Mycobiota of the natural sanctuary "Grigorova ravine" (Volgograd region)

For the first time, the systematic study of the mycobiota of the natural sanctuary «Grigorova ravine» of the Volgograd region was carried out. Mycological survey was conducted from April to November 2019-2020. During the research, 32 species of fungi were identified, belonging to 25 genera, 17 families, 7 orders and 2 divisions. According to a trophic analysis of all the species of fungi found, it can be said that bedding and humus saprotrophes prevail. There are 12 species. There are 10 species of saprotrophes on timber, and 4 species of parasites. Substrate analysis of wood-destroying fungi showed that the largest number of species is confined to the wood Quercus robur L. - 9 species, on Ulmuslaevis Pall. - 3 species. Two species of Ganodermalucidum (Curtis) P. Karst. and Battarreaphalloides (Dicks.) Pers. included in the regional Red Book of the Volgograd region.

Graph hierarchy: a novel framework to analyse hierarchical structures in complex networks

Trophic coherence, a measure of a graph’s hierarchical organisation, has been shown to be linked to a graph’s structural and dynamical aspects such as cyclicity, stability and normality. Trophic levels of vertices can reveal their functional properties, partition and rank the vertices accordingly. Trophic levels and hence trophic coherence can only be defined on graphs with basal vertices, i.e. vertices with zero in-degree. Consequently, trophic analysis of graphs had been restricted until now. In this paper we introduce a hierarchical framework which can be defined on any simple graph. Within this general framework, we develop several metrics: hierarchical levels, a generalisation of the notion of trophic levels, influence centrality, a measure of a vertex’s ability to influence dynamics, and democracy coefficient, a measure of overall feedback in the system. We discuss how our generalisation relates to previous attempts and what new insights are illuminated on the topological and dynamical aspects of graphs. Finally, we show how the hierarchical structure of a network relates to the incidence rate in a SIS epidemic model and the economic insights we can gain through it.

Using Diatom Assemblages and Physicochemical Parameters to Characterize Waterfalls in Western Highlands of Cameroun, West Africa

Diatoms are mostly aquatic plants, growing in various environmental conditions and habitat. Because of their high sensitivity to environmental variations and rapid response to degradation, they are used as biological indicators. This study aimed to analyses the physicochemical parameters and diatoms assemblages of waterfalls. This will allow determining the key environmental factors that are responsible for both diatoms and Podostemaceae spatial and temporal distribution in the studied area.Water and diatoms samples were taken respectively for the physicochemical and biological analysis. Diatoms samples were collected by scraping the bedrocks and submerged plants; diatoms were subsequently identified to the species level using a light microscope. For physicochemical data analysis, a principal component analysis approach was used while diatom’s data were submitted to a correspondence trophic analysis. A total of 169 diatom species were identified in both waterfalls. Podostemaceae poor waterfalls were more species-rich (127) than the rich ones (110). Podostemaceae poor and Podostemaceae rich waterfalls were characterized with low mineralization, low values of pH and oxygen saturated water. The observed assemblages were composed of oligotrophic to eutrophic species, acidophilic, neutrophilic and high to moderate oxygen saturated water taxa. The ecology of different species revealed that dissolved oxygen was the main parameter which controls the distribution of diatoms, and probably the Podostemaeceae one in the two type of waterfalls Podostemaceae poor waterfalls are characterized by Fragilariacapucina and Gomphonema gracile. Podostemacea rich waterfalls were characterized by Eunotiafaba, Eunotiarhomboïdea, Pinnularia microstauron, Gomphonema procerum and Gomphonema clavatum.

Graph Hierarchy: A novel framework to analyse hierarchical structures in complex networks

Trophic coherence, a measure of a graph’s hierarchical organisation, has been shown to be linked to a graph’s structural and dynamical aspects such as cyclicity, stability and normality. Trophic levels of vertices can reveal their functional properties, partition and rank the vertices accordingly. Trophic levels and hence trophic coherence can only be defined on graphs with basal vertices, i.e. vertices with zero in-degree. Consequently, trophic analysis of graphs had been restricted until now. In this paper we introduce a hierarchical framework which can be defined on any simple graph. Within this general framework, we develop several metrics: hierarchical levels, a generalisation of the notion of trophic levels, influence centrality, a measure of a vertex’s ability to influence dynamics, and democracy coefficient, a measure of overall feedback in the system. We discuss how our generalisation relates to previous attempts and what new insights are illuminated on the topological and dynamical aspects of graphs. Finally, we show how the hierarchical structure of a network relates to the incidence rate in a SIS epidemic model.

