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opencc-zeroAug 2020View details →

Data from: Effects of soil particles and convective transport on dispersion and aggregation of nanoplastics via small-angle neutron scattering (SANS) and ultra SANS (USANS)

Terrestrial nanoplastics (NPs) pose a serious threat to agricultural food production systems due to the potential harm of soil-born micro- and macroorganisms that promote soil fertility and ability of NPs to adsorb onto and penetrate into vegetables and other crops. Very little is known about the dispersion, fate and transport of NPs in soils. This is because of the challenges of analyzing terrestrial NPs by conventional microscopic techniques due to the low concentrations of NPs and absence of optical transparency in these systems. Herein, we investigate the potential utility of small-angle neutron scattering (SANS) and Ultra SANS (USANS) to probe the agglomeration behavior of NPs prepared from polybutyrate adipate terephthalate, a prominent biodegradable plastic used in agricultural mulching, in the presence of vermiculite, an artificial soil. SANS with the contrast matching technique was used to study the aggregation of NPs co-dispersed with vermiculite in aqueous media. We determined the contrast match point for vermiculite was 66% D 2 O / 33% H 2 O. At this condition, the signal for vermiculite was ~50-100%-fold lower that obtained using neat H 2 O or D 2 O as solvent. According to SANS and USANS, smaller-sized NPs (50 nm) remained dispersed in water and did not undergo size reduction or self-agglomeration, nor form agglomerates with vermiculite. Larger-sized NPs (300-1000 nm) formed self-agglomerates and agglomerates with vermiculite, demonstrating their significant adhesion with soil. However, employment of convective transport (simulated by ex situ stirring of the slurries prior to SANS and USANS analyses) reduced the self-agglomeration, demonstrating weak NP-NP interactions. Convective transport also led to size reduction of the larger-sized NPs. Therefore, this study demonstrates the potential utility of SANS and USANS with contrast matching technique for investigating behavior of terrestrial NPs in complex soil systems.

opencc-zeroSep 2020View details →

Parentage analyses identify local dispersal events and sibling aggregations in a natural population of Millepora hydrocorals, a free-spawning marine invertebrate

Dispersal is a critical process for the persistence and productivity of marine populations. For many reef species, there is increasing evidence that local demography and self-recruitment have major consequences on their genetic diversity and adaptation to environmental change. Yet empirical data of dispersal patterns in reef-building species remain scarce. Here, we document the first genetic estimates of self-recruitment and dispersal distances in a free-spawning marine invertebrate, the hydrocoral Millepora platyphylla. Using twelve microsatellite markers, we gathered genotypic information from 3,160 georeferenced colonies collected over 9,000 m2 of a single reef in three adjacent habitats in Moorea, French Polynesia; the mid slope, upper slope, and back reef. Although the adult population was predominantly clonal (85% were clones), our parentage analysis revealed a moderate self-recruitment rate with 8 to 37% of sexual propagules produced locally. Assigned offspring often settled at less than 10 meters from their parents and dispersal events decrease with increasing geographic distance. There were no discrepancies between the dispersal distances of offspring assigned to parents belonging to clonal versus non-clonal genotypes. Inter-habitat dispersal events via cross-reef transport were also detected for sexual and asexual propagules. Sibship analysis showed that full siblings recruit together on the reef (more than 40% settled at < 30 m), resulting in sibling aggregations. Our findings highlight the importance of self-recruitment together with clonality in stabilizing population dynamics, which may ultimately enhance local sustainability and resilience to disturbance.

opencc-zeroSep 2020View details →

Data from: Seabirds vary responses to supplemental food under dynamic natural prey availability and feeding aggregation composition

