Testate amoebae have proved a useful group of species to understand the biogeography of larger microorganisms. The Arctic has attracted particular interest in such studies but there are large ...geographic gaps in current knowledge. Here we present what we believe is the first ever study of testate amoebae from the Novaya Zemlya archipelago in Arctic Russia. We investigated testate amoebae from the northernmost island of Novaya Zemlya proper and two smaller islands to the south: Dolgii Island and Matveev Island. We found that testate amoebae were present and active even in the extreme physical environment of northern Novaya Zemlya. Further south in the tundra zone of Dolgii and Matveev islands, testate amoebae were notably abundant and diverse. There were distinct differences in assemblage between all three islands and particularly between Novaya Zemlya and the two more southerly islands. The assemblage of Novaya Zemlya was distinctive with a surprising abundance of larger taxa. Comparisons to previous data suggest that the testate amoeba assemblages of these islands may show more affinity to those further west in Greenland and Svalbard than those further east in Siberia. Results highlight the limited knowledge of the abundance and diversity of these functionally significant protists in large areas of the globe.
Tropical peatlands play an important role in carbon storage and in water regulation on a landscape level. However, our understanding of their ecology and long-term hydrological dynamics remains ...limited. Transfer functions, constructed on the basis of biological indicators (proxies) with known ecological preferences, allow us to infer past environmental conditions and serve as a basis for prediction of future changes in peatlands. Here, we use testate amoebae to develop the first species- and functional trait-based transfer functions for the Southeast Asia. This provides a valuable tool for future reconstructions of past hydrological changes in tropical peatlands, their development, and climatic changes. Surface samples for testate amoeba analysis were taken in various biotopes along two transects across the Sungai Buluh peatland in Central Sumatra. The following environmental characteristics were measured: water table depth (WTD), light intensity, pH, total C and N concentrations. The analysis of the surface samples revealed 145 morphotypes of testate amoebae belonging to 25 genera. A significant fraction of the variance in testate amoeba morphotypes and functional trait composition was explained by WTD and pH. The wide WTD range (0–120 cm) seems more valuable for reconstruction than the extremely short pH gradient (2.5–3.8). Thus, transfer functions were developed only for WTD, based on weighted averaging model for morphotypes and multiple linear regression for functional traits. Both species- and trait-based model have a predictive ability for WTD reconstruction. For traits, the best performance of the model was reached by including five morphological traits: shell width, aperture shape, aperture invagination, shell shape and shell compression. We discuss the ecology of several taxa and highlight the traits, which reflect hydrological changes in this system. Though the hydrological preferences of some species are similar to those in high and middle latitude peatlands, we argue that latitudinal differences in morphospecies composition and variations in environmental relationships of species require the development of region-specific transfer functions. Moreover, our results indicate that ecological preferences of morphotypes within morphospecies also need to be considered and included in future studies.
The genus Euglypha contains the largest number of filose testate amoeba taxa which were mainly described based on the morphological characteristics of shells. Despite the increasing amount of ...molecular data, the phylogenetic relationships within the genus Euglypha remain unresolved. In this work we provide new data on SSU rRNA gene sequences, light and electron microscopy for the two euglyphid species Euglypha bryophilaBrown, 1911 and Euglypha cristataLeidy, 1874. Both species are characterised by the presence of a turf of spines on the aboral pole of the shells but differ in shell cross sections (elliptical and circular, respectively). A newly revealed feature of E. bryophila is a three-lobed thickening at the anterior margin and an elongated lobe at the posterior margin of apertural plates. The phylogenetic analysis shows that the species group together with the previously sequenced taxa of the genus Euglypha according to the shell cross-section. The subdivision of the genus based on the shell symmetry may reflect evolutionary trends to complication of the shell from radial to biradial symmetry. We also suggest that the shape of the anterior thickening of apertural plates and the lobe at the posterior margin can be used to distinguish Euglypha at the species level.
This study aimed to reconstruct the climatic moisture conditions of the Mid- Russian Upland through the Holocene. Surface moisture conditions in the study region were inferred from published pollen ...records from the Klukva peatland, in the north-west of the Mid-Russian Upland. Three climatic indices were derived from previously- published reconstructions of mean annual temperature and precipitation: the Climate Moisture Index, the Aridity Index and the Budyko Dryness Index. A simple modeling approach to reconstruct annual potential evapotranspiration and net radiation was developed and used to estimate the indices for different periods of the Holocene. The moisture indices were compared with independent proxies of climate moisture such as peatland surface wetness, reconstructed from testate amoebae and regional fire activity, reconstructed from charcoal. Results show that the surface moisture conditions in the study region were characterized by large variability. Periods of mild temperature and moderately wet conditions were followed by dry periods, which resulted in significant changes in palaeoenvironments. The method developed for calculation of potential evapotranspiration and indices of surface moisture conditions could be a useful tool for climate reconstructions. Our results demonstrate the detailed and nuanced palaeoclimate data which can be derived from pollen data.