Chemical ecology of an apex predator life cycle

Microbial symbiotic interactions, mediated by small molecule signaling, drive physiological processes of higher order systems. Metabolic analytic technologies advancements provide new avenues to examine how chemical ecology, or conversion of existing biomass to new forms, changes over a symbiotic lifecycle. We examine such processes using the tripartite relationship between nematode host Steinernema carpocapsae, its obligate mutualist bacterium, Xenorhabdus nematophila, and the insects they infect together. We integrate trophic, metabolomics, and gene regulation analyses to understand insect biomass conversion to nematode or bacterium biomass. Trophic analysis established bacteria as the primary insect consumers, with nematodes at trophic position 4.37, indicating consumption of bacteria and likely other nematodes. Significant, discrete metabolic phases were distinguishable from each other, indicating the insect chemical environment changes reproducibly during bioconversion. Tricarboxylic acid cycle components and amino acids were significantly affected throughout infection. These findings contribute to an ongoing understanding of how symbiont associations shape chemical environments.TeaserEntomopathogenic nematodes act as an apex predator in some ecosystems through altering chemical environments of their prey.

Modelling the tri-trophic population dynamics of a host crop (Triticum aestivum; Poaceae), a major pest insect (Sitodiplosis mosellana; Diptera: Cecidomyiidae), and a parasitoid of the pest species (Macroglenes penetrans; Hymenoptera: Pteromalidae): a cohort-based approach incorporating the effects of weather

This paper describes a tri-trophic analysis of the ecological dynamics of a crop, an insect pest, and a natural enemy of the insect pest. Worldwide wheat (Triticum Linnaeus) (Poaceae) production in 2018–2019 was estimated at over 700 million metric tons in 2018–2019. Wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), a serious insect pest of wheat, is widely distributed in many parts of the world where wheat production occurs. Macroglenes penetrans (Kirby) (Hymenoptera: Pteromalidae), a parasitoid of S. mosellana, has successfully established in most wheat midge-infested areas. Mechanistic, or process-based, population models were used in this study to assess the interactive population dynamics of the three species, based on their respective life cycles and meteorological factors. The models were validated with survey data from multiple sites over numerous years (1991–2016). These simulation models helped to detail our understanding of the tri-trophic population dynamics and will help guide pest management decisions both prior to the growing season and until wheat heading, when wheat is no longer susceptible to S. mosellana. The associated models also help identify gaps in system knowledge, provide a foundation for evaluating future innovative management options, and evaluate the potential impact of a changing climate.

Mycobiota in Cemeterial Areas of Volgograd City

Cemeterial areas are an integral part of any urban ecosystem. The flora of cemeteries is diverse due to the large number of introduced species. This fact also implies species diversity in the macromycete biota, which is of interest for further study. Until now, special studies of mycobiota in cemeteries in Volgograd have not been conducted. We have examined three cemeteries in different districts of Volgograd City. Mushroom collection has been carried out by the route method from September to November 2019. To identify the samples we have applied standard light microscopy methods in the laboratory of Experimental biology of Volgograd State University using the guides of wellknown mycologists. Nikon D3500 SLR camera was used for shooting mushrooms. The collected species are stored in the Mycological herbarium of Volgograd State University. As a result we present an annotated list of cemeteria fungi, including 17 species, such as Agaricus arvensis Schaeff., A. xanthodermus Genev., Auricularia mesenterica (Dicks.) Pers., Coprinellus micaceus (Bull.) Vilgalys, Hopple et Jacq. Johnson, Crucibulum laeve (Huds.) Kambly, Hydroporus marginellus (Pers.) Singer, Lepista personata (Fr.) Cooke, Lycoperdon perlatum Pers., Mycena ssp., Myriostoma coliforme (Dicks.) Corda, Phellinus pomaceus (Pers.) Maire, Pilatotrama ljubarskyi (Pilát) Zmitrovich, Pleurotus ostreatus (Jacq.) P. Kumm., Psathyrella conopilea (Fr.) A. Pearson et Dennis, Pseudoclitocybe cyathiformis (Bull.) Singer, Stropharia melanosperma (Bull.) Gillet, Tulostoma brumale Pers. Each annotation includes the date of collection, data on habitats and substrates inhabited by the species, as well as the occurrence of the species. The last index states ‘rare’ if we have no more than 5 finds, ‘often’ – 6–20 finds, ‘frequent’ – 21–50 finds, and ‘very often’ – more than 50 finds. The trophic analysis of the macromycete composition has revealed that all the found species belong to the saprotrophic group. Among them, the largest number of species was recorded on dry and dead wood (10 species). The further research of the diversity of fungi in these areas is necessary.