While foraging, a predator can feed solitarily or in a group. The net energy gain of joining a group is predicted to vary with prey patch quality, species-specific prey capture behavior and the size and species composition of the predator group. In coastal Newfoundland, Canada, capelin (Mallotus villosus), a key forage fish, migrates inshore to spawn during the summer, resulting in a dramatic shift in prey availability. During July-August, 2015-2017, we examined the numerical and behavioral responses of procellarid (Great Shearwater Ardenna gravis, Sooty Shearwater A. grisea, Northern Fulmar Fulmarus glacialis) and gull species (Herring Gull Larus argentatus, Great Black-backed Gull L. marinus) to fish offal under varying capelin availability as well as flock size and composition using an at-sea experiment on the northeast Newfoundland coast. The experiment consisted of providing a offal every 30 s (10-min experimental period), along with 10-min control periods before and after. We recorded the species-specific number of birds on the water, the number of birds simultaneously attempting to capture offal, and the number of successful attempts ('foraging success'). The number of birds on the water was lower during high capelin availability for all species, except for Northern Fulmar. The number of conspecifics simultaneously attempting increased with the number of conspecifics on the water, but plateaued at different numbers (4-17) for each species. The species-specific proportion of successful attempts (i.e. 'foraging success') varied with flock size and composition (i.e. number of conspecifics, heterospecifics, species). Foraging success of Herring Gulls and fulmars were moderately affected by flock size and composition, suggesting that they may be dominant competitors. Findings suggest that seabirds rely more heavily on supplemental food sources, such as fisheries discards and offal, when natural prey availability declines, potentially resulting in a higher risk of by-catch during fisheries activities as forage fish stocks decline.

opencc-by-4.0Aug 2019View details →

Dataset (.esg files) of a multiphase aggregate representative of a lower mantle composition compressed at High P/T in an R rDAC

A collection of .esg files for use in the software package Materials Analysis Using Diffraction (MAUD; Lutterotti et al., 1997). Seven files are included, spanning the range used in data analysis. All are post-conversion from San Carlos olivine. Files are named in the following format: MPBrgFp: Stands for Multiphase, primary phases bridgmanite and ferropericlase ###: Number of the diffraction pattern taken during the experiment ##GPa: Approximate temperature, rounded to the nearest whole number. This is to cross-correlate .esg files with experimental Pt pressures cited within the paper.

opencc-by-4.0Sep 2020View details →

Replication package for: The Aggregate Implications of Mergers and Acquisitions

The package contains the codes to replicate the figures and tables in David (forthcoming). "The Aggregate Implications of Mergers and Acquisitions." Review of Economic Studies. Detailed instructions are also given about accessing the raw data.

opencc-by-4.0Oct 2020View details →

Dataset for formation of amorphous materials causes parallel brittle-viscous flow of crustal rocks: Experiments on quartz – feldspar aggregates

Mechanical and microstructural data saved as .mat data files together with scripts used for plotting saved as .m filed (MATLAB). Experiments are described in Pec and Al Nasser, JGR, 2021.

opencc-zeroDec 2018View details →

Not a melting pot: plant species aggregate in their non-native range

Aim: Plant species continue to be moved outside of their native range by human activities. Here, we aim at determining whether, once introduced, plants assimilate into native communities, or whether they aggregate, thus forming mosaics of native- and alien-rich communities. Alien species may aggregate in their non-native range due to shared habitat preferences, such as their tendency to establish in high-biomass, species-poor areas. Location: 22 herbaceous grasslands in 14 countries, mainly in the temperate zone. Time period: 2012 - 2016. Major taxa studied: Plants. Methods: We used a globally coordinated survey. Within this survey, we found 46 plant species, predominantly from Eurasia, for which we had co-occurrence data in their native and non-native range. We test for differences in co-occurrence patterns of 46 species, between their native (home) and non-native (away) range. We also tested whether species had similar habitat preferences, by testing for differences in total biomass and species richness of the patches species occupy in their native and non-native range. Results: We found the same species to show different patterns of association, depending on whether they were in their native or non-native range. Alien species were negatively associated with native species, and aggregated instead with other alien species in species-poor, high-biomass communities in their non-native, compared to their native range. Main conclusions: The strong differences between the native (home) and non-native (away) range in species co-occurrence patterns are evidence that how species associate with resident communities in their non-native range is not species-dependent, but rather a property of being away from their native range. These results thus highlight that species may undergo important ecological changes when introduced away from their native range. Overall, we show origin-dependent associations that result in novel communities in which alien-rich patches exist within a mosaic of native-dominated communities.

