Biology subjects

Besnard, A.

Publications and source records attributed to Besnard, A..

17 recordsLinked to original sources

bioRxiv2026

Threat imminence and estimates of agency dictate proactive and reactive defensive behaviors in active place avoidance

Defensive survival behaviors are shaped by both danger attributes and internal physiological states. Well-characterized defensive responses depend not only on whether danger is potential or perceived, but also on its spatial and or temporal proximity. The relationship between danger imminence and defensive behaviors is referred to as the threat imminence continuum, which provides a conceptual framework bridging ecology and behavioral neuroscience. Although this theoretical framework is gaining momentum, another much less explored danger attribute is the extent to which the environment may be controllable. Most paradigms assessing defensive behaviors rely on conditioned stimuli as danger warning-signals in stable environments that hamper the study of environment controllability and its impact on defensive behaviors. To address this question, we repurposed the active place avoidance (APA) paradigm combined with supervised machine learning to characterize multivariate exploratory and defensive behaviors in male and female mice. One important benefit of APA is that it allows the study of active avoidance when the platform is rotating as well as deliberative avoidance when the platform is immobile. As such, APA is very well suited to test the impact of environment controllability on the expression of defensive behaviors. Using this unified preparation, we systematically compared quantitative danger attributes (punishment intensity, behavioral agency) across danger states (absence, presence and omission of punishment) and learning experience (early and late learning stages), while considering sex as a biological variable. Our results demonstrate that defensive behaviors depend on punishment intensity in a sex-dependent manner in APA. Defensive responses can be classified as proactive (risk assessment) or reactive (freezing, escape) in APA. Their response probability depends on behavioral agency, is mutually exclusive and depends on danger spatial proximity. Acute treatment with norepinephrine transporter blocker selectively increases reactive defensive behaviors while sparing proactive defensive behavior. Collectively, these results provide experimental evidence that environmental stability calibrate proactive and reactive defensive behaviors whose neural correlates may be divergent.

animal behavior and cognition↗

bioRxiv2025

Long-term population monitoring reveals an alarming decline in the endangered endemic Reunion Harrier Circus maillardi

Insular species are disproportionately vulnerable to extinction due to small population sizes, geographic isolation, and high susceptibility to stochastic and anthropogenic pressures. The endemic Reunion Harrier (Circus maillardi), the last breeding raptor on La Reunion (Indian Ocean), is currently listed as "endangered" (EN) on the IUCN Red List. Concerns have recently emerged regarding the demographic impacts of secondary poisoning from anticoagulant rodenticides used for rat control in agricultural landscapes, in addition to other threats such as habitat loss and fragmentation, and reduced genetic diversity. Here, we analysed data from three standardized island-wide breeding censuses (1998-2000, 2009-2010, 2017-2019), encompassing 355 sampling points and totalising > 1,500 h of observations, to quantify overall population trends and spatial variation within those. Using generalized additive mixed models accounting for spatial variation in the different census designs, we estimated a significant decrease of -46% (95% CI: -61% to -28%) in the relative abundance of breeding pairs at the island scale over 21 years (equivalent to three generations), which supports its current endangered (EN) status. Decline was more pronounced in the eastern part of the island (-56%, 95% CI: -69% to -40%) compared to the western part (-29%, 95% CI: -52% to +0.3%). Combined with previous work on inbreeding and mutational load, exposure to anticoagulant rodenticides and ongoing threats (habitat changes), these results suggest this harrier population is undergoing an extinction vortex that requires immediate and targeted, spatially explicit, conservation actions. We also recommend that population size continues to be monitored and that knowledge of demographic parameters be improved to guide adaptive management for the species.

ecology↗

bioRxiv2025

Feeding-fasting cycle of obesogenic food determines glucocorticoid neuromodulation of cortico-hippocampal activities sustaining long-term memory

