Body Size Distribution Research Articles

Unveiling nematode responses to afforestation from distributions of body size in a subalpine ecosystem

Unveiling nematode responses to afforestation from distributions of body size in a subalpine ecosystem

Stationarity of the Special Relationship Between the Geographical Distribution of Body Size and Day Length in Japanese Adolescents: Spatial and Temporal Analysis Using a GTWR Model.

Northern Japanese children tend to have larger physiques; however, the underlying cause remains unknown. Previous geographical correlation analyses revealed an unusual trend; effective day length was negatively correlated with height and positively correlated with weight (adjusted for height). This paradoxical relationship suggests a thyroid hormone-like effect and possible photoperiodic response. This study aimed to determine whether this phenomenon remains consistent over time and across different regions of Japan. We used geographically and temporally weighted regression (GTWR) to examine whether the relationship between height and effective day length, which differs from the relationship between weight and effective day length, varies by location and time. GTWR models each observation point separately, allowing for spatial and temporal variations. The analysis included the average height and weight data of children and adolescents by prefecture from 1989 to 2019, along with effective day length considering illuminance above 5000 lx derived from the agrometeorological grid square data. Height was used as the dependent variable, whereas weight and effective day length were used as independent variables. For height estimation, the coefficients of weight and effective day length were consistently positive and negative, respectively, although the regression coefficients showed minor geographical and temporal variations. The opposite correlation between height and effective day length and that between weight and effective day length were consistent. This suggests that the phenomenon is more likely driven by environmental factors than by economic or genetic influences.

Oceanographic features boost latitudinal patterns in copepod body size distribution in the South Atlantic

AbstractThe South Atlantic Ocean (SAO) is an under‐sampled ocean where the influence of environmental drivers on copepod body size is poorly understood. This study investigated the body size distribution of copepods from 13°S to 64°S to test Bergmann's rule, which predicts the occurrence of smaller organisms in warmer areas. We hypothesized that additional influence of oceanographic features strengthens this pattern. Zooplankton were sampled during the austral summer from the chlorophyll maximum depth up to the surface, at approximately 100 m depth, using a 200‐μm net. The samples were analyzed using the ZooScan imaging system and were classified using the Ecotaxa tool. We estimated copepod family abundance, biomass, and size structure, and their relationships with environmental variables were assessed through generalized linear mixed models (GLMM). Although most copepods increased in size at higher latitudes, not all families followed Bergmann's rule. Small adults of Clausocalanidae, Paracalanidae, Corycaeidae, and Oncaeidae contributed mostly in the Brazil Current (BC), while Calanidae copepodites disproportionately contributed to overall biomass, and Oithonidae adults were the most abundant in high latitudes. Copepod abundance or biomass hotspots were present in the southern limit of the warm BC, at the Subtropical Confluence Zone, and in the subantarctic waters at the Drake passage. Our results suggest that oceanographic features strengthen latitudinal body size relationships due to food availability, and the importance of different life history strategies.

Intraspecific body size variation across distributional moments reveals trait filtering processes.

Natural populations are composed of individuals that vary in their morphological traits, timing and interactions. The distribution of a trait can be described by several dimensions, or mathematical moments-mean, variance, skew and kurtosis. Shifts in the distribution of a trait across these moments in response to environmental variation can help to reveal which trait values are gained or lost, and consequently how trait filtering processes are altering populations. To examine the role and drivers of intraspecific variation within a trait filtering framework, we investigate variation in body size among five wild bumblebee species in the Colorado Rocky Mountains. First, we examine the relationships between environmental factors (climate and floral food resources) and body size distributions across bumblebee social castes to identify demographic responses to environmental variation. Next, we examine changes in the moments of trait distributions to reveal potential mechanisms behind intraspecific shifts in body size. Finally, we examine how intraspecific body size variation is related to diet breadth and phenology. We found that climate conditions have a strong effect on observed body size variation across all distributional moments, but the filtering mechanism varies by social caste. For example, with earlier spring snowmelt queens declined in mean size and became negatively skewed and more kurtotic. This suggests a skewed filter admitting a greater frequency of small individuals. With greater availability of floral food resources, queens increased in mean size, but workers and males decreased in size. Observed shifts in body size variation also correspond with variation in diet breadth and phenology. Populations with larger average body size were associated with more generalized foraging in workers of short-tongued species and increased specialization in longer-tongued workers. Altered phenological timing was associated with species- and caste-specific shifts in skew. Across an assemblage of wild bumblebees, we find complex patterns of trait variation that may not have been captured if we had simply considered mean and variance. The four-moment approach we employ here provides holistic insight into intraspecific trait variation, which may otherwise be overlooked and reveals potential underlying filtering processes driving such variation within populations.

