Find research datasets worth reusing

opencc-zeroDec 2019View details →

Data from: A critical analysis of the potential for EU Common Agricultural Policy measures to support wild pollinators on farmland

1. Agricultural intensification and associated loss of high-quality habitats are key drivers of insect pollinator declines. With the aim of decreasing the environmental impact of agriculture, the 2014 EU Common Agricultural Policy (CAP) defined a set of habitat and landscape features (Ecological Focus Areas: EFAs) farmers could select from as a requirement to receive basic farm payments. To inform the post-2020 CAP, we performed a European-scale evaluation to determine how different EFA options vary in their potential to support insect pollinators under standard and pollinator-friendly management, as well as the extent of farmer uptake. 2. A structured Delphi elicitation process engaged 22 experts from 18 European countries to evaluate EFAs options. By considering life cycle requirements of key pollinating taxa (i.e. bumble bees, solitary bees and hoverflies), each option was evaluated for its potential to provide forage, bee nesting sites and hoverfly larval resources. 3. EFA options varied substantially in the resources they were perceived to provide and their effectiveness varied geographically and temporally. For example, field margins provide relatively good forage throughout the season in Southern and Eastern Europe but lacked early-season forage in Northern and Western Europe. Under standard management, no single EFA option achieved high scores across resource categories and a scarcity of late season forage was perceived. 4. Experts identified substantial opportunities to improve habitat quality by adopting pollinator-friendly management. Improving management alone was, however, unlikely to ensure that all pollinator resource requirements were met. Our analyses suggest that a combination of poor management, differences in the inherent pollinator habitat quality and uptake bias towards catch crops and nitrogen-fixing crops severely limit the potential of EFAs to support pollinators in European agricultural landscapes. 5. Policy Implications. To conserve pollinators and help protect pollination services, our study highlights the need to create a variety of interconnected, well-managed habitats that complement each other in the resources they offer. To achieve this the CAP post-2020 should take a holistic view to implementation that integrates the different delivery vehicles aimed at protecting biodiversity (e.g. enhanced conditionality, eco-schemes and Agri-Environment and Climate Measures). To improve habitat quality we recommend an effective monitoring framework with target-orientated indicators and to facilitate the spatial targeting of options collaboration between land managers should be incentivised.

opencc-zeroDec 2015View details →

Data from: Mass-flowering crops dilute pollinator abundance in agricultural landscapes across Europe

Mass-flowering crops (MFCs) are increasingly cultivated and might influence pollinator communities in MFC fields and nearby semi-natural habitats (SNHs). Across six European regions and 2 years, we assessed how landscape-scale cover of MFCs affected pollinator densities in 408 MFC fields and adjacent SNHs. In MFC fields, densities of bumblebees, solitary bees, managed honeybees and hoverflies were negatively related to the cover of MFCs in the landscape. In SNHs, densities of bumblebees declined with increasing cover of MFCs but densities of honeybees increased. The densities of all pollinators were generally unrelated to the cover of SNHs in the landscape. Although MFC fields apparently attracted pollinators from SNHs, in landscapes with large areas of MFCs they became diluted. The resulting lower densities might negatively affect yields of pollinator-dependent crops and the reproductive success of wild plants. An expansion of MFCs needs to be accompanied by pollinator-supporting practices in agricultural landscapes.

opencc-zeroDec 2015View details →

Data from: Interactive influences of climate change and agriculture on aquatic habitat in a Pacific Northwestern watershed

