Showing papers by "Andreas Tribsch published in 2014"

Ecological and genetic differentiation of two subspecies of Saussurea alpina in the Western Alps

Abstract: In the Western Alps, two subspecies of Saussurea alpina are found in a partly overlapping distribution area; however, they prefer distinct habitats. While Saussurea alpina ssp. alpina is distributed throughout the Alps and beyond, S. alpina ssp. depressa is endemic to the region ranging from the Maritime Alps (France) to the Valais (Switzerland). The sympatric occurrence of closely related taxa raises general questions which factors drive speciation. In order to investigate the genetic and ecological differentiation of the two subspecies, we applied Amplified Fragment Length Polymorphisms and analyzed the habitat preferences via soil pH measurements and vegetation releves. Overall, we studied 12 populations (five populations of S. alpina ssp. alpina and seven of S. alpina ssp. depressa). The populations were found to be genetically highly differentiated (F ST = 0.42). Nevertheless, a weak, but significant genetic differentiation between the subspecies could be detected (F CT = 0.04) and the results of the ecological analyses showed a clear differentiation in habitat types. While S. alpina ssp. alpina occurs in alpine grasslands, S. alpina ssp. depressa occurs mainly on calcareous scree with a significantly higher soil pH (median pH = 7 and median of pH = 8.14 for S. alpina ssp. alpina and S. alpina ssp. depressa, respectively) and different surrounding vegetation. We conclude from the clear difference in ecology that ecological plant speciation is a major factor in establishing and maintaining a reproductive barrier. We explain the weak genetic differentiation with a recent separation of the two evolutionary units during the last glaciation cycles or even in postglacial periods.