Electrophoretic differentiation in isolated populations of Lolium rigidum Gaud.

Sixteen wild populations of Lolium rigidum Gaud. were collected from island and mainland locations in Mediterranean Europe and western Asia. Five loci , controlling isozymes at four enzyme systems, were assayed on 60 plants pe r population using starch gel electrophoresis. Gene diversity measures and Nei's genetic distance were calculated, and the relationships between the p opulations were analysed using principal component (PCA) and cluster analys es. All populations were found to show a gene diversity index that is consi stent with that expected in a cross-fertilising species. The highest gene d iversity measures were recorded in some of the island populations. Both PCA and cluster analysis grouped the Balearic Island populations together and separated the Spanish and Sardinian populations from any of the others. The results are discussed with respect to a number of theories of migration be tween populations, and in relation to the colonization history of each isla nd. It is suggested that the preservation of these island populations in ge ne banks is important as part of a core collection of the species.