Find research datasets worth reusing

Data from: Effect of distance to edge and edge interaction on seedling regeneration and biotic damage in tropical rainforest fragments: a long‐term experiment

In forest fragments, edge effects can influence forest regeneration, but little is known about how edge effects influence seedling performance and the interaction between seedlings and their natural enemies over time. In central Amazonia, we recorded survival and growth (in height and leaf number) and damage by insect herbivores and leaf‐fungal pathogens of Chrysophyllum pomiferum (Sapotaceae) seedlings that were exposed to different numbers of edges and to different distances from the forest edge. Grown seedlings were transplanted into one‐square‐metre plots within 1‐ha blocks located in the centre (no edge), the edge (one edge), and the corner (two edges), and at different distances from the edge towards the interior (i.e., 20, 40, 60, 80, and 100 m) of two rectangular fragments (10‐ and 100‐ha in size). Plots were visited once every 2 months for 1 year (1992–1993) and thereafter every 2 years for almost 8 years (1993–2001). Overall, results showed that seedling survival, height, leaf number, and biotic damage varied over time with the presence of nearby edges and with the distance from the edge. Survival was lower in fragment edges and corners than in centres. Increase in height was similar for all positions within the 100‐ha fragment, whereas in the 10‐ha fragment seedling height had a greater increase at the edge and corner than in the centre. Furthermore, survival increased with distance from the edge as did leaf number, whereas height showed a lower increase closer to the edge than farther away. Regarding biotic damage, for both fragments herbivory was greater at the centres and decreased with edge proximity over time, whereas leaf‐fungal damage was greater at the corners than in the edges and increased significantly over time. Biotic damage was correlated with seedling size. Small seedlings were more susceptible to fungal attack, whereas larger seedlings were so to herbivores. Synthesis. This study demonstrated that despite stochastic environmental factors seedling survival, growth, and biotic damage by herbivores and fungal pathogens varied with the level of edge exposure and proximity, which may threaten forest regeneration in the long term.

opencc-zeroDec 2018View details →

Data from: Long-term sound and movement recording tags to study natural behaviour and reaction to ship noise of seals

The impact of anthropogenic noise on marine fauna is of increasing conservation concern with vessel noise being one of the major contributors. Animals that rely on shallow coastal habitats may be especially vulnerable to this form of pollution. Very limited information is available on how much noise from ship traffic individual animals experience, and how they may react to it due to a lack of suitable methods. To address this, we developed long‐duration audio and 3D‐movement tags (DTAGs) and deployed them on three harbor seals and two gray seals in the North Sea during 2015–2016. These tags recorded sound, accelerometry, magnetometry, and pressure continuously for up to 21 days. GPS positions were also sampled for one seal continuously throughout the recording period. A separate tag, combining a camera and an accelerometer logger, was deployed on two harbor seals to visualize specific behaviors that helped interpret accelerometer signals in the DTAG data. Combining data from depth, accelerometer, and audio sensors, we found that animals spent 6.6%–42.3% of the time hauled out (either on land or partly submerged), and 5.3%–12.4% of their at‐sea time resting at the sea bottom, while the remaining time was used for traveling, resting at surface, and foraging. Animals were exposed to audible vessel noise 2.2%–20.5% of their time when in water, and we demonstrate that interruption of functional behaviors (e.g., resting) in some cases coincides with high‐level vessel noise. Two‐thirds of the ship noise events were traceable by the AIS vessel tracking system, while one‐third comprised vessels without AIS. This preliminary study demonstrates how concomitant long‐term continuous broadband on‐animal sound and movement recordings may be an important tool in future quantification of disturbance effects of anthropogenic activities at sea and assessment of long‐term population impacts on pinnipeds.

opencc-zeroOct 2019View details →

Data from: Long-term dynamics of liana seedlings suggest decelerating increases in liana relative abundance over time