Climate change and agricultural intensification are two potential stressors that may pose significant threats to aquatic habitats in the inland Pacific Northwest over the next century. Climate change may impact running water through numerous pathways, including effects on water temperature and stream flow. In certain regions of the Pacific Northwest, agricultural activities, such as crop production, may become more profitable if water projects result in more irrigation water. If so, riparian buffers in these areas may be converted into cropland, which may in turn affect aquatic habitats through increases in sediment and agrochemical runoff into streams. We used currently available downscaled temperature and hydrology data in combination with a habitat quality framework developed for Pacific salmon and trout (Oncorhynchus spp.) to predict how different levels of each stressor, alone and in combination, may impact aquatic habitats in an inland Pacific Northwest watershed dominated by high-value agriculture—the Umatilla Subbasin. We developed spatially explicit predictions for how changes in stream flow and water temperature associated with three climate change scenarios and loss of riparian buffers in two agricultural intensification scenarios may impact aquatic habitats. We also examined the cumulative effects of the interaction of extreme climate change and agricultural intensification scenarios. Our results show that all three climate change scenarios are expected to primarily impact aquatic habitat in the upper Subbasin. In contrast, agricultural intensification scenarios did not have large impacts on temperature, but are predicted to affect other water quality variables in the lower Subbasin. A moderate scenario of agricultural intensification had relatively little effect on aquatic habitat, whereas the removal of all riparian buffers in agriculturally viable areas had a substantially negative effect on sediment, embeddedness, and large woody debris in the lower Subbasin. Interactions between the most extreme climate change and agricultural intensification scenarios reflected a complementarity of effects, with climate change primarily affecting the upper Subbasin and agricultural intensification primarily impacting the lower Subbasin. This work suggests that the Umatilla Subbasin and similar watersheds will present a challenging habitat for warm water- and pollution-intolerant species in the coming century.

opencc-zeroDec 2012View details →

Data from: The impact of climate change on the potential distribution of agricultural pests: the case of the coffee white stem borer (Monochamus leuconotus P.) in Zimbabwe

The production of agricultural commodities faces increased risk of pests, diseases and other stresses due to climate change and variability. This study assesses the potential distribution of agricultural pests under projected climatic scenarios using evidence from the African coffee white stem borer (CWB), Monochamus leuconotus (Pascoe) (Coleoptera: Cerambycidae), an important pest of coffee in Zimbabwe. A species distribution modeling approach utilising Boosted Regression Trees (BRT) and Generalized Linear Models (GLM) was applied on current and projected climate data obtained from the WorldClim database and occurrence data (presence and absence) collected through on-farm biological surveys in Chipinge, Chimanimani, Mutare and Mutasa districts in Zimbabwe. Results from both the BRT and GLM indicate that precipitation-related variables are more important in determining species range for the CWB than temperature related variables. The CWB has extensive potential habitats in all coffee areas with Mutasa district having the largest model average area suitable for CWB under current and projected climatic conditions. Habitat ranges for CWB will increase under future climate scenarios for Chipinge, Chimanimani and Mutare districts while it will decrease in Mutasa district. The highest percentage change in area suitable for the CWB was for Chimanimani district with a model average of 49.1% (3 906 ha) increase in CWB range by 2080. The BRT and GLM predictions gave similar predicted ranges for Chipinge, Chimanimani and Mutasa districts compared to the high variation in current and projected habitat area for CWB in Mutare district. The study concludes that suitable area for CWB will increase significantly in Zimbabwe due to climate change and there is need to develop adaptation mechanisms.

Data from: Flower resource and land management drives hoverfly communities and bee abundance in semi-natural and agricultural grasslands

1. Pollination is a key ecosystem service, and appropriate management, particularly in agricultural systems, is essential to maintain a diversity of pollinator guilds. However, management recommendations frequently focus on maintaining plant communities, with the assumption that associated invertebrate populations will be sustained. 2. We tested whether plant community, flower resources and soil moisture would influence hoverfly (Syrphidae) abundance and species richness in floristically-rich semi-natural and floristically-impoverished agricultural grassland communities in Wales (U.K.), and compared these to two Hymenoptera genera, Bombus and Lasioglossum. Interactions between environmental variables were tested using generalised linear modelling, and hoverfly community composition examined using canonical correspondence analysis. 3. There was no difference in hoverfly abundance, species richness, or bee abundance, between grassland types. There was a positive association between hoverfly abundance, species richness and flower abundance in unimproved grasslands. However, this was not evident in agriculturally improved grassland, possibly reflecting intrinsically low flower resource in these habitats, or the presence of plant species with low or relatively inaccessible nectar resources. There was no association between soil moisture content and hoverfly abundance or species richness. 4. Hoverfly community composition was influenced by agricultural improvement and the amount of flower resource. Hoverfly species with semi-aquatic larvae were associated with both semi-natural and agricultural wet grasslands, possibly because of localised larval habitat. Despite the absence of differences in hoverfly abundance and species-richness, distinct hoverfly communities are associated with marshy grasslands, agriculturally improved marshy grasslands and unimproved dry grasslands, but not with improved dry grasslands. 5. Grassland plant community cannot be used as a proxy for pollinator community. Management of grasslands should aim to maximise the pollinator feeding resource, as well as maintain plant communities. Retaining waterlogged ground may enhance the number of hoverflies with semi-aquatic larvae.

