Collaboration and distances between German immunological institutes – a trend analysis

Background

The hypothesis that distance matters but that in recent years geographical proximity has become less important for research collaboration was tested. We have chosen a sample–authors at German immunological institutes–that is relatively homogeneous with regard to research field, language and culture, which beside distance are other possible factors influencing the willingness to co-operate. We analyse yearly distributions of co-authorship links between institutes and compare them with the yearly distributions of distances of all institutes producing papers in journals indexed in the Science Citation Index, editions 1992 till 2002. We weight both types of distributions properly with paper numbers.

Results

One interesting result is that place matters but if a researcher has to leave the home town to find a collaborator distance does not matter any longer. This result holds for all years considered, but is statistically most significant in 2002. The tendency to leave the own town for collaborators has slightly increased in the sample. In addition, yearly productivity distributions of institutes have been found to be lognormal.

Conclusion

The Internet did not change much the collaboration patterns between German immunological institutes.

     

Quantifying suitable late summer brood habitats for willow ptarmigan in Norway

Background

Habitat models provide information about which habitat management should target to avoid species extinctions or range contractions. The willow ptarmigan inhabits alpine- and arctic tundra habitats in the northern hemisphere and is listed as near threatened (NT) in the Norwegian red list due to declining population size. Habitat alteration is one of several factors affecting willow ptarmigan populations, but there is a lack of studies quantifying and describing habitat selection in willow ptarmigan. We used data from an extensive line transect survey program from 2014 to 2017 to develop resource selection functions (RSF) for willow ptarmigan in Norway. The selection coefficients for the RSF were estimated using a mixed-effects logistic regression model fitted with random intercepts for each area. We predicted relative probability of selection across Norway and quantile-binned the predictions in 10 RSF bins ranging from low-(1) to high-(10) relative probability of selection.

Results

Random cross-validation suggest that our models were highly predictive, but validation based spatial blocking revealed that the predictability was better in southern parts of Norway compared to the northernmost region. Willow ptarmigan selected for herb-rich meadows and avoided lichen rich heathlands. There was generally stronger selection for vegetation types with dense field layer and for rich bogs and avoidance of vegetation types with sparse field layer cover and for lowland forest. Further, willow ptarmigan selected for areas around the timberline and for intermediate slopes. Mapping of the RSF showed that 60% of Norway is in the lowest ranked RSF bin and only 2% in the highest ranked RSF bin.

Conclusions

Willow ptarmigan selected for vegetation types with dense field layer and bogs at intermediate slopes around the timberline. Selection coincides with previous habitat selection studies on willow ptarmigan. This is the first attempt to assess and quantify habitat selection for willow ptarmigan at a large scale using data from line transect distance sampling surveys. Spatial variation in predictability suggests that habitat selection in late summer might vary from north to south. The resource selection map can be a useful tool when planning harvest quotas and habitat interventions in alpine areas.

     

Sexual responsiveness is condition-dependent in female guppies, but preference functions are not

Background

Research on the ecological consequences of global climate change has elicited a growing interest in the use of time series analysis to investigate population dynamics in a changing climate. Here, we compare linear and non-linear models describing the contribution of climate to the density fluctuations of the population of wolves on Isle Royale, Michigan from 1959 to 1999.

Results

The non-linear self excitatory threshold autoregressive (SETAR) model revealed that, due to differences in the strength and nature of density dependence, relatively small and large populations may be differentially affected by future changes in climate. Both linear and non-linear models predict a decrease in the population of wolves with predicted changes in climate.

Conclusions

Because specific predictions differed between linear and non-linear models, our study highlights the importance of using non-linear methods that allow the detection of non-linearity in the strength and nature of density dependence. Failure to adopt a non-linear approach to modelling population response to climate change, either exclusively or in addition to linear approaches, may compromise efforts to quantify ecological consequences of future warming.     

Delayed sleep phase cases and controls

Background

Delayed sleep phase disorder (DSPD) is a condition in which patients have difficulty falling asleep before the early morning hours and commonly have trouble awakening before late morning or even early afternoon. Several studies have suggested that variations in habitual bedtime are 40–50% heritable.

