Reinstating Palaeotropical genera of Convolvulaceae: Argyreia, Stictocardia, Turbina and Astripomoea (tribe Ipomoeeae, subtribe Argyreiineae)

Abstract

Ipomoeeae, the most diverse tribe in Convolvulaceae, contains 815 species, nearly half of the species diversity of the family. Its largest genus, Ipomoea, is morphologically highly variable and has repeatedly been demonstrated to be polyphyletic, with several Palaeotropical genera nested within it. A generic reclassification of the tribe is, however, still lagging due to the sizeable task of sequencing and morphologically characterising the 815 species, and an intricacy related to the type species of Ipomoea, which could lead to a major nomenclatural destabilisation - especially in the Neotropicalregion,wherethegreatestdiversityofIpomoea is concentrated. Previous researchers, while making good progress in molecular studies of Ipomoeeae, have opted to consolidate all the previously recognised genera of Ipomoeeae into an even broader, morphologically ambiguous, Ipomoea. This resulted in 206 nomenclatural changes, of which only 5 Neotropical taxa, and the remaining 201 African, Asian, Australian, or Malagasy taxa; therefore, with the greatest impact on species and genera from the Eastern Hemisphere. We suggest that tribe Ipomoeeae is better understood as a collection of smaller, morphologically distinguishable clades rather than a single expanded genus, morphologically more challenging to circumscribe, with greater benefits also for species conservation, as species of genus Ipomoea tend to be negatively perceived as weeds in the Eastern Hemisphere. As the nomenclatural blockage to reclassifying this complex group has now been resolved, with the proposal of a new type species, we propose the reinstatement of the most clearly delimited and phylogenetically distinct, Palaeotropical genera of the tribe - Argyreia, Astripomoea, Turbina and Stictocardia. As these genera are widely recognised (e.g. in herbarium collections, local Floras, and databases), this will allow to minimise nomenclatural disruption caused by the proposed transfer into Ipomoea, before it becomes more widely implemented, and thus mitigating the impact of these name changes on biodiversity monitoring, conservation, horticulture, or citizen science. This will also be a contribution for an improved classification of tribe Ipomoeeae, for which an integrative and more equitable approach, with the contribution of taxonomists from the Eastern Hemisphere, and further sampling in this region, will be pillar.