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Luz Boyero - One of the best experts on this subject based on the ideXlab platform.
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Microplastics have lethal and sublethal effects on stream invertebrates and affect stream ecosystem functioning.
Environmental Pollution, 2020Co-Authors: Naiara López-rojo, Javier Pérez, Francisco Correa-araneda, Alberto Alonso, Luz BoyeroAbstract:Abstract Microplastics (MPs) are contaminants of increasing concern due to their abundance, ubiquity and persistence over time. However, knowledge about MP distribution in fresh waters and their effects on freshwater organisms is still scarce, and there is virtually no information about their potential influence on ecosystem functioning. We used a microcosm experiment to examine the effects of MPs (fluorescent, 10-μm polystyrene microspheres) at different concentrations (from 0 to 103 particles mL−1) on leaf litter decomposition (a key process in stream ecosystems) and associated organisms (the caddisfly Detritivore Sericostoma pyrenaicum), and the extent to which MPs were attached to leaf litter and ingested and egested by Detritivores, thus assessing mechanisms of MP trophic transfer. We found that MPs caused Detritivore mortality (which increased 9-fold at the highest concentration) but did not affect their growth. Analysis of fluorescence in samples suggested that MPs were rapidly ingested (most likely through ingestion of particles attached to leaf litter) and egested. Leaf litter decomposition was reduced as a result of increasing MP concentrations; the relationship was significant only in the presence of Detritivores, but microbially-mediated decomposition showed a similar trend. Our findings provide novel evidence of harmful effects of MPs on aquatic insects and stream ecosystem functioning, and highlight the need for the standardization of methods in future experiments with MPs in order to allow comparisons and generalizations.
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Joint effects of temperature and litter quality on Detritivore-mediated breakdown in streams
Aquatic Sciences, 2018Co-Authors: Andrea Landeira-dabarca, Javier Pérez, Manuel A S Graca, Luz BoyeroAbstract:Global warming causes concomitant changes in several environmental factors that often have synergistic effects on populations and ecosystem processes. We examined how increased water temperature and reduced litter quality affected a leaf-shredding Detritivore’s performance and its effect on litter breakdown. Detritivores were exposed in microcosms at two temperatures (10 and 15 °C) and four categories of litter quality (based on nitrogen and condensed tannin concentrations). We hypothesized that (1) high-quality litter mixtures would breakdown faster, improving Detritivore performance; (2) differences would occur regardless of which plant species in the mixture were preferentially consumed; and (3) litter quality effects on Detritivore-mediated breakdown and performance would be intensified at higher temperatures. Unexpectedly, we found faster breakdown at intermediate litter quality and lower temperature. Additionally, we found cases of Detritivore selection and rejection of different resources driven by litter traits other than nitrogen and tannin concentrations. Detritivore performance increased with temperature, regardless of litter quality. Our results support non-additive and unpredictable joint effects of temperature and litter quality, suggesting that these concomitant changes may affect stream functioning.
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Leaf traits drive plant diversity effects on litter decomposition and FPOM production in streams - Fig 3
2018Co-Authors: Naiara López-rojo, Javier Pérez, Aingeru Martínez, Ana Basaguren, Jesús Pozo, Luz BoyeroAbstract:Changes in mean (± SE) (A-D) litter decomposition (mg leaf mg Detritivore-1), (E-H) FPOM production (mg FPOM mg Detritivore-1) and (I-L) Detritivore growth (%) with plant diversity loss from 3 to 1 species in the different 3-species litter mixtures. A: Alnus glutinosa; C: Corylus avellana; Q: Quercus robur; I: Ilex aquifolium), in microcosms with Detritivores. Different lower-case letters represent significant differences across treatments (p < 0.05).