Data from: Breeding bird species diversity across gradients of land use from forest to agriculture in Europe

Loss, fragmentation and decreasing quality of habitats have been proposed as major threats to biodiversity world-wide, but relatively little is known about biodiversity responses to multiple pressures, particularly at very large spatial scales. We evaluated the relative contributions of four landscape variables (habitat cover, diversity, fragmentation and productivity) in determining different components of avian diversity across Europe. We sampled breeding birds in multiple 1-km2 landscapes, from high forest cover to intensive agricultural land, in eight countries during 2001−02. We predicted that the total diversity would peak at intermediate levels of forest cover and fragmentation, and respond positively to increasing habitat diversity and productivity; forest and open-habitat specialists would show threshold conditions along gradients of forest cover and fragmentation, and respond positively to increasing habitat diversity and productivity; resident species would be more strongly impacted by forest cover and fragmentation than migratory species; and generalists and urban species would show weak responses. Measures of total diversity did not peak at intermediate levels of forest cover or fragmentation. Rarefaction-standardized species richness decreased marginally and linearly with increasing forest cover and increased non-linearly with productivity, whereas all measures increased linearly with increasing fragmentation and landscape diversity. Forest and open-habitat specialists responded approximately linearly to forest cover and also weakly to habitat diversity, fragmentation and productivity. Generalists and urban species responded weakly to the landscape variables, but some groups responded non-linearly to productivity and marginally to habitat diversity. Resident species were not consistently more sensitive than migratory species to any of the landscape variables. These findings are relevant to landscapes with relatively long histories of human land-use, and they highlight that habitat loss, fragmentation and habitat-type diversity must all be considered in land-use planning and landscape modeling of avian communities.

Data from: A glimpse of an ancient agricultural ecosystem based on remains of micromammals in the Byzantine Negev Desert

It is widely believed that Byzantine agriculture in the Negev Desert (4th–7th cent. CE), with widespread construction of terraces and dams, altered local landscapes. However, no direct evidence in archaeological sites yet exists to test this assumption. We uncovered large amounts of small mammalian remains (rodents and insectivores) within agricultural installations built near fields, providing a new line of evidence for reconstructing anthropogenic impact on local habitats. Abandonment layers furnished high abundances of remains, whereas much smaller numbers were retrieved from the period of human use of the structures. Digestion marks are present in low frequencies (20% of long bones and teeth), with a light degree of impact, which indicate the role of owls (e.g., Tyto alba) as the principal means of accumulation. The most common taxa—gerbils (Gerbillus spp.) and jirds (Meriones spp.)—occur in nearly equal frequencies, which do not correspond with any modern Negev communities, where gerbils predominate in sandy low-precipitation environments and jirds in loessial, higher-precipitation ones. Though low-level climate change cannot be ruled out, the results suggest that Byzantine agriculture allowed jirds to colonize sandy anthropogenic habitats with other gerbilids and commensal mice and rats.

opencc-zeroAug 2019View details →

Data from: Seasonal shifts and complementary use of pollen sources by two bee, a lacewing and a ladybeetle species in European agricultural landscapes

