Browsing by Autor "Olivier Dangles"

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Aquatic biota responses to temperature in a high Andean geothermal stream
(Wiley, 2021) Estefania Quenta; Antonio Daza; Xavier Lazzaro; Dean Jacobsen; Olivier Dangles; Sophie Cauvy‐Fraunié
Abstract The impact of global warming on mountain ecosystems is predicted to be high, and particularly in the tropical region. Geothermal streams have provided comprehensive evidence about how aquatic biodiversity changes across natural thermal gradients, but current knowledge is restricted to arctic and temperate zones. Thermal tolerances are different in tropical biological communities, resulting in high thermal sensitivity and low capacity to endure change in their thermal environments. This feature can change the response of aquatic organisms to warming, yet there is little empirical evidence to support this assumption. In this study, we address this issue by evaluating how water temperature affects biodiversity, and the structure of primary and secondary producers of a high‐elevation geothermal stream system (4,500 m above sea level) in the Bolivian Andes. We analysed multi‐taxa responses to increased water temperature using benthic macroinvertebrate families, benthic algae and cyanobacteria, fishes, and macrophytes as study organisms. Different models were run to assess the response of aquatic biota to temperature. In addition, threshold indicator taxa analysis (TITAN) was used to identify changes in macroinvertebrate taxa distributions along the thermal gradient. We found that macroinvertebrate richness decreased at 24–25°C due to the different taxon‐specific responses to temperature. Threshold indicator taxa analysis identified 17 temperature thresholds for each family of macroinvertebrates. Changes in macroinvertebrate community composition were significantly associated with changes in water temperature. Similarly, changes in macrophytes were associated with temperature differences, and high macrophyte richness was found at 19–20°C. Chlorophyll ‐a concentration of green algae and diatoms was higher at intermediate temperatures 20–22°C, macroinvertebrates density peaked at 27°C, and fish body size reduced linearly with temperature. Temperature increase in the geothermal stream resulted in a reduction of aquatic diversity and primary and secondary producers by simplifying the community structure to a few warm‐adapted taxa and reduced body size. These patterns differed from those obtained in temperate/arctic geothermal streams, but are similar to other studies at high‐elevation. In a context of increasing warming, the ecological structure of high‐elevation streams might lose cold‐adapted taxa, and change to smaller populations. Additional studies based on ecosystem functioning of geothermal streams could lead to a better understanding on how warming affects high‐elevation streams.
Biodiversity Patterns and Continental Insularity in the Tropical High Andes
(Institute of Arctic and Alpine Research, 2014) Fabien Anthelme; Dean Jacobsen; Petr Macek; Rosa Isela Meneses; Pierre Moret; Stephan Beck; Olivier Dangles
Alpine areas of the tropical Andes constitute the largest of all tropical alpine regions worldwide. They experience a particularly harsh climate, and they are fragmented into tropical alpine islands at various spatial scales. These factors generate unique patterns of continental insularity, whose impacts on biodiversity remain to be examined precisely. By reviewing existing literature and by presenting unpublished data on beta-diversity and endemism for a wide array of taxonomic groups, we aimed at providing a clear, overall picture of the isolation-biodiversity relationship in the tropical alpine environments of the Andes. Our analyses showed that (1) taxa with better dispersal capacities and wider distributions (e.g., grasses and birds) were less restricted to alpine areas at local scale; (2) similarity among communities decreased with spatial distance between isolated alpine areas; and (3) endemism reached a peak in small alpine areas strongly isolated from main alpine islands. These results pinpoint continental insularity as a powerful driver of biodiversity in the tropical High Andes. A combination of human activities and warming is expected to increase the effects of continental insularity in the next decades, especially by amplifying the resistance of the lowland matrix that surrounds tropical alpine islands.