<ol> <li>Over the past decades, tropical forests have experienced both compositional and structural changes. In the Neotropics, researchers at multiple sites have observed significant increases in the abundance and biomass of lianas (i.e. woody vines) relative to trees. However, the role of dynamics at early life stages in contributing to increasing liana abundance remains unclear. </li> <li>We took advantage of a unique dataset on seedling dynamics over 16 years in ~20,000 1-m<sup>2</sup>plots in a tropical forest in Panama to examine temporal and spatial trends in liana and tree seedling abundance. </li> <li>We found that the relative abundance of liana seedlings increased across the study period, from 0.18 in 2001 to 0.24 in 2017. However, increases in liana seedling relative abundance appear to have leveled off in more recent years. The observed increases in liana relative abundance appear to be the result of both higher survival and higher recruitment rates of liana seedlings compared to tree seedlings.</li> <li>Increasing liana abundance in the seedling layer was not explained by annual variation in dry season length, total rainfall, or the proportion of area occupied by canopy gaps. In addition, liana seedlings did not exhibit a demographic advantage (i.e., higher recruitment or survival) over tree seedlings in dry habitats. </li> <li> <i>Synthesis:</i>Our results reveal that seedling communities experienced important compositional changes in the past, but liana seedling relative abundance may have stabilized in recent years. Longer-term monitoring is needed to determine whether tropical forests will continue to experience compositional changes that may alter forest structure and ecosystem function. </li> </ol>

opencc-zeroDec 2011View details →

Data from: Long-term genetic monitoring reveals contrasting changes in the genetic composition of newly established populations of the intertidal snail Bembicium vittatum

Newly established populations are susceptible to founder events that reduce genetic variation. This may be counterbalanced by gene flow after populations become established or founders coming from genetically different populations. However, initial gains in genetic diversity may be short-lived if there is limited mixing between lineages and subsequent inbreeding or if one lineage sweeps to fixation through selection or genetic drift. Here, we report on the genetic changes taking place within two newly established populations of intertidal snail over a 15-year period (~ 10 generations). Each translocation was set up using multiple, genetically distinct source populations. Our data show that higher levels of variation in the translocated populations compared to the source populations were maintained over time for both nuclear (microsatellite) and mitochondrial genes. Small changes in allele and haplotype frequencies were observed in the source populations and in one of the translocated populations, but marked changes were evident in the other, where there was a dramatic shift towards the genetic make-up of one of the source populations. These genetic changes occurred despite relatively large numbers of founders (200- 374 adults) and no evidence of the population experiencing a severe reduction in effective population size. Our study shows that the genetic composition of newly established populations can vary greatly over time and that genetic outcomes can be highly variable, and significantly different to expectations, even when they are established using high numbers of individuals and involve source populations from the same geographic regions.

opencc-zeroDec 2018View details →

Data from: Long-term prevalence data reveals spillover dynamics in a multi-host (Artemia), multi-parasite (Microsporidia) community

In the study of multi-host parasites, it is often found that host species contribute asymmetrically to parasite transmission. Yet in natural populations, identifying which hosts contribute to parasite transmission and maintenance is a recurring challenge. Here, we approach this issue by taking advantage of natural variation in the composition of a host community. We studied the brine shrimps Artemia franciscana and Artemia parthenogenetica and their microsporidian parasites Anostracospora rigaudi and Enterocytospora artemiae. Previous laboratory experiments had shown that each host can transmit both parasites, but could not predict their actual contributions to the parasites' maintenance in the field. To resolve this, we gathered long-term prevalence data from a metacommunity of these species. Metacommunity patches could contain either or both of the Artemia host species, so that the presence of the hosts could be linked directly to the persistence of the parasites. First, we show that the microsporidian A. rigaudi is a spillover parasite: it was unable to persist in the absence of its maintenance host A. parthenogenetica. This result was particularly striking, as A. rigaudi displayed both high prevalence (in the field) and high infectivity (when tested in the laboratory) in both hosts. Moreover, the seasonal presence of A. parthenogenetica imposed seasonality on the rate of spillover, causing cyclical pseudo-endemics in the spillover host A. franciscana. Second, while our prevalence data was sufficient to identify E. artemiae as either a spillover or a facultative multi-host parasite, we could not distinguish between the two possibilities. This study supports the importance of studying the community context of multi-host parasites, and demonstrates that in appropriate multi-host systems, sampling across a range of conditions and host communities can lead to clear conclusions about the drivers of parasite persistence.

