Biology subjects

Castagneyrol, B.

Publications and source records attributed to Castagneyrol, B..

15 recordsLinked to original sources

bioRxiv2024

Urban tree diversity fosters bird insectivory despite a loss in bird diversity with urbanization

Urbanization is one of the main drivers of biotic homogenization in bird communities worldwide. Yet, only a few studies have addressed its functional consequences on the top-down control birds exert on insect herbivores. We hypothesized that their inconsistent results reflect the overlooked heterogeneity of the urban habitat for birds, and in particular the distribution and diversity of urban trees. We monitored tree diversity, bird diversity, avian predation attempts on artificial prey, and the effect of bird exclusion on insect herbivory in 97 trees distributed among 24 urban experimental plots in the city of Montreal, Canada. We characterized urbanization levels through a combination of variables related to tree density, impervious surfaces, anthropic noise, and human population density. Bird diversity decreased with increasing urbanization, whereas the frequency of generalist synurbic species increased. We found no significant relationship between predation and urbanization or between predation and bird diversity. However, tree diversity was positively correlated with predation attempts on artificial prey, irrespective of bird diversity. We revealed a mismatch between the effects of urbanization on bird diversity and on the regulation service and unraveled the functional importance of tree diversity in shaping the avian predation function in urban ecosystems. Our study advocates for the consideration of intra-urban heterogeneity in the investigation of trophic cascades within cities.

ecology↗

bioRxiv2023

Assessing the potential of BirdNET to infer European bird communities from large-scale ecoacoustic data

O_LIPassive acoustic monitoring has become increasingly popular as a practical and cost-effective way of obtaining highly reliable acoustic data in ecological research projects. Increased ease of collecting these data means that, currently, the main bottleneck in ecoacoustic monitoring projects is often the time required for the manual analysis of passively collected recordings. In this study we evaluate the potential and current limitations of BirdNET-Analyzer v2.4, the most advanced and generic deep learning algorithm for bird recognition to date, as a tool to assess bird community composition through the automated analysis of large-scale ecoacoustic data. C_LIO_LITo this end, we study 3 acoustic datasets comprising a total of 629 environmental soundscapes collected in 194 different sites spread across a 19{degrees} latitude span in Europe. We analyze these recordings both with BirdNET and by manual listening by local expert birders, and we then compare the results obtained through the two methods to evaluate the performance of the algorithm both at the level of each single vocalization and for entire recording sequences (1, 5 or 10 min). C_LIO_LIOur analyses reveal that BirdNET identifications can be highly reliable if a sufficiently high minimum confidence threshold is used. However, the current recall of the algorithm is markedly low when the minimum confidence threshold is adjusted to ensure high levels of precision. Thus, we found that F1-scores remain moderate (<0.5) for all datasets and confidence thresholds studied. We therefore estimate that acoustic datasets of extended duration are currently necessary for BirdNET to provide a reliable and minimally comprehensive picture of the target bird community. Our results also suggest that BirdNET performance is not significantly influenced by the type of recorder used or the habitat recorded but is modulated by the volume of species-specific acoustic data available online. C_LIO_LIWe conclude that a judicious use of AI-based IDs provided by BirdNET can represent a novel and powerful method to assist in the assessment of bird community composition through the automated analysis of large-scale ecoacoustic data. Finally, we provide best use recommendations to ensure optimal results from the algorithm for the ecological study of bird communities. C_LI

ecology↗

bioRxiv2022

Impact of early insect herbivory on the invasive oak lace bug (Corythucha arcuata Say, 1832) in different oak species

Insect herbivores co-occurring on the same host plant interact in various ways. In particular, early-season insect herbivory triggers a wide range of plant responses that can determine the performance of herbivores colonizing the plant later in the course of the season. But the strength and direction of such effects are debated, and virtually unknown in the case of novel interactions involving exotic insects in their introduction range. We conducted an observational field study in SW France, a region recently invaded by the Oak Lace Bug (OLB, Corythucha arcuata Say). We measured early chewing damage and subsequent OLB damage in four oak species (Quercus robur, Q. pubescens, Q. cerris and Q. ilex). We set up a complementary non-choice experiment in the laboratory, feeding OLB with leaves with or without prior herbivory. The four oak species differed in their sensitivity to OLB damage, Q. ilex being broadly resistant. Prior herbivory promoted OLB damage in the laboratory experiment, but not in the field. However, prior herbivory did not alter the rank of oak resistance to the OLB. Our results suggest possible synergistic effects between spring defoliators and the OLB. This study brings insight into herbivore-herbivore interactions and their possible implications for forest management.