1. Continuous availability of food resources, such as pollen, is vital for many insects that provide pollination and pest control services to agriculture. However, there is a lack of knowledge about the shared or complementary use of floral resources by such species, which hampers more effective landscape management to simultaneously promote them in agroecosystems. 2. Here, we simultaneously quantified pollen use by a bumblebee (Bombus terrestris) and a mason bee (Osmia bicornis), two bee species recognized as important crop pollinators, as well as a lacewing (Chrysoperla carnea) and a ladybeetle species (Harmonia axyridis), both common predators of crop aphids, throughout the season in 23 agricultural landscapes in Germany and Switzerland. 3. Pollen diets were more diverse and similar among C. carnea and H. axyridis compared to the two bee species, but all four species shared key pollen types early in the season such as Acer, Quercus, Salix and Prunus. All species exhibited a pronounced shift in pollen sources from primarily woody plants (mainly trees) in spring to primarily herbaceous plants in summer. The majority of pollen (overall ≥64%) came from non-agricultural plants even in crop-dominated landscapes. 4. Synthesis and applications. Our results highlight the importance of trees as pollen sources for many insect species, particularly early in the season. Our findings support incentives that promote heterogeneous agricultural landscapes including both woody and herbaceous semi-natural habitats, ensuring phenological complementarity of floral resources for insect species that can provide pollination and pest control services to agriculture. The identified key plant species can help to design and optimize agri-environment schemes to promote these functionally important insects.

opencc-zeroNov 2019View details →

Data S1 from "Global scale drivers of crop visitor diversity and the historical development of agriculture."

Understanding diversity in flower visitor assemblages helps us improve pollination of crops and support better biodiversity conservation outcomes. Much recent research has focused on drivers of crop-visitor diversity operating over spatial scales from fields to landscapes, such as pesticide and habitat management, while drivers operating over larger scales of continents and biogeographic realms are virtually unknown. Flower and visitor traits influence attraction of pollinators to flowers, and evolve in the context of associations that can be ancient or recent. Plants that have been adopted into agriculture have been moved widely around the world and thereby exposed to new flower visitors. Remarkably little is known of the consequence of these historical patterns for present day crop-visiting bee diversity. We analyze data from 317 studies of 27 crops worldwide and find that crops are visited by fewer bee genera outside their region of origin and outside their family's region of origin. Thus, recent human history and the deeper evolutionary history of crops and bees appear to be important determinants of flower-visitor diversity at large scales that constrain the levels of visitor diversity that can be influenced by field- and landscape-scale interventions.

Data from: Natural habitat does not mediate vertebrate seed predation as an ecosystem dis-service to agriculture

1. Spillover of beneficial organisms from natural habitats to croplands can improve agro-ecosystem services, but wildlife can also negatively influence agricultural production. When managing agricultural landscapes to conserve biodiversity, we need to understand if the availability of natural habitats increases ecosystem dis-services such as vertebrate seed predation to avoid risking higher costs than benefits. 2. We studied whether vertebrates and their impact in crop seed predation are related to the percentage of natural (Chaparral) and semi-natural habitat (planted forest with native and exotic trees) in an agricultural landscape of Israel. We selected 20 almond and 20 sunflower study sites within a landscape with varying percentages of natural (0–61%) and semi-natural (0–70%) habitats within a 1000-m radius of their surroundings. We observed birds, trapped rodents (in almond), counted seeds and noted feeding marks to obtain seed predation rates, at each site. Within the almond crops, we physically excluded birds, rodents and both to determine their relative and combined influence on seed predation. 3. Neither vertebrate abundance nor species richness was influenced by the percentage of natural habitat. However, bird species richness increased with increasing percentage of semi-natural habitat. 4. Seed predation across both crops was not influenced by natural or semi-natural habitat but increased significantly with increasing abundance and species richness of birds. This was also reflected by the exclusions of birds, vertebrates and both to the almond crop, leading to lowest seed predation when both groups were excluded. 5. Synthesis and applications. Natural or semi-natural habitat did not influence the agro-ecosystem dis-service of seed predation by birds and rodents. Policymakers should consider promoting agri-environment schemes that include the conservation of natural habitats and the management of semi-natural habitats adjacent to cropland to enhance agro-ecosystem services meditated by beneficial organisms like natural pest enemies and pollinators without fearing increased vertebrate seed predation. In order to provide more detailed management recommendations tackling the reduction of vertebrate dis-services their feeding behaviour, metabolic needs, behaviour patterns and local abundances should be taken into account.

