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.

Santolina is a plant genus of dwarf aromatic shrubs that includes about 26 species native to the western Mediterranean Basin. In Corsica and Sardinia, two of the main islands of the Mediterranean, Santolina corsica (tetraploid) and S. insularis (hexaploid) are reported. Along with the cultivated pentaploid S. chamaecyparissus, these species form a group of taxa that is hard to distinguish only by morphology. Molecular (using ITS, trnH-psbA, trnL-trnF, trnQ-rps16, rps15-ycf1, psbM-trnD, and trnS-trnG), cypsela morpho-colorimetric, morphometric, and niche similarity analyses were conducted to investigate the diversity of plants belonging to this species group. Our results confute the current taxonomic hypothesis and suggest considering S. corsica and S. insularis as a single species. Moreover, molecular and morphometric results highlight the strong affinity between S. chamaecyparissus and the Santolina populations endemic to Corsica and Sardinia. Finally, the populations from south-western Sardinia, due to their high differentiation in the studied plastid markers and the different climatic niche with respect to all the other populations, could be considered as an evolutionary significant unit.

The use of digital image analysis for discriminating between and comparing groups of seeds is becoming an increasingly common practice in taxonomic studies. For this type of study, many variables, concerning different kinds of data such as size, texture and shape, are generally used as inputs in statistical algorithms without any data pre-processing, thereby generating problems with noise and the consistency of the process for new samples. We propose an approach in which the variables for each kind of data are separately pre-processed by performing Principal Component Analysis and Fourier Analysis. Furthermore, the accuracy of the different kinds of data is measured by comparing the results obtained using several classification algorithms: k-Nearest Neighbour, Linear Discriminant Analysis, Naive Bayes, Support Vector Machines and Random Forest. We have taken as a case study the seeds of 19 cultivars of Sardinian Prunus domestica L. and four cultivars referable to other Prunus species. The combination of size, texture and shape data was able to perform well in discriminating between the seeds of Prunus sp. The present study confirms that image analysis techniques combined with the pre-processing of data are a useful tool for taxonomic investigation in plant biology and for discrimination at the cultivar level.

The taxonomy of the Paeonia mascula group in the Tyrrhenian Islands has always been controversial, especially in Sardinia and Corsica. In this paper, 124 morpho-colorimetric quantitative and qualitative features of seeds of the Paeonia mascula group from the Balearic Islands, Corsica, Sicily, and Sardinia were measured by an image analysis system to evaluate whether differences in seed morphology were present and if the results support the current taxonomic treatment. Digital images of 41 accessions for a total of 3,317 seeds were acquired using a flatbed scanner, and morpho-colorimetric seed features were analysed using a plugin developed for the open source software ImageJ. The data were statistically processed by applying the stepwise Linear Discriminant Analysis (LDA). The results showed that the seeds of the studied taxa were distinguishable with a high percentage of classification and highlighted that three different taxa are identifiable in Corsica (P. corsica, P. mascula subsp. mascula, and P. morisii), while only one (P. cambessedesii) is identifiable in the Balearic Islands. In the same way, the morpho-colorimetric analysis identified two well-defined taxa in Sicily (P. mascula subsp. mascula and P. mascula subsp. russoi). On the other hand, the discriminant analysis suggested that only P. corsica/morisii and P. sandrae were present in Sardinia, while differences were highlighted between Sardinian and Corsican peonies. The present study represents the first attempt to investigate the taxonomy of the P. mascula group, which makes in-depth usage of the seed features as diagnostic characters. The results obtained in this work enable the usefulness of image analysis techniques in taxonomic investigations to be suggested in order to contribute to the future systematic evaluation.