Population Regulation Research Articles

Cba-miR-222-3p involved in photoperiod-induced apoptosis in testes of striped hamsters by targeting TRAF7.

The role of miRNAs in the regulation of seasonal reproduction in rodents, particularly in relation to photoperiod changes, is still poorly understood. Previous studies on miRNA transcriptomes of striped hamster (Cricetulus barabensis) testes have indicated that the photoperiodism of testes, especially apoptosis, may be influenced by miRNAs. As a functional miRNA, cba-miR-222-3p in striped hamster testes exhibits suppression under a short photoperiod. To elucidate the potential role of testicular cba-miR-222-3p in the seasonal reproduction of striped hamsters, we exposed male striped hamsters to different photoperiods or injected miRNA agomir into the testes and observed the effects of these treatments, particularly some indicators related to apoptosis. The results showed that the levels of apoptosis in the testes increased in short daylength, accompanied by a significant decrease in cba-miR-222-3p expression and an increase in TRAF7 expression. Dual luciferase reporter assays verified the targeting relationship between cba-miR-222-3p and TRAF7 predicted by bioinformatics. In addition, the expression of TRAF7 decreased in the testes, which injected miRNA agomir, leading to inhibition of apoptosis, and the expression of key genes (MEKK3, p38, p53) in the downstream MAPK signaling pathway of TRAF7 was suppressed. These results suggest that short daylength induces testicular apoptosis in striped hamsters, and one possible mechanism is that the decreased expression of miR-222-3p in testes reduces the repression of TRAF7 translation, thereby activating the MAPK pathway and affecting the level of testicular apoptosis. These findings reveal the potential role of miR-222-3p in animal reproduction and provide new insights into the regulation of rodent populations.

Antimicrobial Activity of Corynebacterium amycolatum ICIS 53 and Corynebacterium amycolatum ICIS 82 Against Urogenital Isolates of Multidrug-Resistant Staphylococcus aureus.

Intermicrobial interactions play a key role in the regulation of microbial populations and the colonization of various ecological niches. In the present study, we assessed the effect of cell-free supernatants (CFSs) from the vaginal isolates Corynebacterium amycolatum ICIS 53 and Corynebacterium amycolatum ICIS 82 on urogenital test strain biofilm formation of Staphylococcus aureus. Our studies showed that the CFSs of both C. amycolatum strains significantly reduced biofilm formation and disrupted preformed S. aureus biofilms. Pretreatment with C. amycolatum ICIS 53 or C. amycolatum ICIS 82 CFSs decreased the cell surface hydrophobicity and exopolysaccharide production of all the test S. aureus isolates. The scanning electron microscopy (SEM) results showed that the CFSs of corynebacteria caused the S. aureus biofilms to be small clusters scattered across the surface, there were no fibres or adhesions between cells, and the cell membrane was not damaged. Treatment of preformed biofilms with CFSs from both C. amycolatum strains resulted in a flat, scattered, and unstructured architecture. The S. aureus cell membrane was damaged. GC‒MS analysis of the CFS of C. amycolatum ICIS 53 revealed the presence of 22 chemical compounds, including long-chain fatty alcohols, esters, fatty acids and heterocyclic pyrrolizines and pyrazoles, that, according to the literature, exhibit a wide range of biological activities. The results of the present work provide insight for the study of Corynebacterium microorganisms as a source of multifunctional bioactive compounds, which may find promising applications in the medical, biotechnological and pharmaceutical industries.

From European Roots to Settler Soil: Adapting Foucault’s Biopolitics to Canadian Settler Colonialism

This article examines the applicability of Michel Foucault’s biopolitical theory within the Canadian settler colonial context. Foucault’s concept of biopolitics, which describes the shift from sovereign power to the regulation of life and populations, is grounded in European historical contexts. In contrast, the Canadian settler colonial experience diverges significantly, necessitating a re-examination of biopolitics. The article argues that in Canada, the relationship between sovereignty, population, and territory does not follow the European model described by Foucault. Instead, Crown sovereignty established its control through legal mechanisms that defined ‘Indian’ status, displacing Indigenous territorialities and political structures. By analysing the evolution of ‘Indian’ status within the Indian Act (1985), the article highlights the centrality of law in constructing settler colonial biopolitics. This legal framework was used to manage and assimilate Indigenous populations, reflecting a unique biopolitical strategy aimed at creating a relationship to territory and population. The study contributes to a more specific understanding of biopolitics in settler colonial contexts, emphasizing the distinct role of law in these processes.

