Find research datasets worth reusing

opencc-zeroDec 2013View details →

Data from: Species traits and abundances predict metrics of plant–pollinator network structure, but not pairwise interactions

Plant–pollinator mutualistic networks represent the ecological context of foraging (for pollinators) and reproduction (for plants and some pollinators). Plant–pollinator visitation networks exhibit highly conserved structural properties across diverse habitats and species assemblages. The most successful hypotheses to explain these network properties are the neutrality and biological constraints hypotheses, which posit that species interaction frequencies can be explained by species relative abundances, and trait mismatches between potential mutualists respectively. However, previous network analyses emphasize the prediction of metrics of qualitative network structure, which may not represent stringent tests of these hypotheses. Using a newly documented temporally explicit alpine plant–pollinator visitation network, we show that metrics of both qualitative and quantitative network structure are easy to predict, even by models that predict the identity or frequency of species interactions poorly. A variety of phenological and morphological constraints as well as neutral interactions successfully predicted all network metrics tested, without accurately predicting species observed interactions. Species phenology alone was the best predictor of observed interaction frequencies. However, all models were poor predictors of species pairwise interaction frequencies, suggesting that other aspects of species biology not generally considered in network studies, such as reproduction for dipterans, play an important role in shaping plant–pollinator visitation network structure at this site. Future progress in explaining the structure and dynamics of mutualistic networks will require new approaches that emphasize accurate prediction of species pairwise interactions rather than network metrics, and better reflect the biology underlying species interactions.

Data from: Local and landscape-scale heterogeneity shape spotted wing drosophila (Drosophila suzukii) activity and natural enemy abundance: implications for trophic interactions

Like natural enemies, invasive polyphagous pests may respond positively to local and landscape-scale diversity, making them more serious challenges to sustainable management than specialists. Yet the current view of landscape effects on pests rarely considers perennial systems or polyphagous pests. We investigated Drosophila suzukii (SWD) and natural enemy distributions and trophic interactions in blueberry systems of the southeast US in relation to local management and landscape structure. Fields were nested in 1-km landscapes along gradients of crop and forest heterogeneity (landscape compositional diversity) and field border and crop border lengths (landscape configurational diversity). Yeast-sugar bait traps were used to collect SWD and canopy suction sampling for natural enemies. Management practices at the local scale did not influence SWD abundance, but natural enemy abundance was higher in organic systems and fields with vegetation present between rows. Landscape configurational diversity and greater proportion of non-cropping habitat promoted higher SWD populations. Natural enemy communities were composed of highly generalized species, and contrary to our predictions, we observed lower abundances in landscapes with higher proportion of non-cropping area. Few predators were detected to have fed on SWD, and communities were dominated by predators with low specialization on prey in blueberry. Our results indicate that local and landscape features in blueberry landscapes have differential effects on a polyphagous pest and generalist natural enemies. Our initial analysis of predator diets, using a metabarcoding approach, suggests spatial structure in specialization on prey with high diversity of prey in predators collected in forested margins.

opencc-zeroDec 2014View details →

Data from: Abundance inequality in freshwater communities has an ecological origin

The hollow-shaped species abundance distribution (SAD) and its allied rank abundance distribution (RAD)—showing that abundance is unevenly distributed among species—are some of the most studied patterns in ecology. To explain the nature of abundance inequality, I developed a novel framework identifying environmental favorability, which controls the balance between reproduction and immigration, as the ultimate source and species stress tolerance as a proximate factor. Thus, under harsh conditions, only a few tolerant species can reproduce, while some sensitive species can be present in low numbers due to chance immigration. This would lead to high abundance inequality between the two groups of species. Under benign conditions, both groups can reproduce and give rise to higher abundance equality. To test these ideas, I examined the variability in the parameters of a Poisson lognormal fit of the SAD and a square root fit of the RAD in diatom and fish communities across US streams. Indeed, as environmental favorability increased, more sensitive forms were able to establish large populations, diminishing the abundance disparity between locally common and rare species. Finally, it was demonstrated that in diatoms, the RAD belonged to the same family of relationships as those of population density with body size and regional distribution.

