Phylogeny of the popcorn flowers: Use of genome skimming to evaluate monophyly and interrelationships in subtribe Amsinckiinae (Boraginaceae)

Abstract

AbstractSubtribe Amsinckiinae, currently containing 13 genera and approximately 287 species, is a species‐rich group of the family Boraginaceae. Past studies assessing relationships had a limited sample size and generally weak support. Here we study phylogenetic relationships of Amsinckiinae using a large sample size and considerably more sequence data in order to evaluate the interrelationships of genera and clades within this group. Using high‐throughput, genome skimming sequencing of 139 samples of Amsinckiinae and four outgroup taxa, maximum likelihood and Bayesian analyses of separate plastome, cistron, and mitochondrial datasets are presented. In almost all analyses the common ancestor of the Amsinckiinae gives rise to an Andersonglossum or to an Andersonglossum + Adelinia clade. Most genera, including Amsinckia, Eremocarya, Greeneocharis, Harpagonella, Oreocarya, and Pectocarya, are consistently monophyletic with strong support. Plagiobothrys is confirmed to be non‐monophyletic, composed of three clades conforming to generic sections. Cryptantha is also non‐monophyletic, with most species within a strongly supported Cryptantha s.str. clade, but some nesting within Johnstonella or our Maritimae clade, all with strong support. Although genome skimming verifies the monophyly of many genera and clades of Amsinckiinae, relationships among those clades and along the backbone of the trees remain uncertain, their elucidation possibly a factor of short branch lengths and likely requiring different types of molecular data. Our study may serve as a baseline for future work on the morphology, reproductive biology, and biogeography of the Amsinckiinae.