A karyological study ofGenistasect.SpartocarpusSpach (Cytiseae-Fabaceae)

Abstract

Summary Genista sect. Spartocarpus includes about 20 taxa distributed in the Mediterranean region, with one species (G. radiata) extending into the Alps. Two main diversity centers can be identified: one in the East (Balkan Peninsula and Anatolia) and one in the West (Southern Spain and Northwestern Africa), with various species occurring in the Tyrrhenian area. A karyological study was carried out on 30 wild populations of 7 taxa; a comprehensive evaluation of the section is presented. In the G. radiata group (East-Alpine Balkan), both varieties of G. radiata (radiata and sericopetala) and G. holopetala have the same secondary basic chromosome number x = 12, but different levels of ploidy: 4x (2n = 48) in var. radiata and G. holopetala; 8x (2n = 96) in var. sericopetala of Southeastern France; both 4x and 8x (2n = 48 and 2n = 96) in the examined population of Piemonte; G. hassertiana (2n = 52) may be considered as the result of ascending aneuploidy derived from x = 12. The G. sessilifolia group (Central Southern Balkans and Anatolia) appears karyologically homogeneous, displaying the basic number x = 11: G. nissana (2n = 22) is diploid, while in G. sessilifolia, ssp. romanica (Southeastern Europaean, 2n = 22) is diploid and ssp. sessilifolia (Anatolian, 2n = 88) octoploid. In the Western Mediterranean region, G. spartioides and G. haenseleri (Southern Spain and Northwestern Africa) display n = 20 and 2n = 40 (rarely n = 22), with x = 10. In G. aetnensis, endemic to Sardinia and Sicily, the numbers n = 26 and 2n = 52 were found, with x = 13. For the Tyrrhenian species of the G. ephedroides complex (incl. G. dorycnifolia) the number 2n = 48 (with x = 12) has been constantly counted. Sect. Spartocarpus is thus karyologically heterogeneous, displaying four secondary basic numbers (x = 10, 11, 12, 13), that have different geographic patterns and probably diversified following geographical isolation. Besides, more levels of ploidy (2x, 4x, 8x) and some cases of aneuploidy were observed: the level 4x is the most frequent and prevails in all the range of the section, 2x is found only in Southern Balkans (G. sessilifolia group) and 8x is limited to peripheral areas of Turkey and France.