Browsing by Author "Dangles, Olivier Jacques"
Now showing 1 - 20 of 27
Results Per Page
Sort Options
Item Open Access 
Adaptive management in crop pest control in the face of climate variability: an agent-based modeling approach(2015) Dangles, Olivier Jacques; Dangles, Olivier JacquesClimate changes are occurring rapidly at both regional and global scales. Farmers are faced with the challenge of developing new agricultural practices to help them to cope with unpredictable changes in environmental, social, and economic conditions. Under these conditions, adaptive management requires a farmer to learn by monitoring provisional strategies and changing conditions, and then incrementally adjust management practices in light of new information. Exploring adaptive management will increase our understanding of the underlying processes that link farmer societies with their environment across space and time, while accounting for the impacts of an unpredictable climate. Here, we assessed the impacts of temperature and crop price, as surrogates for climate and economic changes, on farmers’ adaptive management in crop pest control using an agent-based modeling approach. Our model simulated an artificial society of farmers that relied on field data obtained in the Ecuadorian Andes. Farmers were represented as heterogeneous autonomous agents who interact with and influence each other, and who are capable of adapting to changing environmental conditions. The results of our simulation suggest that variable temperatures led to less effective pest control strategies than those used under stable temperatures. Moreover, farmers used information gained through their own past experience or through interactions with other farmers to initiate an adaptive management approach. At a broader scale, this study generates more than an increased understanding of adaptive management; it highlights how people depend on one another to manage common problems.Item Open Access An agent-based modeling framework for integrated pest management dissemination programs.(2013) Dangles, Olivier Jacques; Rebaudo, FrançoisThe study of how people acquire and diffuse information among heterogeneous populations has a rich history in the social sciences. However, few approaches have been developed to better understand how information diffusion patterns and processes affect resource management in complex socio-ecological systems. This is a timely issue for crop protection diffusion programs, which have a larger place than ever on the international policy agenda due to the growing number of challenges related to controlling agricultural pests. To assess the impact of heterogeneous farmer behaviors (receptivity toward IPM practices) and types of information diffusion (either active or passive) on the success of integrated pest management (IPM) programs, we developed a socio-ecological model coupling a pest model (population growth and dispersion) with a farmer behavioral model (pest control and diffusion of pest management practices). The main objective of the model was to provide insights to explore effective IPM information diffusion strategies at the farmer community level. Our simulations revealed 1) that passive IPM information diffusion among agents seemed to be more effective to control pests over the community of agents than active diffusion and 2) that increasing levels of agent heterogeneity would significantly slow down pest control dynamics at the community level, but to a lower extent in the case of passive IPM information diffusion. Our findings therefore suggest that IPM diffusion programs should focus their efforts in developing methods to create purposefully the conditions for social learning as a deliberate pest control mechanism, while taking into account potential limitations related to the commonly reported farmer heterogeneity. Our study further stresses the need to develop a comprehensive and empirically based framework for linking the social and ecological disciplines across space and time in agricultural system management. While we specifically focus on pest infestation levels and IPM information diffusion strategies in this study, our approach to understand information diffusion within heterogeneous human populations in interaction with environmental features would be applicable to a much wider range of both social and resource management issues.Item Open Access Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream.(2015-07-03) Dangles, Olivier Jacques; Jacobsen, DeanTemperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier-fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short-term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.Item Open Access The bee and the turtle: a fable from Yasuní National Park.