Phylogenetics of Ochna (Ochnaceae) and a new infrageneric classification.

Abstract

• Advances in high-throughput DNA sequencing are allowing faster and more affordable generation of molecular phylogenetic trees for many organisms. However, resolving relationships at species level is still challenging, particularly for taxonomically difficult groups. Until recently, the classification of Ochna had been based only on morphological data. Here, we present the first comprehensive phylogenomic study for the genus using targeted sequencing with a custom probe kit. We sampled c. 85% of species to evaluate the current infrageneric classification. Our results show that the data generated using the custom probe kit are effective in resolving relationships in the genus, revealing three sections consistent with the current classification and a new section consisting of species from Madagascar and the Mascarene Islands. Our results provide the first insights into the evolutionary relationships of several widespread and morphologically diverse species numerous poorly known and potentially new species to science. We demonstrate that for morphologically challenging groups such as Ochna, an integrated approach to classification is essential. Phylogenomic results are only informative when derived from accurately named samples. There is a symbiotic relationship between molecular phylogenomics and morphology-based taxonomy, with taxonomic expertise a requirement to accurately interpret the phylogenomic results.