BackgroundHighly caloric food consumed around the clock perturbs the metabolism and cognitive functioning. We hypothesized that obesogenic food could alter neuronal representations of memory depending on the feeding-fasting cycle. MethodsWe tracked memory performance, dendritic spine dynamics and neuronal representations of memory in C57Bl6J mice fed obesogenic food ad libitum from peri-adolescence. We aimed to correct energy rich diet-induced plasticity deficits and cognitive impairment with time-restricted feeding in males and females. We further used chemogenetics, pharmacology and knock-in mice to investigate functional correlates underlying diet-induced neurocognitive impairments. ResultsWe find that changes in the feeding-fasting cycle reverted the effects of ad libitum obesogenic food on memory impairment in both sexes (n=55, p=0.003). Concurrently, it also corrected the increased dendritic spine maintenance and neuroactivity in hippocampus and the decreased spine maintenance and activity in parietal cortex (n=48, p<0.005). Bi-directional effects in cortex and hippocampus mediated by glucocorticoid signalling are causal to behavioural changes (n=91, p=0.0008), and scaling hippocampal with cortical activities restored memory in mice fed obesogenic food (n=44, p=0.02). ConclusionThese results indicate that meal scheduling is a promising approach to confront glucocorticoid signalling bias and memory deficits caused by obesogenic food. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWhat and when we eat contributes to our health. This is particularly worrisome for kids and adolescents because of the lifelong effects that unrestricted snacking on highly caloric food could cause on brain maturation. A variety of school policies and nutritional programs have emerged to prevent poor nutritional habits. But obesity is on the rise and a major cause of neurological disabilities difficult to detect and treat. Human studies are limited by the size and duration of sampling with low resolution metrics to prove causality between nutritional habits and cognitive health trajectory. Animal studies showed that all-day snacking on highly caloric food disrupts innate biological rhythms that influence hormonal secretions, neuronal structure and function in brain regions that encode, store and retrieve memories. It isnt known if, like adipocytes and hepatocytes, the brain in obesity can develop glucocorticoid resistance -a state that would prevent the robust but complex effects of this hormone on memory- to the point that researchers still question whether glucocorticoids are a cause or solution to obesity related-brain comorbidities. Added value of this studyLongitudinal sampling of several metrics at multiple timepoints in mice fed highly caloric food since peri-adolescence up to adulthood showed that the trajectory of obesity-related brain comorbidities is corrected when reinstating the feeding/fasting cycle, albeit consuming highly caloric food. Glucocorticoid resistance -manifesting as receptor phosphorylation deficits impeding coincidence detection between glucocorticoid and neuronal activities -was reversible when reinstating the feeding/fasting cycle, albeit consuming highly caloric food. Studies in receptor mutant mice lacking a phosphorylation site-independent of glucocorticoids showed it is required to reinstate neuroplasticity to changes of feeding/fasting cycle, albeit consuming highly caloric food. Fos-trapping experiments showed less engagement of pyramidal neurons in the cortex when activity-dependent phosphorylation of glucocorticoid receptor was low, and more in the hippocampus of mice fed obesogenic diet, which reinstating the feeding/fasting cycle reverted, albeit consuming highly caloric food. Finally, chemogenetic experiments confirmed the requirement for the co-engagement of cortical and hippocampal pyramidal neurons to fully remember, despite poor nutritional habits. Implications of all the available evidenceThe cortico-hippocampal activities necessary for remembering are uncoupled by obesogenic food consumed ad libitum but not on meal scheduling, extending neuroimaging correlation studies in obese adolescents. Poor nutritional habits cause glucocorticoid resistance in the brain as previously suggested, with altered neuronal representation of memory that meal scheduling corrected. This result should transform school policies and familial nutritional habits to promote cognitive health. Future research will develop allosteric ligands targeting phosphorylation motifs in the glucocorticoid receptor as more specific alternative to orthosteric ligands for the treatment of obesity-related brain comorbidities.