Investigating the Biotic and Abiotic Drivers of Body Size Disparity in Communities of Non‐Volant Terrestrial Mammals

ABSTRACTAimThe species that compose local communities possess unique sets of functional and ecological traits that can be used as indicators of biotic and abiotic variation across space and time. Body size is a particularly relevant trait because species with different body sizes typically have different life history strategies and occupy distinct niches. Here we used the body sizes of non‐volant (i.e., non‐flying) terrestrial mammals to quantify and compare the body size disparity of mammal communities across the globe.LocationGlobal.Time PeriodPresent.Major Taxa StudiedNon‐volant terrestrial mammals.MethodsWe used IUCN range maps of 3982 terrestrial mammals to identify 1876 communities. We then combined diet data with data on climate, elevation and anthropogenic pressures to evaluate these variables' relative importance on the observed body size dispersion of these communities and its deviation from a null model.ResultsDispersion for these communities is significantly greater than expected in 54% of communities and significantly less than expected in 30% of communities. The number of very large species, continent, range sizes, diet disparity and annual temperature collectively explain > 50% of the variation in observed dispersion, whereas continent, the number of very large species, and precipitation collectively explain > 30% of the deviation from the null model.Main ConclusionsClimate and elevation have minimal predictive power, suggesting that biotic factors may be more important for explaining community body size distributions. However, continent is consistently a strong predictor of dispersion, likely due to it capturing the combined effects of climate, size‐selective human‐induced extinctions and more. Overall, our results are consistent with several plausible explanations, including, but not limited to, competitive exclusion, unequal distribution of resources, within‐community environmental heterogeneity, habitat filtering and ecosystem engineering. Further work focusing on other confounding variables, at finer spatial scales and/or within more causal frameworks is required to better understand the driver(s) of these patterns.

Habitat preferences of Phycis blennoides (Pisces: Gadiformes): environmental factors and fishing-related ontogenic deepening

Phycis blennoides is a component of the ecosystem of the Atlantic waters of northern Spain and a species of commercial interest for fisheries in this region. However, little is known about the distribution of this species. The present study analyses the relationships between different environmental and spatial variables and distribution of P. blennoides. Biological (presence-absence, abundance, biomass and total length) and environmental data were collected from a bottom trawl survey carried out off the northern coast of Spain. These data were used in 2-step generalised additive models to examine both the relative significance of physical factors in influencing P. blennoides distribution and to generate density distribution maps. Additionally, the role of fishing effort on P. blennoides body size distribution with depth was analysed. Geospatial analyses showed that changes in annual abundance did not influence physical habitat preference. Most of the variation in spatial distribution was explained by the sampling position and depth. The analyses showed that P. blennoides exhibited habitat preferences in the waters of Galicia and the Cantabrian Sea, with higher values of presence, abundance and biomass on the upper slope and on fine-grained sediment bottoms. P. blennoides biomass increased with depth, probably due to the increased mean size of individuals with depth. Modelling results suggest that the observed ontogenetic deepening appears to be mainly driven by the life history strategy of the species, but is also reinforced by fishing effort.

