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opencc-zeroJan 2024View details →

Evaluating bottom-up forcing of a rocky intertidal resource harvest on a high trophic-level consumer group

The importance of ecosystem-based management (EBM) frameworks for resource harvest has increased over the past several decades as ecosystems face numerous anthropogenic stressors. In these frameworks, resource managers must consider the suite of interactions that comprise food webs and how resource harvest drives responses in non-target organisms. In rocky intertidal zones along North Atlantic coastlines, rockweed (Ascophyllum nodosum)—a canopy-forming brown seaweed—has been commercially harvested for centuries, yet most research on the effects of harvest have focused on the responses of the target resource and the macroinvertebrate assemblage. In this study, we used a Before-After Control-Impact experiment to assess the bottom-up effects of commercial rockweed harvest on a high trophic-level consumer group (birds) in Maine (USA). Overall, there was no evidence for strong bottom-up forcing of rockweed harvest on birds' site visitation. There was a small (fewer than two birds) positive effect size of harvest during the one-year post-harvest recovery interval. Several of the trends observed for the full bird assemblage appear to be driven more strongly by the low tide than the high tide bird assemblage. Independent of treatment, site visitation by birds was low in our study (60% of surveys recorded no birds) and highlights questions about the use of rocky intertidal habitats relative to other habitat types in coastal birds' home ranges. To our knowledge, there are no comparable assemblage-level bird studies in this system that can provide context to our results. Further research on coastal birds' habitat use within home ranges and food-web connections with rockweed-associated macroinvertebrates is needed to more confidently incorporate this high trophic-level consumer group into an EBM framework for a rocky intertidal resource harvest.

opencc-zeroJan 2024View details →

Seed mix design and floral resources drive multi-trophic interactions in prairie restoration

<ol> <li>Ecological restoration often targets plant community recovery, but restoration success may depend on the recovery of a complex web of biotic interactions to maintain biodiversity and promote ecosystem services. Specifically, management that drives resource availability, such as seeding richness and provenance, may alter species interactions across multiple trophic levels. Using experimentally seeded prairies, we examine three key groups – plants, pollinators, and goldenrod crab spiders (Misumena vatia, predators of pollinators) – to understand the effects of species richness and admixture seed sourcing of restoration seed mixtures on multi-trophic interactions.</li> <li>Working with prairie plants, we experimentally manipulated seed mix richness and the number of seed source regions (single-source region or admixture seed sourcing). In each experimental prairie, we surveyed floral abundance and richness, pollinator visitation, and plant-M. vatia interactions.</li> <li>A high-richness seed mix increased floral abundance when seeds were sourced from a single geographic region, and floral abundance strongly increased pollinator visitation, M. vatia abundance, and prey capture. Seeding richness and admixture seed sourcing of the seed mixture did not affect floral species richness, but floral species richness increased pollinator visitation.</li> <li>Pollinators interacted with different floral communities across seeding treatments, indicating a shift in visited floral species with restoration practices.</li> <li> Synthesis and applications. Long-term success in prairie restoration requires the restoration of plant-arthropod interactions. We provide evidence that seed mix richness and admixture seed sourcing affect arthropod floral associations, but effective restoration of plant-arthropod interactions should consider total floral resource availability. Incorporating a food web perspective in restoration will strengthen approaches to whole ecosystem restoration.</li> </ol>

opencc-zeroOct 2021View details →

Trophic resource partitioning drives fine-scale coexistence in cryptic bat species

Understanding the processes that enable species coexistence has important implications for assessing how ecological systems will respond to global change. Morphology and functional similarity increase the potential for competition, and therefore, co-occurring morphologically similar but genetically unique species are a good model system for testing coexistence mechanisms. We used DNA metabarcoding and High Throughput Sequencing to characterise for the first time the trophic ecology of two recently-described cryptic bat species with parapatric ranges, Myotis escalerai and Myotis crypticus. We collected faecal samples from allopatric and sympatric regions and from syntopic and allotopic locations within the sympatric region to describe the diets both taxonomically and functionally and compare prey consumption with prey availability. The two bat species had highly similar diets characterised by high arthropod diversity, particularly Lepidoptera, Diptera and Araneae, and a high proportion of prey that is not volant at night, which points to extensive use of gleaning. Diet overlap at the prey-item level was lower in syntopic populations, supporting trophic shift under fine-scale co-occurrence. Furthermore, the diet of M. escalerai had a marginally lower proportion of not nocturnally volant prey in syntopic populations, suggesting that the shift in diet may be driven by a change in foraging mode. Our findings suggest that fine-scale coexistence mechanisms can have implications for maintaining broad-scale diversity patterns. This study highlights the importance of including both allopatric and sympatric populations and choosing meaningful spatial scales for detecting ecological patterns. We conclude that a combination of high taxonomic resolution with a functional approach helps identify patterns of niche shift.

