Browsing by Author "Voutilainen, Inka"

Many historical, spatial and local processes affect the distribution of species on Earth. Because of these processes, some species thrive in a specific environment while others perish. This also holds true for micro-organisms, such as diatoms. Theory of diatoms’ cosmopolitan distribution has been proven to be inaccurate as the distributions of diatoms have been documented to be spatially restricted. Thus, local environmental conditions alone are inadequate for explaining the spatial variation of diatom communities while historical and spatial processes influence diatoms similarly as found for macro-organisms. Diatoms have a significant role in the biogeochemical cycle of substances and as primary producers of ecosystems, so the knowledge of their ecology is crucial. Diatoms are also utilized as bioindicators of water quality and therefore it’s important to have detailed knowledge of their ecological preferences. The aim of this research was to find out which environmental variables affected most the species richness and the community composition of diatoms in 35 mountain lakes and ponds in Italian Dolomites. More specifically, we also addressed whether diatoms show clear elevational patterns in richness and in composition. We compared our results with earlier studies conducted in the same study area as well as with subarctic studies. The data for this research were collected in July-August in 2016 in Adamello-Presanella Nature Park. The water and the diatom samples were collected from the lakes and ponds simultaneously. The degree of spatial autocorrelation was calculated for each environmental variable and multicollinearity was tested with Spearman’s correlation and variance inflation factors. The variation of species richness was analyzed with generalized linear models whereas patterns in species composition was analyzed with redundancy analysis. The alpine and the subarctic datasets were compared with non-metric multidimensional scaling and with analysis of similarities. Elevation and pH were the most important variables explaining the variation of species richness in the research area. The community composition was most affected by conductivity, pH, nitrate content and elevation. The environmental conditions of the subarctic and the alpine lakes were quite similar, yet they differed statistically. The species compositions of the regions differed from each other more strongly than water chemistry. The differences between species compositions were higher, when binomial data was used in the analysis. In this research, the local water chemistry variables, especially that of pH, were more significant drivers for species richness and species composition than the elevation. The comparison of alpine and subarctic datasets indicated that the spatial location of the waters does have an independent effect on the species composition, apart from local environmental variables.