Methods

We recruited a case series of 205 participants, along with 221 controls (DSPD-C) with normal sleep, roughly matched for age, gender, and ancestry. A representative sample of San Diego adults recruited some years before was already available to confirm the control group. Both DSPD and DSPD-C provided blood or saliva samples for DNA and completed extensive questionnaires about sleep habits, sleep history, family history, sleep quality, morningness-eveningness traits, depression, mania, and seasonality of symptoms. The DSPD group wore wrist actigraphs for a median of 13.2 days. The representative sample collected previously had undergone actigraphic recordings, from which 48 hours of data were generally available.

Results

The DSPD and DSPD-C samples showed almost no overlap on morningness-eveningness scores. DSPD cases went to bed and arose about 3 hours later than the DSPD-C and the representative sample. DSPD cases reported more difficulties with sleep, poorer sleep quality, and more depression, but there was no significant difference in a history of mania. DSPD cases reported more family history of late bedtimes, but female DSPD reported that their fathers' bedtimes were later than the fathers of male DSPD.

Conclusion

These results indicate a DSPD phenotype is familial and associated with unipolar depression.     

Interactions between herbivory and warming in aboveground biomass production of arctic vegetation

Background

In the androdioecious nematode Caenorhabditis elegans virtually all progeny produced by hermaphrodite self-fertilization is hermaphrodite while 50% of the progeny that results from cross-fertilization by a male is male. In the standard laboratory wild type strain N2 males disappear rapidly from populations. This is not the case in some other wild type isolates of C. elegans, among them the Hawaiian strain CB4856.

Results

We determined the kinetics of the loss of males over time for multiple population sizes and wild isolates and found significant differences. We performed systematic inter- and intra-strain crosses with N2 and CB4856 and show that the males and the hermaphrodites contribute to the difference in male maintenance between these two strains. In particular, CB4856 males obtained a higher number of successful copulations than N2 males and sired correspondingly more cross-progeny. On the other hand, N2 hermaphrodites produced a higher number of self-progeny, both when singly mated and when not mated.

Conclusion

These two differences have the potential to explain the observed variation in male persistence, since they should lead to a predominance of self-progeny (and thus hermaphrodites) in N2 and, at the same time, a high proportion of cross-progeny (and thus the presence of males as well as hermaphrodites) in CB4856.     

Gastrointestinal helminths may affect host susceptibility to anthrax through seasonal immune trade-offs

Background

Development rates of Aedes aegypti are known to vary with respect to many abiotic and biotic factors including temperature, resource availability, and intraspecific competition. The relative importance of these factors and their interactions are not well established across populations. We performed meta-analysis on a dataset of development rate estimates from 49 studies.

Results

Meta-analytic results indicated that the environmental factor of temperature is sufficient to explain development rate variability in Ae. aegypti. While diet and density may greatly impact other developmental phenotypes, these results suggest that for development rate these factors should never be considered to the exclusion of temperature. The effect of temperature on development rate is not homogenous or constant. The sources of heterogeneity of the effect of temperature are difficult to analyze due to lack of consistent reporting of larval rearing methods.

Conclusions

Temperature is the most important ecological determinant of development rate in Ae. aegypti, but its effect is heterogeneous. Ignoring this heterogeneity is problematic for models of vector population and vector-borne disease transmission.     

Local and regional factors influence the structure of treehole metacommunities

Background

Abiotic and biotic factors in a local habitat may strongly impact the community residing within, but spatially structured metacommunities are also influenced by regional factors such as immigration and colonization. We used three years of monthly treehole census data to evaluate the relative influence of local and regional factors on our study system.

Results

Every species responded to at least one of three local environmental factors measured: water volume, leaf litter mass, and presence of a top predator. Several species were affected by water volume, and a non-exclusive group of species were influenced by leaf litter mass. Relative abundance of Aedes triseriatus was higher in treeholes with higher volumes of water, and relative abundances of three out of six other species were lower in treeholes with higher volumes of water. Leaf litter mass positively affected densities of Aedes triseriatus and relative abundance of several dipteran species. The density of the top predator, Toxorhynchites rutilus, affected the relative abundance of the two most common species, A. triseriatus and Culicoides guttipennis. Treeholes with T. rutilus had an average of two more species than treeholes without T. rutilus. We found little evidence of synchrony between pairs of treeholes, either spatially or temporally. There were high levels of spatial and temporal turnover, and spatial turnover increased with distance between patches.

