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In order to elucidate the biotic diversification of Asteraceae inhabiting the South American Transition Zone, we undertook a panbiogeographic analysis (based on a parsimony analysis of endemicity) and a cladistic biogeographic analysis. The study units were the six biogeographic provinces of this zone plus the seven subregions of the Neotropical and Andean regions, considered as “outgroups”. Species analyzed belonged to the genera Arnaldoa, Barnadesia, Belloa, Berroa, Chevreulia, Chuquiraga, Cuatrecasiella, Dasyphyllum, Doniophyton, Duseniella, Facellis, Fulcaldea, Gamochaetopsis, Huarpea, Hypochaeris, Jalcophila, Lucilia, Luciliocline, and Schlechtendalia. A parsimony analysis of endemicity, based on presence/absence data of the 66 individual tracks ranged on two or more areas, allowed to identify four generalized tracks: (1) Coastal Peruvian Desert and Puna provinces; (2) Central Chilean, Patagonian, and Subantarctic subregions; (3) Amazonian, Chacoan, and Parana subregions; and (4) Puna province and Parana and Chacoan subregions. The Puna and Parana provinces, connected with two different generalized tracks each, constitute nodes. A cladistic biogeographic analysis, based on the paralogy–free subtrees extracted from the taxonomic area cladograms of Barnadesia, Chuquiraga, Dasyphyllum, Hypochaeris, and the Lucilia group, allowed obtaining a general area cladogram, which indicates a basic separation between the Atacama, Monte, and Prepuna provinces closely related to the Andean region, and the North Andean Paramo, Coastal Peruvian Desert, and Puna provinces closely related to the Neotropical region. Our results corroborate once again the transitional character of the provinces assigned to the South American Transition Zone, and allow speculating on their close affinities with the Andean and Neotropical regions. Fil: Urtubey, Estrella. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina Fil: Stuessy, Tod F.. Universidad de Viena; Austria Fil: Tremetsberger, Karin. Universidad de Sevilla; España Fil: Morrone, Juan José. Universidad Nacional Autónoma de México; México

AFLP variation has been assessed within and among populations of Hypochaeris acaulis (Asteraceae), a species isolated in moist seeps and rivulets throughout its range in the southern Andes. Plants in seven papula-dons were sampled with six pairs of primer combinations. Genetic affinities were calculated by Nei-Li distance, and relationships were determined by neighbor-joining. All individuals, except two, clustered with other members of their same population. These results suggest restricted gene flow among populations, perhaps resulting from limited dispersal capability. It was estimated that a migrant is exchanged between two randomly chosen populations approximately once in eight generations, a low level of genetic exchange. A correlation of geographic and genetic distances is seen among populations, corresponding to isolation by distance. Genetic variation largely resides among populations (67.9%) rather than within (32.1%). No deep genetic divisions larger than those seen among the populations were revealed, suggesting no major biogeographic impacts, except for possible isolation of individual populations due to recent local Pleistocene glaciation. A positive correlation of genetic variation exists with population size, and a strong correlation exists with observed flowering and fruiting behavior. Pollen/ovule ratios were used to suggest that the species is facultatively autogamous, a breeding system that would be consistent with the observed pattern of genetic variation.