opencc-zeroDec 2012View details →

Data from: Long-term benefit of hepatitis C therapy in a safety net hospital system: a cross-sectional study with median 5-year follow-up

Objectives: To demonstrate the effectiveness of hepatitis C virus (HCV) therapy and survival benefit from sustained virologic remission (SVR) in a safety net hospital population with limited resources. Design and setting: We conducted a retrospective cross-sectional study at an urban safety-net hospital in the U.S. Participants and intervention: 242 patients receiving standard HCV therapy between 2001 and 2006. Primary and secondary outcome measures: Response rates, including sustained virologic response (SVR), were recorded for each patient. Univariate and multivariate analyses were performed to identify predictors of SVR and 5 year survival. Results: A total of 242 eligible patients were treated. Treatment was completed in 197 (81%) patients, with 43 patients discontinuing therapy early – 32 due to adverse events and 11 due to non-compliance. Complications on treatment were frequent, including 3 deaths. SVR was achieved in 83 patients (34%). On multivariate analysis, independent predictors of a decreased likelihood of achieving SVR included African American race (OR 0.20, 95% CI 0.07 – 0.54), genotype 1 HCV infection (OR 0.25, 95% CI 0.13 – 0.50) and the presence of cirrhosis (OR 0.26, 95% CI 0.12 – 0.58). Survival was 98% in those achieving SVR (median follow-up 72 months) and 71% in non-responders and those discontinuing therapy (n = 91, median known follow-up 65 and 36 months respectively). On multivariate analysis, the only independent predictor of improved survival was SVR (HR 0.12, 95% CI 0.03 – 0.52). Both cirrhosis and hypoalbuminemia were independent predictors of increased mortality. Conclusions: HCV therapy can be effective despite limited resources. Survival is improved in those achieving SVR. Treatment before histologic cirrhosis develops, in combination with careful selection, may improve long-term outcomes without compromising other health care endeavors in safety net hospitals and areas with financial limitations.

opencc-zeroDec 2018View details →

Data from: Long-term recovery of the functional community assembly and carbon pools in an African tropical forest succession

On the African continent, the population is expected to expand fourfold in the next century, which will increasingly impact the global carbon cycle and biodiversity conservation. Therefore, it is of vital importance to understand how carbon stocks and community assembly recover after slash-and-burn events in tropical second-growth forests. We inventoried a chronosequence of 15 1-hectare plots in lowland tropical forest of the central Congo Basin and evaluated changes in aboveground and soil organic carbon stocks and in tree species diversity, functional composition and community-weighted functional traits with succession. We aimed to track long-term recovery trajectories of species and carbon stocks in secondary forests, comparing 5 to 200+ year old secondary forest with reference primary forest. Along the successional gradient, the functional composition followed a trajectory from resource acquisition to resource conservation, except for nitrogen-related leaf traits. Despite a fast initial recovery of species diversity and functional composition, there were still important structural and carbon stock differences between old-growth secondary and pristine forest, which suggests that a full recovery of secondary forests might take much longer than currently shown. As such, the aboveground carbon stocks of 200+ year old forest were only 57% of those in the pristine reference forest, which suggests a slow recovery of aboveground carbon stocks, although more research is needed to confirm this observation. The results of this study highlight the need for more in-depth studies on forest recovery in Central Africa, to gain insight into the processes that control biodiversity and carbon stock recovery.

Data from: Density trends and demographic signals uncover the long-term impact of transmissible cancer in Tasmanian Devils

