Testate amoebae (Protozoa) in lakes of the Qinghai-Tibet Plateau: Biodiversity, community structures, and protozoic biosilicification in relation to environmental properties and climate warming.

The Qinghai-Tibet Plateau (QTP) is characterized by a vast number of frozen and unfrozen freshwater reservoirs, which is why it is also called "the third pole" of the Earth or "Asian Water Tower". We analyzed testate amoeba (TA) biodiversity and corresponding protozoic biosilicification in lake sediments of the QTP in relation to environmental properties (freshwater conditions, elevation, and climate). As TA are known as excellent bio-indicators, our results allowed us to derive conclusions about the influence of climate warming on TA communities and microbial biogeochemical silicon (Si) cycling. We found a total of 113 TA taxa including some rare and one unknown species in the analyzed lake sediments of the QTP highlighting the potential of this remote region for TA biodiversity. >1/3 of the identified TA taxa were relatively small (<30 µm) reflecting the relatively harsh environmental conditions in the examined lakes. TA communities were strongly affected by physico-chemical properties of the lakes, especially water temperature and pH, but also elevation and climate conditions (temperature, precipitation). Our study reveals climate-related changes in TA biodiversity with consequences for protozoic biosilicification. As the warming trend in the QTP is two to three times faster compared to the global average, our results provide not only deeper insights into the relations between TA biodiversity and environmental properties, but also predictions of future developments in other regions of the world. Moreover, our results provide fundamental data for paleolimnological reconstructions. Thus, examining the QTP is helpful to understand microbial biogeochemical Si cycling in the past, present, and future.

Testate Amoebae in Historical parks of Potsdam, Germany.

To explore the potential of urban settings as habitats for testate amoebae, five historical parks in Potsdam (Germany) were sampled at different sites. A total of 32 sampling sites was chosen in proximity to deciduous (Acer, Castanea, Fagus, Tilia, Platanus, Quercus) and coniferous (Fraxinus, Picea, Pinus, Tsuga) trees. Meadows and creeks were also sampled. The overall taxonomic record comprises 76 species and sub-species. High species numbers of >20 per sample were found in meadows and below Fagus, Tilia, and Quercus trees. The species richness per park ranges from 33 to 46 taxa. Most species belong to the eurybiontic ecological group, although litter-inhabiting and hygrophilic and hydrophilic species were also present. Common species found in more than 50% of all samples (superdominants) belong to the genera Centropyxis, Cyclopyxis, Euglypha, and Trinema. Interestingly, the rare Frenopyxis stierlitzi which inhabits tree hollows was found as a recently described species in a new genus FrenopyxisBobrov&Mazei2020 in the Babelsberg Park. The studied testate amoebae are characterized by a high degree of morphological and morphometric plasticity. Therefore, the study of testate amoebae in urban settings will reveal new insights into their ecology and enhance the definition of morphometric variability for single species.

Recent climate change has driven divergent hydrological shifts in high-latitude peatlands.

High-latitude peatlands are changing rapidly in response to climate change, including permafrost thaw. Here, we reconstruct hydrological conditions since the seventeenth century using testate amoeba data from 103 high-latitude peat archives. We show that 54% of the peatlands have been drying and 32% have been wetting over this period, illustrating the complex ecohydrological dynamics of high latitude peatlands and their highly uncertain responses to a warming climate.

Distribution of soil testate amoeba assemblages along an elevation gradient on Mount Fuji (Japan).

Elevation gradients have been useful to study distributional patterns of soil organisms since the time of Humboldt but only recently these patterns have been studied for soil microorganisms. Here we report the results on species diversity and composition of soil- and moss-dwelling testate amoeba assemblages along a 1400 m elevation gradient (904-2377 m a.s.l.) on Mount Fuji (Japan) from temperate forest to alpine vegetation. In total, 95 testate amoeba taxa belonging to 29 genera were identified. The core of testate amoeba assemblages was formed by ubiquitous species such as Trinema lineare, Euglypha laevis, Cryptodifflugia oviformis, and Trinema complanatum. However, several taxa with limited geographic distribution were also observed (e.g., Centropyxis latideflandriana, C. stenodeflandriana, Plagiopyxis cf. barrosi, Heleopera rectangularis, and Distomatopyxis couillardi). Species diversity indices (species richness and Shannon's index) were characterised by bell-shaped patterns peaking at âˆ¼ 1700 m in the subalpine mixed conifer-deciduous forest. The species composition of testate amoeba assemblages was best explained by the vegetation types which accounted for 12.3% of the total variation. Overall, these findings indicate that elevation effects on species composition of testate amoeba assemblages are strongly mediated by vegetation.

Meisterfeldia bitsevi-new testate amoeba of the family Cryptodifflugiidae Jung, 1942 (Amoebozoa: Arcellinida) from the tree hollow in the urban park (Moscow, Russia) with a key to species of the genus Meisterfeldia.

The new testate amoeba species Meisterfeldia bitsevi is described from the linden-tree trunk hollow in the urban park in Moscow (Russia). New species is characterized by elongated ovoid bilaterally symmetrical shell, which is laterally not compressed. The shell is composed of proteinaceous material without mineral particles. Almost circular subterminal aperture is placed on ventral side. The key to the species of the genus Meisterfeldia is developed.

