Phylogeographic and taxonomic considerations on Goniolimon tataricum (Plumbaginaceae) and its relatives from south-eastern Europe and the Apennine Peninsula

Goniolimon species are mainly components of the Eurasian steppe or steppe-like rocky vegetation, with some taxa occurring also in south-eastern Europe and northern Africa. We analysed the variability of: (i) two maternally inherited plastid loci (rpl32-trnL and 3′rps16-5′trnK) in 110 individuals of six currently accepted species from the Balkans and one species from the Apennines, to provide new insights into their origin and evolutionary history; and (ii) quantitative morphological characters (14 independent characters and one ratio character) in 641 individuals of three species of which two are morphologically and ecologically similar (G. italicum and G. tataricum) and the third, G. dalmaticum, was frequently misidentified as G. tataricum in the past, to provide new taxonomic treatment for proposed G. tataricum subspecies. We delineated several quantitative and five qualitative characters studied in a more limited sample as diagnostic for the identification of four subspecies (three newly described and one in a new rank) of G. tataricum. The history of westward peripheral populations of this species in the Balkans and the Apennines was rather complex and driven by local geo-historic events. These events facilitated multiple waves of east–west expansion of lineages originating from sources outside of the Balkan Peninsula which periodically diversified and occupied localised areas in the Balkans during the Pleistocene. An initial spread of an ancient G. tataricum lineage throughout south-eastern Europe probably occurred during the Messinian Salinity Crisis. Inter- and intraspecific hybridisation/introgression, as well as retention of ancestral polymorphisms, was common in G. tataricum and related taxa over time.