opencc-zeroDec 2011View details →

Data from: Oceanographic drivers of offspring abundance may increase or decrease variance in reproductive success in a temperate marine fish

In species that reproduce into uncertain environments, the relationship between mean reproductive success (the abundance of new recruits) and the variance in reproductive success (whether adults contribute disproportionally more offspring) may not be straightforward because of stochastic environmental processes that create high variance in reproductive success among adults. In this study we investigated the relationships between oceanography, reproductive success, and reproductive variance in the black rockfish, Sebastes melanops, a long-lived temperate reef fish with pelagic larvae. We quantified black rockfish recruitment, genetic diversity, and growth rates from otolith microstructure over 5 years (2005-2009) during which oceanographic conditions differed. We used cross-correlations to determine windows of time during which oceanographic variables were significantly correlated with the resulting abundance or genetic diversity of recruits. We found that warmer ocean temperatures were positively correlated with the abundance of recruits, as well as the effective number of breeders. In contrast, the strength of coastal upwelling during settlement was positively correlated with the annual abundance of new recruits, but was negatively correlated with the effective number of breeders. Larval growth rates were explained substantially more by temperature than by upwelling, and suggested that temperature affected survival through growth, while upwelling affected survival through transport. Our results indicated that cold ocean temperatures and intense upwelling caused sweepstakes-like processes to operate on black rockfish populations, despite high abundances of recruits. We propose that a decoupling of the mean and variance in reproductive success may be characteristic of organisms that reproduce into uncertain environments.

Data from: The interplay among intraspecific leaf trait variation, niche breadth and species abundance along light and soil nutrient gradients

It is assumed that widespread, generalist species have high phenotypic variation, but we know little about how intraspecific trait variation (ITV) relates to species abundance and niche breadth. In the temperate rainforest of southern Chile, we hypothesized that species with wide niche breadth would exhibit 1) high among-plot ITV, 2) a strong relationship between trait values and the environment, and 3) a close fit between traits and local environment trait optima. We measured leaf functional traits (leaf area, LMA, leaf N and P concentrations) of saplings in woody species, and compared the relative abundance of each species with its niche breadth, measured as the range of light, soil N and P availability. We used the slope of the linear regression of species' trait-environment relationships to assess the strength and direction of these relationships, and measured the degree to which species' trait values track the environmental optimum across plots. In some cases, species having wide niche breadth had high ITV in leaf N and also matched traits (LMA and leaf P) to local optima along the light gradient; they also had high ITV in general and matched leaf P to local optima along the soil P gradient. The relationship between species with wide niche breadth and the strength of intraspecific trait-environment relationships was generally weak and varied depending on the niche dimension and trait in question. Species varied considerably in the strength of trait-environment relationships and total magnitude of ITV, and this variation was not generally strongly related to species abundances or niche breadth patterns. In conclusion, trait variation at the community level is not driven by a few abundant, widely distributed species, but depends on the aggregate trait responses of both abundant and rare species. This makes it difficult to scale individual species trait responses up to the community level.

opencc-zeroDec 2014View details →

Data from: Effects of mountaintop removal mining and valley filling on the occupancy and abundance of stream salamanders

