Density-dependent Response Research Articles

Title: Systematic insights into cell density-dependent transcriptional responses upon medium replacements.

Understanding the molecular mechanisms governing transfection efficiency and particle secretion in high cell density cultures is critical to overcome the cell density effect upon transient gene expression. The effect of different conditioned media in HEK293 transcriptome at low and high cell density is explored. A systematic pair-wise comparative study was performed to shed light on the effect on previous phenotypical characteristics of different media conditions: fresh, exhausted and media depleted from extracellular vesicles (EVs) as well as associated proteins and RNAs. The obtained results suggest that restorative effects observed in transfection efficiency when employing EV-depleted media may arise predominantly from physicochemical alterations rather than cellular processes. A significant downregulation of genes associated with nucleocytoplasmic transport for the conditions involving the use of exhausted or EV-depleted media was observed. Moreover, upregulation of histone-related genes in EV-depleted media suggest a role for histone signaling in response to cellular stress or growth limitations, thereby highlighting the potential of manipulating histone levels as a promising strategy to enhance transient transfection. It was also corroborated that the accumulation of extracellular matrix proteins upon cell growth may inhibit transfection by an already-known competitive effect between cell membrane-bound and free proteoglycans. Proteomic characterization of EV-depleted media further unveiled enrichment of pathways associated with infection response and double-strand DNA breaks, suggesting that HEK293 cells undergo an induced infection-like state that disrupts cellular processes. Importantly, the study reveals that EV-depleted media stimulates virion release pathways underscoring the complex interplay between extracellular vesicles and viral budding.

Scaling Behavior in the Spectral and Power Density Dependent Photovoltaic Response of Hot Polaronic Heterojunctions

AbstractStrongly correlated manganites can be considered as model systems for the study of photovoltaic harvesting of hot polarons that can be excited from the electronically ordered ground state. In order to gain basic understanding of hot polaron harvesting, the deviations of the photovoltaic response of a heterojunction with polaronic absorber from a conventional semiconductor are analyzed. Specifically, the spectral and photon power density dependence of the open circuit voltage Uoc and the short circuit current density Jsc in heterojunctions consisting of orbital ordered Pr1‐xCaxMnO3 (x = 0.1, PCMO) thin films epitaxially grown on single crystalline (100) SrTiO3 (STO) and Nb‐doped (100) SrTiO3 (STNO) substrates are investigated. The observed behavior is fundamentally different from conventional solar cells, in which Uoc is limited by fast carrier relaxation to the band edges. Whereas the spectral and photon power dependence of Uoc of conventional semiconductor junctions is well described by the Shockley‐Queisser (SQ) theory, the hot polaron junctions surprisingly show a scaling law behavior of Uoc. Such scaling laws otherwise apply to equilibrium order parameters in second‐order phase transitions. It is concluded that its physical origin is the unique dependence of the quasi‐Fermi level splitting on temperature, photon energy, and power density in a hot polaron system.

A taste of space: Remote animal observations and discrete-choice models provide new insights into foraging and density dynamics for a large subarctic herbivore.

Competition for resources and space can drive forage selection of large herbivores from the bite through the landscape scale. Animal behaviour and foraging patterns are also influenced by abiotic and biotic factors. Fine-scale mechanisms of density-dependent foraging at the bite scale are likely consistent with density-dependent behavioural patterns observed at broader scales, but few studies have directly tested this assertion. Here, we tested if space use intensity, a proxy of spatiotemporal density, affects foraging mechanisms at fine spatial scales similarly to density-dependent effects observed at broader scales in caribou. We specifically assessed how behavioural choices are affected by space use intensity and environmental processes using behavioural state and forage selection data from caribou (Rangifer tarandus granti) observed from GPS video-camera collars using a multivariate discrete-choice modelling framework. We found that the probability of eating shrubs increased with increasing caribou space use intensity and cover of Salix spp. shrubs, whereas the probability of eating lichen decreased. Insects also affected fine-scale foraging behaviour by reducing the overall probability of eating. Strong eastward winds mitigated negative effects of insects and resulted in higher probabilities of eating lichen. At last, caribou exhibited foraging functional responses wherein their probability of selecting each food type increased as the availability (% cover) of that food increased. Space use intensity signals of fine-scale foraging were consistent with density-dependent responses observed at larger scales and with recent evidence suggesting declining reproductive rates in the same caribou population. Our results highlight potential risks of overgrazing on sensitive forage species such as lichen. Remote investigation of the functional responses of foraging behaviours provides exciting future applications where spatial models can identify high-quality habitats for conservation.