(2012) Dangles, Olivier Jacques; Dangles, Olivier JacquesA chance observation of an interaction between two very different species while exploring the Ecuadorean Amazon reminds Olivier Dangles and Jeróme Casas of the importance of natural history observations in developing ecological theories.Item Open Access Biodiversity under threat in glacier-fed river systems.(2012) Dangles, Olivier Jacques; Jacobsen, DeanFreshwater biodiversity is under threat across the globe1, with climate change being a significant contributor2,3. One impact of climate change is the rapid shrinking of glaciers4 , resulting in a reduction in glacial meltwater contribution to river flow in many glacierized catchments5,6. These changes potentially affect the biodiversity of specialized glacier-fed river communities7. Perhaps surprisingly then, although freshwater biodiversity is a major conservation priority3 , the effects of shrinkage and disappearance of glaciers on river biodiversity have hitherto been poorly quantified. Here we focus on macroinvertebrates (mainly insect larvae) and demonstrate that local (α) and regional (γ) diversity, as well as turnover among reaches (β-diversity), will be consistently reduced by the shrinkage of glaciers. We show that 11–38% of the regional species pools, including endemics, can be expected to be lost following complete disappearance of glaciers in a catchment, and steady shrinkage is likely to reduce taxon turnover in proglacial river systems and local richness at downstream reaches where glacial cover in the catchment is less than 5–30%. Our analysis demonstrates not only the vulnerability of local biodiversity hotspots but also that extinction will probably greatly exceed the few known endemic species in glacier-fed rivers.Item Open Access A comparative analysis reveals weak relationships between ecological factors and beta diversity of stream insect metacommunities at two spatial levels(2015-02-23) Dangles, Olivier Jacques; Dangles, Olivier JacquesThe hypotheses that beta diversity should increase with decreasing latitude and increase with spatial extent of a region have rarely been tested based on a comparative analysis of multiple datasets, and no such study has focused on stream insects. We first assessed how well variability in beta diversity of stream insect metacommunities is predicted by insect group, latitude, spatial extent, altitudinal range, and dataset properties across multiple drainage basins throughout the world. Second, we assessed the relative roles of environmental and spatial factors in driving variation in assemblage composition within each drainage basin. Our analyses were based on a dataset of 95 stream insect metacommunities from 31 drainage basins distributed around the world. We used dissimilarity-based indices to quantify beta diversity for each metacommunity and, subsequently, regressed beta diversity on insect group, latitude, spatial extent, altitudinal range, and dataset properties (e.g., number of sites and percentage of presences). Within each metacommunity, we used a combination of spatial eigenfunction analyses and partial redundancy analysis to partition variation in assemblage structure into environmental, shared, spatial, and unexplained fractions. We found that dataset properties were more important predictors of beta diversity than ecological and geographical factors across multiple drainage basins. In the within-basin analyses, environmental and spatial variables were generally poor predictors of variation in assemblage composition. Our results revealed deviation from general biodiversity patterns because beta diversity did not show the expected decreasing trend with latitude. Our results also call for reconsideration of just how predictable stream assemblages are along ecological gradients, with implications for environmental assessment and conservation decisions. Our findings may also be applicable to other dynamic systems where predictability is low.Item Open Access Development of a viral biopesticide for the control of the Guatemala potato tuber moth Tecia solanivora.