Frenopyxis stierlitzi gen. nov., sp. nov.-new testate amoeba (Amoebozoa: Arcellinida) from the urban parks with notes on the systematics of the family Centropyxidae Jung, 1942.

New species, Frenopyxis stierlitzi, is described from tree hollows in the urban parks in Moscow (Russia) and Potsdam (Germany). The species belongs to the new genus of the family Centropyxidae and characterized by unique character, i.e. an internal thick organic lip surrounding an aperture and continuing in a bridle, which connects an aperture with the internal side of a shell wall and broaden in the place of connection of a bridle and a shell wall. The systematics of the family Centropyxidae is discussed and the importance of the structures, which divide inner shell volume into compartments, is underlined.

Testate Amoebae of Peru: filling the gap in the Neotropics

Testate amoebae diversity from 28 surface (0-3 cm depth) soil samples found near Cuzco (6 samples), in Machu Piсchu (17 samples), in Aguas Calientes (5 samples), and one bottom sediment sample from the Lake Titicaca near the Puno collected during March of 2016 were analyzed. The 144 testate amoebae species and infra-specific taxa belonging to 27 genera were identified. Nineteen amoebae have not been identified to species level and likely represent new taxa. Species richness varied from one to 54 taxa per sample. The highest diversity was found in rainforests followed by those in meadows and agave habitats. The only bottom sample from Lake Titicaca has yielded two hydrobiont species from the genus Difflugia. In the course of the study, several rare species with limited geographical distribution were observed, namely Centropyxis castaneus, C. compressa, C. deflandriana, C. latideflandriana, C. cf. ohridensis, C. cf. ovoides, C. cf. pannosus, C. stenodeflandriana, Cyclopyxis plana, C. profundistoma, Apodera vas, Argynnia retorta, A. spicata, Certesella certesi, Trachelcorythion pulchellum. Our study fills a geographical gap in the distribution of some flagship species with restricted geographic distribution, e.g. Apodera vas and Certesella certesi in Peru. The results illustrate the continuity of expansion species along the Pacific coast.

La diversidad de amebas testadas de la capa superior del suelo (0-3 cm de profundidad) fue analizada en 28 de muestras recolectadas cerca de Сuzco (seis muestras), Machu Picchu (17 muestras) y Aguas Calientes (cinco muestras), así como una muestra de sedimentos del fondo recolectada en el lago Titicaca, cerca de la ciudad de Puno, en marzo 2016. Se identificaron 144 especies de amebas testadas y taxones infra-específicos pertenecientes a 27 géneros. Un total de 19 amebas no han sido identificadas a nivel de especie y probablemente sean nuevos taxones. La riqueza de especies varía de uno a 54 taxones por muestra. La mayor diversidad fue encontrada en los bosques pluviales, prados y hábitats de agave. En los sedimentos del fondo del lago Titicaca se encontraron 2 especies hidrobiónticas del género Difflugia. En el estudio se encontraron varias especies raras con una limitada distribución geográfica, tales como: Centropyxis castaneus, C. compressa, C. deflandriana, C. latideflandriana, C. cf. ohridensis, C. cf. ovoides, C. cf. pannosus, C. stenodeflandriana, Cyclopyxis plana, C. profundistoma, Apodera vas, Argynnia retorta, A. spicata, Certesella certesi y Trachelcorythion pulchellum. Nuestro estudio llena un vacío en la distribución geográfica de algunas especies importantes de Perú, que tienen una distribución geográfica limitada, por ejemplo: Apodera vas y Certesella certesi. Los resultados muestran la continuidad de la expansión de las especies a lo largo de la costa del Pacífico.

A new testate amoebae species Planhoogenraadia wuchanica sp. nov. from subtropical forest soils in Wuhan, central China.

Here we describe a new testate amoeba species Planhoogenraadia wuchanica sp. nov. identified in subtropical forest soils in Wuhan, central China. The smaller shell length, narrower aperture and distinctive 'cap' structure make P. wuchanica morphologically distinct from similar taxa in the genus. While this new species is morphologically distinctive, phylogenetic analyses would be beneficial to clarify taxonomic relationships within the genus Planhoogenraadia.

Shifts in soil testate amoeba communities associated with forest diversification.

We studied changes of testate amoeba communities associated with the conversion of spruce monocultures into mixed beech-fir-spruce forests in the Southern Black Forest Mountains (Germany). In this region, forest conversion is characterized by a gradual development of beech undergrowth within thinned spruce tree stands leading to multiple age continuous cover forests with a diversified litter layer. Strong shifts in the abundance of testate amoeba observed in intermediate stages levelled off to monoculture conditions again after the final stage of the conversion process had been reached. The average number of species per conversion stage (i.e., local richness) did not respond strongly to forest conversion, but the total number of species (i.e., regional richness) was considerably higher in the initial stage than in the mixed forests, due to the large number of hygrophilous species inhabiting spruce monocultures. Functional diversity of the testate amoeba community, however, significantly increased during the conversion process. This shift was closely associated with improved C and N availability as well as higher niche diversity in the continuous cover stands. Lower soil acidity in these forests coincided with a higher relative abundance of eurytopic species. Our results suggest that testate amoeba communities are much more affected by physicochemical properties of the soil than directly by litter diversity.