Reflections on the cavity expansion problem and its geotechnical applications

A selective review is provided of the methods and solutions used to predict the response of various geomaterials in cavity expansion problems, both cylindrical and spherical cavities. As many authors have recognized, the solutions to these problems have numerous applications in geotechnics, and the more significant of these have been addressed in this paper. Some of the more important solutions already available in the literature are presented in addition to some novel results illustrating the effects of some unique features of soil behaviour, such as softening, rate-dependency, density dependent response and dilation. Some of the solutions are available in closed form, while others have required the use of numerical methods such as the finite element method. It is contended that the relatively simple problem of cavity expansion, be it either a cylindrical or a spherical cavity, is capable of revealing important aspects of the mechanical behaviour captured in both simplified and complex soil constitutive models.

Network of nearshore protected areas provides important benefits to lake whitefish in the Apostle Islands region of Lake Superior

Aquatic protected areas are commonly used for fish conservation, restoration, and management and a spectrum of protection levels exist in the Great Lakes. Using fishery-independent survey data over 43 years, we evaluated whether lake whitefish (Coregonus clupeaformis) population dynamics differed among nearshore partially protected areas (PPAs; commercial fishing prohibited or severely limited), offshore no-take refuges, and unprotected areas in the Apostle Islands region of Lake Superior. Lake whitefish biomass and recruitment to the spawning stock increased at faster rates in nearshore PPAs and offshore refuges than unprotected areas during the initial phase after protected areas were established (1980–2000). Recruitment and biomass stabilized in all management areas in the post-rebuild phase (2002–2022), and mortality was lower in the nearshore PPAs. Mean size of adults decreased within protected areas as abundance increased but not in unprotected areas, suggesting a density-dependent growth response and spillover to the fishing grounds, which was reflected in commercial catch rates. However, nearshore PPAs still harbored larger, faster-growing, and earlier-maturing lake whitefish, likely due to underlying habitat differences. Tag recaptures indicated greater minimum distances traveled near an offshore refuge compared to a nearshore PPA, suggesting habitat gradients may influence boundary porosity. PPAs provided protection and benefits for lake whitefish in areas of higher vulnerability where ceasing all fishing was not reasonable. Great Lakes managers should consider implementing networks of protected areas across multiple habitats as tools for conserving spawning biomass, maintaining diverse population demographics, and preserving portfolio effects to enhance recruitment and population stability.

Who eats the yellowmargined leaf beetle? Field observations and genetic surveillance to identify local predators of a novel invasive pest

The yellowmargined leaf beetle, Microtheca ochroloma Stahl (Coleoptera: Chrysomelidae), invaded the Southeastern United States and rapidly emerged as a leading pest of crucifer crops, yet little is known about which native predators might effectively provide biological control. The objective of this research is to identify potential predators of this understudied invader through field observation and genetic surveillance. Over two years, arthropods were surveyed on a variety of susceptible Brassica cultivars and a shortlist of commonly associated predators was developed. In a survey of turnip plants in year 1, lady beetles were positively predicted by densities of M. ochroloma, suggesting a numerical response to densities of the invasive pest. Surveys at a different site in year 2 revealed that big-eyed bugs were also positively predicted by M. ochroloma, while pink-spotted lady beetles negatively associated, suggesting a pattern of suppression. Ants (primarily the red imported fire ant) and spiders were commonly observed predators on plants in both years, but neither associated with densities of M. ochroloma. No predators were observed consuming M. ochroloma eggs. Molecular gut-content analysis using specially generated M. ochroloma primers confirmed the observed predatory links and suggested a density-dependent tracking response from pink-spotted lady beetles and ground beetles also have density-dependent tracking re Table 3. Our results may enable farmers to bolster these predator populations with fine-tuned habitat management tools and better suppress the spreading pest.

