Genetic diversity and ex situ conservation of Loropetalum subcordatum, an endangered species endemic to China.

BACKGROUND: Loropetalum subcordatum is an endangered species endemic to China that is characterized by narrow distribution, small population size, and delayed fertilization. However, the genetic diversity of the entire extant natural and ex situ populations has not been assessed to date. In this study, we evaluated the genetic diversity and structure of six natural populations and a single ex situ population (the only known ex situ population of L. subcordatum) using sequence-related amplified polymorphism data. RESULTS: In total, 553 reliable DNA bands, of which 359 (63.28%) were polymorphic, were amplified by polymerase chain reaction with combinations of 15 primers. Low average gene diversity within populations and high genetic differentiation were detected in L. subcordatum. A Mantel test demonstrated that there was a positive correlation between genetic and geographic distances, indicating that significant genetic divergence was likely the result of geographic isolation among natural populations. Furthermore, based on genetic structure patterns, populations of L. subcordatum were divided into three clusters. Group 1 was composed of specimens from Libo, Guizhou Province (GZ) and Huanjiang, Guangxi Zhuang Autonomous Region (GX). Group 2 was composed of Mt. Wuguishan, Guangdong Province (GD). Group 3 was composed of three populations in Hong Kong Special Administrative Region. Additionally, clonal reproduction probably existed in GD population. According to the genetic information analysis and field survey, the ex situ population did not match its source population (GD) in terms of genetics, and its habitat was different from the original natural habitat. We observed that a few individual GD seeds were needed to improve ZS ex situ in the future. CONCLUSIONS: Compared to previous SRAP-based studies of endangered plants, L. subcordatum had extremely low average gene diversity within populations and high genetic differentiation among populations. At present, the unique ex situ population has not been successful due to non-representative samples being taken, a smaller population size, and man-made changes in habitat. Potential strategies are suggested to improve the conservation of this species.

A molecular phylogeny of Aeridinae (Orchidaceae: Epidendroideae) inferred from multiple nuclear and chloroplast regions.

The subtribe Aeridinae, which contains approximately 90 genera, is one of the most diverse and taxonomically puzzling groups in Orchidaceae. In the present study, the phylogenetic relationships of Aeridinae were reconstructed utilizing five DNA sequences (ITS, atpI-H, matK, psbA-trnH, and trnL-F) from 211 taxa in 74 genera. The results of the phylogenetic analyses indicate that Aeridinae is monophyletic and that the subtribe can primarily be grouped into 10 clades: (1) Saccolabium clade, (2) Chiloschista clade, (3) Phalaenopsis clade, (4) Thrixspermum clade, (5) Vanda clade, (6) Aerides clade, (7) Trichoglottis clade, (8) Abdominea clade, (9) Gastrochilus clade, and (10) Cleisostoma clade. In our examination, most genera of Aeridinae were well-supported as monophyletic, and several genera, namely, Pteroceras, Cleisostoma, Vandopsis, Diploprora, Malleola, and Robiquetia, were found to be polyphyletic as currently circumscribed. In addition, several classifications of intra-genera, such as the subgenus Codonosepalum of Taeniophyllum and the section Gastrochilus of Gastrochilus, were also revealed to be paraphyletic. Due to the many questions raised by our phylogenies, the present study may serve as a reference for future taxonomic studies of Aeridinae.

Population Diversity Analysis Provide Insights into Provenance Identification of Dendrobium catenatum.

Dendrobium catenatum (Dendrobium officinale) is a valuable genuine herb. The source of this species is difficult to be identified by traditional methods including morphology, spectroscopy, and chromatography. We used the restriction site-associated DNA sequencing (RAD-seq) approach to perform the high-throughput sequencing of 24 D. catenatum provenances. In this study, 371.18 Gb clean data were obtained, and 655,057 high-quality SNPs were selected after their filtration. We used phylogenetic tree, genetic structure, and principal component analyses to examine the genetic diversities and genetic relationships of the 109 accessions. We found that D. catenatum could be divided into two groups, and each group was closely related to the distribution of the sampling sites. At the population level, the average nucleotide diversity (π) of the D. catenatum population mutation parameters was 0.1584 and the expected heterozygosity (HE) was 0.1575. The GXLPTP07 accessions showed the highest genetic diversity in terms of the private allele number, observed heterozygosity, and nucleotide diversity. The Mantel test showed a significant positive correlation between the genetic and geographic distances among the overall distribution. A genetic information database of D. catenatum was established, which confirmed that RAD-seq technology has the potential to be applied in the identification of medicinal Dendrobium of different origins.

Complete plastome sequence of Hoya carnosa (L. f.) R. Br. (Apocynaceae).

Hoya is a remarkable genus with high horticultural ornamental value. In this study, we report and characterize the complete plastid genome sequence of Hoya carnosa. The complete chloroplast genome was 176,340 bp in length, which includes a pair of inverted repeat regions (IRs) of 41,381 bp separated by a large single copy region (LSC) 91,281 bp and a small single copy region (SSC) 2,297 bp. Interestingly, IRs expanded into SSC, with the result that most of the genes in SSC were duplicated. This chloroplast genome contained 110 genes, including 76 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. The complete plastome sequence of H. carnosa will provide some useful information for future phylogenetic study of Hoya and its horticultural application.

Begonia guangdongensis, a new species of Begonia (Begoniaceae) from Guangdong, China.

A new species of Begonia section Coelocentrum, B. guangdongensis W.H. Tu, B.M. Wang & Y.L. Li from Guangdong Province, China, is described and illustrated here. Morphologically, the new species is most similar to B. biflora T. C. Ku and B. longistyla Y. M. Shui & W. H. Chen, but differs from B. biflora by its rugose leaves and glabrous capsules and from B. longistyla by its glabrous stipules without ciliate margin, densely hirsute-pilose leaves and obtuse apex of bracts. Additionally, it is also somewhat similar to B. chongzuoensis Yan Liu, S. M. Ku & C.-I Peng, but there are significant distinctions in their stipules, leaves and bracts. The conservation status of B. guangdongensis is assessed as Critically Endangered (CR), according to the IUCN Red List Categories and Criteria.