neuroscience↗

bioRxiv2024

Midbrain dopamine D2R regulates the salience of threat-related events

Salience attributed to stimuli predicting rewarding or aversive outcomes is critical for adaptive behavior. Dopamine (DA)-neurons play a central role in this process by modulating responses to both rewarding and aversive cues. DA-neurons are tightly and readily modulated by DA D2 autoreceptors (autoD2Rs), but their role in regulating responses to aversive stimuli remains unclear. In this study, we investigated the role of autoD2R in regulating the activity of VTA DA-neurons in response to salient aversive stimuli. Using Drd2Slc6a3 mice, in which Drd2 is selectively deleted in DA-neurons, we observed enhanced excitatory and inhibitory responses of VTA DA-neurons to aversive stimuli, suggesting that autoD2R acts as a critical regulatory brake. Importantly, this modulation occurred independently of either the pacemaker activity of DA-neurons or their coupling to the non-selective sodium leak channel NALCN. Behaviorally, Drd2Slc6a3 male mice showed enhanced discrimination between threat-predicting and non-predicting cues that persisted during extinction learning, highlighting a sex-biased role of autoD2R in threat processing. Our results provide new mechanistic insights through which autoD2R influence behavioral responses to aversive stimuli, with implications for understanding neuropsychiatric disorders characterized by maladaptive threat processing.

neuroscience↗

bioRxiv2024

A dorsal hippocampus-prodynorphinergic dorsolateral septum-to-lateral hypothalamus circuit mediates contextual gating of feeding

Adaptive regulation of feeding depends on linkage of internal states and food outcomes with contextual cues. Human brain imaging has identified dysregulation of a hippocampal-lateral hypothalamic area (LHA) network in binge eating, but mechanistic instantiation of underlying cell-types and circuitry is lacking. Here, we identify an evolutionary conserved and discrete Prodynorphin (Pdyn)-expressing subpopulation of Somatostatin (Sst)-expressing inhibitory neurons in the dorsolateral septum (DLS) that receives primarily dorsal, but not ventral, hippocampal inputs. DLS(Pdyn) neurons inhibit LHA GABAergic neurons and confer context- and internal state-dependent calibration of feeding. Viral deletion of Pdyn in the DLS mimicked effects seen with optogenetic silencing of DLS Pdyn INs, suggesting a potential role for DYNORPHIN-KAPPA OPIOID RECEPTOR signaling in contextual regulation of food-seeking. Together, our findings illustrate how the dorsal hippocampus has evolved to recruit an ancient LHA feeding circuit module through Pdyn DLS inhibitory neurons to link contextual information with regulation of food consumption. HIGHLIGHTSO_LIDLS(Pdyn) neurons receive dense input from the dorsal but not ventral hippocampus C_LIO_LIDLS(Pdyn) neurons inhibit GABAergic neurons in the LHA C_LIO_LISilencing dorsal hippocampus-DLS(Pdyn)-LHA circuit nodes abolishes context-conditioned feeding C_LIO_LIPdyn in the DLS is necessary for context-conditioned feeding C_LI

neuroscience↗

bioRxiv2023

Flight heights of Scopoli s shearwaters Calonectris diomedea in the context of offshore wind farm developments

Seabird face new risks through collisions with offshore wind turbines. Wind energy projects are emerging in the Mediterranean Sea, and unbiased knowledge on seabird flight altitudes are scarce in this area. Indeed, previous flight height observations were carried out from boats during daytime, and only in good weather conditions. We measured flight heights of 13 Scopolis shearwaters, Calonectris diomedea, one of the three endemic shearwater species in the Mediterranean, using highly precise barometric data loggers. The birds were equipped at the largest French colony of Scopolis shearwater in the Marseille archipelago. Birds from this location routinely visit forthcoming wind farm areas, within 50 km of their breeding site. We found that Scopolis shearwaters flew at very low altitudes with a mean flight height of 1.8 {+/-} 2.7 m ({+/-} SD) above sea level. Birds therefore rarely (<0.02%) flew within the vertical envelop of collision risk with wind turbines. Ours results are coherent with field observations and the dynamic soaring flight technique used by shearwaters. Nevertheless, collision risk may increase following behavioural modifications close to wind turbines.

ecology↗

bioRxiv2022

Plants stand still but hide: imperfect and heterogeneous detection is the rule when counting plants

