Phylogenetic relationships of Dryadoideae (Rosaceae): insights from low-copy nuclear genes and morphological-anatomical characters

The subfamily Dryadoideae (Rosaceae) includes the genera Dryas, Cercocarpus, Purshia, and Chamaebatia. Previous phylogenetic studies have recovered conflicting relationships among these genera between nuclear and chloroplast data. Here, we present a phylogenetic reconstruction of Dryadoideae based on broad sampling of taxa and low-copy nuclear data obtained through gene capture. These data were analyzed using the gene-tree summary method ASTRAL-IV and a concatenated analysis employing maximum likelihood. The results recovered Dryadoideae as a well-supported clade. Cercocarpus, Purshia, and Chamaebatia were each recovered as monophyletic, and the three sampled species of Dryas formed a clade. Both methods recovered the same intergeneric topology with high support. Dryas was recovered as the sister group to the other three genera. Chamaebatia and Purshia were recovered as sister, and Cercocarpus as the sister group to both. Nevertheless, a high degree of discordance was detected among the gene trees at some nodes that establish intergeneric relationships. This discordance seems to be compatible with biological processes such as incomplete lineage sorting. Additionally, morphological and foliar anatomy characters were mapped. This allowed for the identification of characteristics consistent with the phylogeny. For example, Dryas has a greater number of sepals and petals compared to the other genera. Cercocarpus, Chamaebatia, and Purshia share anatomical characteristics such as the presence of idioblasts and secondary growth on the primary vein. This work provides a well-supported phylogenetic hypothesis among the genera of Dryadoideae and contributes to understanding the evolution and diversification of the subfamily.