Data from: Response of non-grassland avian guilds to adjacent herbaceous field buffers: testing hypotheses about configuration of targeted conservation practices in agricultural landscapes

1. A substantial part of the world's land base is dominated by agriculture, and forest habitat often consists of discrete patches of forest and linear woody corridors. These natural components provide habitat for some forest birds, but make conservation of these species difficult. In-field practices applied outside forest patches, such as specific juxtapositions of herbaceous field buffers adjacent to forest habitat, could increase avian diversity contributions of existing forest without creation of additional forest habitat. Our prediction was that herbaceous field buffers would increase bird richness in adjacent forest, and we evaluated four potential mechanisms. 2. We used bird count data from a conservation buffer monitoring program and hierarchical community models to estimate species richness of forest generalist, forest interior, and shrubland (edge) species near forest edges with and without adjacent herbaceous field buffers. We accounted for heterogeneity in detection probabilities and forest cover in surrounding landscapes when estimating species- and guild-level responses. 3. Consistent with the drift fence hypothesis, adjacent herbaceous buffers were associated with a modest increase in richness of forest interior birds in woody corridors, but not in forest blocks. Consistent with resource complementation, adjacent herbaceous buffers were associated with modest increases in richness of shrubland (edge) birds in both woody corridors and forest blocks. 4. Across all species and guilds, adjacent buffers generally associated with greater abundance (e.g. 28 of 39 species), but these increases were also relatively small and highly variable (i.e. overlapping 95% credible intervals). Corroborating existing research, effects of adjacent herbaceous buffers are likely real, but neither pervasive nor strong. 5. Synthesis and applications. Conservation practices targeted to grassland species often produce measurable conservation benefits for target species. However, biodiversity return for investment would be further increased if targeted practices could be deployed in ways that also produce benefits for non-target species in adjacent habitats. Our results suggest that additional benefits for non-target species using adjacent forest habitat are likely to be modest, so conservation planning should focus on species targeted by the conservation practices and avoidance of potential negative impacts on those species when positive benefits to adjacent habitat are weak or lacking.

opencc-zeroDec 2017View details →

Data from: Not seeing the grass for the trees: timber plantations and agriculture shrink tropical montane grassland by two-thirds over four decades in the Palani Hills, a Western Ghats Sky Island

Tropical montane habitats, grasslands, in particular, merit urgent conservation attention owing to the disproportionate levels of endemic biodiversity they harbour, the ecosystem services they provide, and the fact that they are among the most threatened habitats globally. The Shola Sky Islands in the Western Ghats host a matrix of native forest-grassland matrix that has been planted over the last century, with exotic timber plantations. The popular discourse on the landscape change is that mainly forests have been lost to the timber plantations and recent court directives are to restore Shola forest trees. In this study, we examine spatiotemporal patterns of landscape change over the last 40 years in the Palani Hills, a significant part of the montane habitat in the Western Ghats. Using satellite imagery and field surveys, we find that 66% of native grasslands and 31% of native forests have been lost over the last 40 years. Grasslands have gone from being the dominant, most contiguous land cover to one of the rarest and most fragmented. They have been replaced by timber plantations and, to a lesser extent, expanding agriculture. We find that the spatial pattern of grassland loss to plantations differs from the loss to agriculture, likely driven by the invasion of plantation species into grasslands. We identify remnant grasslands that should be prioritised for conservation and make specific recommendations for conservation and restoration of grasslands in light of current management policy in the Palani Hills, which favours large-scale removal of plantations and emphasises the restoration of native forests.