The evolutionary and ecological convergence of the raccoon and raccoon dog: A perfect storm of invasive species in Europe

AbstractThis paper initially describes the evolution of body shape in the raccoon (Procyon lotor) and the raccoon dog (Nyctereutes procyonoides). I explain how their similarities are the result of convergent evolution, the process by which unrelated organisms come to resemble one another in form, function, or both. This is the first examination of this phenomenon in these two species. In addition, I consider how their convergent traits and habits as omnivores have contributed to their astounding success as invasive species in Europe. Problems have arisen from these introductions, including impacts on prey species. Considering their broad adaptability as “stout” shaped mesocarnivores should aid in understanding their behavior and ecology, and could assist in addressing their management in Europe. Last, I offer suggestions for the control of raccoons given their compensatory versus additive mortality patterns, a practice that may also have implications for the regulation of raccoon dog populations.

DNA methylation and genetic regulation in natural populations of East Asian and mixed Eurasian ancestry

DNA methylation and genetic regulation in natural populations of East Asian and mixed Eurasian ancestry

Structural characterization of N-acyl-homoserine lactones from bacterial quorum sensing using LC-MS/MS analyses after Paternò-Büchi derivatization in solution.

Bacterial quorum sensing is a chemical language allowing bacteria to interact through the excretion of molecules called autoinducers, like N-acyl-homoserine lactones (AHLs) produced by Gram-negative Burkholderia and Paraburkholderia bacteria known as opportunistic pathogens. The AHLs differ in their acyl-chain length and may be modified by a 3-oxo or 3-hydroxy substituent, or C = C double bonds at different positions. As the bacterial signal specificity depends on all of these chemical features, their structural characterization is essential to have a better understanding of the population regulation and virulence phenomenon. This study aimed at enabling the localization of the C = C double bond on such specialized metabolites while using significantly lower amounts of biological material. The approach is based on LC-MS/MS analyses of bacterial extracts after in-solution derivatization by a photochemical Paternò-Büchi reaction, leading to the formation of an oxetane ring and subsequently to specific fragmentations when performing MS/MS experiments. The in-solution derivatization of AHLs was optimized on several standards, and then the matrix effect of bacterial extracts on the derivatization was assessed. As a proof of concept, the optimized conditions were applied to a bacterial extract enabling the localization of C = C bonds on unsaturated AHLs.

Natural Enemies as Guardians of Crop Ecosystem with Special Emphasis on Rice and Cotton

Natural enemies, including predators, parasitoids, and pathogens, play a crucial role in the regulation of pest populations within agricultural ecosystems. This review examines the role of these biological control agents in maintaining the health and productivity of crop systems, with a specific focus on rice and cotton. In rice ecosystems, natural enemies such as spiders, dragonflies, and various insect parasitoids help manage pest populations like the rice stem borer and the planthopper. Similarly, in cotton crops, natural predators and parasitoids contribute to the control of key pests including the cotton bollworm and aphids. By integrating these natural enemies into pest management strategies, farmers can reduce reliance on chemical pesticides, enhance biodiversity, and promote sustainable agriculture. This review highlights the mechanisms through which these natural enemies operate, the benefits they provide to crop ecosystems, and case studies illustrating successful applications. The major emphasis is placed on understanding the interactions between these biological control agents and their environments, and how these relationships can be optimized to support resilient crop production systems and to manage these pests in cotton and rice crops.