Association of body shape phenotypes and body fat distribution indexes with inflammatory biomarkers in the European Prospective Investigation into Cancer and Nutrition (EPIC) and UK Biobank

BackgroundThe allometric body shape index (ABSI) and hip index (HI), as well as multi-trait body shape phenotypes, have not yet been compared in their associations with inflammatory markers. The aim of this study was to examine the relationship between novel and traditional anthropometric indexes with inflammation using data from the European Prospective Investigation into Cancer and Nutrition (EPIC) and UK Biobank cohorts.MethodsParticipants from EPIC (n = 17,943, 69.1% women) and UK Biobank (n = 426,223, 53.2% women) with data on anthropometric indexes and C-reactive protein (CRP) were included in this cross-sectional analysis. A subset of women in EPIC also had at least one measurement for interleukins, tumour necrosis factor alpha, interferon gamma, leptin, and adiponectin. Four distinct body shape phenotypes were derived by a principal component (PC) analysis on height, weight, body mass index (BMI), waist (WC) and hip circumferences (HC), and waist-to-hip ratio (WHR). PC1 described overall adiposity, PC2 tall with low WHR, PC3 tall and centrally obese, and PC4 high BMI and weight with low WC and HC, suggesting an athletic phenotype. ABSI, HI, waist-to-height ratio and waist-to-hip index (WHI) were also calculated. Linear regression models were carried out separately in EPIC and UK Biobank stratified by sex and adjusted for age, smoking status, education, and physical activity. Results were additionally combined in a random-effects meta-analysis.ResultsTraditional anthropometric indexes, particularly BMI, WC, and weight were positively associated with CRP levels, in men and women. Body shape phenotypes also showed distinct associations with CRP. Specifically, PC2 showed inverse associations with CRP in EPIC and UK Biobank in both sexes, similarly to height. PC3 was inversely associated with CRP among women, whereas positive associations were observed among men.ConclusionsSpecific indexes of body size and body fat distribution showed differential associations with inflammation in adults. Notably, our results suggest that in women, height may mitigate the impact of a higher WC and HC on inflammation. This suggests that subtypes of adiposity exhibit substantial variation in their inflammatory potential, which may have implications for inflammation-related chronic diseases.

Size‐based indicators of unexploited deep‐sea community in the Colombian Caribbean Sea

AbstractComposition, size distribution, structure, and function of deep‐sea marine communities must be understood before they are impacted by anthropogenic effects. The deep‐sea ecosystem of the Colombian Caribbean Sea is unexploited with no fishing activity ever registered. We quantified the current state of the marine community using body size distribution (size‐spectra), size‐based indicators, minimum length (LMIN), maximum length (LMAX), average length (Lmean), standard deviation of length (LSD), 10th and 90th percentiles of the length distribution, Shannon–Wiener diversity (H′), and Pielou's evenness (J′) to generate a baseline of potential ecological indicators that contribute to management and conservation of the Colombian bento‐demersal community of deep‐sea marine ecosystem. Sampling was in the Colombian Caribbean Sea at 58 stations during four samplings in August and December 2009, 21 stations in March and May 2010, and 45 stations from August to December 2020, using the swept area method, at depths of 200–550 m. Catches included >50% families and species of fish, followed by 27 families (30%) and 33 and species (37%) of crustaceans. Chondrichthyes included 14% families and 9–11% species. Cephalopods included 2–3% families and 1–4% species. Size‐spectra analysis confirmed expected values for unexploited communities in three sampling years for teleostei, crustacea, and whole community.

From dinosaurs to birds: paleomacroecological analysis of the body size inversion in the maniraptor lineage

Large taxonomic groups, distributed over vast geological periods, may exhibit wide patterns of morphological variation, such as variation in body size and complexity of living beings. Some studies seek to determine whether these trends of increasing or decreasing size and complexity result from persistent directional forces (e.g., natural selection) or from non-directional (random) trends produced by constraint limits. These mechanisms have been characterized as "active or directed" and "passive" trend processes, respectively. Understanding these variation patterns allows assessing hypotheses within a paleomacroecological context, such as Cope's Rule, which suggests that lineages with longer evolutionary time spans tend to increase in size. This pattern has been demonstrated in various groups of fossil vertebrates, such as dinosaurs. However, the Maniraptora lineage (ancestral to groups that gave rise to birds) seems to exhibit an inverted pattern, with a reduction in body size in recent lineages. Tests indicate that this asymmetry in size evolution can be explained by passive or active trends, i.e., random size variation or directional selection. In this case, an "Inverted Cope's Rule" could indicate directional selection for size reduction in the Maniraptora lineage towards the derivation of birds. Body size and time distribution vectors will be derived for each lineage, evaluating the general trend of size variation. If asymmetry in size evolution is observed, a Subclade Test will be conducted to assess if a specific subclade repeats the asymmetric distribution pattern. The goal of this project is to assess active and/or passive trends related to body size variation in Maniraptora dinosaurs, using fossil data from the Paleobiology Database and the Natural History Museum Database.