Data from: Ditch network sustains functional connectivity and influences patterns of gene flow in an intensive agricultural landscape

In intensive agricultural landscapes, plant species previously relying on semi-natural habitats may persist as metapopulations within landscape linear elements. Maintenance of populations' connectivity through pollen and seed dispersal is a key factor in species persistence in the face of substantial habitat loss. The goals of this study were to investigate the potential corridor role of ditches and to identify the landscape components that significantly impact patterns of gene flow among remnant populations. Using microsatellite loci, we explored the spatial genetic structure of two hydrochorous wetland plants exhibiting contrasting local abundance and different habitat requirements: the rare and regionally protected Oenanthe aquatica and the more commonly distributed Lycopus europaeus, in an 83 km2 agricultural lowland located in northern France. Both species exhibited a significant spatial genetic structure, along with substantial levels of genetic differentiation, especially for L. europaeus, which also expressed high levels of inbreeding. Isolation-by-distance analysis revealed enhanced gene flow along ditches, indicating their key role in effective seed and pollen dispersal. Our data also suggested that the configuration of the ditch network and the landscape elements significantly affected population genetic structure, with (i) species-specific scale effects on the genetic neighborhood and (ii) detrimental impact of human ditch management on genetic diversity, especially for O. aquatica. Altogether, these findings highlighted the key role of ditches in the maintenance of plant biodiversity in intensive agricultural landscapes with few remnant wetland habitats.

Data from: Habitat restoration promotes pollinator persistence and colonization in intensively managed agriculture

Widespread evidence of pollinator declines has led to policies supporting habitat restoration including in agricultural landscapes. Yet, little is yet known about the effectiveness of these restoration techniques for promoting stable populations and communities of pollinators, especially in intensively managed agricultural landscapes. Introducing floral resources, such as flowering hedgerows, to enhance intensively cultivated agricultural landscapes is known to increase the abundances of native insect pollinators in and around restored areas. Whether this is a result of local short-term concentration at flowers or indicative of true increases in the persistence and species richness of these communities remains unclear. It is also unknown whether this practice supports species of conservation concern (e.g., those with more specialized dietary requirements). Analyzing occupancies of native bees and syrphid flies from 330 surveys across 15 sites over eight years, we found that hedgerow restoration promotes rates of between-season persistence and colonization as compared with unrestored field edges. Enhanced persistence and colonization, in turn, led to the formation of more species-rich communities. We also find that hedgerows benefit floral resource specialists more than generalists, emphasizing the value of this restoration technique for conservation in agricultural landscapes.

opencc-zeroDec 2011View details →

Data from: Recent range expansion and agricultural landscape heterogeneity have only minimal effect on the spatial genetic structure of the plant pathogenic fungus Mycosphaerella fijiensis

Understanding how geographical and environmental features affect genetic variation at both the population and individual levels is crucial in biology, especially in the case of pathogens. However, distinguishing between these factors and the effects of historical range expansion on spatial genetic structure remains challenging. In the present study, we investigated the case of Mycosphaerella fijiensis-a plant pathogenic fungus that has recently colonized an agricultural landscape characterized by the presence of potential barriers to gene flow, including several commercial plantations in which disease control practises such as the use of fungicides are applied frequently, and low host density areas. We first genotyped 300 isolates sampled at a global scale on untreated plants in 2 dimensions over a 50x80 Km area. Using two different clustering algorithms, no genetic structure was detected in the studied area, suggesting expansion of large populations and/or no influ ence of potential barriers. Second, we investigated the potential effect of disease control practises on M. fijiensis diversity by comparing populations sampled in commercial vs. food-crop plantations. At this local scale, we detected significantly higher allelic richness inside commercial plantations compared to the surrounding food-crop plantation populations. Analysis of molecular variance (AMOVA) indicated that 99% of the total genetic variance occurred within populations. We discuss the suggestion that high population size and/or high migration rate between populations might be responsible for the absence of any effect of disease control practises on genetic diversity and differentiation.

