A revision of the genus Armeria (Plumbaginaceae) in peninsular Italy and Sicily through an integrative taxonomic approach

The genus Armeria in peninsular Italy has been affected by taxonomic ambiguity for more than a century due to high morphological variability. We present a comprehensive revision of peninsular Italian and Sicilian Armeria species, using an integrated taxonomic approach that combines molecular phylogeny, plant and seed morphometrics, and cytogenetics, taking advantage of species delimitation and data integration methods. Nuclear (ITS) and chloroplast (trnF-trnL, trnH-psbA, trnL-rpl32, trnQ-rps16) markers were sequenced to construct phylogenetic trees and conduct species delimitation using assemble species by automatic partitioning (ASAP), while seed and plant morphometric data were analysed using dimensionality reduction techniques and Gaussian mixture models (GMMs) for conducting Bayesian inference on species boundaries. The results support the hypothesis of 10 species endemic to the Italian peninsula. Armeria gracilis subsp. majellensis is no longer recognised as a distinct subspecies due to insufficient differentiation from A. gracilis s.str., while the occurrence of A. canescens in Italy is definitively excluded. On the contrary, we propose to raise A. gracilis var. pollinensis to species level, with its name lectotypified herein. A new identification key is provided. The findings confirm Italy as a second biodiversity hotspot for the genus, emphasizing the value of integrated data and methods to resolve taxonomically challenging groups, providing also a framework for future genus-wide revisions.