The discovery of these three evolutionary lineages was only possible because, in addition to morphological studies long established in plant systematics, targeted molecular genetic studies of the Marsdenieae were carried out for the first time. The plant systematics group at the University of Bayreuth analyzed 171 of the 740 species using seven markes both from the chloroplast and nuclear genomes. In this way, some erroneous assignments in earlier taxonomic studies could be identified. As the researchers discovered, there were many parallel developments, especially in flower structure. For example, large funnel-shaped white flowers evolved independently at least five times to adapt to pollinating moths. Because such parallel developments were not recognized as such in former times, some species of the Marsdenieae were often assigned to the wrong genus.
The study, now published in Taxon, recognizes and circumscribes 37 genera, two of which are described plant-systematically for the first time. In addition, 26 species could be assigned to the correct genus. "For the correct plant-systematic classification of the Marsdenieae species, our study provides a new key based on morphological characters. However, molecular genetic analyses are sometimes indispensable for the reliable genus assignment of individual species. Only on this basis is it possible to reliably clarify how the development of traits within the different genera are related to each other – for example, whether they are independent parallel developments or successive developments in a larger evolutionary context," says Prof. Dr. Sigrid Liede-Schumann, Chair of Plant Systematics at the University of Bayreuth.
Publication:
Liede-Schumann, S.; Reuss, S. J.; Meve, U.; Gâteblé, G.; Livshultz, T.; Forster, P. I.; Wanntorp, L.; Rodda, M. 2022. Phylogeny of Marsdenieae (Apocynaceae, Asclepiadoideae) based on chloroplast and nuclear loci, with a conspectus of the genera. Taxon 71(4): 833-875. 2022. DOI: https://doi.org/10.1002/tax.12713