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Results of linear models exploring effects of plant diversity loss (from 4 to 1 species in ACQI, or from 3 to 1 species in ACQ, ACI, AQI and CQI) on litter decomposition (mg mg Detritivore-1), FPOM production (mg mg Detritivore-1) and Detritivore gro
2018Co-Authors: Naiara López-rojo, Javier Pérez, Aingeru Martínez, Ana Basaguren, Jesús Pozo, Luz BoyeroAbstract:Results of linear models exploring effects of plant diversity loss (from 4 to 1 species in ACQI, or from 3 to 1 species in ACQ, ACI, AQI and CQI) on litter decomposition (mg mg Detritivore-1), FPOM production (mg mg Detritivore-1) and Detritivore growth (percentage) for different litter mixtures in microcosms with Detritivores.
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latitudinal gradient of nestedness and its potential drivers in stream Detritivores
Ecography, 2015Co-Authors: Luz Boyero, Richard G. Pearson, Marcos Callisto, Eric Chauvet, Christopher M Swan, Ricardo J Albarino, M Arunachalam, Julian Chara, Ana M Charaserna, Aydee CornejoAbstract:Understanding what mechanisms shape the diversity and composition of biological assemblages across broad-scale gradients is central to ecology. Litter-consuming detritivorous invertebrates in streams show an unusual diversity gradient, with a-diversity increasing towards high latitudes but no trend in a-diversity. We hypothesized this pattern to be related to shifts in nestedness and several ecological processes shaping their assemblages (dispersal, environmental filtering and competition). We tested this hypothesis, using a global dataset, by examining latitudinal trends in nestedness and several indicators of the above processes along the latitudinal gradient. Our results suggest that strong environmental filtering 95 and low dispersal in the tropics lead to often species-poor local Detritivore assemblages, nested in richer regional assemblages. At higher latitudes, dispersal becomes stronger, disrupting the nested assemblage structure and resulting in local assemblages that are generally more species-rich and non-nested subsets of the regional species pools. Our results provide evidence that mechanisms underlying assemblage composition and diversity of stream litter-consuming Detritivores shift across latitudes, and provide an explanation for their unusual pattern of increasing a-diversity with latitude. When we repeated these analyses for whole invertebrate assemblages of leaf litter and for abundant taxa showing reverse or no diversity gradients we found no latitudinal patterns, suggesting that function-based rather than taxon-based analyses of assemblages may help elucidate the mechanisms behind diversity gradients.
Eric Chauvet - One of the best experts on this subject based on the ideXlab platform.
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latitudinal gradient of nestedness and its potential drivers in stream Detritivores
Ecography, 2015Co-Authors: Luz Boyero, Richard G. Pearson, Marcos Callisto, Eric Chauvet, Christopher M Swan, Ricardo J Albarino, M Arunachalam, Julian Chara, Ana M Charaserna, Aydee CornejoAbstract:Understanding what mechanisms shape the diversity and composition of biological assemblages across broad-scale gradients is central to ecology. Litter-consuming detritivorous invertebrates in streams show an unusual diversity gradient, with a-diversity increasing towards high latitudes but no trend in a-diversity. We hypothesized this pattern to be related to shifts in nestedness and several ecological processes shaping their assemblages (dispersal, environmental filtering and competition). We tested this hypothesis, using a global dataset, by examining latitudinal trends in nestedness and several indicators of the above processes along the latitudinal gradient. Our results suggest that strong environmental filtering 95 and low dispersal in the tropics lead to often species-poor local Detritivore assemblages, nested in richer regional assemblages. At higher latitudes, dispersal becomes stronger, disrupting the nested assemblage structure and resulting in local assemblages that are generally more species-rich and non-nested subsets of the regional species pools. Our results provide evidence that mechanisms underlying assemblage composition and diversity of stream litter-consuming Detritivores shift across latitudes, and provide an explanation for their unusual pattern of increasing a-diversity with latitude. When we repeated these analyses for whole invertebrate assemblages of leaf litter and for abundant taxa showing reverse or no diversity gradients we found no latitudinal patterns, suggesting that function-based rather than taxon-based analyses of assemblages may help elucidate the mechanisms behind diversity gradients.