Augmenting X-ray micro-CT data with MICP data for high resolution pore-scale simulations of flow properties of carbonate rocks

Pore-scale modeling is essential in understanding and predicting flow and transport properties of rocks. Generally, pore-scale modeling is dependent on imaging technologies such as Micro Computed Tomography (micro-CT), which provides visual confirmation into the pore microstructures of rocks at a representative scale. However, this technique is limited in the ability to provide high resolution images showing the pore-throats connecting pore bodies. Pore scale simulations of flow and transport properties of rocks are generally done on a single 3D pore microstructure image. As such, the simulated properties are only representative of the simulated pore-scale rock volume. These are the technological and computational limitations which we address here by using a stochastic pore-scale simulation approach. This approach consists of constructing hundreds of 3D pore microstructures of the same pore size distribution and overall porosity but different pore connectivity. The construction of the 3D pore microstructures incorporates the use of Mercury Injection Capillary Pressure (MICP) data to account for pore throat size distribution, and micro-CT images to account for pore body size distribution. The approach requires a small micro-CT image volume (7–19 mm3) to reveal key pore microstructural features that control flow and transport properties of highly heterogeneous rocks at the core-scale. Four carbonate rock samples were used to test the proposed approach. Permeability calculations from the introduced approach were validated by comparing laboratory measured permeability of rock cores and permeability estimated using five well-known core-scale empirical model equations. The results show that accounting for the stochastic connectivity of pores results in a probabilistic distribution of flow properties which can be used to upscale pore-scale simulated flow properties to the core-scale. The use of the introduced stochastic pore-scale simulation approach is more beneficial when there is a higher degree of heterogeneity in pore size distribution. This is shown to be the case with permeability and hydraulic tortuosity which are key controls of flow and transport processes in rocks.

Environmental warming increases the importance of high-turnover energy channels in stream food webs.

Warming temperatures are altering communities and trophic networks across Earth's ecosystems. While the overall influence of warming on food webs is often context-dependent, increasing temperatures are predicted to change communities in two fundamental ways: (1) by reducing average body size and (2) by increasing individual metabolic rates. These warming-induced changes have the potential to influence the distribution of food web fluxes, food web stability, and the relative importance of deterministic and stochastic ecological processes shaping community assembly. Here, we quantified patterns and the relative distribution of organic matter fluxes through stream food webs spanning a broad natural temperature gradient (5-27°C). We then related these patterns to species and community trait distributions of mean body size and population biomass turnover (P:B) within and across streams. We predicted that (1) communities in warmer streams would exhibit smaller body size and higher P:B and (2) organic matter fluxes within warmer communities would increasingly skew toward smaller, higher P:B populations. Across the temperature gradient, warmer communities were characterized by smaller body size (~9% per °C) and higher P:B (~7% faster turnover per °C) populations on average. Additionally, organic matter fluxes within warmer streams were increasingly skewed toward higher P:B populations, demonstrating that warming can restructure organic matter fluxes in both an absolute and relative sense. With warming, the relative distribution of organic matter fluxes was decreasingly likely to arise through the random sorting of species, suggesting stronger selection for traits driving high turnover with increasing temperature. Our study suggests that a warming world will favor energy fluxes through "smaller and faster" populations, and that these changes may be more predictable than previously thought.

Molecular and Phylogenetic Character Analysis of Tuna (Auxis rochei) Based on the CO1 Gene in the Waters of West Lombok

Tuna Fish is a type of tuna with a medium body size and fair wide distribution in Indo-Pacific waters. The number of Tuna Fish species that have morphological similarities can cause misidentification. This study aims to determine the genetic and phylogenetic diversity between variations of Tuna Fish species in the West Lombok Waters. This research is an exploratory study with the object of research being a dataset of ingroup sequences of tuna and outgroup sequences from the same family. The amplification of fish samples used DNA primers targeting the CO1 gene, which resulted in a sequence length of approximately 650 bp. Sequence data were analyzed using MEGA XI software known from phylogenetic tree analysis shows that Tuna Fish from the waters of the West Lombok are closely related to Tuna Fish from the South China Sea and have a genetic distance of less than 3%.

