Plastome evolution and phylogenetic relationships among Malvaceae subfamilies.

Malvaceae s.l. is the largest family of Malvales, comprising more than 4225 species. Within Malvaceae, the phylogenetic relationships among subfamilies remain controversial. To resolve these relationships and explore plastome evolution in Malvaceae, we assembled a complete plastome data set of 39 Malvales species, including newly reported sequences for 13 Malvaceae and two Dipterocarpaceae species. All species possessed the typical quadripartite structure of angiosperm plastomes, but significant independent expansions of the Inverted Repeat regions were detected in Abelmoschus esculentus and Durio zibethinus. Nine coding sequences were identified with positively selected sites in Malvaceae. Several highly variable noncoding and coding regions were identified in the plastomes of Malvaceae that may be valuable for phylogenetic reconstruction at lower taxonomic levels. Phylogenetic reconstructions based on 78 protein-coding genes strongly supported nearly all relationships among Malvaceae subfamilies. The diversification of the subfamilies of Malvaceae was dated to the late Cretaceous and early Eocene, during a time of global warmth.