O_LIThe estimation of population size and its variation across space and time largely relies on counts of individuals, generally carried out within spatial units such as quadrats or sites. Missing individuals during counting (i.e. imperfect detection) results in biased estimates of population size and trends. Imperfect detection has been shown to be the rule in animal studies, and most studies now correct for this bias by estimating detection probability. Yet this correction remains exceptional in plant studies, suggesting that most plant ecologists implicitly assume that all individuals are always detected. C_LIO_LITo assess if this assumption is valid, we conducted a field experiment to estimate individual detection probability in plant counts conducted in 1x1 m quadrats. We selected 30 herbaceous plant species along a gradient of conspicuousness at 24 sites along a gradient of habitat closure, and asked groups of observers to count individuals in 10 quadrats using three counting methods requiring progressively increasing times to complete (quick count, unlimited count and cell count). In total, 158 participants took part in the experiment, allowing an analysis of the results of 5,024 counts. C_LIO_LIOver all field sessions, no observer succeeded in detecting all the individuals in the 10 quadrats. The mean detection rate was 0.44 (ranging from 0.11 to 0.82) for the quick count, 0.59 for the unlimited count (range 0.18-0.87) and 0.74 for the cell count (range 0.46-0.94). C_LIO_LIDetection probability increased with the conspicuousness of the target species and decreased with the density of individuals and habitat closure. The observers experience in botany had little effect on detection probability, whereas detection was strongly affected by the time observers spent counting. Yet although the more time-consuming methods increased detection probability, none achieved perfect detection, nor did they reduce the effect on detection probability of the variables we measured. C_LIO_LISynthesis. Our results show that detection is imperfect and highly heterogeneous when counting plants. To avoid biased estimates when assessing the size, temporal or spatial trends of plant populations, plant ecologists should use methods that estimate the detection probability of individuals rather than relying on raw counts. C_LI

ecology↗

bioRxiv2022

Choice of climate data influences current and future global invasion risks for two Phelsuma geckos

Invasion risks may be influenced either negatively or positively by climate change, depending on the species. These can be predicted with species distribution models, but projections can be strongly affected by input environmental data (climate data source, Global Circulation Models and Shared Socio-economic Pathways SSP). We modelled the distribution of Phelsuma grandis and P. laticauda, two Malagasy reptiles that are spreading globally. We accounted for drivers of spread and establishment using socio-economic factors (e.g., distance from ports) and two climate data sources, i.e., Climatologies at High Resolution for the Earths and Land Surface Areas (CHELSA) and Worldclim. We further quantified the degree of agreement in invasion risk models that utilised CHELSA and Worldclim data for current and future conditions. Most areas identified as highly exposed to invasion risks were consistently identified (e.g. in Caribbean and Pacific Islands). However, projected risks differed locally. We also found notable differences in quantitative invasion risk (3% difference in suitability scores for P. laticauda and up to 14% for P. grandis) under current conditions. Despite both species native distributions overlap substantially, climate change will drive opposite responses on invasion risks by 2070 (decrease for P. grandis, increase for P. laticauda). Overall, projections of future invasion risks were the most affected by climate data source, followed by SSP. Our results highlight that assessments of current and future invasion risks are sensitive to the climate data source, especially in Islands. We stress the need to account for multiple climatologies when assessing invasion risks.

ecology↗

bioRxiv2022

The DeepFaune initiative: a collaborative effort towards the automatic identification of the French fauna in camera-trap images

Camera traps have revolutionized how ecologists monitor wildlife, but their full potential is realized only when the hundreds of thousands of collected images can be readily classified with minimal human intervention. Deep-learning classification models have allowed extraordinary progress towards this end, but trained models remain rare and are only now emerging for European fauna. We report on the first milestone of the DeepFaune initiative (https://www.deepfaune.cnrs.fr), a large-scale collaboration between more than 50 partners involved in wildlife research, conservation and management in France. We developed a classification model trained to recognize 26 species or higher-level taxa. The classification model achieved 0.97 validation accuracy and often >0.95 precision and recall for many classes. These performances were generally higher than 0.90 when tested on independent out-of-sample datasets for which we used image redundancy contained in sequence of images. We implemented our model in a software to classify images stored locally on a personal computer, so as to provide a free, user-friendly and high-performance tool for wildlife practitioners to automatically classify camera-trap images.

ecology↗

bioRxiv2021

Noninvasive genetic sampling of two flying fox species provides a high rate of genotyping success and a low error rate during amplification

