Résumé
According to animal signalling theory, social costs incurred by aggressive conspecifics are one mechanism maintaining signal honesty. Although our understanding of signal evolution has much improved for pigment-based colours, the mechanisms maintaining the honesty of structural colour signals, such as ultraviolet (UV), remain elusive. Here, we used the common lizard (Zootoca vivipara) to test whether the honesty of UV-reflecting signals displayed on male throats is under social control. To do so, we staged agonistic interactions between non-manipulated focal males and opponents of either larger or smaller body size. We manipulated the UV component of the male throat colour patch to create small cheaters with UV-enhanced throats, large cheaters with UV-reduced throats, and their respective controls. In support of a conventional signal hypothesis, focal males were aggressive towards large cheaters and became submissive when these large cheaters retaliated, and were less submissive against small cheaters. However, that focal males were not more aggressive towards small cheaters contradicts our initial predictions. We confirm that male UV reflectance and bite force were good predictors of contest outcomes in control conditions. Overall, we provide partial evidence suggesting that social costs enforce UV signal honesty in common lizards.
Auteurs, date et publication :
Auteurs Anna Kawamoto , Jean-Francois Le Galliard , Arnaud Badiane
Publication : BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY
Date : 2021
Volume : 133
Issue : 4
Pages : 1126-1138
Catégorie(s)
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Causal effects of biodiversity on ecosystem functions can be estimated using experimental or observational designs — designs that pose a tradeoff between drawing credible causal inferences from correlations and drawing generalizable inferences. Here, we develop a design that reduces this tradeoff and revisits the question of how plant species diversity affects productivity. Our design leverages longitudinal data from 43 grasslands in 11 countries and approaches borrowed from fields outside of ecology to draw causal inferences from observational data. Contrary to many prior studies, we estimate that increases in plot-level species richness caused productivity to decline: a 10% increase in richness decreased productivity by 2.4%, 95% CI [−4.1, −0.74]. This contradiction stems from two sources. First, prior observational studies incompletely control for confounding factors. Second, most experiments plant fewer rare and non-native species than exist in nature. Although increases in native, dominant species increased productivity, increases in rare and non-native species decreased productivity, making the average effect negative in our study. By reducing the tradeoff between experimental and observational designs, our study demonstrates how observational studies can complement prior ecological experiments and inform future ones.
Auteurs, date et publication :
Auteurs Laura E. Dee , Paul J. Ferraro , Christopher N. Severen , Kaitlin A. Kimmel , Elizabeth T. Borer , Jarrett E. K. Byrnes , Adam Thomas Clark , Yann Hautier , Andrew Hector , Xavier Raynaud , Peter B. Reich , Alexandra J. Wright , Carlos A. Arnillas , Kendi F. Davies , Andrew MacDougall , Akira S. Mori , Melinda D. Smith , Peter B. Adler , Jonathan D. Bakker , Kate A. Brauman
Publication : Nature Communications
Date : 2023
Volume : 14
Issue : 1
Pages : 2607
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In the context of current climate change, municipalities tend to plant more trees in order to benefit from services they provide in urban areas, such as reducing heat islands. However, in cities, trees are subject to severe abiotic constraints, the main ones being soil contamination and the lack of water due to soil compaction and droughts. This can negatively impact the ecological services provided by trees. Our study aims to help managers in monitoring the phytosanitary status of trees in order to be able to react promptly. In a controlled condition experiment, different plant compounds were analyzed (proline, malondialdehyde-MDA, photosynthetic pigments) in the leaves of young linden trees conventionally grown for planting by the City of Paris, France. They were grown on a trace element (TE) contamination soil gradient, and under different water regimes (well-hydrated/no water stress (Ct), dehydration (Dh), rehydration (Rh)) to see if tested compounds could be early stress markers in trees. Chlorophylls (Chl) could be considered as water and TE-mediated stress markers. Indeed Chl a and b concentrations significantly decreased with dehydration (e.g. respectively -34 % and -24 %) and increasing lead concentration in leaves (respectively, correlation coefficients were -1.08; -0.64 (p < 0.001)). On the contrary, Chl concentrations increased with increasing copper concentration in optimal physiological ranges (correlation coefficients for Chla and Chb were respectively 1.3 and 1.08 (p < 0.05)). Proline and malondialdehyde seemed to be good complementary markers of water stress in the Tilia genus. Indeed, proline concentration increased during the dehydration period (early water stress marker) (mean concentration for Ct, Dh and Rh trees were respectively 3.6, 29.6 and 51.3 mu mol.g(-1) DW), while MDA increased during the rehydration process (marker for stress accumulation over time) (mean concentration for Ct, Dh, and Rh were respectively 461.8, 313.9 and 493.5 nmol.g(-1) DW). In order to reinforce the diagnoses of urban tree managers, these stress indicators should be tested in situ.
Auteurs, date et publication :
Auteurs Iry Andrianjara , Cecile Cabassa , Jean-Christophe Lata , Amandine Hansart , Xavier Raynaud , Mathilde Renard , Francois Nold , Patricia Genet , Severine Planchais
Publication : ECOLOGICAL INDICATORS
Date : 2024
Volume : 158
Catégorie(s)
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Intra-annual (i.e. seasonal) temporal niche partitioning is essential to the maintenance of biodiversity in many plant communities. However, understanding of how climate and global change drivers such as eutrophication influence seasonal niche partitioning in plant assemblages remains limited. We used early-season and late-season compositional data collected from 10 grassland sites around the world to explore relationships between climate variability and intra-annual species segregation (i.e. seasonal β-diversity) and to assess how nutrient enrichment alters seasonal β-diversity in plant communities. We then assessed whether changes in seasonal β-diversity in response to nutrient enrichment are underpinned by species turnover or nestedness and determined how specific functional groups (i.e. annual forbs, perennial forbs, C3 and C4 graminoids and legumes) respond to eutrophication within and across early and late sampling dates. We found a positive relationship between intra-annual temperature variability and seasonal β-diversity but observed no relationship between intra-annual precipitation variability and seasonal β-diversity. Nutrient enrichment increased seasonal β-diversity and increased turnover of species between early- and late-season communities. Nutrient enrichment reduced the abundance of C4 graminoids and legumes within and across sampling timepoints and eliminated intra-annual differences in these groups. In contrast, nutrient enrichment resulted in seasonal differences in C3 graminoids, which were not observed in control conditions and increased abundance of C3 graminoids and annual forbs within and across early and late sampling dates. Synthesis: Our understanding of how grasslands respond to various components of global change is primarily based on studies that document community changes at inter-annual scales. Using early-season and late-season compositional data from 10 grassland sites around the world, we show that nutrient enrichment increases seasonal β-diversity and alters intra-annual dynamics of specific functional groups in unique ways.
Auteurs, date et publication :
Auteurs Magda Garbowski , Elizabeth Boughton , Anne Ebeling , Philip Fay , Yann Hautier , Hanna Holz , Anke Jentsch , Stephanie Jurburg , Emma Ladouceur , Jason Martina , Timothy Ohlert , Xavier Raynaud , Christiane Roscher , Grégory Sonnier , Pedro Maximiliano Tognetti , Laura Yahdjian , Peter Wilfahrt , Stan Harpole
Publication : Journal of Ecology
Date : 2025
Volume : n/a
Issue : n/a
Catégorie(s)
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Human activities are transforming grassland biomass via changing climate, elemental nutrients, and herbivory. Theory predicts that food-limited herbivores will consume any additional biomass stimulated by nutrient inputs (‘consumer-controlled’). Alternatively, nutrient supply is predicted to increase biomass where herbivores alter community composition or are limited by factors other than food (‘resource-controlled’). Using an experiment replicated in 58 grasslands spanning six continents, we show that nutrient addition and vertebrate herbivore exclusion each caused sustained increases in aboveground live biomass over a decade, but consumer control was weak. However, at sites with high vertebrate grazing intensity or domestic livestock, herbivores consumed the additional fertilization-induced biomass, supporting the consumer-controlled prediction. Herbivores most effectively reduced the additional live biomass at sites with low precipitation or high ambient soil nitrogen. Overall, these experimental results suggest that grassland biomass will outstrip wild herbivore control as human activities increase elemental nutrient supply, with widespread consequences for grazing and fire risk.
Auteurs, date et publication :
Auteurs E. T. Borer , W. S. Harpole , P. B. Adler , C. A. Arnillas , M. N. Bugalho , M. W. Cadotte , M. C. Caldeira , S. Campana , C. R. Dickman , T. L. Dickson , I. Donohue , A. Eskelinen , J. L. Firn , P. Graff , D. S. Gruner , R. W. Heckman , A. M. Koltz , K. J. Komatsu , L. S. Lannes , A. S. MacDougall
Publication : Nature Communications
Date : 2020
Volume : 11
Issue : 1
Pages : 6036
Catégorie(s)
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Dominance often indicates one or a few species being best suited for resource capture and retention in a given environment. Press perturbations that change availability of limiting resources can restructure competitive hierarchies, allowing new species to capture or retain resources and leaving once dominant species fated to decline. However, dominant species may maintain high abundances even when their new environments no longer favour them due to stochastic processes associated with their high abundance, impeding deterministic processes that would otherwise diminish them. Here, we quantify the persistence of dominance by tracking the rate of decline in dominant species at 90 globally distributed grassland sites under experimentally elevated soil nutrient supply and reduced vertebrate consumer pressure. We found that chronic experimental nutrient addition and vertebrate exclusion caused certain subsets of species to lose dominance more quickly than in control plots. In control plots, perennial species and species with high initial cover maintained dominance for longer than annual species and those with low initial cover respectively. In fertilized plots, species with high initial cover maintained dominance at similar rates to control plots, while those with lower initial cover lost dominance even faster than similar species in controls. High initial cover increased the estimated time to dominance loss more strongly in plots with vertebrate exclosures than in controls. Vertebrate exclosures caused a slight decrease in the persistence of dominance for perennials, while fertilization brought perennials' rate of dominance loss in line with those of annuals. Annual species lost dominance at similar rates regardless of treatments. Synthesis. Collectively, these results point to a strong role of a species' historical abundance in maintaining dominance following environmental perturbations. Because dominant species play an outsized role in driving ecosystem processes, their ability to remain dominant—regardless of environmental conditions—is critical to anticipating expected rates of change in the structure and function of grasslands. Species that maintain dominance while no longer competitively favoured following press perturbations due to their historical abundances may result in community compositions that do not maximize resource capture, a key process of system responses to global change.
Auteurs, date et publication :
Auteurs Peter A. Wilfahrt , Eric W. Seabloom , Jonathan D. Bakker , Lori Biederman , Miguel N. Bugalho , Marc W. Cadotte , Maria C. Caldeira , Jane A. Catford , Qingqing Chen , Ian Donohue , Anne Ebeling , Nico Eisenhauer , Sylvia Haider , Robert W. Heckman , Anke Jentsch , Sally E. Koerner , Kimberly J. Komatsu , Ramesh Laungani , Andrew MacDougall , Jason P. Martina
Publication : Journal of Ecology
Date : 2025
Volume : n/a
Issue : n/a
Catégorie(s)
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Declines in grassland diversity in response to nutrient addition are a general consequence of global change. This decline in species richness may be driven by multiple underlying processes operating at different time-scales. Nutrient addition can reduce diversity by enhancing the rate of local extinction via competitive exclusion, or by reducing the rate of colonization by constraining the pool of species able to colonize under new conditions. Partitioning net change into extinction and colonization rates will better delineate the long-term effect of global change in grasslands. We synthesized changes in richness in response to experimental fertilization with nitrogen, phosphorus and potassium with micronutrients across 30 grasslands. We quantified changes in local richness, colonization, and extinction over 8–10 years of nutrient addition, and compared these rates against control conditions to isolate the effect of nutrient addition from background dynamics. Total richness at steady state in the control plots was the sum of equal, relatively high rates of local colonization and extinction. On aggregate, 30%–35% of initial species were lost and the same proportion of new species were gained at least once over a decade. Absolute turnover increased with site-level richness but was proportionately greater at lower-richness sites relative to starting richness. Loss of total richness with nutrient addition, especially N in combination with P or K, was driven by enhanced rates of extinction with a smaller contribution from reduced colonization. Enhanced extinction and reduced colonization were disproportionately among native species, perennials, and forbs. Reduced colonization plateaued after the first few (<5) years after nutrient addition, while enhanced extinction continued throughout the first decade. Synthesis. Our results indicate a high rate of colonizations and extinctions underlying the richness of ambient communities and that nutrient enhancement drives overall declines in diversity primarily by exclusion of previously established species. Moreover, enhanced extinction continues over long time-scales, suggesting continuous, long-term community responses and a need for long-term study to fully realize the extinction impact of increased nutrients on grassland composition.
