PRJNA791641
Hydrangea sect. Aspera RADseq sequencing
The genus Hydrangea is plagued by taxonomical difficulties, among them the lack of clearly defined species boundaries, which is especially apparent in section Asperae. This group harbors several distinct morphotypes connected by intermediate forms, which obscure species boundaries. This uncertainty translates into fluctuating species numbers in subsequent revisions of Hydrangea. The explicit adoption of a species concept as a rigorous framework, integrating molecular and morphological data will aid in stabilizing species-level taxonomy. Since the application of Sanger sequencing-based markers was unsatisfactory, here the utility of RAD sequencing markers for resolving plant species complexes is evaluated. Based on a sampling of 26 specimens identified as ten nominal taxa, RADseq markers were used to conduct a variety of species delimitation algorithms. Additionally, since the dataset utilized in this study largely coincides with a previous study utilizing low copy nuclear markers for the same goals, both methods can be compared. Despite low and uneven sequencing coverage, the RAD data could be used to gain additional evidence towards recognition of H. involucrata, H. kawakamii, H. longifolia, H. longipes, H. sargentiana, H. sikokiana and H. villosa as independently evolving metapopulation lineages. Nominal taxon H. strigosa contained two genetic lineages, of which only one is recognized as a species, while H. aspera and H. robusta were indistinguishable. Therefore, the current study corroborates the earlier findings based on traditional Sanger sequencing, demonstrating the utility of RADseq for species delimitation in the focal group.