Biogeography and character-mapping of Hiptage (Malpighiaceae) corroborate Indochina's rainforests as one of the main sources of plant diversity in southeastern Asia

In Malpighiaceae, Hiptage represents one of the seven past dispersal events from the Neotropics to the Paleotropical region, being by far the most widely diversified and distributed genus of Paleotropical Malpighiaceae. In this study, we tested the current infrageneric classification of Hiptage with a dated and calibrated molecular phylogeny. We also reconstructed ancestral areas to elucidate which route led to the colonization of southeast Asia by the most recent common ancestor (MRCA) of this genus. The pre-existing infrageneric classification of Hiptage was incompatible with monophyly being based solely on homoplasic morphological characters, such as the presence and number of sepal glands. The MRCA of Hiptage arose in the rainforests of southeast Asia ca 24.0 Mya and greatly diversified in this region. Few lineages have dispersed eastward to the pacific islands or westwards to India. Based on our results, we hypothesize that the MRCA of Hiptage did not take the Indian route to reach southeastern Asia. Instead, it reached this region by past mainland forest connections between North America-Europe (Boreotropical hypothesis) and southeast Asia. Nonetheless, distribution ranges for the species of Hiptage must be carefully revised, and the five species of Hiptage endemic to India must also be sampled so we can properly test which route led the MRCA of Hiptage to reach southeast Asia in the early Miocene.