Monitoring the response of wild mammal populations to threatening processes is fundamental to effective conservation management. This is especially true for infectious diseases, which may have dynamic and therefore unpredictable interactions with their host. We investigate the long-term impact of a transmissible cancer, devil facial tumour disease (DFTD), on the endemic Tasmanian devil. We analyse trends in devil spotlight counts and density across the area impacted by the disease. We investigate the demographic parameters which might be driving these trends, and use spatial capture-recapture models to examine whether DFTD has affected home range size. We found that devils have declined by an average of 77% in areas affected by DFTD, and that there is a congruent trend of ongoing small decline in spotlight counts and density estimates. Despite this, devils have persisted to date within each of nine monitoring sites. One site is showing as yet unexplained small increases in density 8–10 years after the emergence of DFTD. We also found the prevalence of DFTD has not abated despite large declines in density and that diseased sites continue to be dominated by young devils. The long-term impact of the disease has been partially offset by increased fecundity in the form of precocial breeding in 1-year-old females, and more pouch young per female in diseased sites. The lower densities resulting from DFTD did not affect home range size. Synthesis and applications. Transmission of devil facial tumour disease continues despite large declines in devil density over multiple generations. Plasticity in life history traits has ameliorated the impact of devil facial tumour disease, however broad-scale trends in density show ongoing decline. In light of this, devil facial tumour disease and the impact of stochastic events on the reduced densities wrought by the disease, continue to threaten devils. In the absence of methods to manage disease in wild populations, we advocate managing the low population densities resulting from disease rather than disease per se.

opencc-zeroDec 2013View details →

Data from: Species' traits explain differences in Red list status and long-term population trends in longhorn beetles

Some species are more likely to go extinct than others and this is partially due to species' traits. Therefore, it is important to establish links between traits and extinction risks. Different aspects of a species' biology also relates to different sources of threat, such as fragmented populations or low population growth rate. In a comparative study of Swedish longhorn beetles (Coleoptera: Cerambycidae), we related species' traits to two aspects of extinction risk – population decline and small/fragmented populations – measured by long-term population trends and IUCN Red list classifications. Trait relationships were analysed with generalized linear models and multi-model inference. We found that extinction risk generally increased with longer generation times, corresponding to slower life histories. Adult activity period was also related to both metrics of extinction risk, but in different ways. We also found that extinction risk increased with larval host plant specialization, but only for Red list classification. Large body size was related to increased Red list classification in species overwintering as adults, and overwintering stage also structured the effects of several other traits. Our results show that both intrinsic demographic traits and ecological traits affect extinction risks, and also suggest that risks are shaped by multiple mechanisms. Therefore, researchers should carefully choose their metric of extinction risk for comparative studies, as the Red list classification may best capture current risk, whereas population trends can be used more proactively but may reflect historical relationships between traits and extinction risk.

Data from: Long-term consequences of high incubation temperature in a wild bird population

Because incubation by birds is energetically costly, parents frequently trade off investment in incubation against self-maintenance. This can be manifested by a reduction in incubation temperature, which comes at high somatic costs for nestlings. The extent to which these costs constrain fitness is poorly understood. We incubated wild blue tit clutches at three biologically relevant temperatures and subsequently recorded winter survival and survival to the breeding season. Fledglings from the coldest treatment (35.0°C) survived less well than other fledglings, but the proportion of winter and breeding survivors did not differ significantly between treatments. However, survival probability in both seasons increased with body mass at fledging in birds from low and mid incubation temperatures, but decreased with fledging body mass in the high-temperature treatment. Mid-temperature nestlings were heavier as adults, weighing 7% more than low- and high-temperature survivors. Thus, high incubation temperature can be beneficial in the short term, but costs of accelerated embryonic development may equal those of protracted development in the long term. Such hidden consequences of faster development could maintain natural selection for average incubation temperature.

opencc-zeroDec 2012View details →

Data from: Long-term endemism of two highly divergent lineages of the amphibian-killing fungus in the Atlantic Forest of Brazil

The recent global spread of the amphibian-killing fungus [Batrachochytrium dendrobatidis (Bd)] has been closely tied to anthropogenic activities; however, regional patterns of spread are not completely understood. Using historical samples, we can test whether Bd was a spreading or endemic pathogen in a region within a particular time frame, because those two disease states provide different predictions for the regional demographic dynamics and population genetics of Bd. Testing historical patterns of pathogen prevalence and population genetics under these predictions is key to understanding the evolution and origin of Bd. Focusing on the Atlantic Forest (AF) of Brazil, we used qPCR assays to determine the presence or absence of Bd on 2799 preserved postmetamorphic anurans collected between 1894 and 2010 and used semi-nested PCRs to determine the frequency of rRNA ITS1 haplotypes from 52 samples. Our earliest date of detection was 1894. A mean prevalence of 23.9% over time and spatiotemporal patterns of Bd clusters indicate that Bd has been enzootic in the Brazilian AF with no evidence of regional spread within the last 116 years. ITS1 haplotypes confirm the long-term presence of two divergent strains of Bd (BdGPL and Bd-Brazil) and three spatiotemporally broad genetic demes within BdGPL, indicating that Bd was not introduced into southeast Brazil by the bullfrog trade. Our data show that the evolutionary history and pathogen dynamics of Bd in Brazil is better explained by the endemic pathogen hypothesis.

