A general assumption when addressing species whose distribution
ranges span broad latitudinal gradients, is that northern populations
are overall adapted to colder habitat conditions than southern
populations.
The measured genetic distances among populations and the
resulting structure of the network do not support a strong genetic
divergence among the four populations examined in our study. One
haplotype is even shared by PRA and SWE populations. However, our
finding was based on neutral chloroplast DNA markers that are
independent of selection and evolve at a slower rate than nuclear
markers that are instead subject to gene flow. Similar results were
obtained by Frajman et al. (2009) that detected very close
relationships between V. alpina populations in southern and in
northern Europe, as well in populations in Canada and Greenland in cpDNA
markers (Frajman et al. 2009). Only a few nuclear markers showed
divergence in that same study between two groups in Europe that appeared
independent from latitude, but rather suggested independent dispersal
events from glacial refugia, as for other alpine-artic species with
disjunct distribution, like Ranunculus glacialis (Ronikier et al.
2012). In our study, similar genetic background in the four populations
and the conservation of differences in growth rate among populations in
our common garden experiment is also in agreement with local
adaptation.