Karyology of some Convolvulaceae species occurring in NE Brazil inselbergs

Eighteen species belonging to family Convolvulaceae occurring in northeastern Brazil were analyzed to identify the karyotypic variability among rupicolous and non-rupicolous species. The count of 2n = 56 for Evolvulus sp., is the first report of polyploidy for the genus. The similarities among the karyotypes of species of Ipomoea, Merremia, and Operculina suggest that x = 15 is the basic secondary number for these genera, while x = 13 has been observed in Evolvulus. The genus Jacquemontia, with 2n = 18 is karyologically distinct from the other genera of the family. Intraspecific numerical chromosomal variations were not detected, nor were any karyological variations related to the rocky habitat characteristic of inselbergs. The occurrence of other plant groups with polyploid forms linked to this type of habitat suggests that the family Convolvulaceae is karyologically stable. We discuss variations in chromosome numbers, base numbers, and their implications in the evolution of the principal groups within the Convolvulaceae.