Molecular phylogeny, biogeography and character evolution of the montane genus Juss. (Bignoniaceae).

The complex orogeny of the Himalaya and the Qinghai-Tibet Plateau (QTP) fosters habitat fragmentation that drives morphological differentiation of mountain plant species. Consequently, determining phylogenetic relationships between plant subgenera using morphological characters is unreliable. Therefore, we used both molecular phylogeny and historical biogeographic analysis to infer the ancestral states of several vegetative and reproductive characters of the montane genus . We determined the taxonomic position of the genus within its family and inferred the biogeographical origin of taxa through Bayesian inference (BI), maximum likelihood (ML) and maximum parsimony (MP) analyses using three molecular data sets ( sequences, nr ITS sequences, and a data set of combined sequences) derived from 81% of the total species of the genus . Within the genus-level phylogenetic framework, we examined the character evolution of 10 key morphological characters, and inferred the ancestral area and biogeographical history of the genus. Our analyses revealed that the genus is monophyletic and originated in Central Asia during mid-Oligocene ca. 29.42 Ma. The earliest diverging lineages were subsequently split into the Western Himalaya and Sino-Himalaya during the early Miocene ca. 21.12 Ma. These lineages resulted in five re-circumscribed subgenera (, , , , and ). Moreover, character mapping revealed the ancestral character states of the genus (e.g., suffruticose habit, cylindrical capsule shape, subligneous capsule texture, absence of capsule wing, and loculicidal capsule dehiscence) that are retained at the earliest diverging ancestral nodes across the genus. Our phylogenetic tree of the genus differs from previously proposed phylogenies, thereby recommending the placement of the subgenus close to the subgenus and maintaining two main divergent lineages.