Historical Biogeography of a Disjunctly Distributed, Spanish Alpine Plant, Senecio boissieri (Asteraceae)

Little is known about the historical biogeography of alpine plants that are disjunctly distributed across the mountains of the Iberian Peninsula. Randomly Amplified Polymorphic DNA (RAPD) and chloroplast microsatellite (cpSSR) variation were surveyed in the Spanish alpine endemic, Senecio boissieri, to resolve the causes of its disjunct distribution in the southern Sierra Nevada and Baza, centrally located Sierra Guadarrama, and northern Cordillera Cantábrica. RAPD analysis identified two divergent genetic groups, one containing individuals from the Cordillera Cantábrica and another comprising individuals from the three other mountain ranges. Chloroplast DNA variation was much more limited with only one of forty-two cpSSR loci examined showing polymorphism. At this locus the same allele occurred at high frequency in material from each mountain range. A possible reason for RAPD divergence in the Cantabrian material is its derivation from plants surviving the last glacial maximum in a northern refugium, isolated from the main distribution of the species spanning the area between the southern and central Spanish sierras. Postglacial fragmentation of the species range in southern and central Iberia would have resulted in the current disjunction of genetically similar populations in southern and centrally located mountains.