Phylogenomics supported by geometric morphometrics reveals delimitation of sexual species within the polyploid apomictic Ranunculus auricomus complex (Ranunculaceae)

Species are the basic units of biodiversity and evolution. Nowadays, they are widely considered as ancestor-descendant lineages. Their definition remains a persistent challenge for taxonomists due to lineage evolutionary role and circumscription, i.e., persistence in time and space, ecological niche or a shared phenotype of a lineage. Recognizing and delimiting species is particularly methodically challenging in fast-evolving, evolutionary young species complexes often characterized by low genetic divergence, hybrid origin, introgression and incomplete lineage sorting (ILS). Ranunculus auricomus is a large Eurasian apomictic polyploid complex that probably has arisen from the hybridization of a few sexual progenitor species. However, even delimitation and relationships of diploid sexual progenitors have been unclearly ranging from two to twelve species. Here, we present an innovative workflow combining phylogenomic methods based on 86,782 parameter-optimized RADseq loci and target enrichment of 663 nuclear genes together with geometric morphometrics to delimit sexual species in this evolutionary young complex (