A phylogenetic framework for evolutionary study of the nightshades (Solanaceae): a dated 1000-tip tree

The Solanaceae is a plant family of great economic importance. Despite a wealth of phylogenetic work on individual clades and a deep knowledge of particular cultivated species such as tomato and potato, a robust evolutionary framework with a dated molecular phylogeny for the family is still lacking. Here we investigate molecular divergence times for Solanaceae using a densely-sampled species-level phylogeny. We also review the fossil record of the family to derive robust calibration points, and estimate a chronogram using an uncorrelated relaxed molecular clock.

Our densely-sampled phylogeny shows strong support for all previously identified clades of Solanaceae and strongly supported relationships between the major clades, particularly within Solanum. The Tomato clade is shown to be sister to section Petota, and the Regmandra clade is the first branching member of the Potato clade. The minimum age estimates for major splits within the family provided here correspond well with results from previous studies, indicating splits between tomato and potato around 8 Million years ago (Ma) with a 95% highest posterior density (HPD) 7-10 Ma, Solanum and Capsicum c. 19 Ma (95% HPD 17-21), and Solanum and Nicotiana c. 24 Ma (95% HPD 23-26).