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Biodiversity and litter decomposition: a case study in a Mediterranean stream
Freshwater Science, 2015Co-Authors: Jérémy Jabiol, Eric ChauvetAbstract:The importance of riparian diversity for the functioning of headwater streams has been demonstrated repeatedly. For example, mixing litter from different riparian tree species can influence their decomposition rates, an effect that is contingent on both the litter assemblage and the Detritivore community. However, the effects of mixing litter species have been studied mostly in temperate streams, and very few studies have been done in non- temperate streams. Mediterranean streams are often subjected to recurrent flow intermittency, and their riparian tree and stream Detritivore communities have unique sets of species and traits, which probably influence the effects of litter mixtures on decomposition. We hypothesized that high dissimilarity in litter traits could promote effects of litter mixtures on decomposition that would be counteracted by the low abundance and small body size of Detritivores in Mediterranean streams. We manipulated litter diversity and the size-class and presence/absence of Detritivores in a 2nd-order Mediterranean stream in a 46-d experiment and found substantial but contingent effects on litter mixtures. Mixture effects were not significant on average, but both negative and positive effects of litter mixtures occurred. For instance, mixing soft and nutrient-rich litter species led to up to 9.6% increase in leaf mass loss. Microbial activity accounted for 85% of total leaf mass loss, and no effect of litter mixture was observed when Detritivores were excluded. In contrast, the presence of Detritivores, despite their relatively low abundance and diversity, was a key factor for litter decomposition and promoted effects of litter mixture. These results suggest that the extinction of a few key taxa (riparian tree species or large Detritivores) could impair nutrient and C cycling in Mediterranean streams with potential consequences for stream food webs.
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Top-down and bottom-up control of litter decomposers in streams
Freshwater Biology, 2014Co-Authors: Ana Lúcia Gonçalves, Manuel A S Graca, Eric Chauvet, Felix Bärlocher, Cristina CanhotoAbstract:1. Detritivores preferentially consume certain aquatic hyphomycete species while rejecting others. Fungal identity may therefore be a crucial factor determining stream food-web structure and complexity and extend the impact of microbial diversity to effects up through the food web. 2. In this study, we examined if shredder feeding is affected by the identity of fungi on leaves (bottom-up effects) and if preferences of shredders for particular fungi affect the composition of fungal assemblages (top-down effects). Oak leaf discs were conditioned in microcosms with six individual fungal species previously reported as highly palatable (P), unpalatable/rejected (R) and intermediate (I). Additionally, three microcosms were inoculated with three mixtures of four fungal species, each consisting of a different subset of the six species. 3. Colonised discs were offered to three Detritivores with different feeding strategies: Proasellus sp. (Isopoda), Echinogammarus meridionalis (Amphipoda) and Schizopelex festiva (Trichoptera). When offered leaves colonised by single fungal species, consumption rates by E. meridionalis and S. festiva were higher on I, followed by P and, finally, R species. Consumption rates by Proasellus sp. were sim- ilar across fungal treatments. Consumption rates by the three invertebrates were also similar across all fungal multispecies treatments, suggesting that invertebrate preferences for, or rejection of, a given fungal species may be masked when it grows in proximity to other fungi. Composition and structure of fungal communities were not significantly affected by the feeding of any of the three invertebrates. 4. Our results suggest that certain combinations of fungal and Detritivore species result in unpredictable bottom-up and top-down effects in stream food webs.
