Herbariomic approach solved identity crisis of the putatively extinct Armeria arcuata Welw. ex Boiss. & Reut. (Plumbaginaceae)

Background and Aims Nowadays, herbaria are powerful sources of data and material that can be used for analyses other than taxonomic purposes. Improved techniques of DNA extraction from old herbarium specimens combined with modern and relatively cheap genomic tools allow the reassessment of the identity of important specimens, with potential consequences for the conservation status of species. In this study, we used a genomic approach applied to type herbarium specimens from the mid-19th century to elucidate the taxonomic identity of Armeria arcuata and correctly identify a living plant (code: 1984BL00463) cultivated at the Utrecht University Botanic Gardens, which was suggested to represent the last individual of the Portuguese endemic A. arcuata.Methods DNA was extracted from historical herbarium specimens of A. arcuata, the living specimen at Utrecht Botanic Gardens and selected specimens of seven other Armeria species. Genomic sequencing was conducted on chloroplast and nuclear ribosomal DNA regions, using Illumina and Nanopore technologies. Phylogenetic analyses were then performed to compare the sequences extracted.Key Results The chloroplast genome highlights similarities of 1984BL00463 to the Armeria maritima group including the South American Armeria curvifolia, whereas the nuclear ribosomal DNA suggests a relationship of 1984BL00463 to Armeria caespitosa. Our results suggest that 1984BL00463 differs substantially from the type specimens of A. arcuata and might have a hybrid origin. Therefore, A. arcuata is declared extinct. Our results support that A. arcuata was a hybrid, one of whose progenitors was a sand-dune coastal species, Armeria pungens, but are inconclusive regarding whether it was an established or an ephemeral hybrid.Conclusions Armeria arcuata is confirmed as extinct, and the Utrecht specimen represents a distinct lineage, potentially also of hybrid origin. This study highlights the importance of genomic tools in re-evaluating the status of rare or extinct species, demonstrating how herbarium and living botanical collections can complement conservation efforts and resolve taxonomic ambiguities. The approach presented here can inform similar studies on other putatively extinct taxa, guiding conservation priorities and strategies for biodiversity preservation.