There is increasing evidence that extreme weather events such as frequent and intense cold spells and heat waves cause unprecedented deaths and diseases in both developed and developing countries. ...Thus, they require extensive and immediate research to limit the risks involved. Average temperatures in Europe in June-July 2019 were the hottest ever measured and attributed to climate change. The problem, however, of a thorough study of natural climate change is the lack of experimental data from the long past, where anthropogenic activity was then very limited. Today, this problem can be successfully resolved using, inter alia, biological indicators that have provided reliable environmental information for thousands of years in the past. The present study used high-resolution quantitative reconstruction data derived from biological records of Lake Silvaplana sediments covering the period 1181-1945. The purpose of this study was to determine whether a slight temperature change in the past could trigger current or future intense temperature change or changes. Modern analytical tools were used for this purpose, which eventually showed that temperature fluctuations were persistent. That is, they exhibit long memory with scaling behavior, which means that an increase (decrease) in temperature in the past was always followed by another increase (decrease) in the future with multiple amplitudes. Therefore, the increase in the frequency, intensity, and duration of extreme temperature events due to climate change will be more pronounced than expected. This will affect human well-being and mortality more than that estimated in today's modeling scenarios. The scaling property detected here can be used for more accurate monthly to decadal forecasting of extreme temperature events. Thus, it is possible to develop improved early warning systems that will reduce the public health risk at local, national, and international levels.
Understanding the interactions among the functional groups of living organisms within ecosystems is a main challenge in ecology. This question is particularly important in relation to the ...interactions between the above- and below-ground components of terrestrial ecosystems. We investigated the effects of macro- (geographic position and mire size) and micro-environmental (pH, water table depth, water mineralization and temperature) characteristics and vegetation composition (both vascular plants and bryophytes) on the species structure of testate amoeba assemblages in eight Sphagnum-dominated mires across the Northern Caucasus Mountains (Russia). In total, 97 testate amoeba species from 34 genera were identified. A multiple factor analysis indicated the strongest relationships between the species structure of the testate amoeba assemblages and the local vegetation, especially bryophytes, whereas the interaction with the micro-environmental characteristics was the weakest. Among the micro-environmental data, the strongest effects on the species composition of all the assemblages were detected for the pH followed by the water table depth and water temperature. The variance partitioning of the species structure of the testate amoeba assemblages in response to the abiotic and biotic data indicated that most of the variance was related to the bryophyte and vascular plant assemblages, whereas the contribution of the environmental data was lower. Moreover, most of the effects were highly related to each other, so that the proportion of the jointly explained variation was high, whereas the individual effects were much lower.
The origin of animals from their unicellular ancestor was one of the most important events in evolutionary history, but the nature and the order of events leading up to the emergence of multicellular ...animals are still highly uncertain. The diversity and biology of unicellular relatives of animals have strongly informed our understanding of the transition from single-celled organisms to the multicellular Metazoa. Here, we analyze the cellular structures and complex life cycles of the novel unicellular holozoans Pigoraptor and Syssomonas (Opisthokonta), and their implications for the origin of animals.
Syssomonas and Pigoraptor are characterized by complex life cycles with a variety of cell types including flagellates, amoeboflagellates, amoeboid non-flagellar cells, and spherical cysts. The life cycles also include the formation of multicellular aggregations and syncytium-like structures, and an unusual diet for single-celled opisthokonts (partial cell fusion and joint sucking of a large eukaryotic prey), all of which provide new insights into the origin of multicellularity in Metazoa. Several existing models explaining the origin of multicellular animals have been put forward, but these data are interestingly consistent with one, the "synzoospore hypothesis."
The feeding modes of the ancestral metazoan may have been more complex than previously thought, including not only bacterial prey, but also larger eukaryotic cells and organic structures. The ability to feed on large eukaryotic prey could have been a powerful trigger in the formation and development of both aggregative (e.g., joint feeding, which also implies signaling) and clonal (e.g., hypertrophic growth followed by palintomy) multicellular stages that played important roles in the emergence of multicellular animals.