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Top‐down and bottom‐up control of litter decomposers in streams
Freshwater Biology, 2014Co-Authors: Ana Lúcia Gonçalves, Manuel A S Graca, Eric Chauvet, Felix Bärlocher, Cristina CanhotoAbstract:1. Detritivores preferentially consume certain aquatic hyphomycete species while rejecting others. Fungal identity may therefore be a crucial factor determining stream food-web structure and complexity and extend the impact of microbial diversity to effects up through the food web. 2. In this study, we examined if shredder feeding is affected by the identity of fungi on leaves (bottom-up effects) and if preferences of shredders for particular fungi affect the composition of fungal assemblages (top-down effects). Oak leaf discs were conditioned in microcosms with six individual fungal species previously reported as highly palatable (P), unpalatable/rejected (R) and intermediate (I). Additionally, three microcosms were inoculated with three mixtures of four fungal species, each consisting of a different subset of the six species. 3. Colonised discs were offered to three Detritivores with different feeding strategies: Proasellus sp. (Isopoda), Echinogammarus meridionalis (Amphipoda) and Schizopelex festiva (Trichoptera). When offered leaves colonised by single fungal species, consumption rates by E. meridionalis and S. festiva were higher on I, followed by P and, finally, R species. Consumption rates by Proasellus sp. were sim- ilar across fungal treatments. Consumption rates by the three invertebrates were also similar across all fungal multispecies treatments, suggesting that invertebrate preferences for, or rejection of, a given fungal species may be masked when it grows in proximity to other fungi. Composition and structure of fungal communities were not significantly affected by the feeding of any of the three invertebrates. 4. Our results suggest that certain combinations of fungal and Detritivore species result in unpredictable bottom-up and top-down effects in stream food webs.
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Litter identity mediates predator impacts on the functioning of an aquatic detritus-based food web
Oecologia, 2014Co-Authors: Jérémy Jabiol, Julien Cornut, Michaël Danger, Marion Jouffroy, Arnaud Elger, Eric ChauvetAbstract:During past decades, several mechanisms such as resource quality and habitat complexity have been proposed to explain variations in the strength of trophic cascades across ecosystems. In detritus-based headwater streams, litter accumulations constitute both a habitat and a resource for detritivorous macroinvertebrates. Because litter edibility (which promotes trophic cascades) is usually inversely correlated with its structural complexity (which weakens trophic cascades), there is a great scope for stronger trophic cascades in litter accumulations that are dominated by easily degradable litter species. However, it remains unclear how mixing contrasting litter species (conferring both habitat complexity and high quality resource) may influence top–down controls on communities and processes. In enclosures exposed in a second-order stream, we manipulated litter species composition by using two contrasting litter (alder and oak), and the presence–absence of a macroinvertebrate predator (Cordulegaster boltonii larvae), enabling it to effectively exert predation pressure, or not, on Detritivores (consumptive versus non-consumptive predation effects). Leaf mass loss, Detritivore biomass and community structure were mostly controlled independently by litter identity and mixing and by predator consumption. However, the strength of predator control was mediated by litter quality (stronger on alder), and to a lesser extent by litter mixing (weaker on mixed litter). Refractory litter such as oak leaves may contribute to the structural complexity of the habitat for stream macroinvertebrates, allowing the maintenance of Detritivore communities even when strong predation pressure occurs. We suggest that considering the interaction between top–down and bottom–up factors is important when investigating their influence on natural communities and ecosystem processes in detritus-based ecosystems.
Shucun Sun - One of the best experts on this subject based on the ideXlab platform.
