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The genus Phoebe (Lauraceae) includes about 90 evergreen tree species that are an ideal source of timber. Habitat destruction and deforestation have resulted in most of them being endemic to China. The accurate identification of endangered Phoebe species in China is necessary for their conservation. Chloroplast genome sequences can play an important role in species identification. In this study, comparative chloroplast genome analyses were conducted on diverse Phoebe species that are primarily distributed in China. Despite the conserved nature of chloroplast genomes, we detected some highly divergent intergenic regions ( petA-psbE , ndhF-rpl32 , and psbM-trnD -GUC) as well as three highly divergent genes ( rbcL , ycf1 , and ycf2 ) that have potential applications in phylogenetics and evolutionary analysis. The phylogenetic analysis indicated that various Phoebe species in China were divided into three clades. The complete chloroplast genome was better suited for phylogenetic analysis of Phoebe species. In addition, based on the phylogeographical analysis of Phoebe species in China, we inferred that the Phoebe species in China first originated in Yunnan and then spread to other southern areas of the Yangtze River. The results of this research will add to existing case studies on the phylogenetic analysis of Phoebe species and have the potential to contribute to the conservation of Phoebe species that are in danger of extinction., Competing Interests: The authors declare there are no competing interests., (©2023 Shi et al.)

Litsea is a group of evergreen trees or shrubs in the laurel family, Lauraceae. Species of the genus are widely used for a wide range of medicinal and industrial aspects. At present, most studies related to the gene resources of Litsea are restricted to morphological analyses or features of individual genomes, and currently available studies of select molecular markers are insufficient. In this study, we assembled and annotated the complete chloroplast genomes of nine species in Litsea , carried out a series of comparative analyses, and reconstructed phylogenetic relationships within the genus. The genome length ranged from 152,051 to 152,747 bp and a total of 128 genes were identified. High consistency patterns of codon bias, repeats, divergent analysis, single nucleotide polymorphisms (SNP) and insertions and deletions (InDels) were discovered across the genus. Variations in gene length and the presence of the pseudogene ycf1 Ψ , resulting from IR contraction and expansion, are reported. The hyper-variable gene rpl16 was identified for its exceptionally high Ka/Ks and Pi values, implying that those frequent mutations occurred as a result of positive selection. Phylogenetic relationships were recovered for the genus based on analyses of full chloroplast genomes and protein-coding genes. Overall, both genome sequences and potential molecular markers provided in this study enrich the available genomic resources for species of Litsea . Valuable genomic resources and divergent analysis are also provided for further research of the evolutionary patterns, molecular markers, and deeper phylogenetic relationships of Litsea .

Actinodaphne lecomtei C.K.Allen, 1938 is an evergreen tree of the Lauraceae family and grows at the mountainous areas of southwestern China. In this study, we presented the first complete chloroplast genome sequence of A. lecomtei. We analyzed the chloroplast genome structure of A. lecomtei and performed a phylogenetic analysis. The complete chloroplast genome of A. lecomtei was 152,863 bp in length which contains a large single-copy (LSC) region of 93,763 bp, a small single-copy (SSC) region of 18,814 bp, and two inverted repeat (IR) regions of 20,143 bp. The analysis identified 128 genes, comprised of 84 protein-coding genes, 36 tRNAs, and eight rRNAs. The GC content of A. lecomtei complete chloroplast genome was 39.1%. The phylogenetic analysis result demonstrated that A. lecomtei was closely related to A. obovate. [ABSTRACT FROM AUTHOR]