Waldsteinia within Geum s.l. (Rosaceae): Main Aspects of Phylogeny and Speciation History

Waldsteinia is a small plant genus inhabiting the temperate regions of the Northern Hemisphere. According to the latest revisions, Waldsteinia is included in Geum. We have obtained a phylogenetic reconstruction based on the nuclear (ITS) and plastid (trnL-trnF) DNA to understand the phylogenetic structure of Waldsteinia and its relationships with other taxa of Geum s.l. Phylogenetic analysis based on the joint ITS + trnL-trnF dataset demonstrated Waldsteinia monophyly. The phylogenetic relationships of Waldsteinia species were better explained by their geographical distribution than their morphology. Hence, Euro-Siberian, Northeast Asian, and North American phylogeographic groups were distinguished, with East Asia having been suggested as the place of Waldsteinia origin. Considering the incongruence in W. geoides (a type species) position on the plastid and nuclear DNA trees, together with the discrepancy between the species morphology and its location on the plastid DNA tree, a hybrid origin was suggested for this species. Despite the fact that the position of W. maximowicziana is still not fully resolved, we support the point of view that claims it should be separated from the W. ternata aggregate (traditionally including W. trifolia, W. ternata s.str., and W. maximowicziana) and considered a separate species. The American W. doniana, W. fragarioides, and W. lobata belong to a single maternal lineage, but the observed genetic differences are too small to serve as a convincing argument for species segregation, so their relationships still remain unresolved.

Automated summary

This study revealed that Waldsteinia is a part of the Geum genus, with the phylogenetic relationships among Waldsteinia species being better explained by their geographical distribution rather than their morphology. The study suggested that Waldsteinia originated in East Asia and proposed a hybrid origin for W. geoides. The classification of W. maximowicziana is still controversial, but the study supports separating it from the W. ternata group and considering it as a separate species. The relationships among the American species W. doniana, W. fragarioides, and W. lobata remain unresolved.