opencc-by-nc-nd-4.0Dec 2020View details →

Energy consumption and renewable generation data of 5 aggregators - 15 minute resolution (13 bus grid)

Type: Energy consumption and renewable generation data Period of data collection: 19-03-2019 to 25-03-2019 (15-minute 672 periods) Resolution: 15 minutes Network: 13-bus MV grid Aggregator list: <ul> <li>Aggregator 1: Shopping Mall; Hospital; Fire Station</li> <li>Aggregator 2: 15 houses</li> <li>Aggregator 3: 7 Office buildings</li> <li>Aggregator 4: Wind, PV</li> <li>Aggregator 5: Slow and fast-charging stations of electric vehicles</li> </ul> Further data: <ul> <li>Market prices 2019 summer and winter</li> <li>Wind generation curve</li> </ul> Data obtained from CENERGETIC project (<a href="http://www.gecad.isep.ipp.pt/CENERGETIC/">http://www.gecad.isep.ipp.pt/CENERGETIC/</a>) National Funds through the FCT—Portuguese Foundation for Science and Technology, under Project PTDC/EEI-EEE/28983/2017 (CENERGETIC), CEECIND/02814/2017, UIDB/00760/2020.

Data from: Phylogenetic ANOVA: group-clade aggregation, biological challenges, and a refined permutation procedure

Phylogenetic regression is frequently utilized in macroevolutionary studies, and its statistical properties have been thoroughly investigated. By contrast, phylogenetic ANOVA has received relatively less attention, and the conditions leading to incorrect statistical and biological inferences when comparing multivariate phenotypes among groups remains under-explored. Here we propose a refined method of randomizing residuals in a permutation procedure (RRPP) for evaluating phenotypic differences among groups while conditioning the data on the phylogeny. We show that RRPP displays appropriate statistical properties for both phylogenetic ANOVA and regression models, and for univariate and multivariate datasets. For ANOVA, we find that RRPP exhibits higher statistical power than methods utilizing phylogenetic simulation. Additionally, we investigate how group dispersion across the phylogeny affects inferences, and reveal that highly aggregated groups generate strong and significant correlations with the phylogeny, which reduce statistical power and subsequently affect biological interpretations. We discuss the broader implications of this phylogenetic group aggregation, and its relation to challenges encountered with other comparative methods where one or a few transitions in discrete traits are observed on the phylogeny. Finally, we recommend that phylogenetic comparative studies of continuous trait data utilize RRPP for assessing the significance of indicator variables as sources of trait variation.

opencc-zeroDec 2012View details →

Data from: The social factors driving settlement and relocation decisions in a solitary and aggregative spider

Both ecological and social factors play an important role in determining the structure of animal settlement patterns. While the ecological factors determining animal settlement are generally well known, the relative importance of social factors in mediating fine-scale settlement choices is poorly understood. As a result, we have little knowledge of why individuals choose to settle near specific neighbors. Here we used a web-building spider (Nephila plumipes) that settles both solitarily and next to neighbors within aggregations to examine the specific social factors that influence settlement decisions. Within experimental enclosures we observed the settlement patterns of females pre- and post-male release. This allowed us to compare two models of aggregative settlement in lekking species, the hotshot and preferences models, to examine the relative importance of a female's phenotype and mate attraction to further dissect settlement and relocation decisions. We show that mate attraction increased with aggregation size, and that larger females were generally preferred, supporting both the hotshot and preference models of aggregative settlement. We further demonstrate that smaller females that attracted fewer males within an aggregation were most likely to relocate. Our results demonstrate how social feedback can affect initially state-dependent settlement decisions, thereby highlighting the dynamic nature of settlement.

