Plastid phylogenomic analysis of tribe Myoporeae (Scrophulariaceae)

This study presents an analysis of plastomes to assess relationships among the seven genera of tribe Myoporeae (Scrophulariaceae). Sampling included individuals from type species for all seven genera included in Myoporeae (Bontia, Calamphoreus, Diocirea, Eremophila, Glycocystis, Myoporum, Pentacoelium), one additional species of the large genus Eremophila, one representative of the sister tribe Leucophylleae (Leucophyllum), and the previously published plastome of Scrophularia takesimensis as an outgroup. Phylogenetic analyses were performed using maximum parsimony and Bayesian inference analyses based on > 7000 variable nucleotide positions. Maximum parsimony analysis produced a single tree with the same topology as the Bayesian consensus tree, and all nodes were fully resolved with 100% bootstrap support and 1.0 Bayesian posterior probability. Tribe Myoporeae was supported as monophyletic and sister to Leucophylleae. Two lineages are identified within Myoporeae; one containing the Australian endemic genera Calamphoreus, Diocirea, Glycocystis and the type species of Eremophila (E. oppositifolia), the second containing species with distributions outside of Australia (Bontia, Myoporum, Pentacoelium) and a species of Eremophila (E. gibbifolia). Eremophila is thus supported as polyphyletic. The application of genome skimming and assembly of plastomes has resolved generic relationships in tribe Myoporeae and revealed variable regions of the genome that will be useful in further genetic study of the group.