Addressing biases in replacement series: the importance of reference density selection for interpretation of competition outcomes

AbstractReplacement series are used by researchers to understand how competition-related variables influence dynamics from the individual to the population and community levels, but this approach has been criticized because of inherent biases associated with plant size differences and density-dependent responses. The use of functional densities instead of demographic densities was proposed to minimize those biases. This work explored three models to determine reference densities for replacement series experiments based on (1) maximum biomass, (2) biomass at onset of diminishing returns (i.e., inflection point), and (3) nitrogen (N)-uptake equivalency. Replacement series experiments were conducted using redroot pigweed (Amaranthus hybridus L.):maize (Zea mays L.) and giant foxtail (Setaria faberi Herrm.):maize proportions of 1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75, and 0:1. The monoculture density for each species was established according to the three models. Density selection criteria resulted in major differences in competitive interactions between species. The use of functional densities at which the biomass accumulation inflection point for the smaller species allowed both species to exhibit either increases or decreases in biomass production depending on competitive interactions for all interspecific mixtures. Conversely, the maximum biomass model favored the larger species, almost completely inhibiting the growth of the smaller species, which resulted in a poor characterization of competitive responses of the smaller species. The N uptake equivalency model resulted in interactions closer to the predicted neutral competition. The model based on the biomass accumulation inflection point was the most sensitive and informative across all interspecific mixtures for both species. We propose that to reduce bias associated with species size differences when determining reference densities for replacement series experiments, at least two criteria must be met: (1) the experiment sensitivity allows measuring and quantifying the competitive responses for both species in all mixtures, and (2) the balance between density and carrying capacity of the system minimizes intraspecific competition.

Landscape heterogeneity increases the stability of wild ungulate populations facing climatic variability in Mediterranean ecosystems

Mediterranean environments are characterized by strong intra- and inter-annual fluctuations in plant primary production, which are likely to regulate the carrying capacity and density-dependent responses of ungulate populations. These effects may, however, vary across spatial and temporal scales. Habitat heterogeneity, particularly when associated to differentiated phenological responses, may allow wild ungulates to mitigate temporal fluctuations in plant production by using different resources along the year. In this work, we use a 15-years dataset (including remote-sensing data on vegetation distribution, phenology and production, as well as ungulate population counts) to assess how temporal variability in plant primary production and livestock abundance influence the population dynamics of two wild ungulates: native red deer, Cervus elaphus, and introduced fallow deer, Dama dama. Results show that temporal alternation in the phenological cycles of the four different vegetation types increased plant production, thus food availability for ungulates, within each year. Furthermore, complementarity in the responses of different vegetation types to variations in the amount and timing of rainfall increased the predictability of food availability across different years. This complementarity effect was further increased by the contrasting responses of ungulate populations to variation in the production of different vegetation types. Furthermore, domestic ungulates had positive effects on wild ungulate density at low to intermediate abundances, but high livestock densities decreased ungulate density and constrained the stability of the plant-ungulate system in response to the impact of climatic variation, particularly under climate change. Our findings deepen the knowledge on vegetation-ungulate interactions in Mediterranean areas, potentially contributing to develop better management strategies of ungulate populations and adapt them to ongoing climate change.

Selective recognition of over-expressed self-antigens in solid tumors using calibrated CAR-T therapy.

2540 Background: CAR-T has shown promise in patients with a subset of solid tumors. Future development depends on identifying CAR-T that differentiate between normal and malignant cells. The PrismCore platform develops CAR-T targeting self-antigens using three principles: 1) identification of targets uniformly expressed on solid tumors, 2) over-expression on the surface of invasive cancers compared to healthy cells, and 3) elevated levels linked to tumor aggressiveness. PrismCore produces CAR-T for treating multiple solid tumor types by calibrating T-cell activity against self-antigens only when present at elevated densities. Methods: PrismCore generates CAR-T by combining computational biology with empirical observations to target over-expressed self-antigens. Proto-libraries of CARs are created using synthetic single-domain antibodies and structural/signaling components. Bio-screening is performed using combinatorial libraries generated through computational simulation. Lead CAR-T are identified through iterative in vitro and in vivo testing and evaluated for safety in non-human primates (NHP). Results: PrismCore platform has identified engineered T cells against several self-antigens, with the first CAR-T, termed B4t2-001, advanced to clinical testing against the target BT-001. Libraries (1E10 to 1E11) of camelid antibodies were designed, synthesized, and assessed. Selected antibody variants subsets were combinatorially assembled into CAR-Ts and rigorously screened against gradient of BT-001. Six candidates were advanced to further testing in mice to evaluate anti-tumor effect and sustained in vivo biological activity. B4t2-001 was evaluated in NHP that express basal levels of BT-001. No toxicity observed despite measurable circulating CAR-T and in vitro activity to NHP BT-001 when at high density. The turnaround from target selection to B4t2-001 for clinical evaluation was six months. Conclusions: We report pre-clinical data for B4t2-001 that safely and effectively targets BT-001 when overexpressed on tumors. This is a novel target for T-cell therapy and is at elevated levels on multiple different types of solid tumors. BT-001 participates in pathobiology, tumor invasion as well as metastasis, and level of expression inversely correlates with overall survival. B4t2-001 demonstrated target density-dependent response, potency, durability of effect and safety in preclinical models and is undergoing phase I clinical evaluation (NCT05621486) in patients with different types of solid tumors. [Table: see text]

