Distances, climatic differences, and vegetation similarities of alpine grasslands in Europe

The importance of environmental difference among sites and dispersal limitations of species to the explanation of diversity differs among biological systems and geographical regions. We hypothesized that climate and then dispersal limitation will predominantly explain the similarity of alpine vegetation at increasing distances between pairs of regions at sub-continental extent. We computed the similarity of all pairs of 23 European mountain regions below 50°N after dividing the species lists of each region by calcareous or siliceous substrates. Distance decay in similarity was better fitted by a cubic polynomial than a negative exponential function, and the fit was better on calcareous than on siliceous substrate. Commonality analysis revealed that the proportion of explanation of beta diversity by climatic difference had unimodal patterns on a gradient of increasing distance between regions, while explanation by dispersal limitation had consistently rising patterns on both substrates. ...