New insights on entomopathogenic bacteria isolated from soil of citrus crops to combat the polyphagus aphid pest Hyalopterus pruni (Geoffroy 1762) (Hemiptera, Aphididae)

BackgroundThe employment of entomopathogenic microorganisms is a promising approach for ensuring optimal phytosanitary protection in the framework of biological management of insect crop pests. Among these microbes, entomopathogenic soil-borne bacteria are preferred over pesticides because they help successfully in the natural regulation of arthropod populations, as soil has a favorable ecology for the availability and richness of many beneficial bacterial species. In this study, it was focused on the isolation, identification and characterization of entomopathogenic bacteria isolated from cultivated citrus soils and on the evaluation of their insecticidal potential in the laboratory against the mealy plum aphid, Hyalopterus pruni (Geoffroy 1762) (Hemiptera: Aphididae), a polyphagous and major pest attacking and virus-transmitting of several Prunus crops.ResultsIsolation results gave 11 bacterial isolates, which were more than 50% effective in selection tests on H. pruni aphids at 1 × 108 CFU/ml. A total of seven isolates generated significant insecticidal potential at different concentrations, and their molecular identification based on 16S rRNA genome sequencing yielded the following results: Lysinibacillus fusiformis (B4), Bacillus thuringiensis (B13), B. thuringiensis (B22), B. thuringiensis (B23), B. thuringiensis (B24), Pseudomonas sp. (P2) and Enterococcus gallinarum (P4). The most pathogenic potential of these strains was for E. gallinarum (P4), which induced 100% H. pruni mortality after 72 h of treatment at the concentration (C3 = 1 × 106 CFU/ml), followed by B. thuringiensis (B23), (B22), (B4), (P2), (B13) and (B24) isolates, which caused 96, 91, 85, 83, 65 and 50% mortality rates, respectively, at the lowest concentration (C4 = 1 × 105 CFU/ml). The LC50 and LT50 values were calculated for the entomopathogenic isolates of (P2), (P4), (B23) and (B24). A lowest LC50 value was 1.08 × 102 CFU/ml for (P4) E. gallinarum after 72 h of treatment, whereas (P2) Pseudomonas sp. presented the shortest LT50 of 33.6 h at concentration (C4 = 1 × 105 CFU/ml).ConclusionsThe present study's outcomes have confirmed the existence, abundance, and variety of entomopathogenic bacteria at the soil level in citrus groves. Interestingly, these bacteria could be useful for aphids’ population control on a wide scale through the utilization of their toxins and enzymes, even against insect pests of a broad order.

Artificial neural networks as a tool for seasonal forecast of attack intensity of Spodoptera spp. in Bt soybean.

Soybean (Glycine max) is the world's most cultivated legume; currently, most of its varieties are Bt. Spodoptera spp. (Lepidoptera: Noctuidae) are important pests of soybean. An artificial neural network (ANN) is an artificial intelligence tool that can be used in the study of spatiotemporal dynamics of pest populations. Thus, this work aims to determine ANN to identify population regulation factors of Spodoptera spp. and predict its density in Bt soybean. For two years, the density of Spodoptera spp. caterpillars, predators, and parasitoids, climate data, and plant age was evaluated in commercial soybean fields. The selected ANN was the one with the weather data from 25 days before the pest's density evaluation. ANN forecasting and pest densities in soybean fields presented a correlation of 0.863. It was found that higher densities of the pest occurred in dry seasons, with less wind, higher atmospheric pressure and with increasing plant age. Pest density increased with the increase in temperature until this curve reached its maximum value. ANN forecasting and pest densities in soybean fields in different years, seasons, and stages of plant development were similar. Therefore, this ANN is promising to be implemented into integrated pest management programs in soybean fields.

State of Exception or the New Normal? An Evaluation of Pandemic Tracking Technologies and Their Implications for Citizenship

This article forms a critical examination of how the increased digitalization of daily life, exemplified by pandemic digital technologies of tracking apps and digital Covid-19 passports, affects ethical principles of privacy, subjectivity and autonomy, fundamental in a traditional notion of citizenship. The pandemic crisis has been an example of the increasing use of automated technologies across various domains, where society has become deeply reliant on these technologies. I argue that in ethical terms, the pandemic crisis has moved the borders of what is accepted by governments and citizens and have normalised far-reaching tools of registration, calculation, and surveillance. The pandemic state of exception has necessitated and legalised a temporary suspension of normal civil rights and replaced them with spatial ordering, automated surveillance, and the application of advanced and intrusive digital monitoring tools. Based on an empirical account of tracking apps I discuss the consequences for citizenship based on two theoretical figures: Michel Foucault´s concept of “bio-politics” and the concept of “a state of exception” as theorized by German political philosopher Carl Schmidt. Where traditional concepts of citizenships have focused on individual rights, responsibilities and articipation in civic life, bio-politics emphasizes a management and regulation of populations with less focus on individual agency and more on statistical analysis and control mechanisms. Technologies and discourses of automation are inter-related; digital innovation legitimize and strengthen an adherent automation of political logics, framed as a politics of necessity, where calculative predictions and technological facts leave little room for political subjectivity and values. In the concluding section it is discussed whether the rapid automation catalyzed by the pandemic was a state of emergency, necessitated by a pandemic threat, or rather represents a more profound change, a new normal for citizenship.