Direct and indirect effects of glaciers on aquatic biodiversity in high Andean peatlands
(Wiley, 2016) Estefania Quenta; Jorge Molina‐Rodriguez; Karina Gonzales; François Rebaudo; Jérôme Casas; Dean Jacobsen; Olivier Dangles
The rapid melting of glacier cover is one of the most obvious impacts of climate change on alpine ecosystems and biodiversity. Our understanding of the impact of a decrease in glacier runoff on aquatic biodiversity is currently based on the 'glacier-heterogeneity-diversity' paradigm, according to which there is high α-diversity at intermediate levels of glacial influence due to the high degree of environmental heterogeneity caused by glacier water. This α-diversity pattern generates high levels of between-site aquatic community variation (high β diversity) and increases regional diversity (γ-diversity). There is a rich conceptual background in favor of this paradigm, but empirical data supporting it are scarce. We investigated this paradigm by analyzing the different diversity patterns (α, β and γ-diversity) of four aquatic groups (zooplankton, macroinvertebrates, algae and macrophytes) living in high-elevation peatlands (>4500 m above sea level). We sampled 200 pools from 20 peatlands along a glacier gradient in the Cordillera Real of Bolivia. We performed structural equation modeling (SEM) to analyze the potential mechanisms underlying the observed diversity patterns. Intermediate levels of glacial influence (15-20% cover) resulted in high heterogeneity, but α-diversity responded to glacial influence only for the zooplankton group (Cladocera). Our SEM analysis did not identify environmental heterogeneity as a significant variable explaining the relationship between glacier and α-diversity. Peatland area had a strong positive effect on heterogeneity and diversity. β-diversity was significantly associated with glacier gradient, and 12.9% of the total regional diversity (γ-diversity) was restricted to peatlands with a high degree of glacial influence. These species might be lost in a context of glacial retreat. These findings provide new insight into the potential effects of glacial retreat on the aquatic environment and biodiversity in the peatlands of the tropical Andes.
Does heterogeneity in crop canopy microclimates matter for pests? Evidence from aerial high-resolution thermography
(Elsevier BV, 2017) Émile Faye; François Rebaudo; Carlos Carpio; Mario Herrera; Olivier Dangles
Dynamics of Sylvatic Chagas Disease Vectors in Coastal Ecuador Is Driven by Changes in Land Cover
(Public Library of Science, 2014) Mario J. Grijalva; D. Teran; Olivier Dangles
We propose a framework for identifying the factors affecting the yearly distribution of sylvatic T. cruzi vectors. Beyond providing key basic information for the control of human habitat colonization by sylvatic vector populations, our framework highlights the importance of both environmental and sociological factors in shaping the spatio-temporal population dynamics of triatomines. A better understanding of the dynamics of such socio-ecological systems is a crucial, yet poorly considered, issue for the long-term control of Chagas disease.
Ecosystem sentinels for climate change? Evidence of wetland cover changes over the last 30 years in the tropical Andes
(Public Library of Science, 2017) Olivier Dangles; Antoine Rabatel; Martin J. Kraemer; Gabriel Zeballos; Álvaro Soruco; Dean Jacobsen; Fabien Anthelme
While the impacts of climate change on individual species and communities have been well documented there is little evidence on climate-mediated changes for entire ecosystems. Pristine alpine environments can provide unique insights into natural, physical and ecological response to climate change yet broad scale and long-term studies on these potential 'ecosystem sentinels' are scarce. We addressed this issue by examining cover changes of 1689 high-elevation wetlands (temporarily or perennial water-saturated grounds) in the Bolivian Cordillera Real, a region that has experienced significant warming and glacier melting over the last 30 years. We combined high spatial resolution satellite images from PLEIADES with the long-term images archive from LANDSAT to 1) examine environmental factors (e.g., glacier cover, wetland and watershed size) that affected wetland cover changes, and 2) identify wetlands' features that affect their vulnerability (using habitat drying as a proxy) in the face of climate change. Over the (1984-2011) period, our data showed an increasing trend in the mean wetland total area and number, mainly related to the appearance of wet grassland patches during the wetter years. Wetland cover also showed high inter-annual variability and their area for a given year was positively correlated to precipitation intensities in the three months prior to the image date. Also, round wetlands located in highly glacierized catchments were less prone to drying, while relatively small wetlands with irregularly shaped contours suffered the highest rates of drying over the last three decades. High Andean wetlands can therefore be considered as ecosystem sentinels for climate change, as they seem sensitive to glacier melting. Beyond the specific focus of this study, our work illustrates how satellite-based monitoring of ecosystem sentinels can help filling the lack of information on the ecological consequences of current and changing climate conditions, a common and crucial issue especially in less-developed countries.
