Podophyllum and Pachysandra were 8.4-10.6, 7.6-20.0, and 17.6-25.0 mya, respectively. However, the confidence ranges calculated using bootstrapping were much wider, at 3-19, 0-32 and 11-32 mya, respectively. Furthermore, deleting 10 adjacent taxa had a large effect in Pachysandra only, indicating that undersampling effects are significant among Buxales. Changes to sampling density in neighboring clades, or to the position of the fixed fossil calibration point had small to negligible effects. Non-parametric rate smoothing was more sensitive to taxon sampling effects than was penalized likelihood. The wide range for Podophyllum, compared to the other two genera, was probably due to a high degree of rate heterogeneity within this genus. Confidence ranges calculated by this method could be narrowed by sampling more individuals within the genus of interest, and by sequencing multiple DNA regions from all species in the phylogeny.

Genomic variation,environmental adaptation,and feralization in ramie,an ancient fiber crop

Feralization is an important evolutionary process,but the mechanisms behind it remain poorly understood.Here,we use the ancient fiber crop ramie(Boehmeria nivea(L.)Gaudich.)as a model to investigate genomic changes associated with both domestication and feralization.We first produced a chromosome-scale de novo genome assembly of feral ramie and investigated structural variations between feral and domesticated ramie genomes.Next,we gathered 915 accessions from 23 countries,comprising cultivars,major landraces,feral populations,and the wild progenitor.Based on whole-genome resequencing of these accessions,we constructed the most comprehensive ramie genomic variation map to date.Phylogenetic,demographic,and admixture signal detection analyses indicated that feral ramie is of exoferal or exo-endo origin,i.e.,descended from hybridization between domesticated ramie and the wild progenitor or ancient landraces.Feral ramie has higher genetic diversity than wild or domesticated ramie,and genomic regions affected by natural selection during feralization differ from those under selection during domestication.Ecological analyses showed that feral and domesticated ramie have similar ecological niches that differ substantially from the niche of the wild progenitor,and three environmental variables are associated with habitat-specific adaptation in feral ramie.These findings advance our understanding of feralization,providing a scientific basis for the excavation of new crop germplasm resources and offering novel insights into the evolution of feralization in nature.