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cascading effects of predator Detritivore interactions depend on environmental context in a tibetan alpine meadow
Journal of Animal Ecology, 2014Co-Authors: John N. Griffin, Shucun SunAbstract:Studies of grazing food webs show that species traits can interact with environmental factors to determine the strength of trophic cascades, but analogous context dependencies in detrital food webs remain poorly understood. In predator-Detritivore-plant interaction chains, predators are expected to indirectly suppress plant biomass by reducing the density of plant-facilitating Detritivores. However, this outcome can be reversed where above-ground predators drive burrowing Detritivores to lower soil levels, strengthening their plant-facilitating effects. Here, we show that these trait-mediated indirect interactions further depend on environmental context in a Tibetan alpine meadow. In our study system, undulating topography generates higher (dry soil) patches interspersed with lower (wet soil) patches. Because the ability of Detritivores to form deep burrows is likely to be limited by oxygen availability in low patches (wet soil), we hypothesized that (i) burrowing Detritivores would undergo a vertical habitat shift, allowing them to more effectively avoid predation, in high - but not low - patches, and (ii) this shift would transmit positive effects of predators to plants in high patches by improving conditions in the lower soil layer. We tested these hypotheses using complementary field and glasshouse experiments examining whether the cascading effects of above-ground predatory beetles (presence/absence) on the density and behaviour of tunnel-forming detritivorous beetles, soil properties, and plant growth varied with patch type (low/high). Results revealed that predatory beetles did not reduce the density of Detritivores in either patch type but had context-dependent trait-mediated effects, increasing the tunnelling depth of Detritivores, improving soil conditions and ultimately increasing plant biomass in the high but not low patches. This study adds to an emerging predictive framework linking predators to plants in detritus food webs, demonstrating that these indirect interactions depend not just on the relative habitat domains of predators and prey, but also on environmental conditions that can predictably constrain the behavioural response of Detritivores to predation risk.
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Cascading effects of predator–Detritivore interactions depend on environmental context in a Tibetan alpine meadow
The Journal of animal ecology, 2013Co-Authors: John N. Griffin, Shucun SunAbstract:Studies of grazing food webs show that species traits can interact with environmental factors to determine the strength of trophic cascades, but analogous context dependencies in detrital food webs remain poorly understood. In predator-Detritivore-plant interaction chains, predators are expected to indirectly suppress plant biomass by reducing the density of plant-facilitating Detritivores. However, this outcome can be reversed where above-ground predators drive burrowing Detritivores to lower soil levels, strengthening their plant-facilitating effects. Here, we show that these trait-mediated indirect interactions further depend on environmental context in a Tibetan alpine meadow. In our study system, undulating topography generates higher (dry soil) patches interspersed with lower (wet soil) patches. Because the ability of Detritivores to form deep burrows is likely to be limited by oxygen availability in low patches (wet soil), we hypothesized that (i) burrowing Detritivores would undergo a vertical habitat shift, allowing them to more effectively avoid predation, in high - but not low - patches, and (ii) this shift would transmit positive effects of predators to plants in high patches by improving conditions in the lower soil layer. We tested these hypotheses using complementary field and glasshouse experiments examining whether the cascading effects of above-ground predatory beetles (presence/absence) on the density and behaviour of tunnel-forming detritivorous beetles, soil properties, and plant growth varied with patch type (low/high). Results revealed that predatory beetles did not reduce the density of Detritivores in either patch type but had context-dependent trait-mediated effects, increasing the tunnelling depth of Detritivores, improving soil conditions and ultimately increasing plant biomass in the high but not low patches. This study adds to an emerging predictive framework linking predators to plants in detritus food webs, demonstrating that these indirect interactions depend not just on the relative habitat domains of predators and prey, but also on environmental conditions that can predictably constrain the behavioural response of Detritivores to predation risk.
Cristina Canhoto - One of the best experts on this subject based on the ideXlab platform.
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Top-down and bottom-up control of litter decomposers in streams
Freshwater Biology, 2014Co-Authors: Ana Lúcia Gonçalves, Manuel A S Graca, Eric Chauvet, Felix Bärlocher, Cristina CanhotoAbstract:1. Detritivores preferentially consume certain aquatic hyphomycete species while rejecting others. Fungal identity may therefore be a crucial factor determining stream food-web structure and complexity and extend the impact of microbial diversity to effects up through the food web. 2. In this study, we examined if shredder feeding is affected by the identity of fungi on leaves (bottom-up effects) and if preferences of shredders for particular fungi affect the composition of fungal assemblages (top-down effects). Oak leaf discs were conditioned in microcosms with six individual fungal species previously reported as highly palatable (P), unpalatable/rejected (R) and intermediate (I). Additionally, three microcosms were inoculated with three mixtures of four fungal species, each consisting of a different subset of the six species. 3. Colonised discs were offered to three Detritivores with different feeding strategies: Proasellus sp. (Isopoda), Echinogammarus meridionalis (Amphipoda) and Schizopelex festiva (Trichoptera). When offered leaves colonised by single fungal species, consumption rates by E. meridionalis and S. festiva were higher on I, followed by P and, finally, R species. Consumption rates by Proasellus sp. were sim- ilar across fungal treatments. Consumption rates by the three invertebrates were also similar across all fungal multispecies treatments, suggesting that invertebrate preferences for, or rejection of, a given fungal species may be masked when it grows in proximity to other fungi. Composition and structure of fungal communities were not significantly affected by the feeding of any of the three invertebrates. 4. Our results suggest that certain combinations of fungal and Detritivore species result in unpredictable bottom-up and top-down effects in stream food webs.