ecology↗

bioRxiv2022

Tree diversity and density affect damage caused by the invasive pest Cameraria ohridella in urban areas

Invasive, non-native invasive pests pose a growing threat to urban trees and the services they provide to urban residents. With the reluctance to use chemical insecticides in cities, environmentally friendly methods of pest management are needed. Tree diversity is known to affect insect herbivory in forest, with higher tree species diversity leading to lower level of damage. However, the validity of those findings for a non-native insect in an urban environment remains to be demonstrated. We monitored 54 horse chestnut trees attacked by the invasive horse chestnut leafminer Cameraria ohridella in the city of Bordeaux, France. We analyzed the effects of neighboring tree diversity and density on the abundance, damage and parasitism rate of these leafminers. We showed that the abundance and damage of C. ohridella significantly increased with higher local tree canopy cover. We found that the parasitism rate of C. ohridella increased with the species diversity of neighboring trees. However, this increase in parasitism rate was not associated with a decrease in leaf area damaged. Our results pave the way for the management of exotic insect pests in cities based on the manipulation of spatial distribution and species diversity of urban trees.

ecology↗

bioRxiv2021

Following the track: accuracy and reproducibility of predation assessment on artificial caterpillars

Experimental studies of biotic interactions in real field conditions are essential to understand the structure and functioning of ecological networks. The use of artificial caterpillars to mimic actual prey availability is generally seen as a standard approach to compare the activity and diversity of predators along environmental gradients. Yet, even with standardized material and procedures, biases may still affect data from multiple observers with different expertise. We used pictures of artificial caterpillars with or without various predation marks, in an online survey that was targeted for the participants of the project, to evaluate the reliability of predation marks identification made by non-scientists and by scientists with and without previous experience in predation mark identification. Pictures of artificial caterpillars displayed typical marks left by birds, mammals and arthropods, as well as non-predation marks ( false positive). 357 respondents scanned 7140 pictures of these pictures. Self-declared scientists were more confident and accurate in their observations than non-scientists, but the differences in correct identifications among scientists and non-scientists were low. Self-declared scientists with previous experience were also more accurate than scientists without previous experience, while there were no differences in self-confidence among scientists with and without previous experience. Accuracy in predation mark identification did not differ among types of predators, but respondents were more keen to identify marks left by birds or mammals than arthropods. Our results have practical implications for the design of multi-observer projects relying on artificial caterpillars as a proxy to assess predation intensity, in particular in the context of citizen science.

ecology↗

bioRxiv2021

Meta-analysis of tree diversity effects on the abundance, diversity and activity of herbivores' enemies

O_LIThe natural enemies hypothesis predicts that the abundance and diversity of antagonists such as predators and parasitoids of herbivores increases with the diversity of plants, which can lead to more effective top-down control of insect herbivores. However, although the hypothesis has received large support in agricultural systems, fewer studies have been conducted in forest ecosystems and a comprehensive synthesis of previous research is still lacking. C_LIO_LIWe conducted a meta-analysis of 65 publications comparing the diversity, abundance or activity of various groups of natural enemies (including birds, bats, spiders and insect parasitoids) in pure vs. mixed forest stands. We tested the effects of forest biome, natural enemy taxon and type of study (managed vs experimental forest). C_LIO_LIWe found a significant positive effect of forest tree diversity on natural enemy abundance and diversity but not on their activity. The effect of tree diversity on natural enemies was stronger towards lower latitudes but was not contingent on the natural enemy taxon level. C_LIO_LIOverall, our study contributes toward a better understanding of the "natural enemies hypothesis" in forest systems and provides new insights about the mechanisms involved. Furthermore, we outline potential avenues for strengthening forest resistance to the growing threat of herbivorous insects. C_LI

ecology↗

bioRxiv2021

Tree diversity effects on forest productivity: disentangling the effects of tree species addition vs. substitution

