Comparative Chloroplast Genomics Reveals Intrageneric Divergence in .

As the most diverse genus of Salicaceae, is primarily distributed in the temperate zone of the Northern Hemisphere, encompassing 350-500 species worldwide. The genus's evolutionary history is complex due to significant genetic differentiation. Chloroplast genes, being highly conserved, serve as effective tools for studying uniparental inheritance and evolution. In this study, we sequenced and assembled the chloroplast genomes of five representative species. Phylogenetic relationships were constructed using chloroplast genome data, and structural differences among lineages were compared. These chloroplast genomes exhibited a typical quadripartite structure, with lengths ranging from 154,444 to 155,725 bp. We successfully annotated 131 genes, including 88 protein-coding genes, 35 tRNA genes, and 8 rRNA genes. Clade I showed higher variability in the SSC region, identifying five highly variable regions: , , , , and . Two rapidly evolving genes, and , were also identified. The total length of insertions and deletions (InDels) in Clade I was 1046 bp. Clade II exhibited greater variability in the LSC region, with four highly variable regions being identified: , , , and . Four rapidly evolving genes-, , , and -were identified. The total length of InDels in Clade II was 1282 bp. Therefore, this study elucidated the chloroplast genome evolution across different lineages, thereby providing deeper insights into intrageneric phylogenetic relationships.