Conclusion

The strong effects of water volume, leaf litter mass, and presence of a top predator, along with the high temporal turnover strongly suggest that species presence and density are determined by local factors and changes in those factors over time. Both low water volume and high predator densities can eliminate populations in local patches, and those populations can recolonize patches when rain refills or predators exit treeholes. Population densities of the same species were not matched between pairs of treeholes, suggesting variation in local factors and limited dispersal. Distance effects on spatial turnover also support limitations to dispersal in the metacommunity, and we conclude that the weight of evidence favors a strong influence of local factors relative to regional factors.     

The biomass–density relationship in seagrasses and its use as an ecological indicator

Background

Biomass–density relations have been at the centre of a search for an index which describes the health of seagrass meadows. However, this search has been complicated by the intricacy of seagrass demographics and their complex biomass–density relations, a consequence mainly of their modular growth and clonality. Concomitantly, biomass–density upper boundaries have been determined for terrestrial plants and algae, reflecting their asymptotic maximum efficiencies of space occupation. Each stand’s distance to its respective biomass–density upper boundary reflects its effective efficiency in packing biomass, which has proved a reliable ecological indicator in order to discriminate between taxonomic groups, functional groups and clonal vs. non-clonal growth.

Results

We gathered data from 32 studies on 10 seagrass species distributed worldwide and demonstrated that seagrasses are limited by their own boundary line, placed below the boundaries previously determined for algae and terrestrial plants. Then, we applied a new metric—d_grass: each stand’s perpendicular distance to the seagrass boundary—and used this parameter to review fundamental aspects such as clonal growth patterns, depth distribution, seasonality, interspecific competition, and the effects of light, temperature and nutrients.

Conclusions

Seagrasses occupy space less efficiently than algae and terrestrial plants. Using only their biomass and density data we established a new and efficient tool to describe space occupation by seagrasses. This was used with success to evaluate their meadows as an ecological indicator for the health of coastal ecosystems.

     

Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system

Background

A territory as a prerequisite for breeding limits the maximum number of breeders in a given area, and thus lowers the proportion of breeders if population size increases. However, some territorially breeding animals can have dramatic density fluctuations and little is known about the change from density-dependent processes to density-independence of breeding during a population increase or an outbreak. We suggest that territoriality, breeding suppression and its break-down can be understood with an incomplete-control model, developed for social breeders and social suppression.

Results

We studied density dependence in an arvicoline species, the bank vole, known as a territorial breeder with cyclic and non-cyclic density fluctuations and periodically high densities in different parts of its range. Our long-term data base from 38 experimental populations in large enclosures in boreal grassland confirms that breeding rates are density-regulated at moderate densities, probably by social suppression of subordinate potential breeders. We conducted an experiment, were we doubled and tripled this moderate density under otherwise the same conditions and measured space use, mortality, reproduction and faecal stress hormone levels (FGM) of adult females. We found that mortality did not differ among the densities, but the regulation of the breeding rate broke down: at double and triple densities all females were breeding, while at the low density the breeding rate was regulated as observed before. Spatial overlap among females increased with density, while a minimum territory size was maintained. Mean stress hormone levels were higher in double and triple densities than at moderate density.

Conclusions

At low and moderate densities, breeding suppression by the dominant breeders, But above a density-threshold (similar to a competition point), the dominance of breeders could not be sustained (incomplete control). In our experiment, this point was reached after territories could not shrink any further, while the number of intruders continued to increase with increasing density. Probably suppression becomes too costly for the dominants, and increasing number of other breeders reduces the effectiveness of threats. In wild populations, crossing this threshold would allow for a rapid density increase or population outbreaks, enabling territorial species to escape density-dependency.     

Foraging dispersion of Ryukyu flying-foxes and relationships with fig abundance in East-Asian subtropical island forests

Background

Figs are widely distributed key resources to many tropical-subtropical animals, and flying-foxes are major consumers and seed dispersers of figs. Bat-fig interrelationships, however, may vary among species differing in fruiting traits, i.e., bat- versus bird-dispersed figs. We examined Ryukyu flying-fox foraging dispersion and the relationships with tree species composition and fig abundance in forests of Iriomote Island.

