Phylogenetic relationships of Secamonoideae based on the plastid gene matK, morphology, and biomechanics

Relationships between Secamonoideae and their closest relatives in Apocynaceae, as well as genera and species within the subfamily, have been examined, using a molecular phylogeny with the plastid gene matK. Our molecular results show that Secamonoideae form a monophyletic group. Delimitations of genera are also discussed together with the evolution of pollinarium and biomechanical characters within species. The patterns of pollinial organization, as well as change in growth forms, are mapped onto a phylogenetic tree obtained from the plastid gene matK, all of which together significantly contribute toward a better understanding of the evolution of the Apocynaceae s.l.