Genetic diversity and structure of Rhododendron meddianum,a plant species with extremely small populations

Rhododendron meddianum is a critically endangered species with important ornamental value and is also a plant species with extremely small populations.In this study,we used double digest restriction-siteassociated DNA sequencing(ddRAD)technology to assess the genetic diversity,genetic structure and demographic history of the three extant populations of R.meddianum.Analysis of SNPs indicated that R.meddianum populations have a high genetic diversity(p?0.0772±0.0024,HE?0.0742±0.002).Both FST values(0.1582e0.2388)and AMOVA showed a moderate genetic differentiation among the R.meddianum populations.Meanwhile,STRUCTURE,PCoA and NJ trees indicated that the R.meddianum samples were clustered into three distinct genetic groups.Using the stairway plot,we found that R.meddianum underwent a population bottleneck about 70,000 years ago.Furthermore,demographic models of R.meddianum and its relative,Rhododendron cyanocarpum,revealed that these species diverged about 3.05(2.21e5.03)million years ago.This divergence may have been caused by environmental changes that occurred after the late Pliocene,e.g.,the Asian winter monsoon intensified,leading to a drier climate.Based on these findings,we recommend that R.meddianum be conserved through in situ,ex situ approaches and that its seeds be collected for germplasm.

Rhododendron kuomeianum(Ericaceae),a new species from northeastern Yunnan(China),based on morphological and genomic data

Rhododendron kuomeianum Y.H.Chang,J.Nielsen&Y.P.Ma,a new species of Rhododendron(Ericaceae)within subsect.Maddenia in sect.Rhododendron from Yiliang County,NE Yunnan,China,is described and illustrated.The new species is similar to R.valentinianum,but it can be easily distinguished by its sparse scales on the abaxial surface of the leaf blade,fewer flowers per inflorescence and white corolla with pale red margins.There are also differences in the widths of calyx lobes,leaf blade shape and indumentum characteristics of the petiole between the new species and Rhododendron linearilobum.We confirmed that R.kuomeianum is a new species closely related to R.valentinianum and R.changii with phylogenomic studies of 10 species within this subsection based on restriction site-associated DNA sequencing(RADseq)data.These phylogenomic analyses also clarified additional taxonomic problems in this subsection previously raised by morphological analysis.Our findings make a strong case for using next-generation sequencing to explore phylogenetic relationships and identify new species,especially in plants groups with complicated taxonomic problems.

Does the critically endangered Rhododendron amesiae deserve top priority for conservation?

The genus Rhododendron is the largest genus of woody plants in China,having extremely important horticultural value(Chamberlain et al.,1996).However,efforts have only recently been made to assess the conservation status of the genus.According to conservation category assessments on the Red List of Rhododendrons(Gibbs et al.,2011)and the Threatened Species List of China's Higher Plants(Qin et al.,2017),32.03%and 17.13%of rhododendrons are evaluated to be threatened.