Environmental and spatial filters of zooplankton metacommunities in shallow pools in high‐elevation peatlands in the tropical Andes
(Wiley, 2018) Estefania Quenta; Dean Jacobsen; Jérôme Casas; Olivier Dangles
Abstract Understanding metacommunity organisation in freshwater ecosystems is particularly important at high elevation in the tropical Andes, as this region is considered an important biodiversity hotspot with many endemic species threatened by climate change. High levels of dispersal at the regional scale and strong environmental filters at the local scale are thought to structure aquatic communities in these systems. However, metacommunity organisation patterns at the limit of aquatic life (>4,500 m a.s.l.) remain largely unknown. Given the extreme environmental conditions experienced by organisms at high elevation, environment filters would be expected to play a greater role than spatial filters in community assemblages. We assessed the effects of environmental and spatial filters on zooplankton (Cladocera), to gain insight into metacommunity organisation in the shallow high‐elevation pools of the tropical Andes. We sampled zooplankton communities and assessed nine environmental variables, for 200 pools from 20 peatlands in the Cordillera Real of Bolivia. We performed redundancy and variation partitioning analyses on both abundance and presence/absence data, to evaluate the contribution of environmental and spatial processes (geographic and elevation distances) to cladoceran metacommunity assembly at different spatial scales. We identified 18 cladoceran species, eight of which were endemic to the Andes. We found that both environment and spatial filters made a significant contribution to the structuring of cladoceran communities at higher spatial scales (i.e. intervalleys and within valleys), whereas only the environmental filter operated at small spatial scales (i.e. within peatlands). Elevation had a significant effect on cladoceran community variation (e.g. 6.9% within valleys, for abundance data), but not on species diversity. Similar patterns were obtained with presence/absence data. Macrophyte cover, pool area and pH were the most important variables explaining community variation and the species diversity of cladocerans at pool level. These results suggest that species sorting is probably the main process generating variation in cladoceran communities at all spatial scales. At larger spatial scales (intervalleys and within valleys), limited dispersal may also filter species composition. We identified factors significantly contributing to the variation observed, but their overall explanatory power was low. This finding highlights the difficulties involved in evaluating the response of aquatic organisms to their environment and suggests that other environmental variables should be considered. Moreover, frequent and unpredictable disturbances and high stochasticity probably operate simultaneously with environmental filters to structure zooplankton organisation in these unique and harsh aquatic systems.
Facilitation among plants in alpine environments in the face of climate change
(Frontiers Media, 2014) Fabien Anthelme; Lohengrin A. Cavieres; Olivier Dangles
While there is a large consensus that plant-plant interactions are a crucial component of the response of plant communities to the effects of climate change, available data remain scarce, particularly in alpine systems. This represents an important obstacle to making consistent predictions about the future of plant communities. Here, we review current knowledge on the effects of climate change on facilitation among alpine plant communities and propose directions for future research. In established alpine communities, while warming seemingly generates a net facilitation release, earlier snowmelt may increase facilitation. Some nurse plants are able to buffer microenvironmental changes in the long term and may ensure the persistence of other alpine plants through local migration events. For communities migrating to higher elevations, facilitation should play an important role in their reorganization because of the harsher environmental conditions. In particular, the absence of efficient nurse plants might slow down upward migration, possibly generating chains of extinction. Facilitation-climate change relationships are expected to shift along latitudinal gradients because (1) the magnitude of warming is predicted to vary along these gradients, and (2) alpine environments are significantly different at low vs. high latitudes. Data on these expected patterns are preliminary and thus need to be tested with further studies on facilitation among plants in alpine environments that have thus far not been considered. From a methodological standpoint, future studies will benefit from the spatial representation of the microclimatic environment of plants to predict their response to climate change. Moreover, the acquisition of long-term data on the dynamics of plant-plant interactions, either through permanent plots or chronosequences of glacial recession, may represent powerful approaches to clarify the relationship between plant interactions and climate change.