Noninvasive genetic sampling techniques are useful tools for providing genetic data that are crucially needed for determining suitable conservation actions. Yet these methods may be highly unreliable in certain situations for instance, when working with faecal samples of frugivorous species in tropical areas. In this study, we tested the applicability of noninvasive genetic sampling on two Comoro Islands flying fox species: Pteropus livingstonii and P.seychellensis comorensis in order to optimize the sampling and laboratory process. Both mitochondrial (mtDNA) and microsatellite markers were tested using two common faeces conservation protocols (ethanol and silica gel), and the polymerase chain reaction (PCR) success and genotyping error rates were assessed. The average proportion of mtDNA PCRs positive results was 55% for P.livingstonii and 38% for P.s.comorensis, and higher amplification success was obtained for samples preserved in ethanol as compared to silica gel. The average genotyping success rate was high (74% for P.livingstonii and 95% for P.s.comorensis) and the genotyping error rate was low for both species. Despite our results confirm the effectiveness of using noninvasive genetic sampling methods to study flying fox species, the protocol we used can be optimized to provide higher efficiency. Some recommendations related to field sampling protocols and laboratory methods are proposed in order to optimize amplification rate and minimize genotyping errors.

ecology↗

bioRxiv2021

What is the main driver of unsustainable natural resource use in the Comoro Islands?

The Comoros archipelago is a biodiversity hotspot by virtue of its high level of endemism. However, it suffers one of the highest rates of forest loss worldwide, mainly due to strong anthropogenic pressures. As Comorian populations depend on forest resources for subsistence, establishing relevant conservation strategies for their sustainable management requires the consideration of multiple stakeholders perspectives toward biodiversity and habitat conservation. To better understand the relationships between humans and nature; how comorian people use natural resource and the relevance of a protected area for long-term biodiversity conservation, we used Q-methodology to assess local people s perceptions regarding biodiversity and conservation actions. Three discourses are identified during analysis: "Pro-environment discourse", "Keeping things as usual" and "Social and environmental concerns". According to the results, employed respondents, were favorable to long-term forest and biodiversity conservation. In contrast, unemployed respondents were in favor of more immediate benefits while unemployed but educated respondents were in favor to both long-term forest conservation and immediate benefits from forests. This suggests that the lack of livelihoods for rural people is the main factor leading them to overharvest natural resources. These results suggest that biodiversity conservation of the Comoros archipelagos may benefit for plan aiming at (1) developing tourism and maintaining sustainable production of crops and livestock that could allow enhancing the livelihoods and well-being of all social groups, (2) developing projects such as local markets that could allow villagers to sell their agricultural production, (3) setting up awareness campaign for tree-planting and reforestation. Reforestation could allow re-establishing natural plants and make large trees available for long-term purposes.

scientific communication and education↗

bioRxiv2019

Anthropogenic disturbance drives dispersal syndromes, demography, and gene flow in spatially structured amphibian populations

There is growing evidence that anthropogenic landscapes can strongly influence the evolution of dispersal, particularly through fragmentation, and may drive organisms into an evolutionary trap by suppressing dispersal. However, the influence on dispersal evolution of anthropogenic variation in habitat patch turnover has so far been largely overlooked. In this study, we examined how human-driven variation in patch persistence affects dispersal rates and distances, determines dispersal-related phenotypic specialization, and drives neutral genetic structure in spatially structured populations. We addressed this issue in an amphibian, Bombina variegata, using an integrative approach combining capture-recapture modeling, demographic simulation, common garden experiments, and population genetics. B. variegata reproduces in small ponds that occur either in habitat patches that are persistent (i.e. several decades or more), located in riverine environments with negligible human activity, or in patches that are highly temporary (i.e. a few years), created by logging operations in intensively harvested woodland. Our capture-recapture models revealed that natal and breeding dispersal rates and distances were drastically higher in spatially structured populations (SSPs) in logging environments than in riverine SSPs. Population simulations additionally showed that dispersal costs and benefits drive the fate of logging SSPs, which cannot persist without dispersal. The common garden experiments revealed that toadlets reared in laboratory conditions have morphological and behavioral specialization that depends on their habitat of origin. Toadlets from logging SSPs were found to have higher boldness and exploration propensity than those from riverine SSPs, indicating transgenerationally transmitted dispersal syndromes. We also found contrasting patterns of neutral genetic diversity and gene flow in riverine and logging SSPs, with genetic diversity and effective population size considerably higher in logging than in riverine SSPs. In parallel, intra-patch inbreeding and relatedness levels were lower in logging SSPs. Controlling for the effect of genetic drift and landscape connectivity, gene flow was found to be higher in logging than in riverine SSPs. Taken together, these results indicate that anthropogenic variation in habitat patch turnover may have an effect at least as important as landscape fragmentation on dispersal evolution and the long-term viability and genetic structure of wild populations.

