Historical biogeography in a linear system: genetic variation of Sea Rocket (Cakile maritima) and Sea Holly (Eryngium maritimum) along European coasts

The exclusively coastal Cakile maritima and Eryngium maritimum represent a linear biogeographical system. Genetic variation among 25 individuals of C. maritima and 16 individuals of E. maritimum, from the coasts of Europe, North Africa and the Canary Islands, was analysed using random amplified polymorphic DNAs (RAPDs) and intersimple sequence repeats (ISSRs). Genetic distances (Dice) were calculated and used to investigate the correlation between genetic and geographical distances, to construct Neighbour Joining (NJ) trees, and to compare mean genetic distances between areas within and across species. Genetic distances and geographical distances measured along the coast are well correlated…