What is needed to make a simple density-dependent response population model consistent with data for eastern North Pacific gray whales?

Census estimates indicate that the eastern North Pacific gray whale population showed an increase rate of some 3.2% per annum from 1968-1988. Further, historic records suggest that the population was ‘commercially extinct’ at the end of the 19th century. The standard HITTER-FITTER population model trajectories which pass through the 1987-88 census estimate of some 21,113, and utilise the customary historic commercial catch series, are inconsistent with both of these features; in particular, they generally show a decrease over the 1968-1988 period. The quantitative extent of various possible adjustment factors that would be needed to resolve these inconsistencies is examined. Depensation effects alone cannot account for the inconsistencies, while a model used to incorporate an additional response delay in recovery from exploitation produces unrealistic population oscillations. Other adjustment factors can, however, produce a 1968-1988 annual population increase rate of 2% or more, and all also correspond to a depletion of the population in 1900 to less than 25% of its size at the onset of commercial whaling in 1846. These are: an increase in the carrying capacity from 1846-1988 of at least 2.5 times; an underestimation of the historic commercial catch from 1846-1900 of at least 60%; or annual aboriginal catch levels prior to the commercial fishery at least three times those estimated by the 1990 Special Meeting of the Scientific Committee (IWC, 1993). These limits weaken if the adjustment factors are considered in combination rather than separately. The results appear insensitive to values assumed for the biological parameters of the population model (natural mortality, age at first parturition, age at recruitment and MSY level). However, they are sensitive to assumptions concerning data inputs, viz the accuracy of the 1987-88 census estimate used, and a 2:1 female:male ratio assumed for the commercial catches for which this information is not available. All trajectories which reflect a 1968-88 annual increase rate of 2% or more correspond to MSYR values (in terms of a 5+ exploitable population) of at least 4%. Fits of the population model to the series of gray whale census estimates are mis-specified, unless either or both of the historic commercial and aboriginal catches have been substantially underestimated (or carrying capacity has increased). The precision of these fits, conditional on fixed levels for such underestimation, is quite high, with coefficients of variation of about 10% for historic population sizes and about 20% for MSYR. There are indications that even if allowance was made for the uncertainty about these levels of underestimation, MSYR would remain relatively robustly estimated to be some 5% (or about 4% if expressed in terms of uniform selectivity on the 1+ population).

Evidence of a compensatory response in invasive Rusty Crayfish (Faxonius rusticus) following intensive harvest removal from northern Lake Michigan fish spawning reefs.

The online version contains supplementary material available at 10.1007/s10530-023-03076-6.

Abstract 886: Fine-tuned CAIX targeted CAR-T cells exhibit superior efficacy and mitigate on-target off-tumor side effects

