title: Pleistocene refugia and polytopic replacement of diploids by tetraploids in the Patagonian and Subantarctic plant Hypochaeris incana (Asteraceae, Cichorieae).
abstract: We report the phylogeographic pattern of the Patagonian and Subantarctic plant Hypochaeris incana endemic to southeastern South America. We applied amplified fragment length polymorphism (AFLP) and chloroplast DNA (cpDNA) analysis to 28 and 32 populations, respectively, throughout its distributional range and assessed ploidy levels using flow cytometry. While cpDNA data suggest repeated or simultaneous parallel colonization of Patagonia and Tierra del Fuego by several haplotypes and/or hybridization, AFLPs reveal three clusters corresponding to geographic regions. The central and northern Patagonian clusters (approximately 38-51 degrees S), which are closer to the outgroup, contain mainly tetraploid, isolated and highly differentiated populations with low genetic diversity. To the contrary, the southern Patagonian and Fuegian cluster (approximately 51-55 degrees S) contains mainly diploid populations with high genetic diversity and connected by high levels of gene flow. The data suggest that H. incana originated at the diploid level in central or northern Patagonia, from where it migrated south. All three areas, northern, central and southern, have similar levels of rare and private AFLP bands, suggesting that all three served as refugia for H. incana during glacial times. In southern Patagonia and Tierra del Fuego, the species seems to have expanded its populational system in postglacial times, when the climate became warmer and more humid. In central and northern Patagonia, the populations seem to have become restricted to favourable sites with increasing temperature and decreasing moisture and there was a parallel replacement of diploids by tetraploids in local populations.
authors.affiliation: Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, 41080 Sevilla, Spain. k.tremetsberger@gmx.net
authors.forename: Karin
authors.initials: K
authors.lastname: Tremetsberger
authors.forename: Estrella
authors.initials: E
authors.lastname: Urtubey
authors.forename: Anass
authors.initials: A
authors.lastname: Terrab
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Baeza
authors.forename: María Angeles
authors.initials: MA
authors.lastname: Ortiz
authors.forename: María
authors.initials: M
authors.lastname: Talavera
authors.forename: Christiane
authors.initials: C
authors.lastname: König
authors.forename: Eva M
authors.initials: EM
authors.lastname: Temsch
authors.forename: Gudrun
authors.initials: G
authors.lastname: Kohl
authors.forename: Salvador
authors.initials: S
authors.lastname: Talavera
authors.forename: Tod F
authors.initials: TF
authors.lastname: Stuessy
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D019659:Asteraceae / Q000235:genetics*; D016172:DNA Fingerprinting; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D004171:Diploidy; D019143:Evolution, Molecular; D005434:Flow Cytometry; D005828:Genetics, Population; D006239:Haplotypes; D010802:Phylogeny; D011123:Polyploidy; D017422:Sequence Analysis, DNA; D013020:South America
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant