Conclusion
We successfully assembled the genome of Tiarella polyphylla and reported the first chromosome-level assembly of Saxifragales. We leveraged this genome to generate a large nuclear gene dataset covering all superrosid orders, as well as microsynteny data from complete genome assemblies to resolve relationships. We provided strong support for Vitales as a sister to core rosids and Saxifragales. We also resolved the relationships within the core rosids, demonstrating new circumstances for fabids and malvids. There is a strong discordance between nuclear and plastid phylogenetic hypotheses for superrosid relationships, and our work demonstrates that this is best explained by a combination of incomplete lineage sorting and ancient reticulation.