Molecular phylogenetics and character evolution in Haplanthodes (Acanthaceae), an endemic genus from peninsular India.

Haplanthodes (Acanthaceae) is an Indian endemic genus with four species. It is closely related to Andrographis which is also mainly distributed in India. Haplanthodes differs from Andrographis by the presence of cladodes in the inflorescences, sub actinomorphic flowers, stamens included within the corolla tube, pouched stamens and oblate pollen grains. To understand the phylogenetic relationship of Haplanthodes with Andrographis and Haplanthus, another related genus, we used four plastid markers, matK, rbcL, psbA-trnH and trnGR to construct a molecular phylogeny. Our results established the monophyly of this genus and revealed a sister relationship to Andrographis and Haplanthus. Further, to understand the historical biogeography of the genus, we inferred the divergence time and performed ancestral area reconstruction. Our analyses suggest that Haplanthodes has evolved during Late Miocene 5.85 Ma [95%HPD: 2.18-10.34 Ma] in peninsular India where it might have shared a common ancestor with Andrographis. To understand character evolution, the ancestral states of important morphological characters were inferred based on the equal rate model and discussed. The generic status of Haplanthus is not resolved due to incomplete sampling.