The research, conducted by Jacopo Franzoni, Dania Cruz-Tejada, Angelino Carta and Lorenzo Peruzzi of the University of Pisa for the first species, and by Franzoni, Antonio Giacò and Peruzzi for the second, forms part of an ongoing series documenting chromosome numbers for the Italian flora. Italy is one of Europe’s richest countries for plant diversity, yet the chromosome counts of many of its species rest on old literature, ambiguous records, or no data at all. Each verified count is a data point that feeds into larger questions about how plants evolve, diversify, and sometimes vanish.

The first target, Crepis suffreniana, is a small annual in the sunflower family with a strikingly fragmented distribution. It occurs in three main areas: the maritime regions of south-western France, parts of south-eastern France, and a single Italian population confined to the Migliarino-San Rossore-Massaciuccoli Regional Park in Tuscany, near Pisa. That Italian population is the species’ entire national foothold, which makes every biological detail about it matter for conservation. The researchers obtained seeds, germinated them, and examined the dividing cells of young root tips—standard practice in plant cytogenetics, because root tips are where cell division is abundant and chromosomes are easiest to observe.

The laboratory protocol is a beautifully tuned routine. Root tips were pre-treated with 0.4% colchicine for three hours, a chemical that halts cell division at metaphase, when chromosomes are most condensed and countable. The tips were then fixed in Carnoy solution, a mixture that preserves cellular architecture, hydrolysed in 1 normal hydrochloric acid at 60 degrees Celsius to soften the tissue, and finally stained with leuco-basic fuchsine, a dye that renders chromosomes a deep, unmistakable purple. Squash preparations—literally flattening the stained tip onto a slide—spread the chromosomes into a single optical plane where they can be tallied one by one.

The verdict for the Tuscan plants: 2n = 8, meaning eight chromosomes in the somatic cells. That number agrees with the classic account published by the great Crepis specialist Babcock in 1947, but it carries a crucial new significance. Babcock never specified whether his original count came from French or Italian material, leaving the Italian population’s cytology undocumented for nearly eight decades. The genus Crepis is famous among cytologists for its chromosomal diversity: within the section Phytodesia, which includes C. suffreniana, eight out of ten species share 2n = 8, while two relatives, C. capillaris and C. fuliginosa, dip to 2n = 6. The new count confirms the Tuscan population sits squarely within the standard pattern of its group, yet it is the first count ever formally documented from Italian plants of this species.

The second result is the one that made botanists sit up. Dianthus furcatus subsp. furcatus, a Mediterranean mountain plant or orophyte of the western Alps, was previously reported in the literature as tetraploid, with 2n = 60 chromosomes—records dating back to Darlington and Wylie’s landmark chromosome atlas of 1956 and Carolin’s work the following year. Those old citations referred generically to Italy and the Alps, without pinpointing populations. When the team counted chromosomes from plants collected on the southern slope of Monte Frontè in Liguria, at an altitude of 1,668 metres among grasslands with protruding rocks, they found a number nobody expected: 2n = 90.

Ninety chromosomes corresponds to a hexaploid level—six complete sets of the basic genome—in this genus, a level not previously documented for the species. Polyploidy, the possession of multiple whole genome copies, is one of the dominant forces in plant evolution, and discovering which ploidy level a population carries can reshape how scientists draw species boundaries, reconstruct migration histories, and design conservation strategies. The hexaploid finding contrasts sharply with previous studies of D. furcatus in the broad sense from the Italian Alps, which had documented only the diploid level, and with the tetraploid reports inherited from mid-twentieth-century compendia. The Corsican endemic D. gyspergerae, considered by some authors a subspecies of D. furcatus, is reported as diploid, further enriching the picture of chromosomal variation across this tangled species complex.

The Italian populations of D. furcatus are organized into three subspecies: the typical form spanning the western Alps, D. furcatus subsp. dissimilis known only from Vallone degli Alberghi in the Maritime Alps of Piedmont, and D. furcatus subsp. lereschii in the Graian Alps. A hexaploid count in the typical subspecies now raises tantalizing questions. Are the populations of subsp. furcatus uniformly hexaploid, or do ploidy levels vary across the Alpine arc? Could older tetraploid records have been based on misidentified material, or on populations that have since been reinterpreted taxonomically? Answering those questions will require the kind of population-by-population sampling this study exemplifies, and it may ultimately require genome size measurements and molecular markers to trace how the polyploid lineages arose and spread.

What makes these two counts compelling beyond specialist circles is the contrast they present. One species shows textbook stability: its eight chromosomes match an eighty-year-old expectation, and the interest lies in finally pinning the record to the plant’s most vulnerable Italian stronghold. The other shows textbook revision: a number enshrined in reference works since the 1950s dissolves on contact with fresh material from a specific Ligurian mountain. Both outcomes are essential. Verified chromosome numbers underpin karyological databases, inform cytotaxonomic treatments of difficult groups, and provide baselines for detecting hybrids and polyploid ecotypes that standard morphology can miss.

The work also highlights the quiet infrastructure of biodiversity science. Each count is anchored to a voucher specimen—catalogued and preserved in the herbarium of the University of Pisa—collected at a precisely recorded location and date, so that any future researcher can retrace the evidence. The Pisa group actively invites contributions of new chromosome data, with submissions directed to Antonio Giacò and required to include voucher details and methods. In an era when genome sequencing grabs headlines, the humble squash preparation of a root tip continues to deliver results that no database can substitute: a direct, physical count of the hereditary units of a living plant. For Crepis suffreniana and Dianthus furcatus subsp. furcatus, those counts now exist on firm ground, and the Italian flora’s genetic atlas is one step closer to complete.

Subject of Research: Chromosome counts of two native Italian plant species, Crepis suffreniana and Dianthus furcatus subsp. furcatus

Article Title: Chromosome numbers for the Italian flora: 18

Article References: Chromosome numbers for the Italian flora: 18. (n.d.). https://doi.org/10.3897/italianbotanist.21.200391

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.21.200391

Keywords: cytogenetics, chromosome numbers, Italian flora, Crepis suffreniana, Dianthus furcatus, polyploidy, hexaploid, plant taxonomy, conservation botany, western Alps, Tuscany, Italian Botanist