TRACING THE COLONIZATION OF MADEIRA AND THE CANARY-ISLANDS BY DROSOPHILA-SUBOBSCURA THROUGH THE STUDY OF THE RP49 GENE REGION

Nucleotide variation at the nuclear ribosomal protein 49 (rp49) gene r egion has been analysed by fine restriction mapping in a sample of 47 lines from a population from Madeira. Five restriction-site tout of 37 sites scored) and 3 length polymorphisms have been detected, resultin g in 14 different haplotypes. This population shows less variation tha n both continental and Canary Island populations. The population from Madeira shows some differentiation from mainland populations, which do es not favor the idea of extensive migration between the continent and Madeira. Chromosomal and restriction-map variation of the rp49 region in D. subobscura populations, together with data on sequence comparis on of this nuclear region in D. guanche and D. madeirensis clearly ind icate that the Canary Islands underwent at least two colonization even ts from the nearby continent. Although the data for Madeira are compat ible with a single colonization event by a continental sample polymorp hic for gene arrangements O-3 and O3+4, an alternative scenario with a t least two colonization events seems more likely.