Phylogenomic analyses of large-scale nuclear genes provide new insights into the evolutionary relationships within the rosids

• The Myrtales-Geraniales clade was basal to the remaining rosids.
• The COM clade was not monophyletic, Celastrales and Malpighiales formed to be sister to each other.
• The Celastrales-Malpighiales clade and Oxalidales were successive sisters to the malvids.
• Zygophyllales was basal to the “expanded” malvids (including COM orders).

The Rosids is one of the largest groups of flowering plants, with 140 families and ∼70,000 species. Previous phylogenetic studies of the rosids have primarily utilized organelle genes that likely differ in evolutionary histories from nuclear genes. To better understand the evolutionary history of rosids, it is necessary to investigate their phylogenetic relationships using nuclear genes. Here, we employed large-scale phylogenomic datasets composed of nuclear genes, including 891 clusters of putative orthologous genes. Combined with comprehensive taxon sampling covering 63 species representing 14 out of the 17 orders, we reconstructed the rosids phylogeny with coalescence and concatenation methods, yielding similar tree topologies from all datasets. However, these topologies did not agree on the placement of Zygophyllales. Through comprehensive analyses, we found that missing data and gene tree heterogeneity were potential factors that may mislead concatenation methods, in particular, large amounts of missing data under high gene tree heterogeneity. Our results provided new insights into the deep phylogenetic relationships of the rosids, and demonstrated that coalescence methods may effectively resolve the phylogenetic relationships of the rosids with missing data under high gene tree heterogeneity.

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