(2013) Dangles, Olivier Jacques; Carpio, CarlosThe Guatemala potato tuber moth Tecia solanivora (Povolny) (Lep. Gelechiidae) is an invasive species from Mesoamerica that has considerably extended its distribution area in recent decades. While this species is considered to be a major potato pest in Venezuela, Colombia, and Ecuador, currently no specific control methods are available for farmers. To address this issue we developed a biopesticide formulation to be used in integrated pest management of T. solanivora, following three steps. First, search for entomopathogenic viruses were carried out through extensive bioprospections in 12 countries worldwide. As a result, new Phthorimaea operculella granulovirus (PhopGV) isolates were found in T. solanivora and five other gelechid species. Second, twenty PhopGV isolates, including both previously known and newly found isolates, were genetically and/or biologically characterized in order to choose the best candidate for a biopesticide formulation. Sequence data were obtained for the ecdysteroid UDP-glucosyltransferase (egt) gene, a single copy gene known to play a role in pathogenicity. Three different sizes (1086, 1305 and 1353 bp) of egt were found among the virus isolates analyzed. Unexpectedly, no obvious correlation between egt size and pathogenicity was found. Bioassays on T. solanivora neonates showed a maximum of a 14-fold difference in pathogenicity among the eight PhopGV isolates tested. The most pathogenic PhopGV isolate, JLZ9f, had a medium lethal concentration (LC50) of 10 viral occlusion bodies per square mm of consumed tuber skin. Third, we tested biopesticide dust formulations by mixing a dry carrier (calcium carbonate) with different adjuvants (magnesium chloride or an optical brightener or soya lecithin) and different specific amounts of JLZ9f. During laboratory experiments, satisfactory control of the pest (>98% larva mortality compared to untreated control) was achieved with a formulation containing 10 macerated JLZ9f-dead T. solanivora larvae per kg of calcium carbonate mixed with 50 mL/kg of soya lecithin. The final product provides an interesting alternative to chemical pesticides for Andean farmers affected by this potato pest.Item Open Access Differences in morphometry and activity among horse fly populations in an Andean tropical montane cloud forest: indication of altitudinal migration.(2013) Dangles, Olivier Jacques; Dangles, Olivier JacquesExiste evidencia científica que sugiere que las variaciones de un gradiente ecológico moldean algunas características propias de cada organismo como su comportamiento o morfometría. En este estudio, analizamos el efecto de la altura sobre la actividad de vuelo de poblaciones de una especie de tábano del género Stypommisa Enderlein a lo largo de 1 km de gradiente altitudinal en las estribaciones nor-orientales de los Andes ecuatorianos. Nuestros objetivos fueron (1) evaluar la hipótesis que los individuos de zonas altas presentan mayor tamaño en sus estructuras corporales asociadas al vuelo, y (2) comparar los patrones de actividad de vuelo de las diferentes poblaciones y correlacionarlas con factores climáticos. Para esto recolectamos especímenes en trampas Malaise a 1180, 1680 y 2180 m de altura desde las 0600 h hasta las 1800 h por 20 días en cada sitio. Se midieron siete variables climáticas en intervalos de una hora, y la actividad de vuelo fue inferida a partir de los datos de abundancia relativa/hora en las trampas. Dentro de las medidas morfométricas de las moscas incluimos el tamaño del cuerpo, el volumen torácico, el área alar y la carga alar. Los patrones de vuelo de las moscas revelaron una distribución bimodal a 1680 m, y dos distribuciones unimodales y asíncronas a 1180 m y 2180 m. Los análisis GLM mostraron que la temperatura, la neblina, y la pluviosidad fueron los factores climáticos que mejor predijeron los diferentes tipos de actividad de vuelo entre las alturas. Por otra parte, los análisis morfométricos demostraron que tanto el tamaño del cuerpo como el volumen torácico aumentan significativamente de tamaño con la altura. Se encontró que los grupos de moscas con actividad sincrónica a diferentes alturas (1180–1680(pm) m, y 1680(am)–2180 m) fueron morfológicamente similares lo que sugiere que las moscas pueden ser capaces de migrar de las zonas altas hacia las zonas bajas en horas específicas del día dependiendo del clima.Item Metadata only Ecological responses to experimental glacier-runoff reduction in alpine rivers(2016-06) Dangles, Olivier Jacques; Jacobsen, Dean; Dangles, Olivier JacquesGlacier retreat is a worldwide phenomenon with important consequences for the hydrological cycle and downstream ecosystem structure and functioning. To determine the effects of glacier retreat on aquatic communities, we conducted a 4-year flow manipulation in a tropical glacier-fed stream. Compared with an adjacent reference stream, meltwater flow reduction induces significant changes in benthic fauna community composition in less than 2 weeks. Also, both algal and herbivore biomass significantly increase in the manipulated stream as a response to flow reduction. After the flow reduction ceased, the system requires 14–16 months to return to its pre-perturbation state. These results are supported by a multi-stream survey of sites varying in glacial influence, showing an abrupt increase in algal and herbivore biomass below 11% glacier cover in the catchment. This study shows that flow reduction strongly affects glacier-fed stream biota, prefiguring profound ecological effects of ongoing glacier retreat on aquatic systems.Item Open Access Entomology in Ecuador: Recent developments and future challenges.