NK Cells in the Lymph Nodes and Their Role in Anti-Tumour Immunity.

The lymph nodes are vital to enable adaptive immune responses to infection. Natural killer (NK) cells are cytotoxic lymphocytes that directly kill cancer cells and modulate the activation of other immune cells during anti-tumour immune response. NK cells in the lymph nodes are involved in the regulation of T-cell and B-cell populations and the clearance of viral infections. In solid tumours, lymph nodes are a frequent site of metastasis and immune cell priming, whilst in haematological malignancies, tumour cells can proliferate in the lymph nodes. Thus, lymph nodes are an important site in anti-tumour immunity and therapy resistance. It is therefore crucial to identify strategies to increase recruitment and overcome suppression of NK cells in the lymph node microenvironment to improve tumour clearance. In this review, we summarise the literature interrogating NK cell phenotype and function in the lymph nodes in the context of infection and cancer and evaluate both current and potential strategies to mobilise and activate NK cells within the lymph nodes of cancer patients.

CRISPR/Cas9-mediated Nap knockout affects female reproduction and egg shape in Bombyx mori.

Insect reproductive capacity can affect effective pest control and infertility studies and has become an important focus in recent molecular genetic research. Nucleosome assembly protein (Nap) is highly conserved across multiple species and is involved in forming the sperm nucleus in many species. We used clustered regularly interspaced palindromic repeats/Cas9 technology to knockout BmNap in Bombyx mori and observed that the mutations caused female infertility, whereas male fertility was not affected. BmNap mutants grew and mated normally; however, female mutants laid smaller eggs that could not be fertilised and did not hatch. In addition, female sterility produced by the mutation could be inherited stably via male mutants; therefore, Nap could be used as a potential target for lepidopteran pest control through population regulation. In the current study, we elucidated a new function of BmNap, increased the understanding of the oogenesis regulation network in Lepidoptera and promoted the development of insect sterility technologies.

Long-lines for research monitoring and efficient population regulation of an invasive apex predator, European catfish (Silurus glanis)

European catfish is a large-bodied apex predator, a key species in native areas, but invasive in others where it negatively impacts local aquatic fauna necessitates catfish regulation. However, traditional ichthyological methods face challenges in capturing it. The study presents a detailed description of the efficient long-line method, refined through 48 sampling campaigns across twelve European water bodies. This method proves cost-effective and technically undemanding, requiring an average of 5.6 bait fish to catch one European catfish per day. The long-lines outperform other techniques, with the highest Biomass per unit effort (BPUE) of 6.205 kg of catfish per man-hour and minimal by-catch (0.276 kg per man-hour). In contrast, fyke nets, the second most efficient method, achieve a BPUE of 0.621 kg of catfish per man-hour with 3.953 kg of by-catch per man-hour. To optimize long-line catches, a 15 m distance between branch lines and regular relocation is recommended. Live fish is the most effective bait with no significant differences observed among species. However, earthworms, a less controversial alternative, are also efficient, especially for smaller catfish. Our recapture approach using various ichthyological methods revealed no hook avoidance behavior by catfish after a previous catch or avoidance by a certain part of the population. The long-line method is suitable for population regulation, scientific research, and conservation efforts and is the most effective means of capturing live European catfish.