Factors influencing egg parasitism in sub‐social insects: insights from the treehopper <i>Alchisme grossa</i> ( <scp>H</scp> emiptera, <scp>A</scp> uchenorrhyncha, <scp>M</scp> embracidae)
(Wiley, 2013) Luis F. Camacho; Clifford B. Keil; Olivier Dangles
Subsocial insects rely on maternal care in order to enhance offspring survival. Subsocial H oplophorionini treehoppers defend their egg masses from predatory and parasitoid attacks. Egg parasitic wasps are important enemies of the M embracidae. We examined parasitism patterns and female defence mechanisms in the H oplophorionini treehopper Alchisme grossa ( F airmaire). We examined the effect of aggregations of egg‐guarding females, spatial aggregations of host plants and female A. grossa , and host plant identity on the incidence of egg mass parasitism. Additionally, we measured the effect of female maternal care strategies on reducing the amount of parasitism on their egg masses. Aggregation of egg‐guarding females on a single host plant was the most important factor affecting egg mass parasitism. Increased numbers of aggregated females lowered both parasitism risk and parasitism levels on their egg masses. When spatial clumping of host plants and egg‐guarding females occurred simultaneously, parasitism risk was also reduced. Maternal care strategies such as coverage of the egg mass by the females' pronota and intensity of female defensive behaviour also seemed to lower parasitism on egg masses. A reduction of parasitism by female aggregation on host plants can be explained by a selfish herd dilution effect. This dilution effect was potentiated by a possible cooperation between aggregated egg‐guarding females on the host plant. The present study provides a new dimension to sub‐sociality in Hoplophorionini treehoppers.
Fine nurse variations explain discrepancies in the stress‐interaction relationship in alpine regions
(Wiley, 2017) Fabien Anthelme; Rosa Isela Meneses; Nerida Nadia H. Valero; Paola Pozo; Olivier Dangles
Despite a large consensus on increasing facilitation among plants with increasing stress in alpine regions, a number of different outcomes of interaction have been observed, which impedes the generalisation of the ‘stress‐gradient hypothesis’ (SGH). With the aim to reconcile the different viewpoints on the stress‐interaction relationship in alpine environments we hypothesized that fine nurse variations within a single life form (cushion) may explain this pattern variability. To test this hypothesis, we compared the magnitude of the stress‐interaction relationship in a single study area with that observed in existing studies involving cushions, worldwide. We characterized the nurse effects of cushions on the whole plant community at inter‐specific, intra‐specific and intra‐individual levels along a stress gradient in the dry, alpine tropics of Bolivia (4400 m, 4700 m and 4900 m a.s.l). Using a relative index of interaction (RII) we included our data in a meta‐analysis on the nurse effects of cushions along alpine gradients, worldwide. At inter‐specific level, the loose cushion Pycnophyllum was a better nurse than the compact Azorella compacta . However, at intra‐individual level facilitation was higher at the periphery than at the centre of cushions, exceeding in magnitude the variation observed at inter‐specific level. This pattern was associated with higher minimum temperature and lower mortality at the periphery of cushions. The net effects of cushions on plant communities became more positive at higher elevation, corroborating the SGH. Within our single site in Bolivia, fine morphological nurse variations captured a similar variability in the stress‐interaction relationship as that observed in a subset of studies on cushions on a worldwide scale. This suggests that fine variations in nurse traits, in general those not considered in protocols dealing with facilitation or in restoration/conservation management plans, explain in part the current discrepancies among SGH studies in alpine regions.
