Biodiversity, extinctions and evolution of ecosystems with shared resources

We investigate the formation of stable ecological networks where many species share the same resource. We show that such stable ecosystem naturally occurs as a result of extinctions. We obtain an analytical relation for the number of coexisting species and find a relation describing how many species that may go extinct as a result of a sharp environmental change. We introduce a special parameter that is a combination of species traits and resource characteristics used in the model formulation. This parameter describes the pressure on system to converge, by extinctions. When that stress parameter is large we obtain that the species traits concentrate at some values. This stress parameter is thereby a parameter that determines the level of final biodiversity of the system. Moreover, we show that dynamics of this limit system can be described by simple differential equations

Effect of density dependence on coinfection dynamics

In this paper we develop an SIR model for coinfection. We discuss how the underlying dynamics depends on the carrying capacity $K$: from a simple dynamics to a more complicated. This can help in understanding of appearance of more complicated dynamics, for example, chaos etc. The density dependent population growth is also considered. It is presented that pathogens can invade in population and their invasion depends on the carrying capacity $K$ which shows that the progression of disease in population depends on carrying capacity. Our approach is based on a bifurcation analysis which allows to generalize considerably the previous Lotka-Volterra type models.Comment: 23 page

Conditions for successful range shifts under climate change -the role of species dispersal and landscape configuration

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Aim: Ongoing climate change is currently modifying the geographical location of areas that are climatically suitable for species. Understanding a species’ ability to successfully shift its geographical range would allow us to assess extinction risks and predict future community compositions. We investigate how habitat configuration impedes or promotes climate-driven range shifts, given different speeds of climate change and dispersal abilities. Location: Theoretical, but illustrated with European examples. Methods: We model how a species’ ability to track a directional shift in climatic conditions is affected by: i) species’ dispersal abilities; ii) speed of climatic shift; and iii) spatial arrangement of the habitat. Our modeling framework includes within and between-patch population dynamics and uses ecologically realistic habitat distributions and dispersal scenarios (verified with data from a set of European mammal species), and, as such, is an improvement of classical range shift models. Results: In landscapes with a homogeneous distribution of suitable habitats, all but the least dispersive species will be able to range shift. However, species with high dispersal ability will have lower population densities after range shift. In heterogeneous landscapes species’ ability to range shift is far more variable and heavily dependent on the habitat configuration. This means that landscape configuration in combination with the speed of climate change and species dispersal abilities give rise to non-linear effects on population sizes and survival after a climatic shift. Main conclusions: : Our analyses point out the importance of accounting for the interplay of species dispersal and the landscape configuration when estimating future climate impact on species. These results link ecologically important attributes of both species and their landscapes to outcomes of species range shift, and thereby long-term persistence of ecological communities.This research was funded by the ERA-Net BiodivERsA, part of the 2011 BiodivERsA call for research proposals. RE and A.Es acknowledge the ERA-Net BiodivERsA, with the national funder FCT, through the project BIODIVERSA/00003/2011. A.Ek. acknowledge funding from Swedish Research Council grant number 2016-04919. A.Es. has a postdoctoral contract funded by the project CN-17-022 (Principado de Asturias, Spain)

What are the beliefs of pediatricians and dietitians regarding complementary food introduction to prevent allergy?

<p>Abstract</p> <p>Background</p> <p>The timing of complementary food introduction is controversial. Providing information on the timing of dietary introduction is crucial to the primary prevention of food allergy. The American Academy of Pediatrics offers dietary recommendations that were updated in 2008.</p> <p>Objective</p> <p>Identify the recommendations that general pediatricians and registered dietitians provide to parents and delineate any differences in counselling.</p> <p>Methods</p> <p>A 9-item survey was distributed to pediatricians and dietitians online and by mail. Information on practitioner type, gender, length of practice and specific recommendations regarding complementary food introduction and exposure was collected.</p> <p>Results</p> <p>181 surveys were returned with a 54% response rate from pediatricians. It was not possible to calculate a meaningful dietitian response rate due to overlapping email databases. 52.5% of all respondents were pediatricians and 45.9% were dietitians. The majority of pediatricians and dietitians advise mothers that peanut abstinence during pregnancy and lactation is unnecessary. Dietitians were more likely to counsel mothers to breastfeed their infants to prevent development of atopic dermatitis than pediatricians. Hydrolyzed formulas for infants at risk of developing allergy were the top choice of formula amongst both practitioners. For food allergy prevention, pediatricians were more likely to recommend delayed introduction of peanut and egg, while most dietitians recommended no delay in allergenic food introduction.</p> <p>Conclusions</p> <p>In the prophylaxis of food allergy, pediatricians are less aware than dietitians of the current recommendation that there is no benefit in delaying allergenic food introduction beyond 4 to 6 months. More dietitians than pediatricians believe that breastfeeding decreases the risk of atopic dermatitis. Practitioners may benefit from increased awareness of current guidelines.</p