Human-induced land-use changes are among the primary causes of ecosystem degradation and biodiversity loss. Across central Appalachia (USA), mountaintop removal mining and valley filling (MTR/VF) is the prevailing form of land-use change and represents a stressor to stream ecosystems. Salamanders are the dominant vertebrate in Appalachian headwater streams. Thus, we addressed the question: Is salamander occupancy and conditional abundance reduced in streams impacted by MTR/VF? We conducted repeated counts of adult and larval salamanders within 10-m reaches in 11 valley-filled streams and 12 reference streams in south-eastern Kentucky. Relationships between occupancy, conditional abundance, and site type (MTR/VF vs. reference) were modelled using the hurdle model (Ecology, 94, 2013 and 1472), where occupancy is modelled separately from abundance while accounting for differences in per-individual detection probabilities among groups. We found mean occupancy probabilities were >0·85 for all groups in reference reaches, whereas mean occupancy probabilities were relatively lower in MTR/VF reaches (ranging from 0·23 to 0·66). Posterior means of the difference in occupancy between site types were negative across all groups, although MTR/VF stream reaches were at least 95% less likely to be occupied by spring salamander Gyrinophilus porphyriticus, adult southern two-lined salamander Eurycea cirrigera and larval dusky salamanders Desmognathus compared to reference reaches. Posterior means of the difference in conditional abundance between MTR/VF and reference stream reaches were negative across all groups; 95% credible interval for difference in conditional abundance covered zero for only one species (red salamander Pseudotriton ruber). After adjusting for goodness-of-fit, point estimates of differences in occupancy and conditional abundance still remained below zero for most species. Additionally, MTR/VF reaches had higher ion concentrations, total organic carbon and specific conductance compared to reference reaches. Synthesis and applications. Our study concludes that mountaintop removal mining and valley filling (MTR/VF) reduces salamander occupancy and conditional abundance. Although the potential mechanisms responsible for reduction are numerous, our findings suggest a change in the current regulatory framework is needed to offset the impacts of MTR/VF on stream ecosystems and biota. Reclamation techniques that enhance conditions for vegetative succession within catchments may improve habitat on reclaimed surface mines.

Data from: Use of hidden Markov capture-recapture models to estimate abundance in presence of uncertainty: application to estimating the prevalence of hybrids in animal populations

Estimating the relative abundance (prevalence) of different population segments is a key step in addressing fundamental research questions in ecology, evolution, and conservation. The raw percentage of individuals in the sample (naive prevalence) is generally used for this purpose, but it is likely to be subject to two main sources of bias. First, the detectability of individuals is ignored; second, classification errors may occur due to some inherent limits of the diagnostic methods. We developed a hidden Markov (also known as multievent) capture–recapture model to estimate prevalence in free‐ranging populations accounting for imperfect detectability and uncertainty in individual's classification. We carried out a simulation study to compare naive and model‐based estimates of prevalence and assess the performance of our model under different sampling scenarios. We then illustrate our method with a real‐world case study of estimating the prevalence of wolf (Canis lupus) and dog (Canis lupus familiaris) hybrids in a wolf population in northern Italy. We showed that the prevalence of hybrids could be estimated while accounting for both detectability and classification uncertainty. Model‐based prevalence consistently had better performance than naive prevalence in the presence of differential detectability and assignment probability and was unbiased for sampling scenarios with high detectability. We also showed that ignoring detectability and uncertainty in the wolf case study would lead to underestimating the prevalence of hybrids. Our results underline the importance of a model‐based approach to obtain unbiased estimates of prevalence of different population segments. Our model can be adapted to any taxa, and it can be used to estimate absolute abundance and prevalence in a variety of cases involving imperfect detection and uncertainty in classification of individuals (e.g., sex ratio, proportion of breeders, and prevalence of infected individuals).

Data from: Abiotic and habitat drivers of tick vector abundance, diversity, phenology and human encounter risk in southern California