Automated CT Analysis of Body Composition as a Frailty Biomarker in Abdominal Surgery

Prior studies demonstrated consistent associations of low skeletal muscle mass assessed on surgical planning scans with postoperative morbidity and mortality. The increasing availability of imaging artificial intelligence enables development of more comprehensive imaging biomarkers to objectively phenotype frailty in surgical patients. To evaluate the associations of body composition scores derived from multiple skeletal muscle and adipose tissue measurements from automated segmentation of computed tomography (CT) with the Hospital Frailty Risk Score (HFRS) and adverse outcomes after abdominal surgery. This retrospective cohort study used CT imaging and electronic health record data from a random sample of adults who underwent abdominal surgery at 20 medical centers within Kaiser Permanente Northern California from January 1, 2010, to December 31, 2020. Data were analyzed from April 1, 2022, to December 1, 2023. Body composition derived from automated analysis of multislice abdominal CT scans. The primary outcome of the study was all-cause 30-day postdischarge readmission or postoperative mortality. The secondary outcome was 30-day postoperative morbidity among patients undergoing abdominal surgery who were sampled for reporting to the National Surgical Quality Improvement Program. The study included 48 444 adults; mean [SD] age at surgery was 61 (17) years, and 51% were female. Using principal component analysis, 3 body composition scores were derived: body size, muscle quantity and quality, and distribution of adiposity. Higher muscle quantity and quality scores were inversely correlated (r = -0.42; 95% CI, -0.43 to -0.41) with the HFRS and associated with a reduced risk of 30-day readmission or mortality (quartile 4 vs quartile 1: relative risk, 0.61; 95% CI, 0.56-0.67) and 30-day postoperative morbidity (quartile 4 vs quartile 1: relative risk, 0.59; 95% CI, 0.52-0.67), independent of sex, age, comorbidities, body mass index, procedure characteristics, and the HFRS. In contrast to the muscle score, scores for body size and greater subcutaneous and intermuscular vs visceral adiposity had inconsistent associations with postsurgical outcomes and were attenuated and only associated with 30-day postoperative morbidity after adjustment for the HFRS. In this study, higher muscle quantity and quality scores were correlated with frailty and associated with 30-day readmission and postoperative mortality and morbidity, whereas body size and adipose tissue distribution scores were not correlated with patient frailty and had inconsistent associations with surgical outcomes. The findings suggest that assessment of muscle quantity and quality on CT can provide an objective measure of patient frailty that would not otherwise be clinically apparent and that may complement existing risk stratification tools to identify patients at high risk of mortality, morbidity, and readmission.

Geographic differences in body size distributions underlie food web connectance of tropical forest mammals

Understanding variation in food web structure over large spatial scales is an emerging research agenda in food web ecology. The density of predator–prey links in a food web (i.e., connectance) is a key measure of network complexity that describes the mean proportional dietary breadth of species within a food web. Connectance is a critical component of food web robustness to species loss: food webs with lower connectance have been shown to be more susceptible to secondary extinctions. Identifying geographic variation in food web connectance and its drivers may provide insight into community robustness to species loss. We investigated the food web connectance of ground-dwelling tropical forest mammal communities in multiple biogeographic regions to test for differences among regions in food web connectance and to test three potential drivers: primary productivity, contemporary anthropogenic pressure, and variation in mammal body mass distributions reflective of historical extinctions. Mammal communities from fifteen protected forests throughout the Neo-, Afro-, and Asian tropics were identified from systematic camera trap arrays. Predator–prey interaction data were collected from published literature, and we calculated connectance for each community as the number of observed predator–prey links relative to the number of possible predator–prey links. We used generalized linear models to test for differences among regions and to identify the site level characteristics that best predicted connectance. We found that mammal food web connectance varied significantly among continents and that body size range was the only significant predictor. More possible predator–prey links were observed in communities with smaller ranges in body size and therefore sites with smaller body size ranges had higher mean proportional dietary breadth. Specifically, mammal communities in the Neotropics and in Madagascar had significantly higher connectance than mammal communities in Africa. This geographic variation in contemporary mammalian food web structure may be the product of historical extinctions in the Late Quaternary, which led to greater losses of large-bodied species in the Neotropics and Madagascar thus contributing to higher average proportional dietary breadth among the remaining smaller bodied species in these regions.

