Continental-Scale α- and β-Diversity Patterns of Terrestrial Eukaryotic Microbes: Effect of Climate and Microhabitat on Testate Amoeba Assemblages in Eurasian Peatlands

Aim

The role of environmental factors that shape the large-scale distribution of eukaryotic microbes remains understudied. We aimed to disentangle the impacts of latitudinal and longitudinal gradients on the distribution of Sphagnum-dwelling testate amoebae in mires and to understand the influence of environmental factors related to both local habitats (hummock—lawn—hollows) and regional climates.

Location

A range from temperate to subarctic and from the European part to the Far East of Russia (51°–70°N, 32°–158°E).

Taxon

Testate amoeba (Arcellinida, Euglyphida, and Amphitremida).

Methods

We analysed the testate amoeba (TA) composition and abundance data from 816 samples collected in 75 peatlands. Linear mixed-effects models and redundancy analysis were applied to determine the likely environmental drivers of TA α- and β-diversity.

Results

We identified a significant reversed latitudinal gradient in α-diversity which negatively correlated with the mean annual temperature. This gradient is microhabitat-specific, being prominent in lawn and hollow microhabitats, but not in hummocks. Longitude, which corresponds mainly to a gradient of precipitation seasonality, was a significant predictor of TA β-diversity, especially in hollows.

Main Conclusions

Our findings identify climatic factors (e.g., mean annual temperature and precipitation seasonality) as likely shaping the continental-scale TA α- and β-diversity patterns, emphasising the microhabitat-specific nature of these relationships. The absence of pattern in hummocks is interpreted as evidence for a predominant microhabitat stress (i.e., low moisture and pH) in this habitat.