The distribution, abundance and seasonal activity of vector species, such as ticks and mosquitoes, are key determinants of vector-borne disease risk, and are strongly influenced by abiotic and habitat conditions. Despite the numerous species of tick vectors in the heavily populated North American West Coast, all but Ixodes pacificus, the primary vector of the Lyme disease spirochete, is poorly characterized with regard to seasonal activity patterns and fine scale drivers of distribution and abundance, particularly in heavily populated regions of southern California. This lack of knowledge inhibits both scientific understanding and public health efforts to minimize vector exposure and risk of pathogen transmission to humans. Here we address this gap by characterizing the abiotic and habitat drivers of the distribution, abundance, and diversity of the vector tick community using fine scale temporal surveys over two seasons (2014 and 2015) across coastal and inland regions of Santa Barbara County, CA. We also characterize patterns of seasonal activity of the more common vector species to understand seasonality in risk of vector exposure, and specifically focus on human encounter risk using standardized tick drags as our method of collection. Leveraging plot-level habitat and abiotic variables in partial least squares regression analysis, we find the seven different vector species collected in this study have divergent drivers of activity and abundance. For example, I. pacificus is strongly associated with dense forest habitats and cool and moist microclimates, while Dermacentor occidentalis and Dermacentor variabilis, competent vectors of Rocky Mountain Spotted Fever, were found to be more tolerant of higher average temperatures and more open habitats. These results suggest that I. pacificus may be expected to experience reductions in geographic distribution and seasonal activity under projected land cover and climate change in coastal southern California, while D. occidentalis may experience more limited effects. We discuss implications for changing tick-borne disease risk associated with pathogens transmitted by Ixodes as well as Dermacentor species ticks in the western US, and contrast these predictions with eastern North America.

Data from: The abundance and distribution of guilds of riparian woody plants change in response to land use and flow regulation

1. Many riparian ecosystems in Mediterranean Europe are affected by land use and flow alteration by dams. We focused on understanding how these stressors and their components affect riparian forests in the region. We asked: (i) are there well-defined, responsive riparian guilds?; (ii) do dam-induced stream flows determine abundance and distribution of riparian guilds? and (iii) what are the main drivers governing composition and cover of riparian guilds in regulated rivers? 2. We inventoried the cover of riparian woody species in free-flowing rivers and downstream of dams. We performed a cluster analysis and ordination to derive riparian guilds, using abundance data from 66 riparian woody species and 26 functional plant traits. We used a reduced set of principal components for the environment, land use and hydrology, and general linear modelling to explore the effect of these factors (separately and combined) on riparian guilds. 3. We found that: (i) four dominant guilds are responsive to disturbance in Southwestern European streams, namely the obligate riparian, water-stress tolerant, deciduous competitive, and Mediterranean evergreen guilds ; (ii) a set of land use and hydrological variables differentially affect the diverse co-occurring riparian guilds; (iii) frequency and duration of high flow pulses and the low-flow conditions were major drivers of change in landscapes dominated by intensive agriculture and forestry; (iv) storage reservoirs reduced the cover of obligate riparian and Mediterranean evergreen guilds, and increased the abundance of water-stress tolerant and deciduous competitive guilds, while run-of-river dams, having limited water storage, reduced both obligate and deciduous competitive guilds. 4. Synthesis and applications. Future research, especially in Southwestern Europe, should address the resilience of riparian guilds and the effects of interacting landscape factors and stressors on guild distribution. Stream flow regulations downstream of reservoirs should focus on specific flow components, namely the magnitude of flows, and frequency and duration of extreme flow events. For successful mitigation of the dam-induced effects on riparian vegetation, river management plans must incorporate the environmental and land use site-specific contexts.

Data from: A low-cost solution for documenting distribution and abundance of endangered marine fauna and impacts from fisheries

Fisheries bycatch is a widespread and serious issue that leads to declines of many important and threatened marine species. However, documenting the distribution, abundance, population trends and threats to sparse populations of marine species is often beyond the capacity of developing countries because such work is complex, time consuming and often extremely expensive. We have developed a flexible tool to document spatial distribution and population trends for dugongs and other marine species in the form of an interview questionnaire supported by a structured data upload sheet and a comprehensive project manual. Recognising the effort invested in getting interviewers to remote locations, the questionnaire is comprehensive, but low cost. The questionnaire has already been deployed in 18 countries across the Indo-Pacific region. Project teams spent an average of USD 5,000 per country and obtained large data sets on dugong distribution, trends, catch and bycatch, and threat overlaps. Findings indicated that >50% of respondents had never seen dugongs and that 20% had seen a single dugong in their lifetimes despite living and fishing in areas of known or suspected dugong habitat, suggesting that dugongs occured in low numbers. Only 3% of respondents had seen mother and calf pairs, indicative of low reproductive output. Dugong hunting was still common in several countries. Gillnets and hook and line were the most common fishing gears, with the greatest mortality caused by gillnets. The questionnaire has also been used to study manatees in the Caribbean, coastal cetaceans along the eastern Gulf of Thailand and western Peninsular Malaysia, and river dolphins in Peru. This questionnaire is a powerful tool for studying distribution and relative abundance for marine species and fishery pressures, and determining potential conservation hotspot areas. We provide the questionnaire and supporting documents for open-access use by the scientific and conservation communities.