Bayesian hierarchical modelling of size spectra

Abstract A fundamental pattern in ecology is that smaller organisms are more abundant than larger organisms. This pattern is known as the individual size distribution (ISD), which is the frequency distribution of all individual body sizes in an ecosystem. The ISD is described by a power law and a major goal of size spectra analyses is to estimate the exponent of the power law, λ. However, while numerous methods have been developed to do this, they have focused almost exclusively on estimating λ from single samples. Here, we develop an extension of the truncated Pareto distribution within the probabilistic modelling language Stan. We use it to estimate multiple λs simultaneously in a hierarchical modelling approach. The most important result is the ability to examine hypotheses related to size spectra, including the assessment of fixed and random effects, within a single Bayesian generalized mixed model. While the example here uses size spectra, the technique can also be generalized to any data that follow a power law distribution.

Geographic gradients in a functional trait: Drivers of body size and size diversity of ground invertebrate communities

AbstractBody size is a key functional trait governing how an animal community transforms resources and conditions into performance, abundance, and fitness. Here we use the National Ecological Observatory Network of pitfall traps to explore how an ecosystem's plant productivity, temperature, and growing season length accounts for the range of body size across 99 ground invertebrate communities. The 19‐fold continental variation in mean body size failed to covary with latitude, while common ordinal subtaxa grew smaller (e.g., myriapods) to larger (e.g., acari) from Puerto Rico to Alaska. Communities with a larger mean size arose when winters were longer and gross primary productivity was high. The diversity of body sizes in a community (measured as the CV) varied ninefold and decreased with latitude (r2 = 0.24) consistently across common orders. Size‐diverse communities were less likely in ecosystems with long winters (suggesting constraints on the time to build, r2 = 0.34) and those with high invertebrate activity (and hence trap catch, r2 = 0.12). Body size distributions thus appeared to arise from conflicting combinations of constraint (i.e., the ability to build large bodies) and performance (utility of large size in surviving long winters). As warming promotes growing season length, populations of larger, rarer individuals may benefit.

Large durophagous fish from the Spathian (late Early Triassic) of Romania hints at earlier onset of the Triassic actinopterygian revolution

AbstractFossil evidence suggests that ray‐finned fishes (Actinopterygii) diversified greatly after the largest mass extinction event at the Permian–Triassic boundary. This radiation resulted in a diversity peak in the Middle Triassic, which is manifested in diverse feeding specializations, especially among small‐bodied Neopterygii. We present new material from an early Spathian (Early Triassic) outcrop in northern Dobrogea, southeast Romania. The material includes isolated jaw and palatal bones that evidently belong to a single individual, a durophagous actinopterygian, and isolated scales referred to the same taxon. A systematic evaluation of this material indicates affinities with †Polzbergiidae, and provides a first glimpse of internal aspects of the feeding apparatus of that group. A pair of ectopterygoids with crushing dentition show a well‐developed lateral process, a feature that was previously proposed to be a synapomorphy uniting Cladistia (bichirs) with the Triassic †Scanilepiformes. The recognition of this structure in various Triassic ray‐fins (summarized herein) indicates that it was probably widespread among stem neopterygians. The new material belongs to a large individual with a heterodont dentition, therefore representing the earliest large, specialized, durophagous neopterygian. It increases the group's morphological diversity in the Spathian, and hints at an earlier trophic diversification after the mass extinction. Based on new data, we analyse changes in body size of bony fishes through the Early and Middle Triassic. Current evidence suggests that body size distribution remained skewed towards larger sizes in the late Early Triassic, and that the diversification of small‐bodied stem neopterygians had not yet been in full swing.

