Amplified fragment length polymorphism (AFLP) variation within and among populations of Hypochaeris acaulis (Asteraceae) of Andean southern South America

AFLP variation has been assessed within and among populations of Hypochaeris acaulis (Asteraceac), a species isolated in moist seeps and rivulets throughout its range in the southern Andes. Plants in seven populations 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.