Spatial ecological and genetic structure of a mixed population of sexual diploid and apomictic triploid dandelions

Ecological differentiation is widely seen as an important factor enabling the
stable coexistence of closely related plants of different ploidy levels. We studied
ecological and genetic differentiation between co-occurring sexual diploid and
apomictic triploid Taraxacum section Ruderalia by analysing spatial patterns
both in the distribution of cytotypes and in the distribution of genetic variation
within and between the cytotypes. A significant relationship between ploidy
level and elevation was found. This mode of ecological differentiation
however, was not sufficient to explain the significant spatial structure in the
distribution of diploids and triploids within the population. Strong congruence
was found between the spatial genetic patterns within the diploids and within
the triploids. We argue that this congruence is an indication of gene flow
between neighbouring plants of different ploidy levels.