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

Abstract

Background and aims: Herbaria are powerful sources of data and material nowadays 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 on species conservation status. 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: While the chloroplast genome highlights similarities of 1984BL00463 with the Armeria maritima group including the South American A. curvifolia, the nrDNA suggests a relationship of 1984BL00463 with A. caespitosa. Our results suggest that 1984BL00463 differs substantially from the type specimens of A. arcuata and may 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, A. pungens, but are inconclusive as to whether it was an established or an ephemeral hybrid.

Conclusions: Armeria arcuata is confirmed as extinct, while the Utrecht specimen represents a distinct lineage, potentially of hybrid origin too. 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.