Maximum likelihood outperforms binning methods for detecting differences in abundance size spectra across environmental gradients.

Individual body size distributions (ISD) within communities are remarkably consistent across habitats and spatiotemporal scales and can be represented by size spectra, which are described by a power law. The focus of size spectra analysis is to estimate the exponent ( ) of the power law. A common application of size spectra studies is to detect anthropogenic pressures. Many methods have been proposed for estimating most of which involve binning the data, counting the abundance within bins, and then fitting an ordinary least squares regression in log-log space. However, recent work has shown that binning procedures return biased estimates of compared to procedures that directly estimate using maximum likelihood estimation (MLE). While it is clear that MLE produces less biased estimates of site-specific λ's, it is less clear how this bias affects the ability to test for changes in λ across space and time, a common question in the ecological literature. Here, we used simulation to compare the ability of two normalised binning methods (equal logarithmic and log2 bins) and MLE to (1) recapture known values of , and (2) recapture parameters in a linear regression measuring the change in across a hypothetical environmental gradient. We also compared the methods using two previously published body size datasets across a natural temperature gradient and an anthropogenic pollution gradient. Maximum likelihood methods always performed better than common binning methods, which demonstrated consistent bias depending on the simulated values of . This bias carried over to the regressions, which were more accurate when was estimated using MLE compared to the binning procedures. Additionally, the variance in estimates using MLE methods is markedly reduced when compared to binning methods. The error induced by binning methods can be of similar magnitudes as the variation previously published in experimental and observational studies, bringing into question the effect sizes of previously published results. However, while the methods produced different regression slope estimates, they were in qualitative agreement on the sign of those slopes (i.e. all negative or all positive). Our results provide further support for the direct estimation of and its relative variation across environmental gradients using MLE over the more common methods of binning.

How non-target chironomid communities respond to mosquito control: Integrating DNA metabarcoding and joint species distribution modelling

The conservation and management of riparian ecosystems rely on understanding the ecological consequences of anthropogenic stressors that impact natural communities. In this context, studies investigating the effects of anthropogenic stressors require reliable methods capable of mapping the relationships between taxa occurrence or abundance and environmental predictors within a spatio-temporal framework. Here, we present an integrative approach using DNA metabarcoding and Hierarchical Modelling of Species Communities (HMSC) to unravel the intricate dynamics and resilience of chironomid communities exposed to Bacillus thuringiensis var. israelensis (Bti). Chironomid emergence was sampled from a total of 12 floodplain pond mesocosms, half of which received Bti treatment, during a 16-week period spanning spring and summer of 2020. Subsequently, we determined the community compositions of chironomids and examined their genus-specific responses to the Bti treatment, considering their phylogenetic affiliations and ecological traits of the larvae. Additionally, we investigated the impact of the Bti treatment on the body size distribution of emerging chironomids. Our study revealed consistent responses to Bti among different chironomid genera, indicating that neither phylogenetic affiliations nor larval feeding strategies significantly contributed to the observed patterns. Both taxonomic and genetic diversity were positively correlated with the number of emerged individuals. Furthermore, our findings demonstrated Bti-related effects on chironomid body size distribution, which could have relevant implications for size-selective terrestrial predators. Hence, our study highlights the value of employing a combination of DNA metabarcoding and HMSC to unravel the complex dynamics of Bti-related non-target effects on chironomid communities. The insights gained from this integrated framework contribute to our understanding of the ecological consequences of anthropogenic stressors and provide a foundation for informed decision-making regarding the conservation and management of riparian ecosystems.

Pore network simulations of thin porous medium characterization by evapoporometry

Evapoporometry is a technique aiming at characterizing the pore size distribution of a porous medium from evaporated mass measurements. In this work, evapoporometry is studied from numerical simulations on model pore networks allowing a detailed analysis of the underlying physics at play in the technique. Simulations indicate that both the pore body size and throat size distributions can be characterized and pinpoint the need of a very accurate determination of the evaporation rate. This is notably illustrated by varying the evaporated mass acquisition time step. Evapoporometry and liquid-liquid displacement porometry techniques are discussed comparatively in relation with experimental works reporting differences between the pore size distributions identified through both techniques.