opencc-zeroJun 2022View details →

Trophic structure and origin of resources of soil macrofauna in the salt marsh of the Wadden Sea: a stable isotope (15N,13C) study

Salt marshes exist along the gradient of the marine mudflat to the terrestrial dunes, with a gradient of shore height and associated plant zonation. The lower salt marsh (LSM) extends from the mean high tidal level to 35 cm above that level and is followed by the upper salt marsh (USM). Despite changes in the amount of allochthonous marine input and in abiotic conditions, little is known about changes in the trophic structure and used of basal resources by the soil macrofauna along marine – terrestrial boundaries. Natural variations in carbon stable isotope ratios (δ¹³C signatures) allow insight into basal resources of consumers such as marine algae, terrestrial C3 and C4 photosynthesising plants. Furthermore, variations in nitrogen stable isotope ratios (δ¹5N signatures) allow insight into the trophic position of consumers. We investigated spatial and temporal changes in stable isotope signatures in salt marsh soil macrofauna of the island of Spiekeroog, German Wadden Sea. The range of δ¹⁵N signatures indicated no changes in food chain length across salt marsh zones with consumers in both zones comprising primary decomposer, secondary decomposer and first order predators. However, the trophic position of individual species changed between zones, but in particular with season. Contrasting δ¹⁵N signatures, the range in δ¹³C signatures in the LSM was twice that in the USM indicating a wider range of resources consumed. Bayesian mixing models indicated predominant autochthonous resource use in both the LSM and USM, with the use of marine allochthonous resources never exceeding 29.6%. However, the models also indicate an increase in the use of marine resources in certain species in the LSM with no use in the USM. Overall, the results indicate that the resource use of salt marsh macrofauna varies more in space than in time, with the food web being generally based on autochthonous rather than allochthonous resources. However, there also is trophic plasticity in certain species across both temporal and spatial scales including variations in the use of allochthonous resources. Generally, however, marine input contributes little to the nutrition of salt marsh soil macroinvertebrates.

opencc-zeroJun 2021View details →

Data from: Direct and indirect effects of landscape and field management intensity on carabids through trophic resources and weeds

Carabids are important biological control agents of weeds and other pests in agricultural fields. The carabid community is built upon direct and indirect ecological effects of landscape complexity, field management intensity and biotic components that in interaction make any prediction of community size and composition challenging. We analyse a large-scale sample of 60 European cereal fields using Structural Equation Modelling to quantify the direct effects of field management intensity and the surrounding landscape, and their indirect effect via biotic components, on carabid diversity. Our results highlight that direct and indirect effects of increasing landscape complexity, mediated by trophic resources, mainly affect carabids positively. Field management intensity only ever affects carabids through indirect effects that are generally negative, by suppressing standing weeds and weed seeds. Indirect effects on granivore carabid species depended on weed seed availability whereas omnivores depended on the availability of both weed seeds and animal prey. Synthesis and applications: A consideration of both the direct and indirect effects of landscape and field management is necessary for predicting carabid communities and with interactions. These effects, mediated via trophic resources, supports the diversity and abundance of carabid communities and their provision of ecosystem services. Our results show that promoting crop diversity and connectivity to semi-natural habitats will directly enhance carabid communities in farmland by manipulating their migration from source habitats. A reduction in field management intensity will preserve local standing weeds and weed seeds, and indirectly support carabid communities. These local and landscape modifications could contribute to improve the natural regulation of pests and weeds by carabids.

opencc-zeroJul 2021View details →

Data from: Trophic level and basal resource use of soil animals are hardly affected by local plant associations in abandoned arable land

Stable isotope composition of plants and soil animals in abandoned arable land Dataset provides raw data on stable isotope composition of C and N of plants and soil meso- and macrofauna. Dominating animal groups were collected in arable fallow systems 3 and 14-16 years after abandonment. Animals were sampled from the rhizosphere of three plant species of different functional groups: a legume (Medicaco sativa), a non-legume herb (Taraxacum officinale) and a grass (Bromus sterilis). More information can be found in the associated paper.

publicJul 2021View details →

Data from: Trophic level and basal resource use of soil animals are hardly affected by local plant associations in abandoned arable land

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publicJun 2021View details →

Data from: Direct and indirect effects of landscape and field management intensity on carabids through trophic resources and weeds

