Rediscovery of Lysimachia peduncularis in China: amended description, complete plastid genome, and phylogenomic placement in subgenus Idiophyton (Primulaceae)

Background and aims – Lysimachia peduncularis has not been recorded in China for nearly half a century. Its recent rediscovery in southern Yunnan provides a critical opportunity to update its taxonomic description, clarify its nomenclatural history, and re-evaluate its systematic placement using comprehensive genomic data. Material and methods – We conducted detailed comparative morphological analysis based on newly collected specimens.

Molecular phylogenetic relationships were reconstructed using nrITS, three plastid DNA regions (atpF-atpH, trnL-trnF, and rpl 32 - trnL), and the first reported complete plastome for this species. Key results – Phylogenomic evidence strongly supports L. peduncularis as sister to a clade comprising L. laxa and L. lancifolia, nested firmly within L. subg. Idiophyton.

This robust placement revises its traditional classification, which was based solely on morphology. Notably, L. peduncularis exhibits an atypical ratio of filament-to-anther length, departing from the general pattern observed in Lysimachia. While this trait remains a key diagnostic character for the subgenus, its variation in this species underscores the need for caution when using single morphological traits for infrageneric classification.

Conclusion – This rediscovery not only confirms the current status of L. peduncularis in China and expands its known distribution but also resolves its phylogenetic position. These findings contribute to a more nuanced understanding of the evolutionary history and character evolution within Lysimachia.