(2013) Dangles, Olivier Jacques; Dangles, Olivier JacquesWe review and analyze the recent development and future challenges facing entomology as a science in Ecuador, a country with limited fi nancial and human resources and numerous environmental problems. Taxonomic studies of the Ecuadorian insect fauna have been well developed for only a few groups (e.g. Papilionoidea, Carabidae) and remains in its infancy for most insect orders. This is due to the huge diversity of species living in a great diversity of habitats and the diffi culty to identify most species. There is a lack of published basic biological information and to a high rate of endemism of many groups, especially in the Andes. The development of ecological entomology as a formal discipline in Ecuador is a very recent phenomenon, and has been mostly limited to descriptive studies of the environmental factors that govern insect diversity and abundance. We outline a set of research challenges regarding the impact of global environmental changes on insect communities and habitats they live in and propose potential strategies for the development of entomology in Ecuador. Both basic and applied research will be important in this context as well as international collaboration to strengthen the role of entomological science in decision making processes in the country.Item Metadata only Environmental harshness and global richness patterns in glacier-fed streams.(2012) Dangles, Olivier Jacques; Jacobsen, DeanAim: To test for a possible effect of environmental harshness on large-scale latitudinal and elevational patterns in taxon richness of macrofauna in arctic and alpine glacier-fed streams. Location: Svalbard (79° N), Iceland (65° N), Norway (62° N), Switzerland and Italy (46° N), France (43° N), New Zealand (43° S) and Ecuador (0°), covering an elevational gradient from sea level to 4800 m a.s.l. Methods: We gathered data from 63 sites along 13 streams and created an index of glacial influence (the glacial index, GI) as an integrative proxy for environmental harshness. The explicative power of the GI, environmental variables, latitude and elevation on taxon richness was tested in generalized linear models. Taxon richness along geographical gradients was analysed at standardized levels of GI in contour plots. Beta diversity and assemblage similarity was calculated at different GI intervals and compared with a null-model. Results: Overall, taxon richness decreased exponentially with increased GI (r2= 0.64), and of all included factors, GI had the highest explicative power. At low values of GI we found that local taxon richness varied along the coupled gradients of latitude and elevation in a hump-shaped manner. However, this pattern disappeared at high values of GI, i.e. when environmental harshness increased. Beta diversity increased, while similarity among assemblages decreased towards high GI values. Main conclusions: In our study system, the number of taxa able to cope with the harshest conditions was largely independent of the regional taxon pool, and environmental harshness constituted a ‘fixed’ constraint for local richness, irrespective of latitude and elevation. Contrary to expectations, we found that beta diversity was highest and similarity lowest among the harshest sites, suggesting that taxon richness was not solely driven by niche selection based on environmental tolerances, but also stochastic ecological drift, leading to dispersal-limited communities.Item Open Access Experimental support of the stress-gradient hypothesis in herbivore-herbivore interactions.(2013) Dangles, Olivier Jacques; Dangles, Olivier JacquesThe stress-gradient hypothesis (SGH) postulates an increase in the frequency of positive species interactions at increasing amounts of stress. While theSGHhas been extensively tested in plant–plant interactions along abiotic stresses, it remains unclear whether this hypothesis could apply to higher trophic levels, such as herbivores, along biotic stress gradients. To address this issue,weinvestigatedhowthe interaction between two potato herbivoresmay change along a stress gradient created by an assortment of potato varieties with different tuber palatability. We used a tuber resistance trait as a measure for biotic stress and one herbivore as the facilitator to gain access to the tuber of the other herbivore. Our experiment revealed a switch from neutral to positive interactions with increasing stress, confirming for the first time the predictions of the SGH for herbivores. Moreover, the intensity of facilitation decreased