ecology↗

bioRxiv2019

Efficient use of harvest data: An integrated population model for exploited animal populations

O_LIMany populations are affected by hunting or fishing. Models designed to assess the sustainability of harvest management require accurate estimates of demographic parameters (e.g. survival, reproduction) hardly estimable with limited data collected on exploited populations. The joint analysis of different data sources with integrated population models (IPM) is an optimal framework to obtain reliable estimates for parameters usually difficult to estimate, while accounting for imperfect detection and observation error. The IPM built so far for exploited populations have integrated count-based surveys and catch-at-age data into ageclass structured population models. But the age of harvested individuals is difficult to assess and often not recorded, and population counts are often not performed on a regular basis, limiting their use for the monitoring of exploited populations.\nC_LIO_LIHere, we propose an IPM that makes efficient use of data commonly collected in exploited marine and terrestrial populations of vertebrates. As individual measures of body mass at both capture and death are often collected in fish and terrestrial game species, our model integrates capture-mark-recapture-recovery data and data collected at death into a body mass-structured population model. It allows the observed number of individuals harvested to be compared with the expected number and provides accurate estimates of demographic parameters.\nC_LIO_LIWe illustrate the usefulness of this IPM using an emblematic game species distributed worldwide, the wild boar Sus scrofa, as a case study. For this species that has increased in distribution and abundance over the last decades, the model provides accurate and precise annual estimates of key demographic parameters (survival, reproduction, growth) and of population size while accounting for imperfect detection and observation error.\nC_LIO_LITo avoid an overexploitation of declining populations or an under-exploitation of increasing populations, it is crucial to gain a good understanding of the dynamics of exploited populations. When managers or conservationists have limited demographic data, the IPM offers a powerful framework to assess population dynamics. Being highly flexible, the approach is broadly applicable to both terrestrial and marine exploited populations for which measures of body mass are commonly recorded and more generally, to all populations suffering from anthropogenic mortality causes.\nC_LI

ecology↗

bioRxiv2019

Drivers of amphibian population dynamics and asynchrony at local and continental scales

O_LIIdentifying the drivers of population fluctuations in spatially distinct populations remains a significant challenge for ecologists. Whereas regional climatic factors may generate population synchrony (i.e., Moran effect), local factors including the level of density-dependence may reduce the level of synchrony. Although divergences in the scaling of population synchrony and spatial environmental variation have been observed, the regulatory factors that underlie such mismatches are poorly understood.\nC_LIO_LINo previous studies have investigated how density-dependent processes and population-specific responses to weather variation influence spatial synchrony at both local and continental scales. We addressed this issue in a pond-breeding amphibian, the great crested newt (Triturus cristatus). We used capture-recapture data collected through long-term surveys in five T. cristatus populations in Western Europe.\nC_LIO_LIWe found a low level of demographic synchrony at both local and continental levels. Weather has weak and spatially variable effects on survival, recruitment and population growth rate. In contrast, density-dependence was a common phenomenon (at least for population growth) in almost all populations and subpopulations.\nC_LIO_LIOur findings support the idea that Morans effect is low in species where the population dynamics more closely depends on local factors (e.g. population density and habitat characteristics) than on large-scale environmental fluctuation (e.g. regional climatic variation). Those demographic feature likely have far-reaching consequences for the long-term viability of the spatially structured populations and their ability to response to large-scale climatic anomalies.\nC_LI

ecology↗

bioRxiv2018

Survival cost to relocation does not reduce population self-sustainability in an amphibian

