MOLECULAR BIOGEOGRAPHY AND EVOLUTION OF THE MICROTHLASPI-PERFOLIATUM SL POLYPLOID COMPLEX (BRASSICACEAE) - CHLOROPLAST DNA AND NUCLEAR RIBOSOMAL DNA RESTRICTION SITE VARIATION

The genus Thlaspi L. s.l. comprises numerous segregate lineages, which have been recognized as single genera. One of these, Microthlaspi, re presents one such segregate. It consists of morphologically similar an nual species. The species have different ploidy levels (2x, 4x, 6x) an d are usually summarized cinder the designation Thlaspi perfoliatum ag g, The assumed ancestral diploid members of the species complex, Micro thlaspi granatense (Boiss. & Reut.) F.K. Meyer, Microthlaspi umbellatu m (Steven ex DC.) F.K. Meyer, and Microthlaspi natolicum (Boiss.) F.K. Meyer, are restricted to northwestern Africa, southeastern Spain and Turkey, northern Iran, and Lebanon. Microthlaspi perfoliatum (L.) F.K. Meyer is widely distributed all over Europe and shows three ploidy le vels. Diploid M. perfoliatum is restricted to Middle Europe, whereas t etraploid and hexaploid M. perfoliatum are distributed all over Europe . Individual plants from 125 natural populations throughout the geogra phic range were analysed using chloroplast DNA (cpDNA) and nuclear rib osomal DNA (nrDNA) restriction site analysis. Within Microthlaspi, 31 cpDNA restriction site mutations, six nrDNA restriction site variation s, and two length mutations in the IGS region of the nrDNA were found, and a molecular phylogeny of the species complex has been derived. Po lymorphisms in molecular data partitioned cytotypes of M. perfoliatum. The geographical distribution patterns apparently reflect ancient spe ciation processes and postglacial vegetation history.