Testate amoebae are a polyphyletic group of unicellular eukaryotic organisms that are characterised by a rigid shell and inhabit mostly freshwater and terrestrial ecosystems. They are particularly ...abundant in peatlands, especially in Sphagnum -dominated biotopes. Peatland hydrology is the most important influence on testate amoebae communities. The good preservation of the shells in peat deposits and their response to hydrological regime changes are the principles for palaeohydrological reconstructions. Any changes in the water balance of mires should be expected to have far-reaching effects on biogeochemical cycles, productivity, carbon dioxide and methane exchange. This paper presents a dataset (Darwin Core Archive – DwC-A) on the distribution of Sphagnum -dwelling testate amoebae in nine mires located in the forest-steppe subzone of the East European Plane. The dataset includes information about 86 taxa belonging to 29 genera and contains 3,123 occurrences of 49,874 individuals. The following environmental variables are provided: microtopography, oxidising and reducing potential, total mineralisation, substrate temperature, acidity, substrate wetness and water table depth. These data might be used for biogeographical and palaeoecological studies, including quantitative reconstructions.
This paper presents a reconstruction of natural environmental dynamics, wildfires and vegetation change in northwest Putorana Plateau during the last 1300 years. The study area is a remote and poorly ...investigated region of subarctic Siberia, relatively untouched by human impacts, which offers a unique opportunity to examine natural environmental dynamics and climate-vegetation-fire relationships. The paleoenvironmental reconstructions are based on multi-proxy analysis of the Gervi peatland including pollen, plant macrofossil, testate amoebae and charcoal analysis, loss on ignition measurements and AMS radiocarbon dating. The results revealed the main phases of regional paleoenvironmental change: a warm period between 680 and 1200 C.E. (Common Era) corresponding to the Mediaeval Climate Anomaly (MCA), followed by climate cooling during the Little Ice Age (LIA, 1200–1850 C.E.) and subsequent centuries. Climate amelioration during the MCA led to afforestation of northwestern Putorana Plateau and an expansion of spruce extending 70 km northeast of its present geographical range. A quantitative water-table reconstruction was generated using a testate amoebae transfer function and suggested that relatively dry climate conditions during the MCA triggered high fire frequencies. The LIA appeared in the study area as a period of pronounced climate cooling and moderate moistening, which caused an extension of tundra vegetation and a dramatic decline of fire activity. Distinct environmental changes at the study site were detected since 1990 C.E., characterized by a high peat accumulation rate and rising water table. Since 1990 C.E., the macroscopic charcoal accumulation rate in the peat core increased abruptly, suggesting a recent increase in the fire frequency in the study region.
(1) Background: An estuary is a zone in which sea and river waters mix. It is a specific area with a very non-stable environment and salinity gradient. However, little is known about the diversity of ...ciliate communities in estuarine benthic ecosystems in the Arctic. The aim of this paper is to describe the diversity of intertidal ciliates in the Chernaya river estuary (Kandalaksha Gulf, White Sea), which is characterized by a pronounced salinity gradient (0–22‰), on the basis of a recently published dataset. (2) Methods: We conducted our own investigations during the summer periods of 1998–2000. Material was collected at five permanent stations along the salinity gradient (0–22%) of the estuary. For each observation, the coordinates of the sampling sites, the number of individuals observed and the sampling date were recorded. The total effort comprised 35 sampling days, with five sampling sites at each date. (3) Results: The dataset contains 4270 unique occurrences of 119 ciliates taxa (109 species, 8 unidentified species of the genus level and 2 unidentified species on the family level). The total number of specimens represented is 64,475. (4) Conclusions: The largest classes in terms of species diversity are Hypotrichea (27 species), Gymnostomatea (26 species), Oligohymenophorea (17 species) and Karyorelictea (16 species).