O_LIMixture effect on stand productivity is usually apprehended through a substitutive approach, whereby productivity in mixed stands is compared to productivity in monocultures, at equivalent stand density. This approach has proved that in many cases mixed stands perform better than monospecific forests, however, we do not yet have a solid theory about species behaviour in the mixture or even guidelines for combining species. The addition of a second tree species to an existing mono-specific stand has received much less consideration. Yet, this approach has the potential to separate the facilitation effect from the complementarity effect. C_LIO_LIWe compared the effect of tree species substitution vs. addition on the productivity of maritime pine and silver birch in a young tree diversity experiment implemented in 2008 in SW France. C_LIO_LISubstituting pines with birches to create two-species mixtures resulted in an increase of tree productivity at stand level beyond what was expected from monocultures (i.e., overyielding). In contrast, creating mixture through the addition of birches to pine stands had no effect on the maritime pine stand productivity (transgressive mixture effect not significant). This absence of effect is produced by two distinct density-dependence responses at an individual level. C_LIO_LIOur results allow clarifying the cases in which a mixed stand can be considered as an alternative to a monoculture of a productive species. In particular, the addition of a pioneer and soil low-demanding species during young developmental stages is a possibility to diversify the stand and potentially to increase ecosystem services without altering the productivity of the target species. C_LI

ecology↗

bioRxiv2020

Host-mediated, cross-generational intraspecific competition in a multivoltine herbivore species

AO_SCPLOWBSTRACTC_SCPLOWConspecific insect herbivores co-occurring on the same host plant interact both directly through interference competition and indirectly through exploitative competition, plant-mediated interactions and enemy-mediated interactions. However, the situation is less clear when the interactions between conspecific insect herbivores are separated in time within the same growing season, as it is the case for multivoltine species. We hypothesized that early season herbivory would result in reduced egg laying and reduced performance of the next generation of herbivores on previously attacked plants. We tested this hypothesis in a choice experiment with box tree moth females (Cydalima perspectalis Walker, Lepidoptera: Crambidae). These females were exposed to box trees (Buxus sempervirens L., Buxaceae) that were either undamaged or attacked by conspecific larvae earlier in the season. We then compared the performance of the next generation larvae on previously damaged vs undamaged plants. Previous herbivory had no effect on oviposition behaviour, but the weight of next generation larvae was significantly lower in previously damaged plants. There was a negative correlation between the number of egg clutches laid on plants by the first generation and the performance of the next generation larvae. Overall, our findings reveal that early season herbivory reduces the performance of conspecific individuals on the same host plant later in the growing season, and that this time-lagged intraspecific competition results from a mismatch between the oviposition preference of females and the performance of its offspring.

ecology↗

bioRxiv2020

Insect herbivory on urban trees: Complementary effects of tree neighbours and predation

O_LIInsect herbivory is an important component of forest ecosystems functioning and can affect tree growth and survival. Tree diversity is known to influence insect herbivory in natural forest, with most studies reporting a decrease in herbivory with increasing tree diversity. Urban ecosystems, on the other hand, differ in many ways from the forest ecosystem and the drivers of insect herbivory in cities are still debated. C_LIO_LIWe monitored 48 urban trees from five species - three native and two exotic - in three parks of Montreal (Canada) for leaf insect herbivory and predator activity on artificial larvae, and linked herbivory with both predation and tree diversity in the vicinity of focal trees. C_LIO_LILeaf insect herbivory decreased with increasing tree diversity and with increasing predator attack rate. C_LIO_LIOur findings indicate that tree diversity is a key determinant of multitrophic interactions between trees, herbivores and predators in urban environments and that managing tree diversity could contribute to pest control in cities. C_LI This article has been peer-reviewed and recommended by Peer Community in Ecology https://doi.org/10.24072/pci.ecology.100061

ecology↗

bioRxiv2020

Biotic and abiotic drivers of soil microbial functions across tree diversity experiments