at high stress levels, suggesting that benefits by the facilitating species were dampened in the most stressful environment. In view of the ubiquitous role played by positive interactions among herbivores, broadening our search image for facilitative effects among other plant enemies will allow a better awareness of the importance of the SGH in structuring plant communities.Item Metadata only Functional consequences of realistic extinction scenarios in Amazonian soil food webs(2017-02) Cárdenas Muñoz, Rafael Enrique; Dangles, Olivier Jacques; Cárdenas Muñoz, Rafael EnriqueGlobal biodiversity loss is creating a more urgent need to understand the role organisms play in ecosystem functioning and mechanisms of control. Decomposition of dead organic matter is a key ecological process that ensures soil formation, nutrient availability, and carbon sequestration. To gain understanding of how biodiversity and ecosystems function together to control leaf-litter decomposition processes in a tropical rain forest (Yasuní National Park, Ecuador), we predicted the consequences of the decomposition process using a protocol in which we systematically disassemble the structural functionality of the soil macrofauna communities. We (1) describe the structure and function of the edaphic communities in detail and (2) explore the functional consequences of structural changes in these communities using a non-random exclusion experiment to simulate body size-related extinctions. To do this, we manipulated access of five size classes of soil invertebrates to eight types of plant leaf-litter resources. After measuring and identifying about 4400 soil individuals belonging to 541 morphospecies, 12 functional groups, and following the fate of about 2000 tree leaves in a 50-ha plot, we showed that (1) soil invertebrate communities were composed of a few common and many rare morphospecies that included mostly leaf-litter transformer groups, with the most morphospecies and the greatest abundance coming from Hymenoptera, Collembola, and Coleoptera; (2) our survey captured 63–74% of the total soil biodiversity of the study area (meaning there may be up to 860 morphospecies); (3) litter transformers covered the widest range of body volume, and all groups were evenly distributed at small and large spatial scales (i.e., we found no patterns of spatial aggregation); (4) changes in food web structure significantly altered biomass loss for only three of the eight leaf-litter treatments, suggesting the decomposition process was highly resistant to drastic changes such as size-biased biodiversity loss independent of resource quality. We conclude organic matter decomposition may depend on all non-additive effects that arise from multi-species interactions, including facilitation, interspecific interference competition, and top-down control that predators exert over detritivores at all body size ranges.Item Open Access Invertebrate metacommunity structure and dynamics in an Andean glacial stream network facing climate change(2015-08-26) Jacobsen, Dean; Dangles, Olivier Jacques; Dangles, Olivier JacquesUnder 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.Item Open Access Plant-plant interactions in tropical alpine environments.(2012) Dangles, Olivier Jacques; Dangles, Olivier JacquesPlant–plant interactions are increasingly recognized as a key driver of community organization and ecosystem processes in alpine environments. However, patterns and mechanisms of plant–plant interactions remain largely uncharacterized in tropical alpine ecosystems (TAE) which represent as much as 10% of the total surface area of alpine ecosystems worldwide. In this paper, we review (1) the ecological and environmental features that are specific to TAE in comparison with other alpine ecosystems, (2) the existing literature on plant–plant interactions in TAE, and (3) whether patterns and mechanisms of plant–plant interactions established in extratropical alpine zones can be extended to TAE. TAE are located predominantly in South America, East Africa, and South-East Asia where they show a unique combination of environmental characteristics, such as absence of persisting snow cover, high frequency of diurnal freeze–thaw cycles and needle-ice activity, and a decrease in precipitation with increasing altitude. These environmental characteristics result in the presence of giant growth forms with a great architectural diversity. These biotic and abiotic characteristics influence the outcome of plant–plant interactions by imposing other types of environmental constraints than those found in extratropical alpine environments, and by potentially generating distinctive patterns of niche differentiation/complementarity between species and populations. To generalize the conceptual framework of plant–plant interactions in alpine environments, we advocate that TAE should be investigated more thoroughly by applying designs, methods and hypotheses that are used currently in temperate areas and by conducting studies along large latitudinal gradients that include tropical regions.Item Open Access Preferencia de oviposición en tres especies de polilla de la papa (Lepidoptera: Gelechiidae).