Abstract Chimeric Antigen Receptor (CAR) T cell therapy is a new type of “living drug” that has proven to be a powerful immunotherapy for hematologic malignancies. To date, there are six CAR-T products approved by the FDA for hematologic malignancies, four targeting CD19, and two targeting B-cell maturation antigen (BCMA). However, this success has not yet been transferred to solid tumors. A major hurdle is the on-target off-tumor toxicities due to the shared expression of target antigen on normal tissues. Carbonic anhydrase IX (CAIX) is highly expressed in clear cell renal cell carcinoma (ccRCC); however, it is also expressed on bile duct at a lower physiological level leading to off-tumor toxicity of CAIX targeted therapies. The first anti-CAIX CAR-T studies, using the 1st generation G250 CAR-T cells plus IL-2 to treat patients with metastatic ccRCC, caused severe liver enzyme abnormalities in the treated patients after CAR-T cell infusions. To understand CAIX expression on tumor and normal tissues, we quantified CAIX expression on ccRCC patient samples and healthy bile duct tissues using direct stochastic optical reconstruction microscopy (dSTORM) which provides single-molecule resolution. Tet-On inducible CAIX expressing cell lines were established to mimic various CAIX densities on normal tissue and tumor samples. Using biolayer interferometry (BLI) and avidity analyzer, we identified a low-affinity, high-avidity anti-CAIX CAR G9. G9 CAR-T cells only kill CAIX high ccRCC tumor cells but not CAIX low normal cholangiocytes, and exhibited a CAIX density dependent response to Tet-On inducible CAIX expressing cell lines. Compared to high-affinity G250 CAR-T cells, G9 showed a better safety profile and a wider therapeutic window. G9 demonstrated a superior ex vivo efficacy on ccRCC patient derived organotypic tumor spheroids (PDOTS) 3D cultures which recapitulate ccRCC patient tumor microenvironment (TME), as well as low toxicity on cholangiocyte derived organotypic spheroids (CDOS). In summary, affinity/avidity fine-tuned CAIX targeted CAR-T cell therapy holds promise to achieve cures of ccRCC by efficaciously killing tumor cells and mitigating on-target off-tumor toxicity on normal tissues. Citation Format: Yufei Wang, Alicia Buck, Gabriella Kastrunes, Rabia Abbas, Michael Lynch, Zhou Zhong, Song-My Hoang, Andras Miklosi, Kun Huang, Jae-Won Cho, Marion Grimaud, Cecile Razimbaud, Matthew Chang, Atef Fayed, Audrey Apollon, Nithyassree Murugan, Ze-Hua Li, Tran Thai, Luann Zerefa, Brandon Piel, Elena Ivanova, Amy Cameron, Quang-De Nguyen, Zhu Zhu, Kevin Wei, Yasmin Nabil Laimon, Aseman Bagheri Sheshdeh, Sabina Signoretti, David A. Braun, Catherine J. Wu, Toni K. Choueiri, Jon Wee, Cloud P. Paweletz, Martin Hemberg, Aedin C. Culhane, David A. Barbie, Gordon J. Freeman, Wayne A. Marasco. Fine-tuned CAIX targeted CAR-T cells exhibit superior efficacy and mitigate on-target off-tumor side effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 886.

A curated DNA barcode reference library for parasitoids of northern European cyclically outbreaking geometrid moths.

Large areas of forests are annually damaged or destroyed by outbreaking insect pests. Understanding the factors that trigger and terminate such population eruptions has become crucially important, as plants, plant-feeding insects, and their natural enemies may respond differentially to the ongoing changes in the global climate. In northernmost Europe, climate-driven range expansions of the geometrid moths Epirrita autumnata and Operophtera brumata have resulted in overlapping and increasingly severe outbreaks. Delayed density-dependent responses of parasitoids are a plausible explanation for the 10-year population cycles of these moth species, but the impact of parasitoids on geometrid outbreak dynamics is unclear due to a lack of knowledge on the host ranges and prevalences of parasitoids attacking the moths in nature. To overcome these problems, we reviewed the literature on parasitism in the focal geometrid species in their outbreak range and then constructed a DNA barcode reference library for all relevant parasitoid species based on reared specimens and sequences obtained from public databases. The combined recorded parasitoid community of E. autumnata and O. brumata consists of 32 hymenopteran species, all of which can be reliably identified based on their barcode sequences. The curated barcode library presented here opens up new opportunities for estimating the abundance and community composition of parasitoids across populations and ecosystems based on mass barcoding and metabarcoding approaches. Such information can be used for elucidating the role of parasitoids in moth population control, possibly also for devising methods for reducing the extent, intensity, and duration of outbreaks.