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.

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: Temperature drives abundance fluctuations, but spatial dynamics is constrained by landscape configuration: implications for climate-driven range shift in a butterfly

1. Prediction of species distributions in an altered climate requires knowledge on how global- and local-scale factors interact to limit their current distributions. Such knowledge can be gained through studies of spatial population dynamics at climatic range margins. 2. Here, using a butterfly (Pyrgus armoricanus) as model species, we first predicted based on species distribution modelling that its climatically suitable habitats currently extend north of its realized range. Projecting the model into scenarios of future climate, we showed that the distribution of climatically suitable habitats may shift northward by an additional 400 km in the future. 3. Second, we used a 13-year monitoring data set including the majority of all habitat patches at the species' northern range margin to assess the synergetic impact of temperature fluctuations and spatial distribution of habitat, microclimatic conditions and habitat quality, on abundance and colonisation-extinction dynamics. 4. The fluctuation in abundance between years was almost entirely determined by the variation in temperature during the species' larval development. In contrast, colonisation and extinction dynamics were better explained by patch area, between-patch connectivity, and host plant density. This suggests that the response of the species to future climate change may be limited by future land-use and how its host plants respond to climate change. It is thus probable that dispersal limitation will prevent P. armoricanus from reaching its potential future distribution. 5. We argue that models of range dynamics should consider the factors influencing metapopulation dynamics, especially at the range edges, and not only broad-scale climate. It includes factors acting at the scale of habitat patches such as habitat quality and microclimate, and landscape-scale factors such as the spatial configuration of potentially suitable patches. Knowledge of population dynamics under various environmental conditions, and the incorporation of realistic scenarios of future land-use, appear thus essential to provide predictions useful for actions mitigating the negative effects of climate change.

Data from: Predicting community rank-abundance distributions under current and future climates

Understanding influences of environmental change on biodiversity requires consideration of more than just species richness. Here we present a novel framework for understanding possible changes in species' abundance structures within communities under climate change. We demonstrate this using comprehensive survey and environmental data from 1,748 woody plant communities across southeast Queensland, Australia, to model rank-abundance distributions (RADs) under current and future climates. Under current conditions, the models predicted RADs consistent with the region's dominant vegetation types. We demonstrate that under a business as usual climate scenario, total abundance and richness may decline in subtropical rainforest and shrubby heath, and increase in dry sclerophyll forests. Despite these opposing trends, we predicted evenness in the distribution of abundances between species to increase in all vegetation types. By assessing the information rich, multidimensional RAD, we show that climate-driven changes to community abundance structures will likely vary depending on the current composition and environmental context.

Data from: Bryophyte abundance, diversity and composition after retention harvest in boreal mixedwood forest

