Chromosome alterations in two species of <i>Iris</i> (Iridaceae) endemic to southern Italy

In this study, specimens of Iris pseudopumila and I. bicapitata from various habitats on the Gargano Peninsula (Puglia region, Italy) were karyologically analyzed. The chromosome numbers and karyotype features of the two species were investigated by Feulgen staining. I. pseudopumila exhibited a chromosome number of 2n=16, while I. bicapitata had 2n=40. Significant differences in karyotypic indices were observed among the populations of I. pseudopumila. In purple-flowered specimens, the number of subtelocentric and telocentric chromosomes differed from that of the yellow-flowered specimens. Notably, cases of heteromorphy were observed in some chromosome pairs. These findings reveal structural changes in the chromosomes of the studied I. pseudopumila populations, reflecting an ongoing evolutionary process within this species. The variation in the karyotype formula seen in I. pseudopumila suggests karyotype instability, with ongoing genomic changes and chromosomal rearrangements. In contrast, I. bicapitata showed little karyotype variation between the short- and long-stem specimens. The data obtained for these two species can enhance insights into the mechanisms of species evolution within the genus Iris.