Phylogeny of the Styracaceae Revisited Based on Whole Plastome Sequences, Including Novel Plastome Data from Parastyrax

Abstract

Abstract—The phylogenetic relationships among 11 out of the 12 genera of the angiosperm family Styracaceae have been largely resolved with DNA sequence data based on all protein-coding genes of the plastome. The only genus that has not been phylogenomically investigated in the family with molecular data is the monotypic genus Parastyrax, which is extremely rare in the wild and difficult to collect. To complete the sampling of the genera comprising the Styracaceae, examine the plastome composition of Parastyrax, and further explore the phylogenetic relationships of the entire family, we sequenced the whole plastome of P. lacei and incorporated it into the Styracaceae dataset for phylogenetic analysis. Similar to most others in the family, the plastome is 158189 bp in length and contains a large single-copy region of 88085 bp and a small single-copy region of 18540 bp separated by two inverted-repeat regions of 25781 bp each. A total of 113 genes was predicted, including 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. Phylogenetic relationships among all 12 genera of the family were constructed with 79 protein-coding genes. Consistent with a previous study, Styrax, Huodendron, and a clade of Alniphyllum + Bruinsmia were successively sister to the remainder of the family. Parastyrax was strongly supported as sister to an internal clade comprising seven other genera of the family, whereas Halesia and Pterostyrax were both recovered as polyphyletic, as in prior studies. However, when we employed either the whole plastome or the large- or small-single copy regions as datasets, Pterostyrax was resolved as monophyletic with 100% support, consistent with expectations based on morphology and indicating that non-coding regions of the Styracaceae plastome contain informative phylogenetic signal. Conversely Halesia was still resolved as polyphyletic but with novel strong support.