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Top‐down and bottom‐up control of litter decomposers in streams
Freshwater Biology, 2014Co-Authors: Ana Lúcia Gonçalves, Manuel A S Graca, Eric Chauvet, Felix Bärlocher, Cristina CanhotoAbstract:1. Detritivores preferentially consume certain aquatic hyphomycete species while rejecting others. Fungal identity may therefore be a crucial factor determining stream food-web structure and complexity and extend the impact of microbial diversity to effects up through the food web. 2. In this study, we examined if shredder feeding is affected by the identity of fungi on leaves (bottom-up effects) and if preferences of shredders for particular fungi affect the composition of fungal assemblages (top-down effects). Oak leaf discs were conditioned in microcosms with six individual fungal species previously reported as highly palatable (P), unpalatable/rejected (R) and intermediate (I). Additionally, three microcosms were inoculated with three mixtures of four fungal species, each consisting of a different subset of the six species. 3. Colonised discs were offered to three Detritivores with different feeding strategies: Proasellus sp. (Isopoda), Echinogammarus meridionalis (Amphipoda) and Schizopelex festiva (Trichoptera). When offered leaves colonised by single fungal species, consumption rates by E. meridionalis and S. festiva were higher on I, followed by P and, finally, R species. Consumption rates by Proasellus sp. were sim- ilar across fungal treatments. Consumption rates by the three invertebrates were also similar across all fungal multispecies treatments, suggesting that invertebrate preferences for, or rejection of, a given fungal species may be masked when it grows in proximity to other fungi. Composition and structure of fungal communities were not significantly affected by the feeding of any of the three invertebrates. 4. Our results suggest that certain combinations of fungal and Detritivore species result in unpredictable bottom-up and top-down effects in stream food webs.
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Effect of increased atmospheric CO2 on the performance of an aquatic Detritivore through changes in water temperature and litter quality.
Global Change Biology, 2009Co-Authors: Verónica Ferreira, Ana Lúcia Gonçalves, Douglas L. Godbold, Cristina CanhotoAbstract:Cold water woodland streams, where terrestrially derived organic matter fuels aquatic food webs, can be affected by increases in atmospheric CO 2 concentrations, as these are predicted to lead to increases in water temperature and decreases in organic matter quality. In fact, elevated CO 2 (580 ppm) decreased the initial phosphorus concentration of birch litter by 30% compared with litter grown under ambient conditions (380 ppm). Here, we first assessed the effect of differences in litter quality on mass loss, microbial colonization and conditioned litter quality after submersion in a mountain stream for 2 weeks. Leaching did not change the relative differences between litter types, while fungal biomass was two fold higher in elevated litter. We then offered this litter (conditioned ambient and elevated) to a stream Detritivore that was kept at 10 and 15 °C to assess the individual and interactive effects of increased temperature and decreased litter quality on invertebrate performance. When given a choice, the Detritivore preferred elevated litter, but only at 10 °C. When fed litter types singularly, there was no effect of litter quality on consumption rates; however, the effect of temperature depended on individual size and time of collection. Growth rates were higher in individuals fed ambient litter at 10 °C when compared with individuals fed elevated litter at 15 °C. Mortality did not differ between litter types, but was higher at 15 °C than at 10 °C. Increases in temperature led to alterations in the individual body elemental composition and interacted with litter type. The performance of the Detritivore was therefore more affected by increases in temperature than by small decreases in litter quality. However, it seems conceivable that in a future global warming scenario the simultaneous increases in water temperature and decreases in litter quality might affect Detritivores performance more than predicted from the effects of both factors considered individually.