Data from: Eighty-five million years of Pacific Ocean gyre ecosystem structure: long-term stability marked by punctuated change

While the history of taxonomic diversification in open ocean lineages of ray-finned fish and elasmobranchs is increasingly known, the evolution of their roles within the open ocean ecosystem remains poorly understood. To assess the relative importance of these groups through time, we measured the accumulation rate of microfossil fish teeth and elasmobranch dermal denticles (ichthyoliths) in deep-sea sediment cores from the North and South Pacific gyres over the past 85 million years (Myr). We find three distinct and stable open ocean ecosystem structures, each defined by the relative and absolute abundance of elasmobranch and ray-finned fish remains. The Cretaceous Ocean (pre-66 Ma) was characterized by abundant elasmobranch denticles, but low abundances of fish teeth. The Palaeogene Ocean (66–20 Ma), initiated by the Cretaceous/Palaeogene mass extinction, had nearly four times the abundance of fish teeth compared with elasmobranch denticles. This Palaeogene Ocean structure remained stable during the Eocene greenhouse (50 Ma) and the Eocene–Oligocene glaciation (34 Ma), despite large changes in the overall accumulation of both groups during those intervals, suggesting that climate change is not a primary driver of ecosystem structure. Dermal denticles virtually disappeared from open ocean ichthyolith assemblages approximately 20 Ma, while fish tooth accumulation increased dramatically in variability, marking the beginning of the Modern Ocean. Together, these results suggest that open ocean fish community structure is stable on long timescales, independent of total production and climate change. The timing of the abrupt transitions between these states suggests that the transitions may be due to interactions with other, non-preserved pelagic consumer groups.

Data from: The consequences of daily cyclic hypoxia on a European grass shrimp: from short-term responses to long-term effects

1. Salt marshes are a key coastal environment for their important role as nursery habitats for marine and estuarine fish and crustaceans. Salt marshes are variable environments where species can experience daily cyclic hypoxic stress, characterized by profound variations in oxygen partial pressure (pO2) from supersaturated conditions (~42kPa) to extremely hypoxic conditions (~3kPa) in ~12-hours. 2. Here, under laboratory conditions, we assessed the physiological consequences of exposing the shrimp Palaemon varians, a species commonly found in the salt marshes of northern Europe, to the daily cyclic hypoxic regime currently experienced in its habitat in August (7.1±1.8 hours day-1 below 4.0kPa). In the laboratory adults were kept at water pO2 <4.5kPa for 7-hours each night and in normoxic conditions for the rest of the time. 3. We recorded an acceleration of P. varians' moult cycle, which was 15% shorter in animals kept in cyclic hypoxia compared to animals in normoxia. Similarly, the pattern of expression of two cuticular proteins over an entire moult cycle indicated an effect of cyclic hypoxia on moult stage-related genes. After 16 days, morphological changes to the gills were detected, with shrimps in cyclic hypoxia having a 13.6% larger lamellar surface area (measured in µm2/mg animal) than normoxic animals, which could improve gas exchange capacity. Overall, phenotypic and morphological data indicate that faster moulting is triggered in response to cyclic hypoxia, with the benefit that gill modifications can be prompted more rapidly in order to meet oxygen requirements of the body. 4. On the first experimental day, in cyclic hypoxic exposed animals, we recorded a 50% decrease in feeding rates (during hypoxic conditions) in comparison to normoxic animals. Similarly, ammonium excretion was reduced by 66-75% during the 1st and 21st experimental day. Body size was reduced by ~4% after 28 days. Females that reproduced in cyclic hypoxic conditions reduced the amount of yolk in each egg by ~24%. Overall, results underline how, in a decapod shrimp living in a key coastal environment, many physiological parameters are impaired by a cyclic hypoxic regime that is currently found in its natural habitat.