Results

Bat foraging dispersion showed no spatial patterns with respect to different areas of the island, and was not explained by heterogeneity, density, or basal area (BA) of total trees, nor by relative density or BA of fruiting trees or total fruiting figs among sites. Instead, bat densities were positively dependent on the relative density of total figs, and particularly the relative BA of bat-dispersed figs Ficus septica and F. variegata. Both species were dominant figs in forests, fruiting asynchronously with long crop seasons, and were used as predominant foods. Bats foraged mostly solitarily and the mean density was in a hump-shaped relationship with crop sizes of the dominant bat-figs. These two species and Ficus benguetensis are larger-sized bat-figs, all contained more seeds, higher dry-pulp mass and water mass, but not necessarily water content. By approximate estimation, higher proportions of seeds of these bat-figs would have been removed from fruits through the bat consumption, than that of small-sized bird-figs like F. virgata, F. superba, and F. microcarpa.

Conclusions

The foraging dispersion of Ryukyu flying-foxes in forests depends on the availability of the most abundant bat-figs that serve as predominant foods. Intermediate levels of crop sizes of theses figs appear most fit with their solitary foraging. Our results suggest that as density and BA coverage of these dominant bat-figs are below a certain level, their effectiveness to attract bats may dwindle and so would their chance of dispersal by bats.

     

Microsatellite data suggest significant population structure and differentiation within the malaria vector Anopheles darlingi in Central and South America

Background

Anopheles darlingi is the most important malaria vector in the Neotropics. An understanding of A. darlingi's population structure and contemporary gene flow patterns is necessary if vector populations are to be successfully controlled. We assessed population genetic structure and levels of differentiation based on 1,376 samples from 31 localities throughout the Peruvian and Brazilian Amazon and Central America using 5–8 microsatellite loci.

Results

We found high levels of polymorphism for all of the Amazonian populations (mean R _S = 7.62, mean H _O = 0.742), and low levels for the Belize and Guatemalan populations (mean R _S = 4.3, mean H _O = 0.457). The Bayesian clustering analysis revealed five population clusters: northeastern Amazonian Brazil, southeastern and central Amazonian Brazil, western and central Amazonian Brazil, Peruvian Amazon, and the Central American populations. Within Central America there was low non-significant differentiation, except for between the populations separated by the Maya Mountains. Within Amazonia there was a moderate level of significant differentiation attributed to isolation by distance. Within Peru there was no significant population structure and low differentiation, and some evidence of a population expansion. The pairwise estimates of genetic differentiation between Central America and Amazonian populations were all very high and highly significant (F _ST = 0.1859 – 0.3901, P < 0.05). Both the D _A and F _ST distance-based trees illustrated the main division to be between Central America and Amazonia.

Conclusion

We detected a large amount of population structure in Amazonia, with three population clusters within Brazil and one including the Peru populations. The considerable differences in N _e among the populations may have contributed to the observed genetic differentiation. All of the data suggest that the primary division within A. darlingi corresponds to two white gene genotypes between Amazonia (genotype 1) and Central America, parts of Colombia and Venezuela (genotype 2), and are in agreement with previously published mitochondrial COI gene sequences interpreted as incipient species. Overall, it appears that two main factors have contributed to the genetic differentiation between the population clusters: physical distance between the populations and the differences in effective population sizes among the subpopulations.     

Resistance of rumen bacteria murein to bovine gastric lysozyme

Background

In many species of birds, pair bonded males and females precisely co-ordinate their vocalisations to form duets. Duetting behaviour, although still somewhat of an enigma, is thought to function primarily in territorial defence and mate guarding. We identify an additional function of duetting in an afrotropical bird, the tropical boubou (Laniarius aethiopicus), that uses one duet type as a postconflict display probably to advertise victory to other boubous.

Results

We simulated intrusions into boubou territories in the field in Ivory Coast, West Africa using playbacks of four different types of boubou duets to test the use of the presumptive acoustic victory display before, during and after playbacks. These staged encounters resulted in either retreat of the focal birds during playback or continued presence accompanied by vocal displays after playback had ceased. Losers of encounters never sung after retreating whereas 11 out of 18 pairs sung the presumptive victory duet after the encounter. Analysis revealed that the presumptive victory display was sung significantly more often after than before or during the playback treatment.