Martin Zimmer - One of the best experts on this subject based on the ideXlab platform.
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Effects of warming, nutrient enrichment and Detritivore presence on litter breakdown and associated microbial decomposers in a simulated temperate woodland creek
Hydrobiologia, 2015Co-Authors: Fatemeh Sanaei Moghadam, Martin ZimmerAbstract:Current scenarios of global environmental change predict rapid temperature increases, which can directly affect freshwater ecosystems. Leaf litter breakdown in aquatic environments constitutes a fundamental ecosystem process that is mediated by microbial decomposers and animal Detritivores. In this study, we examined interactive effects of water temperature (two levels), nutrient concentration (two levels) and grazing pressure by Gammarus pulex (two levels) on breakdown rates of birch leaf litter, biomass and structure of the colonizing microbial community. Litter breakdown rates were stimulated by Detritivores, with Detritivore effects being enhanced by simultaneously increasing the temperature and adding the nutrients. The interaction between the three factors was synergistic and thus unpredictable from the effects of changes in individual factors. Bacterial community composition was affected by both Detritivores and temperature, but less so by nutrient levels and fungal community composition changed upon Detritivore activity but was independent of temperature and nutrients. These factors depended on each other in how they affected bacterial communities, but this did not prove true for fungal communities. Relative growth rates of G. pulex were not affected by temperature or nutrient level. We conclude that both abiotic and biotic factors that potentially affect ecosystem processes should be considered simultaneously in studies on effects of environmental change at the community and ecosystem level.
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Litter traits and palatability to Detritivores: a case study across bio-geographical boundaries
Nauplius, 2014Co-Authors: Aline Ferreira De Quadros, Martin Zimmer, Paula Beatriz Araujo, Jair Gilberto KrayAbstract:The activity of the litter-feeding macrofauna affects litter decomposition rates at the local scale, and their preference for particular litter types is mediated by litter traits. Environmental changes such as invasion by exotic plants may change the characteristics of the litter at a local scale, with consequences to ecosystem processes. Here we evaluated the feeding preferences of four Detritivores (terrestrial isopods) from two biogeographic regions (neotropical and palearctic), offering them native or non-native litter in cafeteria experiments. Our results show that isopods from different geographical regions exhibit essentially the same food preference, irrespective of whether or not they previously had encountered the litter tested. Combining the isopods' preference ranks with the principal component analysis of nine litter traits, we show that preference increases with increasing nitrogen and calcium contents and decreases with increasing toughness, C:N ratio and thickness, irrespective of the geographical origin of both litter and Detritivores. We conclude that the palatability of a non-native litter to the native Detritivore community can be predicted from their respective litter traits and thus, native Detritivores will feed on a particular non-native litter type as likely as do Detritivores in the native range of the plant. As the combination of traits that indicates palatability to the isopods also indicates litter decomposability, it could be possible to predict ecosystem responses in terms of litter decomposition rates upon changes in litter composition.
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Influence of changing plant food sources on the gut microbiota of saltmarsh Detritivores.
