Extremely low nucleotide diversity among thirty-six new chloroplast genome sequences from (Heliantheae, Asteraceae) and comparative chloroplast genomics analyses with closely related genera.

(Heliantheae, Asteraceae) is a diverse genus in the sunflower family. To date, nearly 200 Asteraceae chloroplast genomes have been sequenced, but the plastomes of remain undescribed. Plastomes in Asteraceae usually show little sequence divergence, consequently, our hypothesis is that species of will be overall conserved. In this study, we newly sequenced 36 plastomes of and of five species belonging to other Heliantheae genera selected as outgroups (i.e., var. We analyzed the structure and gene content of the assembled plastomes and performed comparative analyses within and with other closely related genera. As expected, plastomes are very conserved, with the overall gene content and orientation being similar in all studied species. The length of the plastome is also consistent and the junction between regions usually contain the same genes and have similar lengths. A large ∼20 kb and a small ∼3 kb inversion were detected in the Large Single Copy (LSC) regions of all assembled plastomes, similarly to other Asteraceae species. The nucleotide diversity is very low, with only 1,509 variable sites in 127,466 bp (i.e., 1.18% of the sites in the alignment of 36 plastomes, with one of the IRs removed, is variable). Only one gene, , shows signatures of positive selection. The plastomes of the selected outgroups feature a similar gene content and structure compared to and also present the two inversions in the LSC region. Deletions of different lengths were observed in the gene . Multiple SSRs were identified for the sequenced and outgroups. The phylogenetic analysis shows that is not monophyletic due to the position of the Mexican species . All Brazilian species form a strongly supported clade. Our results bring new understandings into the evolution and diversity of plastomes at the species level.