A Predator–Prey Model with Beddington–DeAngelis Functional Response and Multiple Delays in Deterministic and Stochastic Environments

In view of prey’s delayed fear due to predators, delayed predator gestation, and the significance of intra-specific competition between predators when their populations are sufficiently large, a prey–predator population model with a density-dependent functional response is established in a deterministic environment. We research the existence and asymptotic stability of the equilibrium statuses. Then, taking into consideration environmental disturbances, we extend the deterministic model to a stochastic model and research the existence and stationary distributions of stochastic solutions. Finally, we perform some numerical simulations to verify the theoretical results. Numerical examples indicate that fear, delays and environmental disturbance play crucial roles in the system stability of the equilibrium status.

Chemical footprints mediate habitat selection in co-occurring aphids.

Habitat selection is a critical process that shapes the spatial distribution of species at local and regional scales. The mechanisms underlying habitat preference rely on environmental factors, species traits, and ecological interactions with other species. Here, we examined spatial segregation between two co-occurring aphid species (Rhopalosiphum maidis and R. padi) on wheat plants. We hypothesized that spatial segregation between these aphid species was mediated by aphid cuticular compounds left as chemical "footprints" on plant surfaces. Combining field and laboratory experiments, we first examined how plant microsites alter fitness by measuring the fecundity of each species. Next, we tested whether intra- and interspecific pre-inhabitation modified habitat selection in both aphid species. Both aphid species preferred and exhibited higher fecundity on wheat stems versus leaves. Laboratory trials showed that R. maidis pre-inhabitation altered R. padi spatial preference. By gas chromatography-mass spectrometry analysis and bioassays testing the effects of aphid density and footprint extracts, we found a density-dependent response, with R. padi avoiding locations previously inhabited by R. maidis. The chemical analysis of footprint crude extracts revealed a highly abundant compound, 1-hexacosanol, and when presented in the synthetic form, also elicited R. padi displacement. Altogether, it indicated that R. maidis footprints altered R. padi habitat selection with cuticular compounds playing a relevant role in the habitat selection process in co-occurring aphid species.

Augmentative biological control of Halyomorpha halys using the native European parasitoid Anastatus bifasciatus: Efficacy and ecological impact

We report the first large-scale augmentative biological control project carried out in Europe against Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) using the native egg parasitoid Anastatus bifasciatus (Geoffroy) (Hymenoptera: Eupelmidae). During summer 2020, a total of 325,000 adults of A. bifasciatus were released at a rate of 1000 individuals/ha of orchard in 11 sites in Trentino-Alto Adige (Northern Italy). Parasitism parameters were compared between release and control (no release) sites, in which at least three egg masses naturally laid by H. halys were collected (for a total of 262 egg masses). Anastatus bifasciatus and Trissolcus mitsukurii (Ashmead) (Hymenoptera: Scelionidae) were the dominant parasitoids, but parasitism by both species fluctuated widely among sites. At release sites, A. bifasciatus showed a significantly higher discovery efficiency (31.4%) and parasitism rate (16.7%) of H. halys egg masses than at control sites (1.7% and 1.2%, respectively). Parasitism by A. bifasciatus was not dependent on egg mass abundance at release sites, but at control sites a host density-dependent response was revealed by a positive relationship between parasitism and number of H. halys egg masses. On the other hand, parasitism by the adventive T. mitsukurii was not affected by either the releases of A. bifasciatus or by the abundance of H. halys egg masses per site. In conclusion, augmentative releases of A. bifasciatus contributed to increasing its parasitization of H. halys, without causing any negative effects on parasitization by naturally occurring species.

Defect Density-Dependent pH Response of Graphene Derivatives: Towards the Development of pH-Sensitive Graphene Oxide Devices.

In this study, we demonstrate that a highly pH-sensitive substrate could be fabricated by controlling the type and defect density of graphene derivatives. Nanomaterials from single-layer graphene resembling a defect-free structure to few-layer graphene and graphene oxide with high defect density were used to demonstrate the pH-sensing mechanisms of graphene. We show the presence of three competing mechanisms of pH sensitivity, including the availability of functional groups, the electrochemical double layer, and the ion trapping that determines the overall pH response. The graphene surface was selectively functionalized with hydroxyl, amine, and carboxyl groups to understand the role and density of the graphene pH-sensitive functional groups. Later, we establish the development of highly pH-sensitive graphene oxide by controlling its defect density. This research opens a new avenue for integrating micro–nano-sized pH sensors based on graphene derivatives into next-generation sensing platforms.