Testate amoebae are widely used in ecological and palaeoecological studies of peatlands, particularly as indicators of surface wetness. To ensure data are robust and comparable it is important to ...consider methodological factors which may affect results. One significant question which has not been directly addressed in previous studies is how sample size (expressed here as number of Sphagnum stems) affects data quality. In three contrasting locations in a Russian peatland we extracted samples of differing size, analysed testate amoebae and calculated a number of widely-used indices: species richness, Simpson diversity, compositional dissimilarity from the largest sample and transfer function predictions of water table depth. We found that there was a trend for larger samples to contain more species across the range of commonly-used sample sizes in ecological studies. Smaller samples sometimes failed to produce counts of testate amoebae often considered minimally adequate. It seems likely that analyses based on samples of different sizes may not produce consistent data. Decisions about sample size need to reflect trade-offs between logistics, data quality, spatial resolution and the disturbance involved in sample extraction. For most common ecological applications we suggest that samples of more than eight Sphagnum stems are likely to be desirable.
In the Caucasus, the total area taken up by glaciers is known to have reduced by 23% over the last 20 years. This natural experiment allows for additive and replacement models of autogenic succession ...of biocoenoses within paraglacial landscapes to be tested. A certain risk of the extinction of cryophilic species also exists. However, montane paraglacial successions of invertebrate assemblages have hitherto been studied neither in the Caucasus nor in Russia as a whole. Structural changes of taxocoenoses were traced in a spatial and temporal sequence of ten properly dated paraglacial sites in the Tsey Gorge, North Ossetia − Alania (1–170-years old) among the testate amoebae, earthworms, molluscs, myriapods, mites, spiders, harvestmen, pseudoscorpions, collembolans, and beetles. As the glacier retreats, in place of bare paraglacial wastelands, grassland communities are formed that, after 10–14 years, are replaced by shrub vegetation and, on 30–35-year old surfaces, by forest communities. Most of the invertebrate groups, once “appearing” along a postglacial transect, were recorded from most older plots as well. Yet, their taxocoenoses underwent considerable transformations through increasing (or an increase turning into some decline in beetles) the species diversity and a strong, often complete change in the taxonomic composition and dominance structure. The most considerable transformations were observed at all major vegetation changes. The “appearance” of some groups in the transect was determined not only by dispersion capacities but mainly by the environmental conditions of particular habitats. When comparing the composition of the pioneer postglacial species complex of the study region with that in the mountains of Europe’s south and north, its high-degree regional specificity was noted, sometimes shown at the family level (in spiders). Spatial β-diversity of all larger taxa studied was mainly attributed to turnover (due to “the replacement model” of succession). The general level of change diminished towards the later succession stages. Endemic arthropod species were revealed both in pioneer grassland and developed forest communities.
•Uncertainty surrounds the role of human activity in microbial biogeography.•We considered an unusual soil translocation ‘accidental experiment’.•We find no evidence for testate amoeba species ...translocation.•It appears that over thirty years the assemblage may have acclimated to Arctic conditions.
The role of human activity as a vector in the movement of soil microorganisms is uncertain and disputed. It is increasingly clear that some larger microorganisms have restricted distributions and plausible to imagine that many human activities could lead to exotic species introductions, but concrete examples are lacking. We investigated an unusual case study: the former mining settlement of Pyramiden on the island of Spitsbergen in the Svalbard archipelago. In around 1983 large quantities of chernozem soils were imported from the southern USSR as part of an urban greening initiative, bringing large numbers of soil organisms to a very different physical environment. Focusing on a readily-identifiable group of protists with documented regional endemism (testate amoebae), we assessed morphospecies assemblages after thirty years. We analysed communities from Pyramiden imported soils and conducted comparisons to: i) nearby locations with non-imported near-natural soils; ii) previously-established datasets from near-natural Svalbard soils and chernozem soils in southern Russia, and iii) regional species inventories from both regions. Our aims were to assess how the community has adapted to the change in physical conditions and identify any evidence for the import of exotic taxa. Our results show significant differences between the assemblages of imported soils and those of nearby reference sites but strict comparisons are complicated by the different treatment of soils in different locations. No taxa were identified which can be unambiguously identified as atypical for the region. Assemblages of imported soils were more similar to those of other sites on Svalbard than to assemblages from southern Russia. Our data are equivocal but suggest that the testate amoeba assemblages of soils transported more than 3000 km northwards have substantially acclimated to the new conditions, contrasting with micro-invertebrates in the same site. ‘Accidental experiments’ like the soils of Pyramiden provide unique opportunities for long-term, large-scale, soil biological research.