Following a button: a transdisciplinary journey
(2023) Irene Teixidor‐Toneu; Olivier Dangles; Thomas Auffray; D. González‐Zeas; Anne‐Gaël Bilhaut; Rommel Montúfar
The Ethnobotanical Assembly, vol. 9, En ligne : https://tea-assembly.com/issues/9/following-a-button
Glacier influence on bird assemblages in habitat islands of the high Bolivian Andes
(Wiley, 2021) Tatiana Cárdenas; Kazuya Naoki; Carlos Miguel Landivar; Quentin Struelens; María Isabel Gómez; Rosa Isela Meneses; Sophie Cauvy‐Fraunié; Fabien Anthelme; Olivier Dangles
Abstract Aim Climate projections for the upcoming decades predict a significant loss of ice mass particularly critical for glaciers in tropical mountains. In the dry landscapes of the southern Andes (from Southern Peru to Chile), this global trend has strong ecological impacts on high‐altitude wetlands that support a unique avifauna for feeding, roosting and nesting. As glacier runoffs are expected to affect the area and the quality of wetland habitats, these changes may potentially affect bird communities. To address this issue, we studied the structural and functional diversity of bird assemblages in glacier‐fed high‐altitude wetlands (>4500 m). Location Five valleys of the Cordillera Real, Bolivia. Methods We surveyed bird communities during dry, wet and intermediate seasons in 40 wetlands (total of 27,720 observations of birds and habitats from 540 transects) showing different degrees of dependence on glacial meltwater. We examined the potential effect of glacier retreat on bird communities through changes in wetland area and environmental quality and heterogeneity. Results We found strong relationship between wetland area and taxonomic and functional diversity, but not on phylogenetic diversity. Generalized additive models revealed that avian diversity was influenced by wetland's productivity and elevation and maximized at intermediate levels of glacier influence. Multivariate analysis further showed that habitat productivity and humidity, both potentially influenced by future glacial retreat trends, are the main drivers of bird community composition, with the wettest habitats being crucial for aquatic birds and uncommon species. Main conclusions Glacier retreat may significantly affect bird community diversity and composition through changes in both area and quality of high‐altitude wetlands, with a particular concern for aquatic birds.
Invertebrate Metacommunity Structure and Dynamics in an Andean Glacial Stream Network Facing Climate Change
(Public Library of Science, 2015) Sophie Cauvy‐Fraunié; Rodrigo Espinosa; Patricio Andino; Dean Jacobsen; Olivier Dangles
Under the ongoing climate change, understanding the mechanisms structuring the spatial distribution of aquatic species in glacial stream networks is of critical importance to predict the response of aquatic biodiversity in the face of glacier melting. In this study, we propose to use metacommunity theory as a conceptual framework to better understand how river network structure influences the spatial organization of aquatic communities in glacierized catchments. At 51 stream sites in an Andean glacierized catchment (Ecuador), we sampled benthic macroinvertebrates, measured physico-chemical and food resource conditions, and calculated geographical, altitudinal and glaciality distances among all sites. Using partial redundancy analysis, we partitioned community variation to evaluate the relative strength of environmental conditions (e.g., glaciality, food resource) vs. spatial processes (e.g., overland, watercourse, and downstream directional dispersal) in organizing the aquatic metacommunity. Results revealed that both environmental and spatial variables significantly explained community variation among sites. Among all environmental variables, the glacial influence component best explained community variation. Overland spatial variables based on geographical and altitudinal distances significantly affected community variation. Watercourse spatial variables based on glaciality distances had a unique significant effect on community variation. Within alpine catchment, glacial meltwater affects macroinvertebrate metacommunity structure in many ways. Indeed, the harsh environmental conditions characterizing glacial influence not only constitute the primary environmental filter but also, limit water-borne macroinvertebrate dispersal. Therefore, glacier runoff acts as an aquatic dispersal barrier, isolating species in headwater streams, and preventing non-adapted species to colonize throughout the entire stream network. Under a scenario of glacier runoff decrease, we expect a reduction in both environmental filtering and dispersal limitation, inducing a taxonomic homogenization of the aquatic fauna in glacierized catchments as well as the extinction of specialized species in headwater groundwater and glacier-fed streams, and consequently an irreversible reduction in regional diversity.
Les bio-invasions d'insectes
(Centre de Coopération Internationale en Recherche Agronomique pour le Développement, 2013) Alain Roques; Olivier Dangles; Nathalie Gaultier; Jean‐Louis Sarah; Jean‐François Vayssières; Claire Vidal
chapitre 2
Logiques paysannes, production agricole et lutte contre les ravageurs des cultures à Salcedo dans les Andes équatoriennes : stratégies individuelles ou collectives ?
