Corresponding author: Lorenzo Peruzzi (
Academic editor: Joan Vallés
The Italian endemic vascular flora is composed of 1,286 specific and subspecific taxa. From the critical analysis of “Chrobase.it”, 711 of them (about 55%) have been studied from a karyological point of view. These taxa belong to 52 out of 56 families and 204 out of 284 genera. These data suggest that endemic species are more studied than the flora as a whole. Mean chromosome number for Italian endemics is 2n = 30.68 ± 20.27 (median: 2n = 26, mode: 2
The number of chromosome count databases, either hardprinted or online, matches current research trends, and attests to the usefulness of chromosome data in current taxonomic, genetic and cytogeographic research (
The Italian endemic vascular flora, according to ongoing research carried out in collaboration with CRFA (Centro di Ricerca per la Flora dell’Appennino) of Barisciano (L’Aquila, Italy), comprises 1,286 specific and subspecific taxa(L. Peruzzi, F. Bartolucci and F. Conti, unpublished data), including those species which eventually occur also in Corse (France). The present work aims to summarize the karyological knowledge focusing on the endemic component of Italian vascular flora, extracted from the online database “Chrobase.it” (
Data about chromosome numbers (
Concerning the list of endemics, for the difficult and critical genera
Mean (± standard deviation), median, modal chromosome number, and frequencies (histograms) were calculated for the entire dataset of Italian vascular flora endemics. Frequency and mean number (± standard deviation) of Bchromosomes for the whole dataset and for each genus were also calculated. The frequencies of basic chromosome numbers (x) in those complements (2n) where more than one basic number can occur were obtained by a taxon by taxon screening of relevant karyological literature quoted in Chrobase.it (
Chromosome counts are available for 711 out of the 1,286 (ca. 55%) currently accepted specific and infraspecific endemic taxa, resulting in 839 different cytotypes; they are representative of 204 out of the 284 genera (72%) – and 52 out of the 56 families (91%) – encompassing the endemic taxa. The geographic distribution of counts is shown in
Map of Italian regions, showing the % endem. of Italian vascular flora karyologically studied with respect to the Italian endemics growing in each region (derived from
Number of karyologically studied Italian endemic vascular flora for each region. The sequence of regions is the same as the one used in



Valle d’Aosta  0 
Piedmont  7 
Lombardy  13 
TrentinoAlto Adige  9 
Veneto  10 
FriuliVenezia Giulia  6 
Liguria  9 
EmiliaRomagna  9 
Tuscany  89 
Marche  10 
Umbria  9 
Latium  26 
Abruzzo  61 
Molise  2 
Campania  26 
Apulia  33 
Basilicata  10 
Calabria  75 
Sicily  193 
Sardinia  156 
The distribution of the 711 taxa across families is shown in
Pie plot showing the distribution of karyologically studied Italian endemic taxa across families. Families with less than 20 studied taxa were merged.
For 92 genera, of which 7 have ≥ 5 endemics, 100% of Italian endemics was covered (
Most karyologically studied genera of Italian endemics (≥ 5 taxa). They are arranged firstly according their decreasing % of coverage, secondly their number of taxa studied and, thirdly, alphabetically.




7  100%  
7  100%  
6  100%  
6  100%  
6  100%  
6  100%  
5  100%  
26  93%  
18  90%  
17  85%  
83  84%  
5  83%  
5  83%  
8  80%  
14  77%  
10  77%  
8  75%  
6  75%  
8  73%  
8  73%  
10  71%  
5  71%  
11  69%  
9  69%  
6  67%  
45  66%  
6  60%  
9  53%  
8  53%  
6  50%  
16  48%  
7  47%  
14  38%  
10  38%  
8  30%  
5  10% 
Genera with 100% karyological coverage but with less than 5 Italian endemics:
Chromosome numbers range from 2n = 8, reported in 8 endemic taxa [
The mean chromosome number is 2n = 30.68 ± 20.27, with median 2n = 26 and mode 2n = 18.
Histograms showing the percentage frequencies (yaxis) of 2n chromosome numbers (xaxis) known for the Italian endemic vascular flora.
Concerning chromosome complements where more than one basic number can occur, the most heterogeneous, among those up to 2n= 72 (
Chromosome complements up to 2n = 72, where more than one basic number (x) can occur, and respective x frequencies. The frequencies were obtained by a taxonpertaxon literature screening. Higher chromosome numbers (very rare, in our dataset) were not considered.



