Large shallow lake response to anthropogenic stressors and climate change: Missing macroinvertebrate recovery after oligotrophication (Lake Balaton, East-Central Europe)

East-Central Europe's largest shallow lake, Balaton, experienced strong eutrophication in the 1970–80s, followed by water quality improvement and oligotrophication by 2010 CE. Recently however, repeated cyanobacterial blooms occurred and warned that internal P-recycling can act similarly to external P load, therefore we need a better understanding of past water level (WL) and trophic changes in the lake. In this study we discuss the last 500-yr trophic, WL and habitat changes of the lake using paleoecological (chironomids, pollen) and geochemical (sediment chlorophyll, TOC, TS, TN, C/H ratio, major and trace element) methods. We demonstrate that the most intensive and irreversible change in the macroinvertebrate fauna occurred during the period of economic boom between the First and Second World War (∼1925–1940 CE), when large-scale built-in and leisure use of the lake has intensified. At that time, the Procladius-Microchironomus-Stempellina dominated community transformed to Procladius-Chironomus plumosus-type-Microchironomus community that coincided with land use changes, intensified erosion and water-level regulation in the lake with the maintenance of year-round high WL. This was followed by the impoverishment and population size decrease of the chironomid fauna and Procladius dominance since 1940 CE, without any recovery after 1994 CE despite the ongoing oligotrophication. Accelerated rate of change and turnover of the fauna was connected to an increase in the benthivorous fish biomass and eutrophication. The basin lost almost completely its once characteristic Stempellina species between 1927 and 1940 CE due to trophic level increase and seasonal anoxia in the Szemes Basin. Reference conditions for ecosystem improvement were assigned to 1740–1900 CE. We conclude that in spite of the ongoing oligotrophication, the re-establishment of the Procladius-Microchironomus-Stempellina assemblage is hampered, and requires fish population regulation.

The changing faces of racism: Tracing the racial state through mixed-race categories in South Korea

This paper examines the emergence and development of mixed-race categories in South Korea in the context of the shift in the state's governing practices from the postwar period to the present. In particular, “mixed-race” serves as a conceptual framework for tracing the formation of Korea's racial state with respect to the distinct categories of Amerasians and the children of multicultural families. Drawing on theoretical approaches to racism, racial state, and biopower, I examine the treatment of mixed-race individuals in the regulation of the Korean population since the middle of the previous century. I document a shift in the subject-positions of these individuals from the status of homo sacer to that of homo economicus, each of which is associated with distinct modes of racism. The findings presented here have implications for critical mixed-race studies in Korea and East Asia more broadly and for expanding the understanding of the nexus of race, state, and power.

Assessing soil functioning: What is the added value of soil organic carbon quality measurements alongside total organic carbon content?

Soil organic carbon (SOC) content is the most widely used soil health indicator, but many soil functions are also influenced by the quality of SOC. Yet, standardized SOC quality parameters that can be used in soil health assessments in addition to SOC content are still in development. Here, we investigated the relationships between various SOC parameters (both quantity and quality) and soil functions.We collected 223 soil samples from arable fields in two contrasting Dutch soil types i.e., marine clay and sand. For each sample, we assessed three soil functions (i.e., biological population regulation, element cycling, and soil structure and water regulation) by measuring five indicators per function. We also analyzed SOC quality with four techniques (C:N-ratio, POX-C, Rock-Eval, POM-MAOM fractionation), resulting in 21 SOC quality parameters, and measured SOC content. We then determined for each soil type how much variation in each function indicator was explained by the SOC parameters and other measured intrinsic soil properties.We found that SOC parameters and intrinsic soil properties explained at most 30 ± 22% of the variation in soil function indicators. SOC content explained 9 ± 16% of the variation across functions and soil types. Including one single SOC quality parameter alongside SOC content never had significant added value in explaining soil functions. Only including multiple Rock-Eval parameters alongside SOC content significantly increased the explained variation compared to SOC content alone, as well as combining multiple parameters from the four different SOC quality techniques.We conclude that the relationships between the SOC quality parameters and soil functions are insufficiently straight-forward to add significant explanatory power to SOC content alone. We recommend that before including SOC quality parameters in soil health monitoring, more emphasis should be put on evaluating their relation to soil functions and their potential redundancy when used alongside SOC content.