(Éditions en environnement VertigO, 2016) Nasser Rebaï; François Rebaudo; Julien Rebotier; Olivier Dangles
En Équateur, le débat sur l’avenir de l’agriculture familiale demeure important en raison de la vulnérabilité des communautés paysannes, en particulier dans la région andine, et d’une situation alimentaire encore préoccupante en milieu rural. Dans ce contexte, la lutte contre les ravageurs des cultures, identifiée par la FAO comme une priorité pour réduire efficacement l’insécurité alimentaire des agriculteurs dans les Suds, apparaît comme un défi de taille pour les communautés paysannes de la sierra équatorienne. Toutefois, le succès de cette lutte reste pour le moment limité en raison d’une faible coordination des pratiques agricoles entre agriculteurs. En s’appuyant sur un travail de terrain réalisé dans la province du Cotopaxi, cet article propose, en premier lieu, de mener une réflexion sur les déterminants du manque d’action collective contre les ravageurs des cultures. Puis, en second lieu, d’ouvrir une discussion sur le besoin d’une plus grande collaboration entre sciences du vivant et sciences sociales afin d’envisager des stratégies plus efficaces pour renforcer la coordination des agriculteurs dans la lutte contre les ravageurs des cultures, et d’améliorer ainsi leur sécurité alimentaire.
Market access and community size influence pastoral management of native and exotic livestock species: A case study in communities of the Cordillera Real in Bolivia's high Andean wetlands
(Public Library of Science, 2017) Quentin Struelens; Karina Gonzales Pomar; Susi Loza Herrera; Gaby Nina Huanca; Olivier Dangles; François Rebaudo
Grazing areas management is of utmost importance in the Andean region. In the valleys of the Bolivian Cordillera Real near La Paz, pastoralism constitutes the traditional way for people to insure food security and economical sustainability. In these harsh mountains, unique and productive wetlands sustained by glacial water streams are of utmost importance for feeding cattle herds during the dry season. After the colonization by the Spanish, a shift in livestock species has been observed, with the introduction of exotic species such as cows and sheep, resulting in a different impact on pastures compared to native camelid species-llamas and alpacas. Here we explored some of the social-economical and environmental drivers that motivate Bolivian pastoralists to prefer exotic over native livestock species, based on 36 household surveys in the Cordillera Real. We constructed a Partial Least Squares Structural Equation Model in order to assess the relationships between these drivers. Our results suggest that the access to market influenced pastoralists to reshape their herd composition, by increasing the number of sheep. They also suggest that community size increased daily grazing time in pastures, therefore intensifying the grazing pressure. At a broader scale, this study highlights the effects of some social-economical and environmental drivers on mountain herding systems.
Metodología para evaluar el potencial productivo y la dinámica socioecológica de la ganadería en bofedales altoandinos
(2014) N. Cochi; Guillermo Prieto; Olivier Dangles; Abel Eduardo Rojas; C. Ayala; Bruno Condori; José Luis Casazola
High-Andean wetlands (bofedales) provide crucial resources for the inhabitants of the Altiplano, among which pasture for camelid livestock. This resource is particularly vulnerable in the face of Ecologia en Bolivia 49(3): 120-131. Diciembre 2014. ISSN 1605-2528.
