Karyology and distribution of Sesleria tenuifolia complex (Poaceae) in the Italian Peninsula

Karyological analyses of wild populations of Sesleria tenuifolia complex collected from throughout the Italian peninsula was performed to check the stability of the chromosome number along both geographical and ecological gradients. The chromosome counts showed that the Italian populations of the Sesleria tenuifolia complex consist of octoploid plants (2n=8x=56) and dodecaploid plants (2n=12x=84). The discovery of a dodecaploid chromosome number is the first for the genus Sesleria. The distribution of octoploid and dodecaploid populations follows strictly geographical boundaries and seems to be uninfluenced by synecological or physical factors. No overlapping between octoploid and dodecaploid populations was found; in fact, octoploid populations occupy northern, central and part of Peninsular Italy, whereas dodecaploid ones are restricted to the Pollino massif and the Orsomarso range, which together form the southernmost limit of the distribution area of the Sesleria tenuifolia complex.