A thorough understanding of the structure of high-altitude lake communities and patterns of altitudinal-diversity gradients is of key importance for the prediction of their response to ongoing climate warming. We have already proved that local catchment conditions, particularly topographic shading, may be significantly involved in the modification of large-scale temperature signals in high-altitude lakes (Novikmec et al. 2013).
Here, we analysed littoral benthic communities of 18 glacial lakes distributed along an elevation gradient and belonging into two categories of intensity of topographic shading: shaded vs unshaded lakes. We hypothesized that local topographic shading could modify the species richness-elevation relationships and affect the pattern of community changes along the elevation gradient.
Our data revealed a significant overall trend in diversity along the elevation gradient and a significant deviation from that trend manifested in shaded lakes. Both lake types showed a sigmoidal decrease of species richness with altitude, however, the pattern was more pronounced in shaded than unshaded lakes. Community composition also showed significantly different altitudinal trends in shaded and unshaded lakes. Investigated lake groups hosted distinct invertebrate communities in lower altitudes However, the community composition of shaded and unshaded lakes converged towards higher altitudes in communities typical for a higher abundance of cold stenothermic species.
It seems that some topographically shaded lakes can be resistant to climate signals and may provide refuges for relict communities under continuing global warming. The occurrence of such communities in lakes located at lower altitudes could indicate extreme temperature conditions that differ from the scheme of changes along an altitudinal gradient.
The study was funded by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Academy of Sciences, Grant No. VEGA 1/0400/21.