opencc-zeroMay 2019View details →

Data from: Stressor dominance and sensitivity-dependent antagonism: disentangling the freshwater effects of an insecticide among co-occuring agricultural stressors

1. Pesticide concentrations are correlated with regional declines in stream invertebrate diversity. Experimental studies have identified that pesticides can have strong and persistent negative effects on aquatic ecosystems. These effects may occur at concentrations orders of magnitude lower than laboratory toxicity studies predict. Synergism among stressors is one explanation for the observed laboratory-field difference. However, the true effect of pesticides on stream invertebrates remains uncertain, given interactions between stressors and natural environmental conditions. 2. We experimentally examined multiple-stressor effects on stream invertebrate assemblages and leaf-litter breakdown using 24 independent ~900 L re-circulating outdoor mesocosms in a semi-orthogonal design. Two pulses of the pesticide malathion (C10H19O6PS2) were delivered at low and high concentrations (Pulse 1: low at 0.1 and high at 1 µg L-1¬; Pulse 2: at 2.5 and 25 µg L-1). These were crossed with a treatment mimicking the combined stressors from agricultural development; nitrogen, phosphorus and clay (kaolin) sediment (hereafter agricultural stressors). 3. Malathion degradation was rapid (<24 hr half-life) in all treatments, likely because of photolysis, hydrolysis, the presence of biofilms and sorptive processes. There were significant differences in invertebrate assemblages between treatments, where malathion contributed to 48% and 87% of deviance during Pulse 1 and 2 respectively. Malathion had strong negative effects during Pulse 2, decreasing Ephemeroptera, Plecoptera and Trichoptera abundance (P<0.05), invertebrate richness (P<0.01) and total abundance (P<0.01). 4. Despite the dominant effects of malathion on invertebrates, agricultural stressors inhibited rates of leaf litter breakdown (P<0.05), increased invertebrate densities and weakly mitigated malathion toxicity in mesocosms (e.g. PERMANOVA, P≈0.1). Malathion breakdown analysis indicated sediment addition reduced malathion concentrations through alkaline hydrolysis and sorption. Experimental assays on common taxa indicated sediment was antagonistic with malathion. 5. Pesticide effects were not synergistic with the stressors tested here. Indeed, sensitivity-dependent stressor antagonisms were observed, reinforcing a mechanistic understanding of stressor effects and interactions is important. Among aquatic stressors examined, malathion had dominant effects on invertebrate assemblages, despite rapid degradation. Our results suggest that pesticide effects may be underestimated within ecosystems, where pesticides can have severe community wide effects, but rapid pesticide breakdown and sorptive processes may conceal causal links.01-May-2019

Data from: Dispersal and establishment limitation slows plant community recovery in post-agricultural longleaf pine savannas

Abandoned agricultural lands often have distinct plant communities from areas with no history of agriculture because plant species fail to recolonize. This may be due to dispersal limitation from a lack of seeds, or establishment limitation because of unsuitable environmental conditions. However, few experiments have directly tested how restoration activities may overcome these limitations. We studied longleaf pine savannas in South Carolina abandoned from agriculture >60 years ago that were immediately adjacent to remnant habitats (areas with no history of agriculture). Using 27 sites, we conducted a factorial experiment that sowed seeds of 12 species indicative of remnant communities and conducted restoration thinning of overstorey trees in half of 126, 1-ha patches to mimic canopy density of natural savannas. We also established vegetation transects to examine if restoration promotes spread of remnant species into post-agricultural areas. We found strong evidence for dispersal limitation in post-agricultural areas as over 99% of the occurrences of our focal species were in seed addition plots. Seed additions increased total species richness by 27%. Restoration thinning increased establishment in seed addition plots (measured as richness of sown species) by 126% and increased total richness by 88%. Restoration thinning also increased seed production in remnant habitats by an average of 6506% across our focal species. However, after 4 years, restoration thinning did not facilitate the natural spread of remnant species into adjacent post-agricultural sites. Synthesis and applications. We show that both dispersal and establishment limitation are key factors causing some plant species to be absent from post-agricultural sites. Dense canopy conditions limit seed production in remnant habitats and reduce establishment in post agricultural areas. Restoration thinning helps overcome these limitations and should facilitate the natural spread of species from remnant habitats but natural recovery may still be slow. Our results suggest that accelerating the recovery of post-agricultural habitats will require active restoration that reduces dispersal limitation (seed additions) and reinstates appropriate ecological conditions.