Data from: Genetic data reveal mixed-stock aggregations of gray whales in the North Pacific Ocean

Gray whales (Eschrichtius robustus) in the Western Pacific are critically endangered whereas in the Eastern Pacific they are relatively common. Holocene environmental changes and commercial whaling reduced their numbers, but gray whales in the Eastern Pacific now outnumber their Western counterparts by more than 100-fold. Herein, we investigate the genetic diversity and population structure within the species using a panel of genic SNPs. Results indicate the gray whale gene pool is differentiated into two substocks containing similar levels of genetic diversity, and that both our Eastern and Western geographic samples represent mixed-stock aggregations. Ongoing or future gene flow between the stocks may conserve genetic diversity overall but admixture has implications for conservation of the critically endangered Western gray whale.

Data from: Towards a better understanding of the Chenopodium album aggregate (Amaranthaceae) in the Middle East: a karyological, cytometric and morphometric investigation

The study of variation in nuclear genome size, especially when combined with common garden experiments, significantly contributes to disentangling interspecies relationships within taxonomically complicated plant groups. The Chenopodium album aggregate is among the morphologically most variable groups and consists of many weakly differentiated cosmopolitan entities. We analysed nuclear genome size variation in diploid and polyploid species of the aggregate from Iran using flow cytometry of 282 accessions from 88 populations of 7 species. To this end, we also determined chromosome numbers and performed a morphometric study to reveal the extent of intraspecific morphological variation. We found that Iranian species are exclusively diploid (C. vulvaria), tetraploid (C. novopokrovskyanum, C. strictum, C. sosnowskyi and C. chaldoranicum) or hexaploid (C. album subsp. album, C. album subsp. iranicum and C. opulifolium). Six homogeneous relative genome size groups were distinguished among the species studied. Our morphometric study surprisingly revealed that under similar ecological conditions Chenopodium species are morphologically stable and well distinguishable, exhibited very little morphological variation. Hence, immense variation in leaf shapes, branching and inflorescence organization seen in the field has not been repeated under greenhouse conditions. The only exception was C. album s. str. which exhibited numerous morphotypes, covering the variation of remaining species.

opencc-zeroDec 2016View details →

Data from: Whether larval amphibians school does not affect the parasite aggregation rule: testing the effects of host spatial heterogeneity in field and experimental studies

Almost all macroparasites show over-dispersed infections within natural host populations such that most parasites are distributed among a few heavily-infected individuals. Despite the importance of parasite aggregation for understanding system stability, the potential for population regulation, and super-spreading events, many questions persist about its underlying drivers. Theoretically, aggregation results from heterogeneity in host exposure, resistance, and tolerance. However, few studies have examined how host spatial arrangement – which likely affects both parasite encounter and density-dependent interactions – influences infection and dispersion, representing a critical gap in our current knowledge regarding the possible drivers of parasite aggregation. Using field data from over 165 ponds and 8,000 hosts, we evaluated how the spatial clustering of amphibian larvae within ponds 1) varied among different amphibian species, and 2), affected the distribution of parasites within the host population using Taylor's Power Law. A complementary mesocosm experiment used field-guided manipulations of the spatial arrangement of larval amphibians to create a gradient in host clustering while controlling host density, thereby testing for spatial effects on both infection success and aggregation by three different trematode species. Our field data indicated that larval amphibians exhibited significant spatial clustering that was well captured by Taylor's Power Law (R2 0.92 to 0.97 for different host species), but the residual variation only weakly correlated with observed patterns of trematode parasite over-dispersion. Correspondingly, experimental manipulation of host clustering had no effects on parasite infection success or the degree of parasite aggregation among cages or mesocosms. Given the importance of parasite over-dispersion for host populations and disease dynamics, we advocate for further investigations of host and parasite spatial aggregation, particularly studies that incorporate and/or control for heterogeneity in exposure and susceptibility.