In order to better understand the distribution patterns of terrestrial eukaryotic microbes and the factors governing them, we studied the diversity partitioning of soil testate amoebae across levels ...of spatially nested habitat hierarchy in the largest European old-growth dark coniferous forest (Pechora-Ilych Biosphere Reserve; Komi Republic, Russia). The variation in testate amoeba species richness and assemblage structure was analysed in 87 samples from six biotopes in six vegetation types using an additive partitioning procedure and principal component analyses. The 80 taxa recorded represent the highest value of species richness for soil testate amoebae reported for taiga soils so far. Our results indicate that testate amoeba assemblages were highly aggregated at all levels and were mostly controlled by environmental factors rather than dispersal processes. The variation in species diversity of testate amoebae increased from the lowest to the highest hierarchical level. We conclude that, similarly to macroscopic organisms, testate amoeba species richness and community structure are primarily controlled by environmental conditions within the landscape and suggest that metacommunity dynamics of free-living microorganisms are driven by species sorting and/or mass effect processes.
Testate amoeba transfer functions are widely used for reconstruction of palaeo-hydrological regime in peatlands. However, the limitations of this approach have become apparent with increasing ...attention to validation and assessing sources of uncertainty. This paper investigates effects of peatland type and sampling depth on the performance of a transfer function using an independent test-set from four Sphagnum-dominated sites in European Russia (Penza Region). We focus on transfer function performance along localised hydrological gradients, which is a useful analogue for predictive ability through time. The performance of the transfer function with the independent test-set was generally weaker than for the leave-one-out or bootstrap cross-validations. However, the transfer function was robust for the reconstruction of relative changes in water-table depth, provided the presence of good modern analogues and overlap in water-table depth ranges. When applied to subsurface samples, the performance of the transfer function was reduced due to selective decomposition, the presence of deep-dwelling taxa or vertical transfer of shells. Our results stress the importance of thorough testing of transfer functions, and highlight the role of taphonomic processes in determining results. Further studies of stratification, taxonomy and taphonomy of testate amoebae will be needed to improve the robustness of transfer function output.
•Estimates of temporal variation may resolve the “everything is everywhere” dispute.•Seasonal species turnover comprises up to 50 % of the total species diversity.•Assemblages are more diverse and ...heterogeneous in spring than in autumn.•Assemblages are considerably controlled by substrate moisture in summer and autumn.•Hydrophilic testate amoebae in spring are replaced by xerophilic species in autumn.
Understanding the spatial and temporal variation in protist communities is essential for comprehensive studies on diversity and biogeography, yet most research focuses on either spatial or temporal processes, ignoring their combined effects. Here we use an additive partitioning approach to estimate the contribution of temporal and spatial components to the total taxonomical (morphospecies) diversity of testate amoebae in a swampy forest (the forest-steppe zone, Russia) during a snow-free season (from April to November). Testate amoebae have been chosen as model organisms for the study because they are a diverse and abundant group of protists that play important roles in soil communities mostly as consumers in decomposer food webs. Our results indicate that seasonality considerably contributed to the variation in the total species richness (γ) of both live and empty shell assemblages of testate amoebae (48 and 38 %, respectively). The beta component of species richness related to the spatial variation among sampling plots explained 22 % of γ-diversity in live assemblages and 28 % in empty shell assemblages. Beta diversity (both as species richness and species composition) decreased towards the end of the snow-free season. Spring assemblages were dominated by hydrophilous species of testate amoebae, whereas xerophilic species were more abundant in autumn. Our results imply that the snowmelt phase could be an important factor setting the heterogeneity of testate amoeba assemblages in the early spring, whereas in the rest of snow-free season the assemblages were considerably controlled by substrate moisture. Overall, temporal sampling is essential for adequate estimates of species diversity of soil-dwelling testate amoebae.
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