100%  

100%  

2.8%  97.2%  

3.1%  96.9%  

4.2%  20.8%  71%  

51%  49%  

71.9%  28.1%  

62.8%  2.3%  34.9%  

20.7%  62%  17.3%  

22%  11%  67%  














92.3%  7.7%  

12%  88%  

90%  10%  

25%  12.5%  37.5%  25%  

80%  20%  

75%  25%  

12.5%  87.% 
The relationships among the different even ploidy levels, within each considered basic chromosome number (x = 7, x = 8, x = 9), was best described by an exponential function (
Goodness of fit of different models. The coefficients (a, b) matching the leastsquares estimates are given for each model. RSS = Residual Sum of Squares. **= significant at 0.01 level.






y = a*x + b  7.786  66.714  3353.531  0.6844** 
y = a*x^b  297.600  2.060  235.400  0.9780** 
y = a + b*log(x)  91.940  43.580  1422.000  0.8660** 
y = e^(a + b*x)  5.539  0.637  170.400  0.9840** 
Plot showing the percentage frequencies (yaxis) of even ploidy levels from 2x to 10x (paxis), for three frequent basic chromosome numbers (x = 7, x = 8 and x = 9) and the curve fitted to the data points by nonlinear leastsquare estimate.
More than one cytotype was shown by 65 out of 711 taxa, with a maximum number of seven in
Bchromosomes occur in 16/711 taxa and in 24 cytotypes (3.3% of the dataset), grouped in 10/284 genera (3.5%), 9/56 families (16%). Among the taxa showing Bchromosomes, their mean number is 1.73 ± 0.91, mode = 1 and median = 1.5. The highest number of Bchromosomes is 4, from a single accession of
Families and genera showing Bchromosomes in Italian vascular flora endemics, with the respective number of taxa (cytotypes), and the range of Bs.
Family  Genus  No. cytotypes with B  range of Bs 


10  1–2  

4  1–4  

2  1, 3  

2  1  

1  2  

1  2  

1  1  

1  4  

1  1  

1  1 
The taxonomic and geographic distribution of karyological knowledge in Italian endemics closely parallels that dealing with the whole Italian vascular flora (
The precise relationship [exponential function f(p) = e^{(5.539 – 0.637p)} (R^{2} = 0.984)] found among even ploidy levels from 2
Odd ploidy levels are generally very rare in our dataset, with the noteworthy exception of triploids with 2n = 27. As already evidenced by
The meaning of the precise relationship found in this work must be clarified by further analyses on large datasets of chromosome counts (e.g. PhytoKaryon;
Despite the efforts of Italian and foreign botanists in studying the endemic flora, the data here highlighted clearly show how much work is still to be done, concerning the karyological knowledge of Italian endemics. However, we were able to summarize the uptodate knowledge, which accounts for more than one half of the endemic flora, and to suggest that these species likely followed karyological evolutionary processes similar to the whole flora. Moreover, as far as we are aware, it is the first time that a precise quantitative relationship between (even) ploidy levels is shown to occur. We demonstrated indeed that, for the frequent basic chromosome numbers x = 7, x = 8 and x = 9 the diploids dominate and are related to higher even ploidy levels by an exponential relationship. In our mind, this intriguing phenomenon opens a new line of investigation in cytogenetics, aimed to clarify the evolutionary mechanisms giving rise to these constant relationships among increasing even ploidy levels.
Financial funding (EX60%) from University of Pisa is gratefully acknowledged.