Conclusion

We conclude that, most likely, the investigated duet type is a postconflict victory display – a novel function of duets. Furthermore the duet is a rare example among birds of a context-specific song. The conspicuousness of the display suggests that it is directed not only to losers of an agonistic encounter but also to other pairs of birds in neighbouring territories.     

Identification of the vascular plants of Churchill,Manitoba, using a DNA barcode library

Background

Using phylogenies in community ecology is now commonplace, but typically, studies assume and test for a single common phylogenetic signal for all species in a community, at a given scale. A possibility that remains little-explored is that species differing in demographic or ecological attributes, or facing different selective pressures, show different community phylogenetic patterns, even within the same communities. Here I compare community phylogenetic patterns for fire-killed and fire-resistant Banksia species in the fire-prone shrublands of southwest Australia.

Results

Using new Bayesian phylogenies of Banksia, together with ecological trait data and abundance data from 24 field sites, I find that fire regeneration mode influences the phylogenetic and phenotypic signal of species co-occurrence patterns. Fire-killed species (reseeders) show patterns of phylogenetic and phenotypic repulsion consistent with competition-driven niche differentiation, but there are no such patterns for fire-resistant species (resprouters). For pairs of species that differ in fire response, co-occurrence is mediated by environmental filtering based on similarity in edaphic preferences.

Conclusions

These results suggest that it may be simplistic to characterize an entire community by a single structuring process, such as competition or environmental filtering. For this reason, community analyses based on pairwise species co-occurrence patterns may be more informative than those based on whole-community structure metrics.     

Nomenclature report on rice WRKY's - Conflict regarding gene names and its solution

Background

Since whole genome sequences of rice were made publically accessible, the number of articles on new rice genes has increased remarkably. The Committee on Gene Symbolization, Nomenclature and Linkage (CGSNL) of the Rice Genetics Cooperative published the gene nomenclature system for rice and encouraged researchers to follow the rules before publishing their results. The CGSNL provides an on-line registration system for newly identified rice genes to prevent conflicts and/or duplication of gene name in journal articles.

Findings

Recently, the CGSNL surveyed genes in the rice WRKY family in published journal articles and found several duplicated gene names.

Conclusions

To discuss and resolve inconsistencies in WRKY gene nomenclature, the rice WRKY working group was established and redefined the nomenclature. This report announces the conclusion.     

Summer activity patterns among teenage girls: harmonic shape invariant modeling to estimate circadian cycles

Background

Physical activity as measured by activity counts over short time intervals across a 24 h period are often used to assess circadian variation. We are interested in characterizing circadian patterns in activity among adolescents and examining how these patterns vary by obesity status. New statistical approaches are needed to examine how factors affect different features of the circadian pattern and to make appropriate covariate adjustments when the outcomes are longitudinal count data.

Methods

We develop a statistical model for longitudinal or repeated activity count data that is used to examine differences in the overall activity level, amplitude (defined as the difference between the lowest and highest activity level over a 24 hour period), and phase shift. Using seven days of continuous activity monitoring, we characterize the circadian patterns and compare them between obese and non-obese adolescent girls.

Results

We find a statistically significant phase delay in adolescent girls who were obese compared with their non-obese counterparts. After the appropriate adjustment for measured potential confounders, we did not find differences in mean activity level between the two groups.

Conclusion

New statistical methodology was developed to identify a phase delay in obese compared with non-obese adolescents. This new approach for analyzing longitudinal circadian rhythm count data provides a useful statistical technique to add to the repertoire for those analyzing circadian rhythm data.     

Coping with continuous human disturbance in the wild: insights from penguin heart rate response to various stressors

Background

Studies of host-parasite interactions have the potential to provide insights into the ecology of both organisms involved. We monitored the movement of sucking lice (Lemurpediculus verruculosus), parasites that require direct host-host contact to be transferred, in their host population of wild mouse lemurs (Microcebus rufus). These lemurs live in the rainforests of Madagascar, are small (40 g), arboreal, nocturnal, solitary foraging primates for which data on population-wide interactions are difficult to obtain. We developed a simple, cost effective method exploiting the intimate relationship between louse and lemur, whereby individual lice were marked, without removal from their host, with an individualized code, and tracked throughout the lemur population. We then tested the hypotheses that 1) the frequency of louse transfers, and thus interactions, would decrease with increasing distance between paired individual lemurs; 2) due to host polygynandry, social interactions and hence louse transfers would increase during the onset of the breeding season; and 3) individual mouse lemurs would vary in their contributions to the spread of lice.

