Phylogenetic and evolutionary insights into the Saxifraga pentadactylis complex (Saxifragaceae): variation in nrITS sequences

Variation in nrlTS sequences among seven members of a seemingly natural group of Saxifraga (the S. pentadactylis complex; series Pentadactyles ) is phylogenetically analyzed. The two most parsimonious trees indicate that the S. pentadactylis complex is not a monophyletic group, because 5. intricata is excluded and is most closely related to S. exarata (series Cespitosae ). A well-defined lineage includes, however, six of the seven members of the S. pentadactylis complex. The tree topology suggests that this remaining group of six taxa may have diverged in the northeastern part of the Iberian Peninsula. Two sublineages can be identified from the ITS phylogenetic reconstruction: S. losae-S.moncayensis and the three subspecies of S. pentadactylis (subspp. pentadactylis, willkommiana , and almanzorii ). The relationships between S. losae and S. moncayensis provide an example of north-south speciation along the Sistema Ibérico mountain range. The three subspecies of S. pentadactylis form a monophyletic group resolved into one clade containing subspp. willkommiana and almanzorii , sister to subsp. pentadactylis. The molecular evidence agrees with chorological, cytotaxonomical, chemosystematic, and reproductive data indicating two differentiation patterns within S. pentadactylis. Transition to predominant autogamy in subsp. almanzorii probably resulted in rapid reproductive isolation from the outcrossing subsp. willkommiana in part of the Sistema Central mountain range, as suggested by their two distinct floral types but similar ITS sequences. Allopatric separation of populations of subsp. willkommiana from subsp. pentadactylis (the Pyrenees) has resulted in molecular divergence and some morphological differentiation.