Biology subjects

Royaute, R.

Publications and source records attributed to Royaute, R..

8 recordsLinked to original sources

bioRxiv2026

Toxicokinetics of a Pesticide Mixture in Earthworms Reveal Concentration-Dependent Bioaccumulation and Limited Interactions

Despite their fundamental role in sustaining terrestrial biodiversity and ecosystem functioning, soils are increasingly contaminated by pesticides, often occurring as complex mixtures. Understanding chemical uptake, distribution, and elimination in soil organisms is essential for reliable risk assessment. We investigated the toxicokinetics of a binary mixture of imidacloprid and epoxiconazole in the earthworm Aporrectodea caliginosa. Single-substance experiments were conducted to estimate uptake and elimination rates, and allowed the implementation of single substance toxicokinetic models. A mixture experiment tested five concentration ratios to assess potential interactions. Epoxiconazole, an azole fungicide, exhibited rapid uptake and elimination (k_u = 1.9 gsoil*gworm-1*d-1; k_e = 1.7 d-1), resulting in low bioaccumulation (BAF = 0.9), whereas imidacloprid, a neonicotinoid insecticide, accumulated slowly with low elimination (k_u = 1.6 gsoil*gworm-1* d-1; k_e = 0.12 d-1), producing high bioaccumulation (BAF = 20). The explicit inclusion of the 24-hour Petri dish depuration phase proved to be critical, especially for epoxiconazole, highlighting the influence of gut-clearance procedures on apparent kinetics. In accordance with only a small synergistic effect in the mixture, no toxicokinetic interactions were detected in the mixture; internal concentrations of each compound were consistent across ratios. Concentration-dependent patterns were observed, with indications of a saturation process at high exposure levels for imidacloprid, and an increased BAF at high concentrations for epoxiconazole. This finding questions the use of single, concentration-independent bioaccumulation factors for hazard assessment and highlights the value of integrated TKTD approaches.

ecology↗

bioRxiv2026

Toxic cocktails in soils - Evidence for synergistic effects of the imidacloprid-epoxiconazole mixture on earthworm life-history traits

Soils are vital reservoirs of biodiversity and providers of ecosystem services, yet they are increasingly threatened by agricultural intensification and pesticide use. Residues often persist as complex mixtures, while environmental risk assessment still largely focuses on single substances, potentially underestimating mixture effects. Earthworms play a key role in soil functioning and are particularly vulnerable to pesticide contamination. We investigated the effects of a binary mixture of epoxiconazole and imidacloprid, two persistent and frequently detected pesticides, on life-history traits of Aporrectodea caliginosa. We estimated each compound relative potency using dose-response experiments on juvenile growth and cocoon production. Next, we assessed the potential for synergy or antagonism in a fixed-ratio ray design including five concentration ratios and seven additive isoboles (36 conditions). Both compounds showed significant toxicity. Imidacloprid showed high potency (juvenile growth NOEC = 0.28 mg/kg; reproduction EC50 = 0.55 mg/kg), whereas epoxiconazole had moderate effects (juvenile growth NOEC = 9.3 mg/kg; reproduction EC50 = 126.8 mg/kg). Reproductive endpoints were more sensitive than adult growth, with juvenile growth being the most sensitive overall. Mixture analysis using Jonkers models revealed significant deviation from Independent Action only under the simple interaction model, indicating synergism, consistent with cytochrome P450 interference reported in other taxa. Field-reported imidacloprid concentrations often approach effect thresholds, suggesting potential risks for earthworm populations. Overall, the combined effects of epoxiconazole and imidacloprid may exceed predictions not taking interactions into account. These results highlight the need to incorporate pesticide mixture effects into environmental risk assessment. Environmental ImplicationsPesticide residues persist in agricultural soils as complex mixtures, yet risk assessment still focuses mainly on single substances. This study shows that the combined effects of imidacloprid and epoxiconazole on earthworm reproduction can exceed predictions based on Independent Action, with evidence of synergistic interactions. Effect thresholds for imidacloprid approach reported maximum environmental concentrations, indicating limited safety margins for soil organisms. These findings suggest that mixture exposures may pose greater ecological risks than currently anticipated and highlight the need to integrate pesticide mixture toxicity and potential synergism into environmental risk assessment frameworks. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/707680v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@18c89ceorg.highwire.dtl.DTLVardef@1ab4dd2org.highwire.dtl.DTLVardef@1823edaorg.highwire.dtl.DTLVardef@1ec9782_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2025

