Dissolution of Convolvulaceae tribe Merremieae and a new classification of the constituent genera

Abstract

The classification of Convolvulaceae tribe Merremieae has remained a challenge. Merremia, the largest genus, encompasses a wide range of morphological variation, particularly in characters such as fruit dehiscence and pollen apertures, which are usually diagnostic at the generic and even tribal level in the family. The taxonomy of the tribe and the included genera has been difficult, especially in assigning species to genera. Recent molecular phylogenetic studies did not find support for the monophyly of Merremieae and demonstrated that Merremia is polyphyletic. However, strongly supported monophyletic groups were discovered and diagnosable synapomorphies were identified for these. The present study addresses the taxonomic issues with 'Merremieae', highlighted by previous molecular results. The tribal rank for 'Merremieae' is abandoned due to lack of morphological and molecular evidence and the constituent genera are re-assessed. Morphological, palynological and molecular data are synthesized to propose a new generic classification for the group. The delimitation of Merremia is drastically narrowed. Three new genera are circumscribed and names previously published are here applied to these. New combinations are published for all taxa that can confidently be placed in this new generic scheme based on existing molecular and/or morphological data.