Comparative plastome analyses and phylogenetic insights of Stellaria (Caryophyllaceae)

Stellaria (Caryophyllaceae) comprises approximately 112 species globally, with China serving as a significant center of diversity hosting about 64 species. Despite its taxonomic importance, the genus remains insufficiently studied in China. Previous phylogenetic studies relying on limited DNA barcodes produced weakly supported inferences, while those based on chloroplast genomes are currently lacking. Here, we characterize the chloroplast genome structure and reconstruct its highly resolved infrageneric phylogeny using 60 newly sequenced plastomes. All plastomes displayed a conserved quadripartite structure, with lengths varying from 147,205 bp to 149,409 bp, GC contents ranging from 36.6% to 36.7%, and gene counts spanning 128 to 129 genes. Codon usage patterns were highly conserved with leucine encoded by UUA exhibiting the highest relative synonymous codon usage. A total of 55-74 simple sequence repeats and 42-64 long repeats were detected. Three hypervariable regions-petN-psbM, trnP-rpl33, and ycf1 were identified as promising candidate DNA barcodes. Phylogenomic analysis resolved Stellaria into three strongly supported major clades and 15 well-defined subclades. The results are largely consistent with the established phylogeny of Stellaria. However, we observed certain discrepancies within specific clades. We propose some suggestions for these clades and species based on morphological and molecular evidence. This study provides the first comprehensive phylogenetic framework for Stellaria based on the chloroplast genome, establishing a robust foundation for future taxonomic revisions and evolutionary studies.