Genetic and environmental sources of behavioral individuality: a test of the standard model

Behavioral variation is typically assumed to arise from the combination and interaction of genetic and environmental variation. However, recent work with genetically identical individuals has found that substantial behavioral individuality is expressed even when genetic and environmental variation are negligible. This surprising result requires direct testing of our standard model for the sources of behavioral individuality. Here, we tested the standard model by comparing among-individual variation in highly inbred crickets versus outbred crickets. Comparing inbred and outbred lines allows for direct testing of the standard model by contrasting the magnitude of among-individual variation in a uniform versus varied genetic background. We found substantial and significant differences in among-individual variances, with among-individual variances being roughly three times greater in outbred versus inbred crickets (posterior probability, p = 0.974). Repeatability was also significantly different between inbred and outbred crickets (0.15 versus 0.41, respectively; p = 0.984). This result supports our standard model and suggests that the surprising expression of behavioral variation in clonal and parthenogenic species may represent an important but unique pathway for the expression of behavioral individuality.

animal behavior and cognition↗

bioRxiv2025

MoveTraits - A database for integrating animal behaviour into trait-based ecology

Trait-based approaches are key to understanding eco-evolutionary processes but rarely account for animal behaviour despite its central role in ecosystem dynamics. We propose integrating behaviour into trait-based ecology through movement traits - standardised and comparable measures of animal movement derived from biologging data, such as daily displacements or range sizes. Accounting for animal behaviour will advance trait-based research on species interactions, community structure, and ecosystem functioning. Importantly, movement traits allow for quantification of behavioural reaction norms, offering insights into species acclimation and adaptive capacity to environmental change. We outline a vision for a living global movement trait database that enhances trait data curation by (1) continuously growing alongside shared biologging data, (2) calculating traits directly from individual-level data using standardised, consistent methodology, and (3) providing information on multi-level (species, individual, within-individual) trait variation. We present a proof-of-concept MoveTraits database with 55 mammal and 108 bird species, demonstrating calculation workflows for 5 traits across multiple time scales. Movement traits have significant potential to improve trait-based global change predictions and contribute to global biodiversity assessments as Essential Biodiversity Variables. By making animal movement data more accessible and interpretable, this database could bridge the gap between movement ecology and biodiversity policy, facilitating evidence-based conservation.

ecology↗

bioRxiv2022

Classifying the activity states of small vertebrates using automated VHF telemetry

O_LIThe most basic behavioural states of animals can be described as active or passive. However, while high-resolution observations of activity patterns can provide insights into the ecology of animal species, few methods are able to measure the activity of individuals of small taxa in their natural environment. We present a novel approach in which the automated VHF radio-tracking of small vertebrates fitted with lightweight transmitters (< 0.2 g) is used to distinguish between active and passive behavioural states. C_LIO_LIA dataset containing > 3 million VHF signals was used to train and test a random forest model in the assignment of either active or passive behaviour to individuals from two forest-dwelling bat species (Myotis bechsteinii (n = 50) and Nyctalus leisleri (n = 20)). The applicability of the model to other taxonomic groups was demonstrated by recording and classifying the behaviour of a tagged bird and by simulating the effect of different types of vertebrate activity with the help of humans carrying transmitters. The random forest model successfully classified the activity states of bats as well as those of birds and humans, although the latter were not included in model training (F-score 0.96-0.98). C_LIO_LIThe utility of the model in tackling ecologically relevant questions was demonstrated in a study of the differences in the daily activity patterns of the two bat species. The analysis showed a pronounced bimodal activity distribution of N. leisleri over the course of the night while the night-time activity of M. bechsteinii was relatively constant. These results show that significant differences in the timing of species activity according to ecological preferences or seasonality can be distinguished using our method. C_LIO_LIOur approach enables the assignment of VHF signal patterns to fundamental behavioural states with high precision and is applicable to different terrestrial and flying vertebrates. To encourage the broader use of our radio-tracking method, we provide the trained random forest models together with an R-package that includes all necessary data-processing functionalities. In combination with state-of-the-art open-source automated radio-tracking, this toolset can be used by the scientific community to investigate the activity patterns of small vertebrates with high temporal resolution, even in dense vegetation. C_LI