1. Variable-retention harvest is widely recognised as an alternative to more intensive methods such as clear-cutting. However, present information is inadequate to judge impact of variable-retention on biodiversity of indigenous forest organisms intolerant of canopy removal, such as forest-inhabiting bryophytes. 2. We examined how bryophyte species cover, richness, diversity and composition change with time in response to a broad range of dispersed retention harvest treatments (2% (clear-cut), 10%, 20%, 50%, 75% retention of original basal area) contrasted with uncut controls (100% retention)) in broadleaf deciduous, mixedwood and conifer-dominated boreal forests in NW Alberta, Canada. Bryophytes were studied in 432 permanent sample plots within 72 compartments before harvest and at three, six and eleven years after harvest. 3. Clear-cut and lower (10% and 20%) retention levels resulted in lower cover and richness of bryophytes than in unharvested control compartments in mixed and conifer-dominated forests, but less so in deciduous-dominated forests, which generally supported low cover and richness. Species composition in each forest type varied along the gradient of harvesting intensity; clear-cuts and lower levels of retention supported similar composition, as did control plots and those representing higher retention levels. Over time the retention harvest treatments became more similar to uncut controls. 4. Synthesis and applications. Increased retention moderated the negative impacts of harvesting on bryophyte assemblages across all forest types, and our results suggest that even 10% retention will facilitate faster post-harvest recovery of bryophytes.02-Aug-2017

Data from: Decline in abundance and apparent survival rates of fin whales (Balaenoptera physalus) in the northern Gulf of St. Lawrence

Estimates of abundance and survivorship provide quantifiable measures to monitor populations and to define and understand their conservation status. This study investigated changes in abundance and survival rates of fin whales (Balaenoptera physalus) in the northern Gulf of St. Lawrence (GSL) in the context of anthropogenic pressures and changing environmental conditions. A long-term data set, consisting of 35 years of photo-identification surveys and comprising more than 5,000 identifications of 507 individuals, formed the basis of this mark-recapture study. Based on model selection using corrected Akaike Information Criterion, the most parsimonious Cormack-Jolly-Seber model included a linear temporal trend in non-calf apparent survival rates with a sharp decline in the last five years of the study and a median survival rate of 0.946 (95% confidence interval (CI) 0.910-0.967). To account for capture heterogeneity due to divergent patterns of site fidelity, agglomerative hierarchical cluster (AHC) analysis was employed to categorise individuals based on their annual and survey site fidelity indices. However, the negative trend in survivorship remained and was corroborated by a significant decline in the estimated super-population size from 335 (95% CI 321-348) individuals in 2004-2010 to 291 (95% CI 270-312) individuals in 2010-2016. Concurrently, a negative trend was estimated in recruitment to the population, supported by a sharp decrease in the number of observed calves. Ship strikes and changes in prey availability are potential drivers of the observed decline in fin whale abundance. The combination of clustering methods with mark-recapture represents a flexible way to investigate the effects of site fidelity on demographic variables and is broadly applicable to other individual-based studies.

opencc-zeroDec 2013View details →

Data from: High food abundance permits the evolution of placentotrophy: evidence from a placental lizard, Pseudemoia entrecasteauxii

Mechanisms of reproductive allocation are major determinants of fitness because embryos cannot complete development without receiving sufficient nutrition from their parents. The nourishment of offspring via placentae (placentotrophy) has evolved repeatedly in vertebrates, including multiple times in squamate reptiles (lizards and snakes). Placentotrophy has been suggested to evolve only if food is sufficiently abundant throughout gestation to allow successful embryogenesis. If scarcity of food prevents successful embryogenesis, females should recoup nutrients allocated to embryos via abortion, reabsorption, and/or cannibalism. We tested these hypotheses in the placentotrophic Southern Grass Skink, Pseudemoia entrecasteauxii. We fed females one of four diets (high constant, high variable, low constant, and low variable) during gestation, and tested the effects of both food amount and schedule of feeding on developmental success, cannibalism rate, placental nutrient transport, offspring size, and maternal growth and body condition. Low food availability reduced developmental success, placental nutrient transport, offspring size, and maternal growth and body condition. Cannibalism of offspring also increased when food was scarce. Schedule of feeding did not affect offspring or mothers. We suggest that high food abundance and ability to abort and cannibalize poor-quality offspring are permissive factors necessary for placentotrophy to be a viable strategy of reproductive allocation.

opencc-zeroJun 2019View details →

Data from: Butterfly abundance declines over 20 years of systematic monitoring in Ohio, USA

