Molecular evidence for multiple diversification patterns of alpine plants in Mediterranean Europe

A preliminary synthesis of diversification patterns of alpine plants in the Mediterranean region of Europe is presented based on seven plant groups displaying morphological differentiation and infraspecific taxa. Both previous and new phylogenetic results from ITS sequences and fingerprinting data suggest different colonization routes and modes of speciation in Androsace vitaliana (recent differentiation in the Iberian Peninsula), Anthyllis montana (west-to-east colonization and differentiation in Europe), Arenaria tetraquetra (colonization and differentiation from SE Iberian mountains to the Pyrenees; increasing number of chromosome complements), Saxifraga oppositifolia (colonization from the arctic to the Iberian Peninsula), Saxifraga pentadactylis (differentiation in Mediterranean and Eurosiberian mountains by geographic isolation), and Soldanella alpina (differentiation and colonization from northern Iberia to the Alps, and then to the Pyrenees and the Balkan Peninsula). Relative static diversification of Juniperus communis var. saxatilis in Europe, based on identity of chloroplast trnL-F sequences, is also described. Most morphological variation, expressed by number of subspecies recognized in previous taxonomic treatments of the seven plant groups, appears to have occurred during the Pleistocene (< 1.75 Myr). Recurrent change of Quaternary climatic conditions in the Mediterranean Basin, coupled with geographic characteristics, life cycle, dispersal mechanisms, and pre-Holocene genetic structure are not convincing factors to account for all the observed diversification. Additionally, stochastic processes are also considered for evaluating present-day distributions and processes of speciation.