animal behavior and cognition↗

bioRxiv2021

Drift on holey landscapes as a dominant evolutionary process

An organisms phenotype has been shaped by evolution but the specific processes have to be indirectly inferred for most species. For example, correlations among traits imply the historical action of correlated selection and, more generally, the expression and distribution of traits is expected to be reflective of the adaptive landscapes that have shaped a population. However, our expectations about how quantitative traits--like most behaviors, physiological processes, and life-history traits--should be distributed under different evolutionary processes is not clear. Here we show that genetic variation in quantitative traits is not distributed as would be expected under dominant evolutionary models. Instead, we found that genetic variation in quantitative traits across 6 phyla and 60 species (including both Plantae and Animalia) is consistent with evolution across high dimensional "holey landscapes". This suggests that the leading conceptualizations and modeling of the evolution of trait integration fail to capture how phenotypes are shaped and that traits are integrated in a manner contrary to predictions of dominant evolutionary theory. Our results demonstrate that our understanding of how evolution has shaped phenotypes remains incomplete and these results provide a starting point for reassessing the relevance of existing evolutionary models. Significance StatementWe found that empirical estimations of how quantitative genetic variation is distributed do not correspond to typical Gaussian representations of fitness landscapes. These Gaussian landscapes underpin major areas of evolutionary biology and how selection is estimated in natural populations. Rather than being consistent with evolution on Gaussian landscapes, empirical estimates of genetic variation are, instead, consistent with evolution on high-dimensional "holey" landscapes. These landscapes represent situations where specific combinations of trait values are either viable or not and populations randomly drift among the viable combinations. This finding suggests that we have substantially misunderstood how selection actually shapes populations and thus how evolution typically proceeds.

evolutionary biology↗

bioRxiv2020

Integration of intra- and inter-sexual selection signaling

Sexual selection can drive the evolution of dramatic morphological and behavioral signals. This selection acts on both specific components of signals and overall signals that combine multiple sources of information. By studying the structure and variability of signals and their components we can improve our understanding of how sexual selection operates. Signal integration can be understood through the lens of classical signaling hypotheses or more recently defined systems approaches. Using crickets (Acheta domesticus), we evaluated competing hypotheses about signal integration and how observed patterns of signal integration fit into both systems approaches and classic signaling hypotheses. We measured three call types of 127 male crickets multiple times for a total of 930 observations. We found evidence for an underlying integrated signaling syndrome from which both intra- and intersexual signals stemmed. This syndrome was also affected by mass, suggesting honest signaling in the species. The presence of an integrated syndrome demonstrates that intra- and intersexual signals are incorporated in a redundant signal strategy in Acheta domesticus. This support for honest and redundant signaling is also consistent with a systems framework description of signals as degenerate and functionally modular--demonstrating one way in which classic hypotheses can be integrated with modern systems approaches.

animal behavior and cognition↗

bioRxiv2019

Animal personality shapes evolutionary trajectories via conserved genetic architecture

Behaviors are often correlated within broader syndromes, creating the potential for evolution in one behavior to drive evolutionary changes in other behaviors. Despite demonstrations that behavioral syndromes are common across taxa, whether this potential for evolutionary effects is realized has not yet been demonstrated. Here we show that populations of field crickets (Gryllus integer) exhibit a genetically conserved behavioral syndrome structure despite differences in average behaviors. We found that the distribution of genetic variation and genetic covariance among behavioral traits was consistent with genes and cellular mechanisms underpinning behavioral syndromes rather than correlated selection. Moreover, divergence among populations average behaviors was constrained by the genetically conserved behavioral syndrome. Our results demonstrate that a conserved genetic architecture linking behaviors has shaped the evolutionary trajectories of populations in disparate environments--illustrating an important way by which behavioral syndromes result in shared evolutionary fates.

genetics↗