O_LIRelocations are increasingly popular among wildlife managers despite sharp debate and low rate of relocation success in vertebrates. In this context, understanding the influence of extrinsic (e.g., relocation design, habitat characteristics) and intrinsic factors (e.g., age and sex) on demographic parameters such as survival that regulate the dynamics of relocated populations is critical to improve relocation protocols and better predict relocation success.\nC_LIO_LIWe investigated survival in naturally established and relocated populations of yellow-bellied toads (Bombina variegata), an amphibian that was nearly extinct in Belgium by the late 1990s. We quantified survival at three ontogenetic stages (juvenile, subadult, and adult) in the relocated population, the source population, and a control population. In the relocated population, we quantified survival in captive bred individuals and their locally born descendants.\nC_LIO_LIWe showed that survival at juvenile and subadult stages was relatively similar in all populations. In contrast, relocated adult survival was lower than adult survival in the source and control populations. Despite this, offspring of relocated animals (the next generation, regardless of life stage) survived at similar rates to offspring in the source and control populations. Our simulations revealed that the relocated population was self-sustaining under different scenarios and that the fate (e.g., stability or finite rate of increase) of the simulated populations was highly dependent on the fecundity of relocated adults and their offspring.\nC_LIO_LIPolicy implications. Our results indicate that survival in relocated individuals is lower than in non-relocated individuals but that this cost (= reduced survival) disappears in the second generation. A finer understanding of how relocation affects demographic processes is an important step in improving relocation success of amphibians and other animals.\nC_LI

ecology↗

bioRxiv2018

Environmentally mediated reproductive success predicts breeding dispersal decisions in an early successional amphibian

Dispersal is a central mechanism in ecology and evolution. Dispersal evolution is driven by a trade-off between costs and benefits, which is influenced by inter-individual variability and local environmental conditions (context-dependent dispersal). Many studies have investigated how dispersal decisions may be influenced by environmental factors, including density, predation, and interspecific competition. Yet few have attempted to examine how habitat disturbance may affect the dispersal process in spatially structured populations. In early successional species, one might expect individuals to adjust their dispersal decisions based on two main factors that potentially have an influence on reproductive success: patch size and the level of patch disturbance. In this study, we examined how these two factors affect breeding success and dispersal decisions in an early successional amphibian, the yellow-bellied toad (Bombina variegata). To this end, we used capture-recapture data collected on a spatially structured population occupying 28 breeding patches. We took advantage of recent developments in multievent capture-recapture models to detect signs of context-dependent dispersal. The results revealed that the probability of successful reproduction and the number of newly metamorphosed individuals increased with both the size and the proportion of disturbance of a patch. In addition, our results showed that the factors affecting breeding success also influenced breeding dispersal probability. Large patch size negatively influenced emigration probability; in contrast, it positively influenced immigration probability. Equally, higher disturbance (in terms of the proportion of the patchs surface area disturbed each year) had a strong negative influence on emigration probability and slightly positively affected immigration probability. These findings strongly suggest that individuals make context-dependent dispersal decisions, adjusted to maximize future fitness prospects in a patch, allowing them to better cope with rapid changes in environmental conditions resulting from the ecological succession process. This opens new areas of potential research into the role of dispersal in organism specialization along an ecological succession gradient.

ecology↗

bioRxiv2018

Toads and roads: transport infrastructure severely impacts dispersal regardless of life stage

Transport infrastructure such as roads has been reported to negatively affect dispersal. Their effects on dispersal are thought to be complex, depending on the characteristics of the structure and the intensity of the traffic using it. In addition, individual factors, such as age, may strongly affect dispersal decisions and success when individuals are confronted with transport infrastructure. Despite the importance of this topic for wildlife conservation, few studies have investigated the effect of transport infrastructure on individuals dispersal decisions before and after sexual maturity. We examined the effects on two kinds of infrastructure, gravel tracks and paved roads, on the dispersal of an endangered amphibian, the yellow-bellied toad (Bombina variegata). We used capture-recapture data collected during a five-year period on a large, spatially structured population of B. variegata. Our study revealed that emigration rates increased with an individuals age, while dispersal distance decreased. It also showed that both tracks and roads had negative effects on dispersal. The negative effect of roads was stronger than that of tracks. We additionally found that the effect of tracks on dispersal slightly decreased with a toads age. In contrast, the negative effect of roads was severe and relatively similar across age classes.

ecology↗