Auteurs, date et publication :
Auteurs Andrew J. Muehleisen , Carmen R. E. Watkins , Gabriella R. Altmire , E. Ashley Shaw , Madelon F. Case , Lina Aoyama , Alejandro Brambila , Paul B. Reed , Marina LaForgia , Elizabeth T. Borer , Eric W. Seabloom , Jonathan D. Bakker , Carlos Alberto Amillas , Lori Biederman , Qingqing Chen , Elsa E. Cleland , Philip A. Fay , Nicole Hagenah , Stan Harpole , Yann Hautier
Publication : Journal of Ecology
Date : 2025
Volume : n/a
Issue : n/a
Catégorie(s)
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Auteurs Elizabeth T. Borer , Carly J. Stevens
Publication : Trends in Ecology & Evolution
Date : 2022
Volume : 37
Issue : 6
Pages : 541-552
Catégorie(s)
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Prenatal maternal effects can be a source of phenotypic plasticity and may play a role in adaptation to climate change. However, we do not know how far temperature could influence such effects, if at all. We studied the influence of temperature during egg laying on maternal reproductive investment and on the phenotype of adult females, adult males, and nestlings. We expected temperature to have an effect, as it influences maintenance costs for females, who can also use it as a cue of the advancement of the breeding season. We experimentally increased night-time nest-box temperatures by approximately 1 degrees C throughout the entire laying period in great tits (Parus major). Clutch size was negatively correlated with laying date in heated females. Heated females did not delay incubation after clutch completion as frequently as control females did. Finally, blood sedimentation rate, which is an indicator of acute infections and inflammatory diseases, was positively correlated with hatching date in control broods. This suggests that nestlings were of lower quality in late-hatched broods than in early-hatched broods. This seasonal effect was not detected in heated nests. Our results show that a small increase in temperature during laying can influence breeding strategy and nestling characteristics. These results suggest that birds used temperature as a cue of seasonal advancement to adjust breeding phenology, with beneficial effects on nestling health. To better understand the consequences of maternal adjustments during egg laying, it would be interesting to combine studies with heating treatment during different periods of the breeding cycle.
Auteurs, date et publication :
Auteurs Josefa Bleu , Simon Agostini , Clotilde Biard
Publication : BEHAVIORAL ECOLOGY
Date : 2017
Volume : 28
Issue : 3
Pages : 793-802
Catégorie(s)
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Anthropogenic nutrient enrichment is driving global biodiversity decline and modifying ecosystem functions. Theory suggests that plant functional types that fix atmospheric nitrogen have a competitive advantage in nitrogen-poor soils, but lose this advantage with increasing nitrogen supply. By contrast, the addition of phosphorus, potassium, and other nutrients may benefit such species in low-nutrient environments by enhancing their nitrogen-fixing capacity. We present a global-scale experiment confirming these predictions for nitrogen-fixing legumes (Fabaceae) across 45 grasslands on six continents. Nitrogen addition reduced legume cover, richness, and biomass, particularly in nitrogen-poor soils, while cover of non–nitrogen-fixing plants increased. The addition of phosphorous, potassium, and other nutrients enhanced legume abundance, but did not mitigate the negative effects of nitrogen addition. Increasing nitrogen supply thus has the potential to decrease the diversity and abundance of grassland legumes worldwide regardless of the availability of other nutrients, with consequences for biodiversity, food webs, ecosystem resilience, and genetic improvement of protein-rich agricultural plant species.
Auteurs, date et publication :
Auteurs Pedro M. Tognetti , Suzanne M. Prober , Selene Báez , Enrique J. Chaneton , Jennifer Firn , Anita C. Risch , Martin Schuetz , Anna K. Simonsen , Laura Yahdjian , Elizabeth T. Borer , Eric W. Seabloom , Carlos Alberto Arnillas , Jonathan D. Bakker , Cynthia S. Brown , Marc W. Cadotte , Maria C. Caldeira , Pedro Daleo , John M. Dwyer , Philip A. Fay , Laureano A. Gherardi
Publication : Proceedings of the National Academy of Sciences
Date : 2021
Volume : 118
Issue : 28