Predicting the abundances of aphids and their natural enemies in cereal crops: Machine-learning versus linear models

Predicting the effects of crop management and landscape structure on biological pest control is a key challenge for implementing innovative pest management systems. Here, we compare the performances of two machine-learning methods (regression trees and random forests) with those of linear models in predicting cereal aphid abundance, parasitism, and natural enemies.We trained models using data describing the landscapes, cropping systems, and margins of 88 cereal fields in France. To assess the predictive performances of our models, we measured pseudo-R2 and root-mean-square error using cross-validation.The two machine-learning methods performed reasonably well in comparison with linear models. Aphid abundance, parasitism, and natural enemies were predicted by both biological (abundances of functional groups) and environmental variables (describing fields, crop management and landscape structure). Parasitoids and hoverfly larvae, unlike coccinellid and lacewing larvae, presented a density-dependent numerical response to aphid populations. At the landscapes scale, linear elements (both grassy strips and hedgerows) were the most important predictors of aphid abundance and parasitism. In contrast, hoverfly larvae were more influenced by the proportion of cultivated areas and woodlands. At the field scale, our models ranked factors related to field size, margins, and soil type as the most important predictors of aphids and their natural enemies.Our analysis shows that machine-learning models outperform classical statistical ones, and therefore provide useful tools for predicting highly variable ecosystem services such as biological pest control.

Realism in Immune Ecology Studies: Artificial Diet Enhances a Caterpillar's Immune Defense but Does Not Mask the Effects of a Plastic Immune Strategy.

The immune system is considered a functional trait in life-history theory and its modulation is predicted to be costly and highly dependent on the host's nutrition. Therefore, the nutritional status of an individual has a great impact on an animal's immune ecology. Herbivorous insects are commonly used as model organisms in eco-immunology studies and the use of an artificial diet is the predominant rearing procedure to test them. However, this diet differs from what herbivores experience in nature and it is unclear to what degree this distinction might impact on the relevance of these studies for the real world. Here, we compared plant-based vs. artificial diet in a set of three experiments to investigate the interaction of both diets with a plastic immune strategy known as Density-Dependent Prophylaxis (DDP). We used as a model organism the velvetbean caterpillar Anticarsia gemmatalis, which is known to adjust its immune defense in line with the DDP hypothesis. Our main results showed that larvae fed with artificial diet had 20.5% more hemocytes circulating in the hemolymph and died 20% more slowly when infected with an obligate (viral) pathogen. Crucially, however, we did not find any indication of fitness costs related to DDP. The use of artificial diet did not interact with that of DDP except in the case of host survival after infection, where the DDP effect was only observable in this diet. Our findings suggest the use of an artificial diet does not mask resource allocation conflicts between immune investment and fitness related traits, but to some extent it might lead to an overestimation of immune parameters and host survival time after infection. We believe that this is the first study to compare an artificial diet and a host plant covering all these aspects: immune parameters, life-history traits, and host survival after infection. Here we provide evidence that, besides the quantitative effects in immune parameters and host survival time, the use of artificial diet interacts only marginally with a density-dependent immune response. This provides support for the use of artificial diets in eco-immunology studies with insects.

Response of specialist and generalist predators to nonprogressive annual fluctuations in herbivorous insect populations

To control sawfly populations that cause a forest management problem due to feeding damage, it is necessary to understand the mechanism of eruptive outbreak in erratic intervals by clarifying the responses of natural enemies to the host population fluctuations. In this study, we investigated annual beech sawfly population fluctuations and its predator, ichneumonid parasitoid wasps (as specialists) and predatory soldier beetles (as generalists). In addition, yearly responses of predators to the host emerging patterns were examined using structural equation modeling. The results revealed that ichneumonid wasps showed a non-delayed synchronous response to erratic fluctuation of the host population, resulting in the maintenance of a constant parasitism ratio. In contrast, soldier beetle population, which tends to moderately fluctuate while maintaining a specific density, showed a low-intensity delayed response without significance in the model. These predator populations without strong delayed density-dependent response are quite unlikely to highly densify causing mass mortality to the host population in the both the current and following years of outbreak. In places where eruptive outbreaks of sawfly species repeatedly occur in erratic intervals, sawfly populations are possibly maintained in high density due to the low mortality ratio caused by predators.