Data from: Alaskan brown bears (Ursus arctos) aggregate and display fidelity to foraging neighborhoods while preying on Pacific salmon along small streams

The interaction between brown bears (Ursus arctos) and Pacific salmon (Oncorhynchus spp.) is important to the population dynamics of both species and a celebrated example of consumer-mediated nutrient transport. Yet, much of the site-specific information we have about the bears in this relationship comes from observations at a few highly visible but unrepresentative locations and a small number of radio-telemetry studies. Consequently, our understanding of brown bear abundance and behavior at more cryptic locations where they commonly feed on salmon, including small spawning streams, remains limited. We employed a non-invasive genetic approach (barbed wire hair snares) over four summers (2012-2015) to document patterns of brown bear abundance and movement among six spawning streams for sockeye salmon, O. nerka, in southwestern Alaska. The streams were grouped into two trios on opposite sides of Lake Aleknagik. Thus, we predicted that most bears would forage within only one trio during the spawning season because of the energetic costs associated with swimming between them or traveling around the lake, and show fidelity to particular trios across years because of the benefits of familiarity with local salmon dynamics and stream characteristics. Huggins closed-capture models based on encounter histories from genotyped hair samples revealed that as many as 41 individuals visited single streams during the annual six-week sampling season. Bears also moved freely among trios of streams but rarely moved between these putative foraging neighborhoods, either during or between years. By implication, even small salmon spawning streams can serve as important resources for brown bears, and consistent use of stream neighborhoods by certain bears may play an important role in spatially structuring coastal bear populations. Our findings also underscore the efficacy of non-invasive hair snagging and genetic analysis for examining bear abundance and movements at relatively fine spatial and temporal scales.

opencc-zeroAug 2019View details →

Data from: Grouper (Epinephelidae) spawning aggregations affect activity space of grey reef sharks, Carcharhinus amblyrhynchos, in Pohnpei, Micronesia

Fish spawning aggregations (FSA) act as biological hotspots that concentrate food and nutrients across a broad trophic spectrum. In Pohnpei (Federated States of Micronesia), 20 female grey reef sharks (Carcharhinus amblyrhynchos) were acoustically tagged at two multi-species grouper (Epinephelidae) FSA to examine the likelihood that these mesopredators utilize FSA as a seasonal food source. Both FSA sites are within small-scale MPAs, thus providing a secondary opportunity to examine their conservation potential during these ephemeral events. Shark movement and residency was gauged against known spatial and temporal grouper reproductive patterns using an array of 15 and 50 acoustic receivers at Ant Atoll and Pohnpei (Island), respectively. Activity space was investigated using Kernel Density estimates of individual sharks, and residency indices (RI) were analyzed based on daily and monthly occurrence at the array. Three distinct residency patterns were identified: transient, semi-transient, or resident (Daily RI <0.40, >0.40<0.80, or >0.80, respectively). Generalized linear mixed models (GLMMs) were used to identify biological and environmental factors influencing shark activity space, including month, temperature, shark size, spawning month, and residency pattern. Findings revealed significant changes in average monthly residency indices and kernel densities during spawning months in support of an opportunistic foraging strategy around FSA. Monthly residency was higher during spawning months among semi-resident and transient sharks, while average monthly activity space was concentrated around FSA. Best-fit models for the GLMM indicated that activity spaces were most influenced by month and grouper spawning month. Seven of 20 sharks demonstrated inter-island movement and wide variations in individual movement and spatial requirements were shown. The concentration of sharks and groupers at unprotected FSA sites increases their vulnerability to fishing and supports the need for combined area and non-area management measures to effectively protect these species.

opencc-zeroDec 2015View details →

Data from: Soil aggregate stability and grassland productivity associations in a northern mixed-grass prairie

Soil aggregate stability data are often predicted to be positively associated with measures of plant productivity, rangeland health, and ecosystem functioning. Here we revisit the hypothesis that soil aggregate stability is positively associated with plant productivity. We measured local (plot-to-plot) variation in grassland community composition, plant (aboveground) biomass, root biomass, % water-stable soil aggregates, and topography. After accounting for spatial autocorrelation, we observed a negative association between % water-stable soil aggregates (0.25-1 and 1-2 mm size classes of macroaggregates) and dominant graminoid biomass, and negative associations between the % water-stable aggregates and the root biomass of a dominant sedge (Carex filifolia). However, variation in total root biomass (0-10 or 0-30 cm depths) was either negatively or not appreciably associated with soil aggregate stabilities. Overall, regression slope coefficients were consistently negative thereby indicating the general absence of a positive association between measures of plant productivity and soil aggregate stability for the study area. The predicted positive association between factors was likely confounded by variation in plant species composition. Specifically, sampling spanned a local gradient in plant community composition which was likely driven by niche partitioning along a subtle gradient in elevation. Our results suggest an apparent trade-off between some measures of plant biomass production and soil aggregate stability, both known to affect the land's capacity to resist erosion. These findings further highlight the uncertainty of plant biomass-soil stability associations.