opencc-zeroDec 2016View details →

Data from: Programmed and flexible: long-term Zugunruhe data highlight the many axes of variation in avian migratory behaviour

Studies of Zugunruhe – the 'migratory restlessness' behaviour of captive birds – have been integral to our understanding of animal migration, revealing an inherited propensity to migrate and an endogenous timing and navigation system. However, differences between Zugunruhe in captivity and migration in the wild call for more data, in particular on variation within and among taxa with diverse migration strategies. Here, we characterise Zugunruhe in a long-term dataset of activity profiles from stonechats (genus Saxicola) with diverse migratory phenotypes (976 migration periods from 414 birds), using a flexible and consistent quantitative approach based on changepoint analysis. For east African, Austrian, Irish, and Siberian stonechats and hybrids, we report key inter-population differences in the occurrence, timing, and intensity of Zugunruhe. In line with expectations, we found the highest Zugunruhe intensity in the longest-distance migrants, more variable patterns in short-distance migrants, and intermediate characteristics of hybrids relative to their parental groups. Inter-population differences imply high evolutionary lability of Zugunruhe timing within a robustly structured annual cycle. However, counter to theory, Irish partial migrants showed no segregation between migrant and resident individuals, and previously reported nocturnal restlessness was confirmed for resident African stonechats. Further features of nocturnal restlessness that did not align with migratory behaviour of stonechats were juvenile nocturnal restlessness even prior to postjuvenile moult, and protandry in spring, although stonechats winter in heterosexual pairs. Importantly, Zugunruhe of all populations declined with age, and the intensity of an individual bird's Zugunruhe was correlated with activity levels during other parts of the annual cycle. Our results confirm endogenous, population-specific migration programmes but also reveal apparent discrepancies between Zugunruhe and migration in the wild. We thus highlight both the continued potential of Zugunruhe study and the need for circumspect interpretation when using migratory restlessness to make inferences about migration in the wild.

Data from: Relating fitness to long-term environmental variations in natura

Quantifying links between ecological processes and adaptation dynamics in natura remains a crucial challenge. Many studies have documented the strength, form and direction of selection, and its variations in space and time, but only a few managed to link these variations to their proximal causes. This step is, however, crucial, if we are to understand how the variation in selective pressure affects adaptive allele dynamics in natural settings. We used data from a long-term survey (about 30 years) monitoring the adaptation to insecticides of Culex pipiens mosquitoes in Montpellier area (France), focusing on three resistance alleles of the Ester locus. We used a population genetics model taking temporal and spatial variations in selective pressure into account, to assess the quantitative relationships between variations in the proximal agent of selection (amounts of insecticide sprayed) and the fitness of resistance alleles. The response to variations in selective pressure was fast, and the alleles displayed different fitness-to-environment relationships: the analyses revealed that even slight changes in insecticide doses could induce changes in the strength and direction of selection, thus changing the fitness ranking of the adaptive alleles. They also revealed that selective pressures other than the insecticides used for mosquito control affected the resistance allele dynamics. These fitness-to-environment relationships, fast responses and continuous evolution limit our ability to predict the outcome of adaptive allele dynamics in a changing environment, but they clearly contribute to the maintenance of polymorphism in natural populations. Our study also emphasizes the necessity of long-term surveys in evolutionary ecology.

Data from: Decomposition of coarse woody debris in a long-term litter manipulation experiment: a focus on nutrient availability