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publicOct 2021View details →

Trophic resource partitioning drives fine-scale coexistence in cryptic bat species

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publicJan 2024View details →

Data for: Evaluating bottom-up forcing of a rocky intertidal resource harvest on a high trophic-level consumer group

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publicJun 2022View details →

Trophic structure and origin of resources of soil macrofauna in the salt marsh of the Wadden Sea: a stable isotope (15N,13C) study

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publicFeb 2020View details →

Trophic selectivity in aquatic isopods increases with the availability of resources

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publicFeb 2024View details →

Seed mix design and floral resources drive multi-trophic interactions in prairie restoration

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dryad32/100

Data from: Land use alters trophic redundancy and resource flow through stream food webs

1. The changes to physical and chemical ecosystem characteristics as a response to pervasive and intensifying land use have the potential to alter the consumer-resource interactions and to rewire the flow of energy through entire food webs. 2. We investigated these structural and functional properties of food webs in stream ecosystems distributed across woodland, agricultural and urban areas in the Zagreb region of Croatia. We compared resource availability and consumer diet composition using stable isotope mixing models and tested how the isotopic variance of basal resources, primary consumers, macroinvertebrate predators, and other food-web characteristics change with different land use types. 3. Combination of increased loading and altered composition of nutrients, lower water discharge and higher light availability at urban sites likely promoted the contribution of aquatic macrophytes to diets of primary consumers. Macroinvertebrate predators shifted their diet, relying more on active filterers at urban sites relative to woodland and agricultural sites. Urban food webs also had lower trophic redundancy (i.e. fewer species at each trophic level) and a more homogenised energy flow from lower to higher trophic levels. There was no effect of land use on isotopic variation of basal resources, primary consumers or macroinvertebrate predators, but all these trophic groups at urban and agricultural sites were 15N-enriched relative to their counterparts in woodland stream food webs. 4. The physical and chemical ecosystem characteristics associated with intensive land use altered the resource availability, trophic redundancy and the flow of energy to other trophic levels, with potentially negative consequences for community dynamics and ecosystem functioning. These empirical findings indicate that reducing nutrient pollution, agricultural runoffs and maintaining riparian vegetation can mitigate the impacts of land use on structure and function of stream ecosystems.

opencc-zeroDec 2018View details →

Fig. 3 in Structure and Composition of Dung Beetle Assemblages (Coleoptera: Scarabaeidae) in a Livestock Ranch in Central Uruguay: Responses of Functional Groups and Species to Local Habitats and Trophic Resources

Fig. 3. Dominance/diversity curves based on a) abundance and b) biomass of the dung beetle species of Scarabaeidae in three habitats in Puntas de Sauce Maciel, Florida, Uruguay. PHS = pasture on humid soil; PDS = pasture on dry soil; EP = Eucalyptus plantation.

Fig. 1. a in Structure and Composition of Dung Beetle Assemblages (Coleoptera: Scarabaeidae) in a Livestock Ranch in Central Uruguay: Responses of Functional Groups and Species to Local Habitats and Trophic Resources

Fig. 1. a) Sample completeness curves as a function of dung beetle abundance in three study habitats in Puntas de Sauce Maciel, Florida, Uruguay, b) Coverage-based rarefaction (solid lines) and extrapolation (dash above endpoint for PHS) sampling curves for species richness of the dung beetle data from the three habitats. PHS = pasture on humid soil; PDS = pasture on dry soil; EP = Eucalyptus plantation.

Fig. 2 in Structure and Composition of Dung Beetle Assemblages (Coleoptera: Scarabaeidae) in a Livestock Ranch in Central Uruguay: Responses of Functional Groups and Species to Local Habitats and Trophic Resources

Fig. 2. Diversity profiles for dung beetle assemblages in three habitats in Puntas de Sauce Maciel, Florida, Uruguay as a function of Hill numbers (q) with 95% confidence intervals (shaded areas). PHS = pasture on humid soil; PDS = pasture on dry soil; EP = Eucalyptus plantation.

Fig. 4 in Structure and Composition of Dung Beetle Assemblages (Coleoptera: Scarabaeidae) in a Livestock Ranch in Central Uruguay: Responses of Functional Groups and Species to Local Habitats and Trophic Resources

Fig. 4. Detrended correspondence analysis ordination of dung beetle species sampled with baited pitfall traps in three different habitats in Puntas de Sauce Maciel, Florida, Uruguay. PHS = pasture on humid soil; PDS = pasture on dry soil; EP = Eucalyptus plantation.