Systematics and character evolution of Vinceae (Apocynaceae)

Abstract

AbstractVinceae comprises 9 genera and about 153 species. The genera differ greatly in a number of morphological traits, especially those relating to fruit and seeds, which resulted in their placement in different tribes and/or subtribes by earlier taxonomists. Here, 378 new chloroplast DNA sequences from 98 species from 5 tribes of the rauvolfioid grade were analyzed phylogenetically to test the monophyly of Vinceae, its 6 subtribes, and constituent genera, as well as the sectional treatments of Rauvolfia, and to find morphological synapomorphies for major clades. Vinceae, as currently circumscribed, was found to be monophyletic as were four of the six subtribes. Kopsia and Ochrosia were confirmed as successive sister groups to the rest. All nine genera currently recognized in the tribe were resolved as monophyletic, Laxoplumeria and Tonduzia for the first time. The broad circumscription of Petchia and Ochrosia proposed by previous authors was supported. The pantropical genus Rauvolfia is divided into two major lineages: one comprised entirely of paleotropical species, and the other the neotropical species, a recurring geographic pattern in the family. Surprisingly, the Hawaiian species of Vinceae have probably arisen by two different trans‐oceanic routes, either by long‐distance dispersal from Australasian (Ochrosia spp.) or Caribbean (Rauvolfia sandwicensis) ancestors. Within Rauvolfia, most of the sections, series and subseries recognized in previous classifications are paraphyletic. Only 2 of the 14 sections of Rauvolfia proposed by Pichon and 1 of the 11 sections proposed by Rao that are not monospecific were found to be monophyletic. Mapping of 30 morphological characters onto the molecular tree identified an unlobed upper wreath on the style head as an unambigous synapomorphy characterizing the tribe as well as synapomorphies for each of its genera. The two earliest‐branching genera, Kopsia and Ochrosia, have dextrorse corolla lobe aestivation, in contrast to the sinistrorse corollas of the other Vinceae and the great majority of genera throughout the rauvolfioid grade. Drupes have arisen in parallel at least three times within Vinceae. The adaptations of the endocarp for water dispersal are possibly ancestral in the tribe, and the observed morphological differences between the drupaceous fruits of Kopsia/Ochrosia versus Petchia and Rauvolfia may be due to their abiotic versus biotic dispersal mode, respectively.