ABSTRACT
Rhododendron shanii W.P. Fang 1983 (Ericaceae) is woody plant naturally distributed in the southwest of Anhui, China. The complete chloroplast genome sequence of R. shanii was generated by whole-genome next-generation sequencing data and assembled based on three Rhododendron species chloroplast genome. The complete chloroplast genome sequence of R. shanii was 204,170 bp and divided into four distinct regions: small single-copy region (2615 bp), large single-copy region (107,189 bp), and a pair of inverted repeat regions (47,183 bp). The genome annotation displayed 150 genes, including 95 protein-coding genes, 47 tRNA genes, and eight rRNA genes. Phylogenetic analysis with the Ericaceae reported chloroplast genomes revealed that R. shanii is sister to the clade comprising R. delavayi, R. griersonianum and R. platypodum.
ABSTRACT
The disjunctive distribution (Europe-Caucasus-Asia) and species diversification across Eurasia for the genus Allium sect. Daghestanica has fascinating attractions for researchers aiming to understanding the development and history of modern Eurasia flora. However, no any studies have been carried out to address the evolutionary history of this section. Based on the nrITS and cpDNA fragments (trnL-trnF and rpl32-trnL), the evolutionary history of the third evolutionary line (EL3) of the genus Allium was reconstructed and we further elucidated the evolutionary line of sect. Daghestanica under this background. Our molecular phylogeny recovered two highly supported clades in sect. Daghestanica: the Clade I includes Caucasian-European species and Asian A. maowenense, A. xinlongense and A. carolinianum collected in Qinghai; the Clade II comprises Asian yellowish tepal species, A. chrysanthum, A. chrysocephalum, A. herderianum, A. rude and A. xichuanense. The divergence time estimation and biogeography inference indicated that Asian ancestor located in the Qinghai-Tibetan Plateau (QTP) and the adjacent region could have migrated to Caucasus and Europe distributions around the Late Miocene and resulted in further divergence and speciation; Asian ancestor underwent the rapid radiation in the QTP and the adjacent region most likely due to the heterogeneous ecology of the QTP resulted from the orogeneses around 4-3 million years ago (Mya). Our study provides a picture to understand the origin and species diversification across Eurasia for sect. Daghestanica.
ABSTRACT
The genus Allium (Amaryllidaceae, Allioideae) is one of the largest monocotyledonous genera and it includes many economically important crops that are cultivated for consumption or medicinal uses. Recent advances in molecular phylogenetics have revolutionized our understanding of Allium taxonomy and evolution. However, the phylogenetic relationships in some Allium sections (such as the Allium section Daghestanica) and the genetic bases of adaptative evolution, remain poorly understood. Here, we newly assembled six chloroplast genomes from Chinese endemic species in Allium section Daghestanica and by combining these genomes with another 35 allied species, we performed a series of analyses including genome structure, GC content, species pairwise Ka/Ks ratios, and the SSR component, nucleotide diversity and codon usage. Positively selected genes (PSGs) were detected in the Allium lineage using the branch-site model. Comparison analysis of Bayesian and ML phylogeny on CCG (complete chloroplast genome), SCG (single copy genes) and CDS (coding DNA sequences) produced a well-resolved phylogeny of Allioideae plastid lineages, which illustrated several novel relationships with the section Daghestanica. In addition, six species in section Daghestanica showed highly conserved structures. The GC content and the GC3s content in Allioideae species exhibited lower values than studied non-Allioideae species, along with elevated pairwise Ka/Ks ratios. The rps2 gene was lost in all examined Allioideae species, and 10 genes with significant posterior probabilities for codon sites were identified in the positive selection analysis, seven of them are associated with photosynthesis. Our study uncovered a new species relationship in section Daghestanica and suggested that the selective pressure has played an important role in Allium adaptation and evolution, these results will facilitate our further understanding of evolution and adaptation of species in the genus Allium.
