Integrative Taxonomy of Armeria arenaria (Plumbaginaceae), with a Special Focus on the Putative Subspecies Endemic to the Apennines

SIMPLE SUMMARY: Armeria arenaria is a highly variable Western European species, for which three subspecies are recorded in Italy. Armeria arenaria subsp. arenaria has been reported from Northern Italy, while A. arenaria subsp. marginata and A. arenaria subsp. apennina are considered endemic to the Apennines. The taxonomic value of these two latter taxa is unclear and the actual occurrence of A. arenaria s.str. in Italy has never been addressed. Following an integrated taxonomic approach, in this study we show that all the Italian records of A. arenaria s.str. should be actually referred to A. arenaria subsp. praecox and that only one Northern Apennine endemic taxon can be recognized, namely, A. arenaria subsp. marginata. ABSTRACT: Three subspecies of Armeria arenaria are reported from Italy, two of which are considered endemic to the Apennines. The taxonomic value of these two taxa (A. arenaria subsp. marginata and A. arenaria subsp. apennina) is unclear. Moreover, the relationships between A. arenaria subsp. praecox and Northern Italian populations—currently ascribed to A. arenaria subsp. arenaria—have never been addressed. Accordingly, we used an integrated taxonomic approach, including morphometry, seed morpho–colorimetry, karyology, molecular systematics (psbA–trnH, trnQ–rps16, trnF–trnL, trnL–rpl32, and ITS region), and comparative niche analysis. According to our results, French–Northern Italian populations are clearly distinct from Apennine populations. In the first group, there is evidence which allows the recognition of A. arenaria s.str. (not occurring in Italy) and A. arenaria subsp. praecox. In the second group, the two putative taxa endemic to the Northern Apennines cannot be separated, so a single subspecies is here recognized: A. arenaria subsp. marginata.