Severe insect declines make headlines, but they are rarely based on systematic monitoring outside of Europe. We estimate the rate of change in total butterfly abundance and the population trends for 81 species using 21 years of systematic monitoring in Ohio, USA. Total abundance is declining at 2% per year, resulting in a cumulative 33% reduction in butterfly abundance. Three times as many species have negative population trends compared to positive trends. The rate of total decline and the proportion of species in decline mirror those documented in three comparable long-term European monitoring programs. Multiple environmental changes such as climate change, habitat degradation, and agricultural practices may contribute to these declines in Ohio and shift the makeup of the butterfly community by benefiting some species over others. Our analysis of life-history traits associated with population trends shows an impact of climate change, as species with northern distributions and fewer annual generations declined more rapidly. However, even common and invasive species associated with human-dominated landscapes are declining, suggesting widespread environmental causes for these trends. Declines in common species, although they may not be close to extinction, will have an outsized impact on the ecosystem services provided by insects. These results from the most extensive, systematic insect monitoring programs in North America demonstrate an ongoing defaunation in butterflies that on an annual scale might be imperceptible, but cumulatively has reduced butterfly numbers by a third over 20 years.

opencc-zeroDec 2012View details →

Data from: Impacts of bioturbation on temporal variation in bacterial and archaeal nitrogen-cycling gene abundance in coastal sediments

In marine environments, macrofauna living in or on the sediment surface may alter the structure, diversity and function of benthic microbial communities. In particular, microbial nitrogen (N)-cycling processes may be enhanced by the activity of large bioturbating organisms. Here, we study the effect of the burrowing mud shrimp Upogebia deltaura upon temporal variation in the abundance of genes representing key N-cycling functional guilds. The abundance of bacterial genes representing different N-cycling guilds displayed different temporal patterns in burrow sediments in comparison with surface sediments, suggesting that the burrow provides a unique environment where bacterial gene abundances are influenced directly by macrofaunal activity. In contrast, the abundances of archaeal ammonia oxidizers varied temporally but were not affected by bioturbation, indicating differential responses between bacterial and archaeal ammonia oxidizers to environmental physicochemical controls. This study highlights the importance of bioturbation as a control over temporal variation in nitrogen-cycling microbial community dynamics within coastal sediments.

Data from: Linking species abundance and overyielding from experimental communities with niche and fitness characteristics

1) So far, the principal force shaping local plant abundance patterns remains unclear. Rarity can result from poor competitive ability or from small vegetative or generative reproduction, but also from strong self-limitation. The same mechanisms can drive species-specific overyielding, i.e. increased species productivity at high community diversity. Rare species can then benefit more (i.e. overyield to a larger extent) from growing in species-rich communities because of altered competitive hierarchies or smaller conspecific frequencies. Here we test which mechanism is the most important determinant of species rarity and of species-specific productivity across a diversity gradient ranging from one- to 60-species plots. 2) For that we measured vegetative growth, competitive ability (competitive effect), and negative frequency dependence for 49 perennial grassland species from Central Europe. We then linked these characteristics with species abundance (measured as species biomass from 60-species plots) and with species-specific overyielding in The Jena Experiment. 3) Species with higher rates of vegetative growth (when grown without neighbors) were also more abundant in the Jena Experiment. Larger species-specific overyielding was then associated with a stronger negative frequency dependence. As species with greater vegetative growth were also more self-limited, larger overyielding in species-rich communities was characteristic for common rather than for rare species, refuting our initial hypothesis. Finally, path analysis indicated that species with poor capacity to suppress neighbors also profited more from growing in diverse communities. 4) Synthesis. Our results identify key mechanisms driving abundance and productivity of species in synthetic communities differing in species richness. While vegetative reproduction was closely associated with abundance, intraspecific interactions (strength of negative frequency dependence) shaped species productivity across a richness gradient. Our study sheds light on the abundance patterns of species and their influence on community functions, such as biomass production, of species-rich and -poor vegetation.