(2012) Dangles, Olivier Jacques; Herrera, Mario AndrésLos insectos plaga son una de las principales causas de pérdidas en cultivos y en almacenes a nivel mundial. En los Andes tropicales, el complejo de polillas de la papa (CPP) (Lepidoptera: Gelechiidae) está conformado por tres especies principales (Tecia solanivora, Symmetrischema tangolias y Phthorimaea operculella) y constituye una de las principales amenazas de los cultivos y almacenes de papas en la región. Se ha demostrado que las interacciones entre las larvas de las tres especies tienen un efecto significativo en la dinámica poblacional del CPP y en los daños causados a los cultivos. Sin embargo, los patrones de interacción inter-especificas durante otras fases del ciclo de vida de estas especies son desconocidos. Este estudio analizó la preferencia de oviposición de hembras del CPP mediante la realización de experimentos en los que hembras del CPP tuvieron que elegir el lugar de oviposición. Hembras de las tres especies del CPP prefirieron ovipositar en tubérculos dañados artificialmente ya que estos podrían ofrecer mejores condiciones para el desarrollo de su descendencia. Cuando hembras del CPP tuvieron que elegir ovipositar entre tubérculos sanos y tubérculos previamente infestados mostraron diferentes comportamientos, encontramos que T. solanivora no tiene sitios de oviposición preferidos mientras que S. tangolias y P. operculella tienen sitios de oviposición preferidosItem Open Access Relationships between stream macroinvertebrate communities and new flood-based indices of glacial influence.(2014) Dangles, Olivier Jacques; Cauvy-Fraunié, SophyAs glacier shrinkage is accelerating due to climate change, it is important to understand the effect of changes in glacier runoff on downstream aquatic communities. The overall goal of this study was to test the relevance of recently developed wavelet-based metrics of flow variations caused by glacial melting cycles to deepen our knowledge about the relationship between glacial influence and aquatic biodiversity. In an equatorial glacierised catchment, we selected 15 stream sites covering a gradient of direct contribution from glacial runoff. At each site, we recorded water level time series for 10 months and sampled benthic macroinvertebrates. Wavelet analyses on the water level time series were used to calculate three indices: glacial flood intensity, frequency and temporal clustering. We then examined how these three indices were related to macroinvertebrate community composition using generalised additive models. While macroinvertebrate density decreased significantly with glacial flood intensity, we found a significant hump-shaped relationship between local taxon richness and glacial flood intensity, a pattern that was not produced simply by overlapping broad taxon distributions from either end of the environmental gradient. These results suggest that glacial meltwater contribution creates local peaks in macroinvertebrate richness and enhances regional diversity in the catchment. The significant relationships between faunal metrics and the new glacial influence indices suggest the latter are valuable for assessing the effects of altered meltwater contributions on aquatic communities of glacier-fed rivers. Relationships differed depending on the feature of the glacial disturbance considered (glacial flood intensity, frequency, temporal clustering). We anticipate that these distinctions may help disentangle the mechanisms driving aquatic biodiversity in glacierised catchments, especially in terms of identifying resistance and/or resilience as key processes in glacial macroinvertebrate communities.Item Open Access Runoff and the longitudinal distribution of macroinvertebrates in a glacier-fed stream: implications for the effects of global warming.