Data from: Discovery of a multi-species shark aggregation and parturition area in the Ba Estuary, Fiji Islands

Population declines in shark species have been reported on local and global scales, with overfishing, habitat destruction and climate change posing severe threats. The lack of species-specific baseline data on ecology and distribution of many sharks, however, makes conservation measures challenging. Here we present a fisheries-independent shark survey from the Fiji Islands, where scientific knowledge on locally occurring elasmobranchs is largely still lacking despite the location's role as a shark hotspot in the Pacific. Juvenile shark abundance in the fishing grounds of the Ba Estuary (north-western Viti Levu) was assessed with a gillnet- and longline-based survey from December 2015 to April 2016. A total of 103 juvenile sharks identified as blacktip Carcharhinus limbatus (n = 57), scalloped hammerhead Sphyrna lewini (n = 35), and great hammerhead Sphyrna mokarran (n = 11) sharks were captured, tagged, and released. The condition of umbilical scars (68 % open or semi-healed), mean sizes of individuals (± SD) (C. limbatus: 66.5 ± 3.8 cm, S. lewini: 51.8 ± 4.8 cm, S. mokarran 77.4 ± 2.8 cm), and the presence of these species over recent years (based on fishermen interviews), suggest that the Ba Estuary area is a critical habitat for multiple species that are classified as "Near Threatened" or "Endangered". Specifically, the area likely acts as a parturition ground over the studied period, and potentially as a subsequent nursery area. We identified subareas of high abundance and found that temperature, salinity and depth acted as small-scale environmental drivers of shark abundance. The data suggests a tendency for species-specific spatial use, both horizontally (i.e. between sampling areas) and vertically (i.e. across the water column). These results enhance the understanding of shark ecology in Fiji and provide a scientific basis for the implementation of local conservation strategies that contribute to the protection of these threatened species.

opencc-zeroDec 2015View details →

Data from: Aggregation and a strong Allee effect in a cooperative outbreak insect

Most species that are negatively impacted when their densities are low aggregate to minimize this effect. Aggregation has the potential to change how Allee effects are expressed at the population level. We studied the interplay between aggregation and Allee effects in the mountain pine beetle (Dendroctonus ponderosae Hopkins), an irruptive bark beetle that aggregates to overcome tree defenses. By cooperating to surpass a critical number of attacks per tree, the mountain pine beetle is able to breach host defenses,oviposit and reproduce. Mountain pine beetles and Hymenopteran parasitoids share some biological features, the most notable of which is obligatory host death as a consequence of parasitoid attack and development. We developed spatiotemporal models of mountain pine beetle dynamics that were based on the Nicholson-Bailey framework but which featured beetle aggregation and a tree-level attack threshold. By fitting our models to data from a local mountain pine beetle outbreak, we demonstrate that due to aggregation, attack thresholds at the tree level can be overcome by a surprisingly low ratio of beetles per susceptible tree at the stand level. This results confirms the importance of considering aggregation in models of organisms that are subject to strong Allee effects.

opennotspecifiedDec 2005View details →

FIGURE 5 in Two new species of Ostracoda from hydrothermal vents of Riftia pachyptila aggregations on the East Pacific Rise (Halocypridina; Cladocopina)

FIGURE 5. Archiconchoecia chavturi, new species, adult female, holotype: A, right mandible, mv; B, endopod left mandible, lv; C, part basis and endopod left mandible, lv; D, part coxa and basis right mandible, mv; E, coxa endite right mandible as seen through basis (indistinct), lv. (lv = lateral view; mv = medial view.)