AimSoil microorganisms are essential for the functioning of terrestrial ecosystems. Although soil microbial communities and functions may be linked to the tree species composition and diversity of forests, there has been no comprehensive study of how general potential relationships are and if these are context-dependent. A global network of tree diversity experiments (TreeDivNet) allows for a first examination of tree diversity-soil microbial function relationships across environmental gradients. LocationGlobal Major Taxa StudiedSoil microorganisms MethodsSoil samples collected from eleven tree diversity experiments in four biomes across four continents were used to measure soil basal respiration, microbial biomass, and carbon use efficiency using the substrate-induced respiration method. All samples were measured using the same analytical device in the same laboratory to prevent measurement bias. We used linear mixed-effects models to examine the effects of tree species diversity, environmental conditions, and their interactions on soil microbial functions. ResultsAcross biodiversity experiments, abiotic drivers, mainly soil water content, significantly increased soil microbial functions. Potential evapotranspiration (PET) increased, whereas soil C-to-N ratio (CN) decreased soil microbial functions under dry soil conditions, but high soil water content reduced the importance of other abiotic drivers. Tree species richness and phylogenetic diversity had overall similar, but weak and context-dependent (climate, soil abiotic variables) effects on soil microbial respiration. Positive tree diversity effects on soil microbial respiration were most pronounced at low PET, low soil CN, and high tree density. Soil microbial functions increased with the age of the experiment. Main conclusionsOur results point at the importance of soil water content for maintaining high levels of soil microbial functions and modulating effects of other environmental drivers. Moreover, overall tree diversity effects on soil microbial functions seem to be negligible in the short term (experiments were 1-18 years old). However, context-dependent tree diversity effects (climate, soil abiotic variables) have greater importance at high tree density, and significant effects of experimental age call for longer-term studies. Such systematic insights are key to better integrate soil carbon dynamics into the management of afforestation projects across environmental contexts, as todays reforestation efforts remain focused largely on aboveground carbon storage and are still dominated by less diverse forests stands of commercial species.

ecology↗

bioRxiv2019

Leaf chemical defences and insect herbivory in oak: accounting for canopy position unravels marked genetic relatedness effects

Background and AimsHighly controlled experiments revealed that plant genetic diversity and relatedness can shape herbivore communities and patterns of herbivory. Evidence from the field is scarce and inconsistent. We assessed whether a genetic signal underlying herbivory can be detected in oak forest stands when accounting for variation at smaller (within-tree) and larger (among-stand) scales. MethodsWe tested relationships between tree genetic relatedness, leaf chemical defences and insect herbivory at different canopy layers in 240 trees from 15 Pedunculate oak (Quercus robur) forest stands and partitioned sources of variability in herbivory and defences among stands, individuals, and branches. Key ResultsLeaf defences, insect herbivory, and their relationship differed systematically between the upper and the lower tree canopy. When accounting for this canopy effect, the variation explained by tree genetic relatedness rose from 2.8 to 34.1 % for herbivory and from 7.1 to 13.8 % for leaf defences. The effect was driven by markedly stronger relationships in the upper canopy. ConclusionsOur findings illustrate that properly accounting for other sources of variation acting at different scales can reveal potentially relevant effects of the host plant genotype on patterns of leaf chemical defences and associated insect herbivory in natural tree populations.

ecology↗

bioRxiv2019

Growth and mortality of the oak processionary moth, Thaumetopoea processionea L., on two oak species: direct and trait-mediated effects of host and neighbour species identity

The presence of heterospecific neighbours can affect damage caused by pest insects on focal plants. However, how plant neighbours influence herbivore performance is poorly understood. We tested the independent and interactive effects of tree species identity and tree neighbour type (conspecific vs. heterospecific) on the performance of a major oak pest, the oak processionary moth larvae (OPM, Thaumetopoea processionea) fed on Quercus robur and Q. petraea. We performed a factorial greenhouse experiment in which we grew two oak saplings per pot, either from the same species or from both species. We quantified growth and mortality of OPM larvae, leaf phenolic compounds, C:N ratio and bud phenology. OPM larvae performed significantly better on Q. petraea than on Q. robur, regardless of plant neighbour type. Phenolic compounds and C:N, but not phenology, differed between oak species and neighbour species identity. Only bud phenology had a significant effect on OPM performance, which was better when young larvae had access to recently unfolded leaves, regardless of oak species and neighbour identity. Although oak neighbour identity altered the expression of leaf traits, this effect had no measurable consequences on OPM performance. However, further studies should consider the effect of oak species neighbour on OPM preferences for either Q. robur or Q. petraea, in pure and mixed stands, before translating current results into recommendations for forest management. Author ContributionTD and BC conceived the study and acquired the data. TD performed experiment and analysed the data. EV, TD and XM performed the chemical analyses. TD and BC drafted the first version of the manuscript and all authors wrote the final version of the manuscript. TD, BC conceived and designed research. TD performed experiment and analysed data. EV, TD, XM performed the chemical analyses. TD, BC wrote the manuscript. All authors read and approved the manuscript. AM and DB conceived and designed research. AM and BB conducted experiments. GR contributed new reagents or analytical tools. AM, BB and GR analysed data. AM wrote the manuscript. All authors read and approved the manuscript.