opencc-zeroDec 2012View details →

Data from: The link between host density and egg production in a parasitoid insect: comparison between agricultural and natural habitats

1. Theory predicts that organisms should invest in overcoming a factor that may limit their reproductive success in direct proportion to their probability of being limited by it. The occurrence of egg limitation (where female insects deplete their eggs while oviposition opportunities are still available) is predicted to impose selection for increased fecundity at the expense of other fitness components. 2. We tested the hypothesis that the fecundity of a proovigenic parasitoid (where females emerge with their full egg load) should be positively correlated with the mean expectation for oviposition opportunities in the environment. More specifically, we tested whether females from agricultural systems, where hosts are often relatively abundant, emerge with more eggs than those from natural habitats. 3. We studied the proovigenic parasitoid wasp Anagrus daanei, which parasitizes eggs of leafhoppers of the genus Erythroneura. Erythroneura spp. leafhoppers feed on Vitis spp. (grapes) and are major pests of commercial vineyards as well as common herbivores of wild Vitis californica, which grows in riparian habitats. We sampled leafhoppers and parasitoids from eight vineyards and eight riparian habitats in central California. 4. We found that leafhopper density was higher at vineyards than in riparian habitats, whereas leafhopper egg size and parasitoid body size did not differ among these habitat types. Parasitoids from vineyards had higher egg loads than parasitoids from wild grapes, and fecundity was positively related to host density across field sites. Parasitoid egg volume was larger in natural sites; however, this variation was not significantly correlated with host density across field sites. Within a single population of parasitoids collected from a vineyard, parasitoid egg load was negatively correlated with longevity, suggesting a trade-off between reproduction and lifespan. 5. The results may be explained by a rapid evolution of reproductive traits in response to oviposition opportunities; or alternatively, by the occurrence of maternal effects on the fecundity of daughters based on the foraging experience of their mothers. 6. The ability of parasitoid fecundity to track mean host availability may strengthen the ability of parasitoids to suppress the population densities of their hosts, and hence may represent an important ecological or eco-evolutionary feedback.

opencc-zeroDec 2015View details →

Data from: Diversity and composition of tropical butterflies along an Afromontane agricultural gradient in the Jimma Highlands, Ethiopia

Afromontane landscapes are typically characterized by a mosaic of smallholder farms and the biodiversity impacts of these practices will vary in accordance to local management and landscape context. Here, we assess how tropical butterfly diversity is maintained across an agricultural landscape in the Jimma Highlands of Ethiopia. We used transect surveys to sample understory butterfly communities within degraded natural forest, semi-managed coffee forest (SMCF), exotic timber plantations, open woodland, croplands and pasture. Surveys were conducted in 29 one-hectare plots and repeated five times between January and June 2013. We found that natural forest supports higher butterfly diversity than all agricultural plots (measured with Hill's numbers). SMCF and timber plantations retain relatively high abundance and diversity, but these metrics drop off sharply in open woodland, cropland and pasture. SMCF and timber plantations share the majority of their species with natural forest and support an equivalent abundance of forest-dependent species, with no increase in widespread species. There was some incongruence in the responses of families and sub-families, notably that Lycaenidae are strongly associated with open woodland and pasture. Adult butterflies clearly utilize forested agricultural practices such as SMCF and timber plantations, but species diversity declines steeply with distance from natural forest suggesting that earlier life-stages may depend on host plants and/or microclimatic conditions that are lost under agricultural management. From a management perspective, the protection of natural forest remains a priority for tropical butterfly conservation, but understanding functioning of the wider landscape mosaic is important as SMCF and timber plantations may act as habitat corridors that facilitate movement between forest fragments.