Plastome‐Based Phylogenomics Resolves Phylogenetic Complexity in Lysimachia and Reveals Unexpected Placement of L. thyrsiflora <

ABSTRACT

The genus Lysimachia is taxonomically complex, especially in East Asia. We analyzed the complete chloroplast (cp) genomes of four Lysimachia species ( L . acroadenia , L. leucantha , L. thyrsiflora , and L. arvensis ). The cp genomes (153–155 kb) showed the typical quadripartite structure. Comparative analysis identified two highly variable regions, which are promising molecular markers. Most protein‐coding genes showed Ka/Ks ratios below 1, but rps 12 and psa I showed elevated Ka/Ks ratios that require further validation using codon‐based selection tests. The Maximum likelihood phylogenetic tree confirmed the monophyly of Lysimachia . Importantly, L. thyrsiflora clustered within subgenus Lysimachia section Lysimachia , contradicting its traditional classification and suggesting a complex biogeographic history, potentially involving historical connections across the Bering Land Bridge. Divergence time analysis estimated the genus origin at approximately 33 Mya. Our results clarify the phylogenetic status of key taxa and provide essential genomic resources for future evolutionary and taxonomic research on Lysimachia .