Arecaceae is a species-rich clade of Arecales, while also being regarded as a morphologically diverse angiosperm family with numerous species having significant economic, medicinal, and ornamental value. Although in-depth studies focused on the chloroplast structure of Arecaceae, as well as inferring phylogenetic relationships using gene fragments, have been reported in recent years, a comprehensive analysis of the chloroplast structure of Arecaceae is still needed. Here we perform a comprehensive analysis of the structural features of the chloroplast genome of Arecaceae, compare the variability of gene sequences, infer phylogenetic relationships, estimate species divergence times, and reconstruct ancestral morphological traits. In this study, 74 chloroplast genomes of Arecaceae were obtained, covering five subfamilies. The results show that all chloroplast genomes possess a typical tetrad structure ranging in size between 153,806-160,122 bp, with a total of 130-137 genes, including 76-82 protein-coding genes, 29-32 tRNA genes, and 4 rRNA genes. Additionally, the total GC content was between 36.9-37.7%. Analysis of the SC/IR boundary indicated that the IR region underwent expansion or contraction. Phylogenetic relationships indicate that all five subfamilies in Arecaceae are monophyletic and that Ceroxyloideae and Arecoideae are sister groups (BS/PP = 100/1). The results of molecular dating indicate that the age of the crown group of Arecaceae is likely to be 96.60 [84.90-107.60] Ma, while the age of the stem group is 102.40 [93.44-111.17] Ma. Reconstruction of ancestral traits indicate that the ancestral characteristics of the family include monoecious plants, one seed, six stamens, and a smooth pericarp.

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Artocarpus altilis (Parkinson ex F.A. Zorn) Fosberg is native to the Pacific Islands, India, and the Philippines. It is also cultivated in Taiwan and Hainan. The complete plastome of the species was assembled and annotated in this study. The circular genome was 160,184 bp in size, presenting a typical quadripartite structure including two inverted repeats (IRs) of 25,734 bp, a large single-copy (LSC) of 88,791 bp, and a small single-copy (SSC) of 19,925 bp. The genome contained 132 genes, including 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The total G/C content of complete plastome was 36.0%, with the corresponding values of the LSC, SSC, and IR being 33.7%, 28.8%, and 42.7%, respectively. The complete plastome sequence of A. altilis (Parkinson ex F.A. Zorn) Fosberg will make contributions to the conservation genetics of this species as well as to phylogenetic studies of Moraceae.

Cymbidium tortisepalum (Orchidaceae) has been ranked as an endangered (EN) herb species in China. In this study, we report and characterize the complete plastid genome sequence of C. tortisepalum var. longibracteatum in order to provide genomic resources helpful for promoting its conservation and garden utilization. The complete plastome is 150,198 bp in length and contains the typical quadripartite structure of angiosperm, including two Inverted Repeat (IRs) regions of 25,682 bp, a Large Single-Copy (LSC) region of 85,035 bp and a Small Single-Copy (SSC) region of 13,799 bp. The plastome contains 111 genes, consisting of 77 unique protein-coding genes, 30 unique tRNA gene and 4 unique rRNA genes. The overall A/T content in the plastome of C. tortisepalum var. longibracteatum is 62.90%. The complete plastome sequence of C. tortisepalum var. longibracteatum will provide a useful resource for the conservation and garden utilization of this species as well as for the phylogenetic studies of Orchidaceae.