The colonization history of Olea europaea L. in Macaronesia based on internal transcribed spacer 1 (ITS-1) sequences, randomly amplified polymorphic DNAs (RAPD), and intersimple sequence repeats (ISSR)

Phylogenetic relationships in the Olea europaea complex and the phylogeogra phy of 24 populations of the Macaronesian olive (O. europaea ssp. cerasifor mis) were assessed by using three molecular markers: nuclear ribosomal inte rnal transcribed sparer 1 (ITS-1) sequences, randomly amplified polymorphic DNAs (RAPD), and intersimple sequence repeats (ISSR). Parsimony analysis o f the ITS-1 sequences and Neighbour-joining (NJ) analyses of RAPD and ISSR banding variation revealed four major lineages in the O. europaea complex: (1) ssp. cuspidata; (2) ssp. cerasiformis from Madeira; (3) ssp. laperrinei ; and (4) ssp. cerasiformis from the Canary Islands plus ssp. europaea. The se results provide unequivocal support for two independent dispersal events of Olea to the Madeira and Canary Islands. Molecular and morphological evi dence led to recognition of two separate olive taxa in Macaronesia, to date included in ssp. cerasiformis. NJ analyses of the combined RAPD and ISSR d ata suggest that the colonization of the Canaries by O. europaea may have f ollowed an east to west stepping-stone model. An interisland dispersal sequ ence can be recognized, starting from the continent to Fuerteventura, Gran Canaria, Tenerife, La Gomera, and finally La Palma. High dispersal activity of the lipid-rich Olea fruits by birds in the Mediterranean region is cong ruent with multiple dispersal of olives to Macaronesia and successive colon ization of the archipelagos. The observation of strong genetic isolation be tween populations of different islands of the Canary Islands suggests, howe ver, that subsequent interisland dispersal and establishment has been very rare or may not have occurred at all.