Microbial ecology, 2012Co-Authors: Jessica Dittmer, Martin Zimmer, Jérôme Lesobre, Roland Raimond, Didier BouchonAbstract:Changes in agricultural land-use of saltmarshes along the German North Sea coast have favoured the succession of the marsh grass Elytrigia atherica over the long-established Spartina anglica. Consequently, E. atherica represents a potential food source of increasing importance for plant-feeding soil Detritivores. Considering the importance of this ecological guild for decomposition processes and nutrient cycling, we focussed on two sympatric saltmarsh soil macroDetritivores and their associated gut microbiota to investigate how the digestive processes of these species may be affected by changing plant food sources. Using genetic fingerprints of partial 16S rRNA gene sequences, we analysed composition and diversity of the bacterial gut community in a diplopod and an amphipod crustacean in relation to different feeding regimes representing the natural vegetation changes. Effects of syntopy on the host-specific gut microbiota were also taken into account by feeding the two Detritivore species either independently or on the same plant sample. Bacterial community composition was influenced by both the host species and the available plant food sources, but the latter had a stronger effect on microbial community structure. Furthermore, bacterial diversity was highest after feeding on a mixture of both plant species, regardless of the host species. The gut microbiota of these two Detritivores can thus be expected to change along with the on-going succession at the plant community level in this environment. Cloning and sequencing of bacterial 16S rRNA gene fragments further indicated a host-related effect since the two Detritivores differed in terms of predominant bacterial taxa: diplopods harboured mainly representatives of the phyla Bacteroidetes and Gammaproteobacteria. In contrast, the genus Vibrio was found for the amphipod host across all feeding conditions.
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Salt marsh litter and Detritivores: A closer look at redundancy
Estuaries, 2004Co-Authors: Martin Zimmer, Steven C. Pennings, Tracy L. Buck, Thomas H. CarefootAbstract:Most primary production of angiosperms in coastal salt marshes enters the Detritivore food web; studies of this link have predominantly focused on one plant species ( Spartina alterniflora ) and one Detritivore species ( Littoraria irrorata ). In mesocosm experiments, we studied the rates and pattern of decomposition of litter derived from four plant species common in southeastern United States coastal salt marshes and marsh-fringing terrestrial habitats. Crustanceans and gastropods were selected as Detritivores feeding on, and affecting degradation of, the litter of two monocotyledons and two dicotyledons. Despite interspecific similarities in consumption, Detritivores exhibited species-specific effects on litter chemistry and on the activity of litter-colonizing microbiota. The chemical composition of feces depended upon both the litter type and the Detritivores’ species-specific digestive capabilities. Growth rates and survival of Detritivores differed among litter species. Different salt marsh Detritivores are likely to have different effects on decomposition processes in the salt marsh and cannot be regarded as functionally redundant nor can the litter of different plant species be regard ed as redundant as food for marsh Detritivores.
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bacterial endosymbionts in asellus aquaticus isopoda and gammarus pulex amphipoda and their contribution to digestion
Limnology and Oceanography, 2003Co-Authors: Martin Zimmer, Silvia BartholmeAbstract:We demonstrate for the first time the presence of bacterial endosymbionts in the midgut glands (hepatopancreas) of the freshwater Detritivore Asellus aquaticus (Isopoda), whereas the hepatopancreas of another crustacean Detritivore, Gammarus pulex (Amphipoda), which coexists with the former species, was devoid of such bacteria. We detected both phenol oxidase and cellulase activity in hepatopancreatic extracts from both Detritivores, which suggests that both of these enzymes are produced in the midgut glands of both species. After treatment with antibiotics, both the number of hepatopancreatic bacteria and enzymatic activity were reduced in the isopod hepatopancreas, but antibiotics had no effect on enzyme activity in the amphipod hepatopancreas. Feeding on microbially inactivated leaf litter did not affect enzyme activity in hepatopancreatic extracts from A. asellus, but increased cellulase activity was seen in the hepatopancreas of G. pulex. These results (1) confirm the hypothesized enzymatic adaptation of crustacean freshwater Detritivores to their food sources of terrestrial origin, (2) demonstrate that the isopod A. aquaticus, like its terrestrial relatives, contains endosymbiotic bacteria that contribute to digestive processes, and (3) show interspecific differences between these coexisting crustacean Detritivores in terms of enzyme origin and their dependence on microbiota.