1.The majority of aboveground carbon in tropical forests is stored in wood, which is returned to the atmosphere during decomposition of coarse woody debris. However, the factors controlling wood decomposition have not been experimentally manipulated over time scales comparable to the length of this process. 2.We hypothesized that wood decomposition is limited by nutrient availability and tested this hypothesis in a long-term litter addition and removal experiment in a lowland tropical forest in Panama. Specifically, we quantified decomposition using a 15 year chronosequence of decaying boles, and measured respiration rates and nutrient limitation of wood decomposer communities. 3.The long-term probability that a dead tree completely decomposed was decreased in plots where litter was removed, but did not differ between litter addition and control treatments. Similarly, respiration rates of wood decomposer communities were greater in control treatments relative to litter removal plots; litter addition treatments did not differ from either of the other treatments. Respiration rates increased in response to nutrient addition (nitrogen, phosphorus, and potassium) in the litter removal and addition treatments, but not in the controls. 4.Established decreases in concentrations of soil nutrients in litter removal plots and increased respiration rates in response to nutrient addition suggest that reduced rates of wood decomposition after litter removal were caused by decreased nutrient availability. The effects of litter manipulations differed directionally from a previous short-term decomposition study in the same plots, and reduced rates of bole decomposition in litter removal plots did not emerge until after more than 6 years of decomposition. These differences suggest that litter-mediated effects on nutrient dynamics have complex interactions with decomposition over time.

opencc-zeroDec 2016View details →

Data from: Evolution of organismal stoichiometry in a long-term experiment with Escherichia coli

Organismal stoichiometry refers to the relative proportion of chemical elements in the biomass of organisms, and it can have important effects on ecological interactions from population to ecosystem scales. Although stoichiometry has been studied extensively from an ecological perspective, much less is known about the rates and directions of evolutionary changes in elemental composition. We measured carbon, nitrogen and phosphorus content of 12 Escherichia coli populations that evolved under controlled carbon-limited, serial-transfer conditions for 50 000 generations. The bacteria evolved higher relative nitrogen and phosphorus content, consistent with selection for increased use of the more abundant elements. Total carbon assimilated also increased, indicating more efficient use of the limiting element. We also measured stoichiometry in one population repeatedly through time. Stoichiometry changed more rapidly in early generations than later on, similar to the trajectory seen for competitive fitness. Altogether, our study shows that stoichiometry evolved over long time periods, and that it did so in a predictable direction, given the carbon-limited environment.

Data from: EB Ford revisited: assessing the long-term stability of wing-spot patterns and population genetic structure of the meadow brown butterfly on the Isles of Scilly

Understanding selection in the wild remains a major aim of evolutionary ecology and work by Ford and colleagues on the meadow brown butterfly Maniola jurtina did much to ignite this agenda. A great deal of their work was conducted during the 1950s on the Isles of Scilly. They documented island-specific wing-spot patterns that remained consistent over about a decade, but patterns on some islands changed after environmental perturbation. It was suggested that these wing-spot patterns reflected island-specific selection and that there was little migration between islands. However, genetic studies to test the underlying assumption of restricted migration are lacking and it is also unknown whether the originally described wing-spot patterns have persisted over time. We therefore collected female butterflies from five of Ford's original study locations, including three large islands (St Mary's, St Martin's and Tresco) and two small islands (Tean and St Helen's). Wing-spot patterns had not changed appreciably over time on three of the islands (two large and one small), but were significantly different on the other two. Furthermore, analysis of 176 amplified fragment length polymorphisms revealed significant genome-wide differentiation among the five islands. Our findings are consistent with Ford's conclusions that despite the close proximity of these islands, there is restricted gene flow among them.

Data from: Long-term effective population size dynamics of an intensively monitored vertebrate population

Long-term genetic data from intensively monitored natural populations are important for understanding how effective population sizes (Ne) can vary over time. We therefore genotyped 1622 common buzzard (Buteo buteo) chicks sampled over 12 consecutive years (2002–2013 inclusive) at 15 microsatellite loci. This data set allowed us to both compare single-sample with temporal approaches and explore temporal patterns in the effective number of parents that produced each cohort in relation to the observed population dynamics. We found reasonable consistency between linkage disequilibrium-based single-sample and temporal estimators, particularly during the latter half of the study, but no clear relationship between annual Ne estimates (hdy201667e1gif(239)1917) and census sizes. We also documented a 14-fold increase in hdy201667e2gif(239)1917 between 2008 and 2011, a period during which the census size doubled, probably reflecting a combination of higher adult survival and immigration from further afield. Our study thus reveals appreciable temporal heterogeneity in the effective population size of a natural vertebrate population, confirms the need for long-term studies and cautions against drawing conclusions from a single sample.