Molecular phylogenetic analysis of Hawaiian Rutaceae (Melicope, Platydesma and Zanthoxylum) and their different colonization patterns

Melicope (Rutaceae) is one of the largest plant genera on the Hawaiian Islands. We present here a detailed molecular phylogenetic analysis of the Hawaiian species of this genus and compare the results with the other genera of Hawaiian Rutaceae, Platydesma and Zanthoxylum. Four nuclear and two plastid markers were sequenced, with the goals of untangling phylogenetic relationships, inferring biogeographic events and comparing patterns of distribution among the three genera. Our results show that there were two colonization events (Melicope+Platydesma, and Zanthoxylum) to the Hawaiian Islands, that Hawaiian Rutaceae have an Asian, Australian or Pacific origin and that there were two independent colonization events of Hawaiian Melicope lineages to the Marquesas Islands. The two most widely distributed Hawaiian Melicope spp. are not monophyletic and the current subgeneric classification of Hawaiian Melicope is highly artificial. On the Hawaiian Islands, Melicope and Zanthoxylum show contrasting biogeographic patterns, suggesting different patterns of dispersal. Melicope has a high percentage of single-island endemics suggesting low dispersal ability, whereas Zanthoxylum taxa tend to occur across multiple islands.