Microclimate Data Improve Predictions of Insect Abundance Models Based on Calibrated Spatiotemporal Temperatures
(Frontiers Media, 2016) François Rebaudo; Émile Faye; Olivier Dangles
A large body of literature has recently recognized the role of microclimates in controlling the physiology and ecology of species, yet the relevance of fine-scale climatic data for modeling species performance and distribution remains a matter of debate. Using a 6-year monitoring of three potato moth species, major crop pests in the tropical Andes, we asked whether the spatiotemporal resolution of temperature data affect the predictions of models of moth performance and distribution. For this, we used three different climatic data sets: (i) the WorldClim dataset (global dataset), (ii) air temperature recorded using data loggers (weather station dataset), and (iii) air crop canopy temperature (microclimate dataset). We developed a statistical procedure to calibrate all datasets to monthly and yearly variation in temperatures, while keeping both spatial and temporal variances (air monthly temperature at 1 km² for the WorldClim dataset, air hourly temperature for the weather station, and air minute temperature over 250 m radius disks for the microclimate dataset). Then, we computed pest performances based on these three datasets. Results for temperature ranging from 9 to 11°C revealed discrepancies in the simulation outputs in both survival and development rates depending on the spatiotemporal resolution of the temperature dataset. Temperature and simulated pest performances were then combined into multiple linear regression models to compare predicted vs. field data. We used an additional set of study sites to test the ability of the results of our model to be extrapolated over larger scales. Results showed that the model implemented with microclimatic data best predicted observed pest abundances for our study sites, but was less accurate than the global dataset model when performed at larger scales. Our simulations therefore stress the importance to consider different temperature datasets depending on the issue to be solved in order to accurately predict species abundances. In conclusion, keeping in mind that the mismatch between the size of organisms and the scale at which climate data are collected and modeled remains a key issue, temperature dataset selection should be balanced by the desired output spatiotemporal scale for better predicting pest dynamics and developing efficient pest management strategies.
Modelling temperature‐dependent development rate and phenology in arthropods: The <scp>devRate</scp> package for <scp>r</scp>
(Wiley, 2017) François Rebaudo; Quentin Struelens; Olivier Dangles
Abstract Thermal biologists are interested in generating paired data on development rates and temperatures, but they are in need of automated tools to accurately analyse this data. Fed with a database of more than 30 existing development models, the devRate package provides tools for plotting and visualizing data, selecting the most appropriate model, and mapping and forecasting ectotherm phenology using temperature time‐series data. Most proposed models are for arthropods, mainly insects (e.g. Lepidoptera, Coleoptera, Hemiptera, Diptera, Hymenoptera). This paper presents the main functions of the package and provides an example using an empirical dataset. The devRate package provides investigators with a unique set of tools and a database that allows them to fit development rate models, and to compare arthropod response to temperature.
Plant traits predict inter‐ and intraspecific variation in susceptibility to herbivory in a hyperdiverse Neotropical rain forest tree community
(Wiley, 2014) Rafael E. Cárdenas; Renato Valencia; Nathan J. B. Kraft; Adriana Argoti; Olivier Dangles
Summary A key issue in plant/herbivore interaction research is to understand which plant traits drive differences in herbivore damage. Variation in chemical, physical or phenological traits of plants may all modulate the degree of herbivore damage among species and individuals, yet the relative importance of these factors is still subject to debate, particularly in species‐rich systems such as tropical rain forests. To address this issue, we quantified leaf herbivore damage in 28 common tree species of the Yasuní forest dynamic plot ( YFDP ) in the Ecuadorian Amazon over 11 months. Census data from the YFDP allowed us to quantify several aspects of tree ecology potentially affecting herbivory including leaf turnover and spatial distribution patterns. We measured six chemical, eight physical and four ecological traits of the focal species. Using a combination of multivariate analyses and phylogenetic generalized linear regression model ( PGLS ), we assessed trade‐offs between physical and chemical traits and the relative effect of all these traits on leaf herbivore damage. Herbivore damage was highly variable among species and individuals, with leaves on average displaying damage over 13.4% (2.5–29.5%) of their area. We found no significant trade‐off between physical and chemical defences for the 28 studied tree species. Overall, leaf size, shearing resistance, cellulose, ash content and leaf size × ash were the best predictors of herbivore damage. Surprisingly, condensed tannins and latex did not significantly correlate with herbivore damage. In addition, we found no relationships between herbivory and local tree density. However, we did find a weak effect of tree clustering and strong effect of tree leaf turnover rates on herbivore damage. Synthesis . In the western Amazon, leaves are defended against herbivores through a combination of physical (toughness), chemical (toughness‐related elements), and phenological (rapid leaf replacement) characteristics that do not appear to be subject to obvious trade‐offs. Conventional strategies, such as condensed tannins or latex, do not seem to be strongly involved as a defence against herbivores in this community.