Genome size (GS) is an important characteristic that may be helpful in delimitation of taxa, and multiple studies have shown correlations between intraspecific GS variation and morphological or environmental factors, as well as its geographical segregation. We estimated a relative GS (RGS) of 707 individuals from 162 populations of Dianthus sylvestris with a geographic focus on the Balkan Peninsula, but also including several populations from the European Alps. Dianthus sylvestris is morphologically variable species thriving in various habitats and six subspecies have been recognized from the Balkan Peninsula. Our RGS data backed-up with chromosome counts revealed that the majority of populations were diploid (2n = 30), but ten tetraploid populations have been recorded in D. sylvestris subsp. sylvestris from Istria (Croatia, Italy). Their monoploid RGS is significantly lower than that of the diploids, indicating genome downsizing. In addition, the tetraploids significantly differ from their diploid counterparts in an array of morphological and environmental characteristics. Within the diploid populations, the RGS is geographically and only partly taxonomically correlated, with the highest RGS inferred in the southern Balkan Peninsula and the Alps. We demonstrate greater RGS variation among the Balkan populations compared to the Alps, which is likely a result of more pronounced evolutionary differentiation within the Balkan Peninsula. In addition, a deep RGS divergence within the Alps likely points to persistence of the alpine populations in different Pleistocene refugia.

European wild carnations (Dianthus) are represented by a high number of taxa organized in unresolved taxonomies. In particular, taxa belonging to the Dianthus virgineus L. complex in the Central Mediterranean have been delimited mainly with qualitative morphological data and still await quantitative investigations, which are vital to understand boundaries and relations among plant diversity groups. Here, we examine the phenotypic features of nuclear genome organization testing for species boundaries in this complex. We have studied the chromosome number, the total haploid length (THL), and the relative genome size (RGS) in 122 populations belonging to 25 out of 33 taxa of the complex. All the studied populations have 2n = 2x = 30 chromosomes, and the THL ranges from 14.09 to 20.71 μm. Genome size estimations support the absence of polyploidization events, but show a certain degree of variation (0.318–0.423 arbitrary units). The RGS variation is not in agreement with current taxonomic treatment, but rather shows a geographical pattern, with higher values in Sicily and Sardinia. No correlation between the THL and the RGS was detected, possibly due to the stable chromosome number and the small size of chromosomes. A number of evolutionary unique groups lower than the number of currently accepted taxa may be hypothesized.

The nomenclature of 14 taxa from Central and Southern Europe within the Dianthus virgineus group is discussed. Dianthus aggericola Jord., D. collivagus Jord., D. consimilis Jord., D. orophilus Jord., D. saxicola Jord., D. juratensis Jord. are here lectotypified by specimens from the Jordan herbarium in LY, while D. godronianus Jord. by a specimen in P. Dianthus subacaulis Vill. is neotypified by a specimen collected on Mont Ventoux (S. France) and housed in MPU. For D. sylvestris Wulfen, a lectotype is here designated and its previous neotypification is discussed. Dianthus caryophyllus var. tenuifolius Moris, D. caryophyllus f. minor Moris and D. sylvestris var. garganicus Ten. are lectotypified by specimens housed in herbarium Moris (TO) and herbarium Tenore (K). Dianthus virgineus var. tergestinus Rchb. is lectotypified by a drawing from the Icones florae Germanicae & Helveticae, while D. contractus var. evolutus Lojac. is neotypified by a specimen in P. For each taxon the currently accepted name is provided including new synonymies. The type indication is followed by nomenclatural and taxonomic notes, in which the original material found is commented and the reasons for the identification of the types are discussed.

In order to initiate a taxonomical revision of the Dianthus sylvestris group, an inventory of historical herbarium materials from ZA and ZAHO collections was conducted. Herbarium specimens of D. sylvestris group from these two herbaria were digitized and the data from the original herbarium labels were inserted in the Flora Croatica Database. A total of 344 herbarium sheets were digitized and six taxa (D. sylvestris Wulfen in Jacq. ssp. sylvestris, D. sylvestris ssp. tergestinus (Rchb.) Hayek, D. sylvestris ssp. longicaulis (Ten.) Greuter et Burdet, D. sylvestris ssp. nodosus (Tausch) Hayek, D. siculus C. Presl and D. arrosti C. Presl) were registered within studied collections. Inventory of herbarium sheets from ZA and ZAHO historical collections provided a significant insight into historical distributional data of D. sylvestris taxa related to the area of the Balkan Peninsula, which is a prerequisite for accurate taxonomic/ geographic sampling for further morphological and molecular analyses.

A detailed morphometric analysis and scanning electron microscopy of seed coat structure of three currently recognised subspecies of the endemic amphi-Adriatic Dianthus ciliatus (Caryophyllaceae) was carried out for the first time. Petal limb shape and denticulation, the woody base of the plant, epicalyx scale’s length and height of the epicalyx turned out to be the most informative characters in distinguishing the investigated populations of D. ciliatus. Based on significant differences in morphological characters, a new identification key is offered. The names D. ciliatus, D. ciliatus var. cymosus, D. dalmaticus, D. medunensis, and D. racemosus are here lectotypified.