1) Can we, with what is available in terms of data, rule out that walser stems from an ancient ‘hybrid’ origin?
mtDNA and nuDNA are really different from all known species/subspecies/clades. So this species really has an old history. Some old hybridisation cannot be excluded, as µsat markers should be investigated in this case. But the results of the nDNA sequencing also suggests that on this part the nDNA is very different.
2) Is one specimen per species enough for the applied nuclear analysis, or are these markers just highly conservative (within each species)?
More would be for sure ideal. But these genes are generally very conservative, and it is likely that all individuals have more or less the same haplotype.
3) How would you interprete the berus-like morphology of walser? Often, people would shout “convergence”, but I don’t really see what the evolutionary drivers would be to force this taxon into the looks of an equally useful design.
For me it’s really convergence and selection for this pattern in this condition. Think about all viper species living in Mountains: V. berus, V. a. zinninkeri in the Pyrenees, V. a. “atra”, in a lesser extent V. a. gregorwalneri in Austria; similarly in the southern part when you compare V. l. gaditana, V. a. hugyi and V. a. meridionalis. You can also think about V. darevskii and V. eriwanensis which look very similar but are complete different lineages….
4) Is there any hybridisation with aspis documented? If not, how likely would you consider it to be.
For the moment, we do not have any sign of hybridisation with V. aspis and I do not remember places where both species occur. However, this point (as numerous others) should be investigated.
This last is point is particularly interesting, because we observed clear syntopy last weekend. The information will be passed on to the Italian researchers who will work on the species in the future. It is possible/likely they did know this already.
The third issue still puzzles me, because there's of course the counterexample of bosniensis-macrops...