Plastid genome evolution of a monophyletic group in the subtribe Lauriineae (Laureae, Lauraceae).

, a non-monophyletic group of the tribe Laureae (Lauraceae), plays important roles in the tropical and subtropical forests of Asia, Australia, Central and North America, and the islands of the Pacific. However, intergeneric relationships between and , , and of the tribe Laureae remain unresolved. In this study, we present phylogenetic analyses of seven newly sequenced plastomes, together with 47 Laureae plastomes obtained from public databases, representing six genera of the Laureae. Our results highlight two highly supported monophyletic groups of taxa. One is composed of 16 taxa and two taxa. The 18 plastomes of these taxa were further compared for their gene structure, codon usage, contraction and expansion of inverted repeats, sequence repeats, divergence hotspots, and gene evolution. The complete plastome size of newly sequenced taxa varied between 152,377 bp () and 154,117 bp (). Seven of the 16 plastomes have a pair of insertions in the IRa (-) and IRb () regions. The 18 plastomes of and taxa exhibit similar gene features, codon usage, oligonucleotide repeats, and inverted repeat dynamics. The codons with the highest frequency among these taxa favored A/T endings and each of these plastomes had nine divergence hotspots, which are located in the same regions. We also identified six protein coding genes (, , , , and ) under positive selection in ; these genes may play important roles in adaptation of species to various environments.