Article

The Mediterranean flora contains many examples of disjunct species distributions. In the genus Cyclamen (Primulaceae) three species show disjunct distribution patterns in the western Mediterranean basin that suggest the importance of physical isolation events for speciation in the genus. C. balearicum occurs in five fragmented sites in southern France and on four of the Balearic Islands, C. creticum is endemic to Crete and Karpathos and C. repandum is more widely distributed from southern France to southern Greece including ali the main Mediterranean Islands. The purpose of this paper is to illustrate how studies of the ecology and genetics of spatial population structure within and between species can provide important information on the role of physical isolation events for speciation. Continental populations of C. balearicum show extremely high levels of genetic differentiation which greatly exceed those among true island populations. Human fragmentation and/or glaciation may have drastically reduced population sizes on the continent causing such higher levels of differentiation. Il is also possible that because Balearic island populations have a wider ecological amplitude than continental populations they show less differentiation. C. repandum also shows significant levels of population differentiation. The genetic distances among the three species indicate that this species, or an ancestral form, has given rise to C. balearicum and C. creticum at each of its distribution limits. Our data indicate that such speciation would have been facilitated by high levels of genetic isolation among populations. Variation in floral traits and levels of inbreeding within and among these species suggest that the evolution of selfmg variants in the derivative species may have contributed to this speciation