ecology↗

bioRxiv2019

Can school children support ecological research? Lessons from the ‘Oak bodyguard’ citizen science project

Scientific knowledge in the field of ecology is increasingly enriched by data acquired by the general public participating in citizen science (CS) programs. Yet, doubts remain about the reliability of such data, in particular when acquired by school children. We built upon an ongoing CS program - Oak bodyguards - to assess the ability of European schoolchildren to accurately estimate the strength of biotic interactions in terrestrial ecosystems. We used standardized protocols to estimate predation rates on artificial caterpillars and insect herbivory on oak leaves and compared estimates made by school children, trained and untrained professional scientists (with no or limited expertise in predation or herbivory assessment). Compared to trained scientists, both schoolchildren and untrained professional scientists overestimated predation rates, but assessments made by the latter were more consistent. School children overestimated insect herbivory, as did untrained professional scientists. Thus, raw data acquired by school children participating in CS programs cannot be used and require several quality checks. However, such data are of no less value than data collected by untrained professional scientists and can be calibrated for bias.

scientific communication and education↗

bioRxiv2019

Insect herbivory and avian insectivory in novel native oak forests: divergent effects of stand size and connectivity

The value of novel native broadleaf woodlands for biodiversity conservation is important to consider for adequate forest management in rural landscapes. Passive reforestation has been proposed as a cost-efficient tool for creating networks of novel native forest stands that would help restoring biodiversity and associated ecosystem services. Yet to date the ecological functioning of such stands remains strongly understudied compared to forest remnants resulting from longer-term fragmentation. We assessed how the size and connectivity of newly established Pedunculate oak (Quercus robur L.) stands in rural landscapes of SW France affect rates of herbivory by different insect guilds as well as rates of avian insectivory and the abundance and richness of insectivorous birds. Comparing 18 novel forest stands along a gradient of size (0.04-1.15 ha) and cover of broadleaf forests in the surroundings (0-30% within a 500 radius), we found that even the smallest stands are colonised by leaf miners and chewers/skeletonizers, and that rates of herbivory are globally comparable to those reported from older and larger oak forests. The size of stands had a relatively minor effect on herbivory, whereas it increased the abundance of insectivorous bird. It also determined rates of avian insectivory as estimated by an experiment with plasticine caterpillars. These rates were however rather low and unrelated with the extent of herbivory in the stand. Overall, our study indicates that insect herbivores tend to react more rapidly to the establishment of novel native forests than their avian predators as the latter may depend on the development of larger patches of suitable habitat in the surrounding landscape. To favour a rapid build-up of diverse, and hence stable, trophic networks involving insect herbivores and their predators, woodland creation schemes should therefore primarily focus on habitat size and quality.

ecology↗

bioRxiv2019

Asymmetry in marginal population performance foreshadows widespread species range shifts

AimRange shifts are expected to occur when populations at one range margin perform better than those at the other margin, yet no global trend in population performances at range margins has been demonstrated empirically across a wide range of taxa and biomes. Here we test the prediction that, if impacts of ongoing climate change on population performance are widespread, then populations from the high-latitude margin (HLM) should perform as well as or better than central populations, whereas populations at low-latitude margins (LLM) populations should perform worse. LocationGlobal Time period1898-2020 Major taxa studiedPlants and animals MethodsTo test our prediction, we used a meta-analysis quantifying the empirical support for asymmetry in the performance of high- and low-latitude margin populations compared to central populations. Performance estimates were derived from 51 papers involving 113 margin-centre comparisons from 54 species and 705 populations. We then related these performance differences to climatic differences among populations. We also tested whether patterns are consistent across taxonomic kingdoms (plants vs. animals) and across habitats (marine vs. terrestrial). ResultsPopulations at margins performed significantly worse than central populations and this trend was primarily driven by the low-latitude margin. Although the difference was of small magnitude, it was largely consistent across biological kingdoms and habitats. The differences in performance were positively related to the difference in average temperatures between populations during the period 1985-2016. Major conclusionsThe observed asymmetry in marginal population performance confirms predictions about the effects of global climate change. It indicates that changes in demographic rates in marginal populations, despite extensive short-term variation, can serve as early-warning signals of impending range shifts.

ecology↗