(2014) Dangles, Olivier Jacques; Jacobsen, DeanThe downstream pattern in benthic macroinvertebrate assemblages along glacier-fed streams is a result of decreasing glacial influence on environmental conditions. However, meltwater run-off shows temporal variation, reflected in differences in, for example, temperature, conductivity and turbidity. Consequently, depending on their run-off patterns, comparable environmental conditions may occur at different distances along glacier-fed streams. Our aim was to assess whether short-term variations in glacial run-off were reflected by changes in longitudinal distribution patterns of macroinvertebrates along a glacier-fed stream in the Ecuadorian Andes. We measured environmental parameters, obtained continuous gauging data, measured macroinvertebrate drift rate with an hourly resolution during glacial floods and sampled benthic macroinvertebrates c. 3-monthly for 30 months at three sites at varying distances (0.1–4.3 km) from the glacier. For each sampling date, we fitted logarithmic equations to plots of taxon richness versus distance from the glacier, calculated similarity in assemblage composition between sites and calculated weighted averages of mid-points of taxon distributions. These data were analysed in relation to mean maximum flow over the 45 days prior to sampling. Mean conductivity and temperature increased while turbidity decreased downstream. During glacial afternoon floods, conductivity decreased while temperature and turbidity increased. High flow moved maximal taxon richness downstream (reduced the slopes from logarithmic fits), while low flow made assemblages more downstream like (higher similarity with downstream assemblages). No significant relationships were found between weighted average distributions and flow. Drift rate (ind. h−1) increased by an order of magnitude at the onset of afternoon floods, and the taxa that contributed most to total drift were those whose benthic densities were most reduced by increases in flow. Our study provides hints as to how biological distribution patterns in glacier-fed streams might be affected by more permanent changes in run-off caused by glacial shrinkage. This study predicts a multidirectional shift in altitudinal/longitudinal species ranges, with a potential downward shift in species ranges as a consequence of global change.Item Open Access SimAdapt: An individual-based genetic model for simulating landscape management impacts on populations.(2013) Dangles, Olivier Jacques; Rebaudo, Francois1. Simulation models are essential tools in landscape genetics to study how genetic processes are affected by landscape heterogeneity.However, there is still a need to develop different simulation approaches in landscape genetics, so that users may dispose of additional programs to explore further the impact of land-use and land-cover changes on population genetics. 2. We developed a spatially explicit, individual-based, forward-time, landscape-genetic simulation model combined with a landscape cellular automaton to represent evolutionary processes of adaptation and population dynamics in changing landscapes, using the NetLogo environment. 3. This simulation model represents a unique tool for scientists and scholars looking for a practical and pedagogical framework to explore both empirical and theoretical situations.Item Open Access Size-dependent species removal impairs ecosystem functioning in a large-scale tropical field experiment.(2012) Dangles, Olivier Jacques; Herrera, Mario AndrésA major challenge of ecological research is to assess the functional consequences of species richness loss over time and space in global biodiversity hotspots, where extinctions are happening at an unprecedented rate. To address this issue, greater realism needs to be incorporated into both conceptual and experimental approaches. Here we propose a conceptual model that incorporates body size as a critical aspect of community responses to environmental change, which we tested in the Western Amazonian rain forest, one of the most speciose ecosystems on the planet. We employed an exclosure removal experiment (replicated under 10 microhabitats and four climatic conditions) in which we manipulated access to two types of resource by the whole community of dung and carrion beetles (>60 species), depending on their size. Our 400 independent measurements revealed that changes in the number of species and functional groups, and temporal patterns in community composition, all affected resource burial rates, a key ecosystem process. Further, the functional contribution of species diversity in each size class was tightly dependent on beetle abundance, and while the role of large species could be performed by abundant smaller ones, and other naturally occurring decomposers, this was not the case when environmental conditions were harsher. These results demonstrate, for the first time in an animal assemblage in a tropical ecosystem, that although species may appear functionally redundant under one set of environmental conditions, many species would be needed to maintain ecosystem functioning at multiple temporal and spatial scales. This highlights the potential fragility of these systems to the ongoing global “Sixth Great Extinction,” whose effects are likely to be especially pronounced in the Tropics.