Prickly scorpion's tail (Scorpiurus muricatus L.) is a self-reseeding annual legume widely distributed in natural pastures of the Mediterranean area and appreciated by farmers for its productivity, forage quality and palatability. Twenty-eight natural populations were collected throughout Sicily in 2005; two field experiments were carried out in 2005/06 in a hilly area of the Sicilian inland to assess the genetic variation based on pheno-morphological and agronomic characters. The pheno-morphological traits observed were analysed using a principal component analysis (PCA). The first four components of PCA (eigenvalues >1) explained 0·84 of the total variation. Similarities obtained by PCA were investigated by means of cluster analysis, which clearly identified five clusters.
The pheno-morphological and agronomic traits were mainly affected by latitude of the collection site (0·69 of the correlations were significant), spring rainfall (0·63) and rain days per year (0·63). Altitude was not significantly correlated with any of the traits.
A strong positive correlation was found between the days to the first flower and spring rainfall at the collection site. Populations originating from subhumid or dry-subhumid Mediterranean climate zones showed greater leaf dimensions when compared with those originating from semi-arid zones. Seed weight decreased with increasing number of rain days per year and spring rainfall. Populations from drier environments showed, on the whole, a more prostrate growth habit. Dry matter yield at spring cut exhibited a significant correlation with latitude (positive) and longitude (negative). Seed production was highly correlated with spring rainfall, number of rain days per year and latitude of collection site. The presence of a large diversity among populations appears to be valuable when searching for suitable S. muricatus material to exploit in pastures and crop–livestock farming systems of Mediterranean areas.