Results

We show that louse transfers involved 43.75% of the studied lemur population, exclusively males. Louse transfers peaked during the breeding season, perhaps due to increased social interactions between lemurs. Although trap-based individual lemur ranging patterns are restricted, louse transfer rate does not correlate with the distance between lemur trapping locales, indicating wider host ranging behavior and a greater risk of rapid population-wide pathogen transmission than predicted by standard trapping data alone. Furthermore, relatively few lemur individuals contributed disproportionately to the rapid spread of lice throughout the population.

Conclusions

Using a simple method, we were able to visualize exchanges of lice in a population of cryptic wild primates. This method not only provided insight into the previously unseen parasite movement between lemurs, but also allowed us to infer social interactions between them. As lice are known pathogen vectors, our method also allowed us to identify the lemurs most likely to facilitate louse-mediated epidemics. Our approach demonstrates the potential to uncover otherwise inaccessible parasite-host, and host social interaction data in any trappable species parasitized by sucking lice.     

Gastrointestinal complaints in shift-working and day-working nurses in Iran

Background

There is evidence in the scientific literature of the adverse physiological and psychological effects of shift work. The work of nurses in hospitals is connected with shift and night work. Several publications have described gastrointestinal disturbances in shift workers. The aim of this study was to compare the frequency of gastrointestinal (GI) complaints of nurses on a rotating shift with that of nurses on a regular day shift.

Methods

The study involved 160 nurses (133 working in shifts and at night and 27 working on day shifts) in the Shahid Beheshti Hospital in Kashan, Iran. These nurses answered a Gastrointestinal Symptom Questionnaire regarding the presence of gastrointestinal symptoms (including heartburn, regurgitation, constipation, diarrhea and bloating). Positive responses required frequent symptom occurrence in the past 4 weeks. Significance of group differences was assessed by chi-square and Fisher-exact tests.

Results

Prevalence of GI symptoms was significantly higher (p = 0.009) in rotating-shift nurses (81.9%) than in day-shift nurses (59.2%). Irregular meal consumption (p = 0.01) and GI medications (p = 0.002) were all significantly higher among the rotating shift nurses. In both groups, regurgitation was the most common symptom.

Conclusion

Nurses on rotating shifts in Iran experience more GI disturbances than do nurses on day shifts.     

Chronic inhibition of endoplasmic reticulum calcium-release channels and calcium-ATPase lengthens the period of hepatic clock gene Per1

Background

The Magel2 gene is most highly expressed in the suprachiasmatic nucleus of the hypothalamus, where its expression cycles in a circadian pattern comparable to that of clock-controlled genes. Mice lacking the Magel2 gene have hypothalamic dysfunction, including circadian defects that include reduced and fragmented total activity, excessive activity during the subjective day, but they have a normal circadian period. Magel2 is a member of the MAGE family of proteins that have various roles in cellular function, but the specific function of Magel2 is unknown.

Methods

We used a variety of cell-based assays to determine whether Magel2 modifies the properties of core circadian rhythm proteins.

Results

Magel2 represses the activity of the Clock:Bmal1 heterodimer in a Per2-luciferase assay. Magel2 interacts with Bmal1 and with Per2 as measured by co-immunoprecipitation in co-transfected cells, and exhibits a subcellular distribution consistent with these interactions when visualized by immunofluorescence. As well, Magel2 induces the redistribution of the subcellular localization of Clock towards the cytoplasm, in contrast to the nucleus-directed effect of Bmal1 on Clock subcellular localization.

Conclusion

Consistent with the blunted circadian rhythm observed in Magel2-null mice, these data suggest that Magel2 normally promotes negative feedback regulation of the cellular circadian cycle, through interactions with key core circadian rhythm proteins.