Modelling decisions and density dependence in monarch butterflies: A comment on Meehan and Crossley (2023)

Abstract Decisions about which processes to include in a population model can have substantial impact on estimates of population trends and extinction risk. This is particularly important for species of conservation concern, whose conservation status is decided in part on the basis of these models. In their recent paper, Meehan and Crossley (2023) Insect Conservation and Diversity, 16, 566–573 revisit a time series of overwintering monarch butterfly abundances, which previous assessments had characterised as rapidly declining and at risk of extinction. The authors, in contrast, reported no evidence for declines in the past 10 years and characterised extinction risk as low. A primary reason for the difference between these conclusions was that Meehan and Crossley used a more complex model that included a parameter for density dependence. While negative density dependence may play a role in monarch population regulation, there are a variety of unresolved issues with how and if density dependence should be included in models of monarch populations, including widely known issues with separating observation error from density dependence in noisy time series and taxon‐specific issues with fitting models to data surveyed every fourth generation and pooled at continental scales. These issues make the conclusions of Meehan and Crossley about monarch population viability much less robust than implied in their article. They do not provide convincing evidence that density dependence reduces extinction risk in monarch butterflies. Our commentary supports their general conclusion that population viability projections depend on model assumptions, but the ways in which monarch butterfly populations are regulated remains an open question.

Urea regulates soil nematode population by enhancing the nematode-trapping ability of nematode-trapping fungi

As the most abundant animal in the soil, nematodes are directly or indirectly involved in almost all soil ecological processes. Studying soil nematode population regulation is essential to understanding soil ecological processes. This study found urea combines nematode-trapping fungi to regulate the population of soil nematodes. In soil, compared with no urea, adding 0.2 mg/mL urea after applying Arthrobotrys oligospora and Dactylellina ellipsospora reduced the number of nematodes by 34.7% and 31.7%. Further, the mechanism of urea couple nematode-trapping fungi to regulate the nematode population was explored in the medium environment. The results showed that the addition of 0.2 mg/ml urea accelerated the trap formation of A. oligospora and D. ellipsosporas by 50% and 46.5%, and increased the yield of traps of A. oligospora and D. ellipsosporas by 39.5% and 40.6%, thus, the predatory efficiency of A. oligospora and D. ellipsospora on nematodes was increased by 34.2% and 32.7%. In conclusion, urea regulates the predation ability of A. oligospora and D. ellipsosporas to regulate the soil nematode population. This study deepens the understanding of the regulatory pathways of the soil nematodes but also provides a potential new strategy for harmful nematode bio-control.

White-tailed deer population dynamics in a multipredator landscape shaped by humans.

Large terrestrial mammals increasingly rely on human-modified landscapes as anthropogenic footprints expand. Land management activities such as timber harvest, agriculture, and roads can influence prey population dynamics by altering forage resources and predation risk via changes in habitat, but these effects are not well understood in regions with diverse and changing predator guilds. In northeastern Washington state, USA, white-tailed deer (Odocoileus virginianus) are vulnerable to multiple carnivores, including recently returned gray wolves (Canis lupus), within a highly human-modified landscape. To understand the factors governing predator-prey dynamics in a human context, we radio-collared 280 white-tailed deer, 33 bobcats (Lynx rufus), 50 cougars (Puma concolor), 28 coyotes (C. latrans), and 14 wolves between 2016 and 2021. We first estimated deer vital rates and used a stage-structured matrix model to estimate their population growth rate. During the study, we observed a stable to declining deer population (lambda = 0.97, 95% confidence interval: 0.88, 1.05), with 74% of Monte Carlo simulations indicating population decrease and 26% of simulations indicating population increase. We then fit Cox proportional hazard models to evaluate how predator exposure, use of human-modified landscapes, and winter severity influenced deer survival and used these relationships to evaluate impacts on overall population growth. We found that the population growth rate was dually influenced by a negative direct effect of apex predators and a positive effect of timber harvest and agricultural areas. Cougars had a stronger effect on deer population dynamics than wolves, and mesopredators had little influence on the deer population growth rate. Areas of recent timber harvest had 55% more forage biomass than older forests, but horizontal visibility did not differ, suggesting that timber harvest did not influence predation risk. Although proximity to roads did not affect the overall population growth rate, vehicle collisions caused a substantial proportion of deer mortalities, and reducing these collisions could be a win-win for deer and humans. The influence of apex predators and forage indicates a dual limitation by top-down and bottom-up factors in this highly human-modified system, suggesting that a reduction in apex predators would intensify density-dependent regulation of the deer population owing to limited forage availability.

Population regulation and limitation-insights from lemming cycles: past, present and future.

Population regulation and limitation-insights from lemming cycles: past, present and future.