Size-structured food webs form integrated trophic systems where energy is channeled from small to large consumers. Empirical evidence suggests that size structure prevails in aquatic ecosystems, ...whereas in terrestrial food webs trophic position is largely independent of body size. Compartmentalization of energy channeling according to size classes of consumers was suggested as a mechanism that underpins functioning and stability of terrestrial food webs including those belowground, but their structure has not been empirically assessed across the whole size spectrum. Here we used stable isotope analysis and metabolic regressions to describe size structure and energy use in eight belowground communities with consumers spanning 12 orders of magnitude in living body mass, from protists to earthworms. We showed a negative correlation between trophic position and body mass in invertebrate communities and a remarkable nonlinearity in community metabolism and trophic positions across all size classes. Specifically, we found that the correlation between body mass and trophic level is positive in the small-sized (protists, nematodes, arthropods below 1 μg in body mass), neutral in the medium-sized (arthropods of 1 lg to 1 mg), and negative in the large-sized consumers (large arthropods, earthworms), suggesting that these groups form compartments with different trophic organization. Based on this pattern, we propose a concept of belowground food webs being composed of (1) size-structured micro-food web driving fast energy channeling and nutrient release, for example in microbial loop; (2) arthropod macro-food web with no clear correlation between body size and trophic level, hosting soil arthropod diversity and subsidizing aboveground predators; and (3) “trophic whales,” sequestering energy in their large bodies and restricting its propagation to higher trophic levels in belowground food webs. The three size compartments are based on a similar set of basal resources, but contribute to different ecosystem-level functions and respond differently to variations in climate, soil characteristics and land use. We suggest that the widely used vision of resource-based energy channeling in belowground food webs can be complemented with size-based energy channeling, where ecosystem multifunctionality, biodiversity, and stability are supported by a balance across individual size compartments.
Peatlands play an important role in the global carbon cycle but have been exploited over many centuries, which reduces their carbon storage capacity. To investigate peatland development during the ...late Holocene and their restoration after peat extraction, we applied a multi-proxy paleoecological (pollen, plant macrofossils, testate amoebae, loss on ignition, peat humification, etc.) approach to undisturbed and floating vegetation mat deposits of the Gorenki peatland (Meshchera Lowlands, East European Plain). Peatland development started around 2550 before the common era (BCE) as a waterlogged eutrophic birch forest (terrestrial paludification) surrounded by a broadleaf forest. Around 2400 BCE, the peatland turned into an open mire with Sphagnum mosses, sedges, and willows. During 900–800 BCE, the mire transformed into a wet mesotrophic peatland surrounded by a spruce forest. The first human settlements and deforestation around 300–400 CE coincided with oligotrophization of the mire. The growth of the Slavic population in the region in 14th century CE caused transformation of indigenous spruce–broadleaf forests into croplands, and the mire became drier and forested. Since peat extraction was abandoned in the beginning of 20th century CE, the mire has undergone self-restoration starting with the formation of a Sphagnum cuspidatum/obtusum quagmire on the floating peat remains. The Sphagnum mat stabilized during 1960–2000 CE. During the last twenty years, agricultural activity decreased and pine forests were restored in the adjacent area; the floating mat became drier and more oligotrophic, which can lead to the formation of a bog in the absence of considerable anthropogenic impact.
Aim
This study aims to evaluate the role of various factors in structuring biogeographical distribution of small‐sized organisms. More specifically, we analysed the distribution of three groups of ...marine benthic organisms differing in body size, both unicellular and metazoans, to assess the relevance of geographical and environmental factors on their taxonomic composition.
Location
Global.
Taxon
Heterotrophic flagellates, Ciliophora, Harpacticoida (Copepoda).
Methods
The set of predictors included species richness (a proxy for sampling effort), geographical distance, isolation by geographical or hydrological barriers and three environmental variables (sea surface temperature, its annual variation and salinity). Multiple regression on the distance matrices and null modelling were used to quantify the relative effects of these variables in taxonomic similarity among 21 regions of the Ocean.
Results
Each group showed a unique biogeographical pattern. The smallest‐sized organisms, the flagellates, had high regional but low global diversity and low endemicity and demonstrated worldwide, environmentally driven distribution without any dispersal limitation (only the effects of climatic variables, but neither distance nor isolation effects, were significant). Thus, flagellates basically meet the ‘ubiquity model’ of global distribution. The ciliates showed a moderate level of endemicity, and their distribution depended on both spatial distance and the climatic variables, in accord with the ‘moderate endemicity model’. In contrast, harpacticoids demonstrated high endemicity level, and their distribution was mostly geographically driven, indicating the considerable role of dispersal limitation—the pattern typical of other multicellular taxa with ‘classical biogeography’. Species richness significantly influenced the interregional similarity of each group and explained 26%–65% of the total variance, indicating the strong impact of undersampling on faunistic similarity estimations.
Main conclusions
Our results support the hypothesis that body size is the ‘master trait’ that shapes global biogeographical patterns towards higher predictability and increasing role of dispersal limitation for larger organisms.
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