Surveillance study of apparent life-threatening events (ALTE) in the Netherlands

SIDS and ALTE are different entities that somehow show some similarities. Both constitute heterogeneous conditions. The Netherlands is a low-incidence country for SIDS. To study whether the same would hold for ALTE, we studied the incidence, etiology, and current treatment of ALTE in The Netherlands. Using the Dutch Pediatric Surveillance Unit, pediatricians working in second- and third-level hospitals in the Netherlands were asked to report any case of ALTE presented in their hospital from January 2002 to January 2003. A questionnaire was subsequently sent to collect personal data, data on pregnancy and birth, condition preceding the incident, the incident itself, condition after the incident, investigations performed, monitoring or treatment initiated during admission, any diagnosis made at discharge, and treatment or parental support offered after discharge. A total of 115 cases of ALTE were reported, of which 110 questionnaires were filled in and returned (response rate 97%). Based on the national birth rate of 200,000, the incidence of ALTE amounted 0.58/1,000 live born infants. No deaths occurred. Clinical diagnoses could be assessed in 58.2%. Most frequent diagnoses were (percentages of the total of 110 cases) gastro-esophageal reflux and respiratory tract infection (37.3% and 8.2%, respectively); main symptoms were change of color and muscle tone, choking, and gagging. The differences in diagnoses are heterogeneous. In 34%, parents shook their infants, which is alarmingly high. Pre- and postmature infants were overrepresented in this survey (29.5% and 8.2%, respectively). Ten percent had recurrent ALTE. In total, 15.5% of the infants were discharged with a home monitor. In conclusion, ALTE has a low incidence in second- and third-level hospitals in the Netherlands. Parents should be systematically informed about the possible devastating effects of shaking an infant. Careful history taking and targeted additional investigations are of utmost importance

GENERATING STRUCTURE SPECIFIC NETWORKS

Theoretical exploration of network structure significance requires a range of different networks for comparison. Here, we present a new method to construct networks in a spatial setting that uses spectral methods in combination with a probability distribution function. Nearly all previous algorithms for network construction have assumed randomized distribution of links or a distribution dependent on the degree of the nodes. We relax those assumptions. Our algorithm is capable of creating spectral networks along a gradient from random to highly clustered or diverse networks. Number of nodes and link density are specified from start and the structure is tuned by three parameters (γ, σ, κ). The structure is measured by fragmentation, degree assortativity, clustering and group betweenness of the networks. The parameter γ regulates the aggregation in the spatial node pattern and σ and κ regulates the probability of link forming.Network, spectral, assortativity, fragmentation, clustering, betweenness centralization, spatial network, network algorithm

Latitudinal diversity of biting midge species within the Obsoletus group across three habitats in Europe

Culicoides species from the Obsoletus group are important vectors of bluetongue and Schmallenberg virus. This group consists of several species that cannot easily be identified using morphological characteristics. Therefore, limited information is available about their distribution and habitat preferences. In this study, we aimed to elucidate the species composition of the Obsoletus group in three habitat types at climatically different latitudes across Europe. Traps were placed in three habitat types in three countries at different latitudes. After DNA extraction, biting midges were identified using PCR and gel electrophoresis. Extraction of DNA using Chelex proved to be a cost and time efficient method for species identification. A latitudinal effect on the relative abundance of species from the Obsoletus group was found. Species composition was unique for most country-habitat combinations. The majority of biting midges were either C. obsoletus s.s. or C. scoticus, and both species were found at all latitudes and habitats. Their wide distribution and their high abundance at livestock farms make these species likely candidates for rapid farm-to-farm transmission of pathogens throughout Europe. Our results emphasize the need to differentiate Obsoletus group species to better understand their ecology and contribution to pathogen transmission.</p

Biting midge dynamics and bluetongue transmission: a multiscale model linking catch data with climate and disease outbreaks.

Bluetongue virus (BTV) serotype 8 has been circulating in Europe since a major outbreak occurred in 2006, causing economic losses to livestock farms. The unpredictability of the biting activity of midges that transmit BTV implies difficulty in computing accurate transmission models. This study uniquely integrates field collections of midges at a range of European latitudes (in Sweden, The Netherlands, and Italy), with a multi-scale modelling approach. We inferred the environmental factors that influence the dynamics of midge catching, and then directly linked predicted midge catches to BTV transmission dynamics. Catch predictions were linked to the observed prevalence amongst sentinel cattle during the 2007 BTV outbreak in The Netherlands using a dynamic transmission model. We were able to directly infer a scaling parameter between daily midge catch predictions and the true biting rate per cow per day. Compared to biting rate per cow per day the scaling parameter was around 50% of 24 h midge catches with traps. Extending the estimated biting rate across Europe, for different seasons and years, indicated that whilst intensity of transmission is expected to vary widely from herd to herd, around 95% of naïve herds in western Europe have been at risk of sustained transmission over the last 15 years

Approximations of population growth in a noisy environment: on the dichotomy of non-age and age structure

By simulations of population growth exposed to environmental noise, we compared realised long-run growth rate of age structured populations of four different life histories, with four approximations. One approximation used a non-structured population model, including specific population growth rates for each time step, determined by actual vital rates, while the other three used age-structured data to estimate a mean growth rate, then applicable for all time steps. In general, approximations were reasonable accurate. Yet some were completely erroneous and inaccurate enough to move stationary populations to become species on the red list as an endangered species according to International Union for Conservation of Nature (IUNC). The inaccuracies depended, in the following decreasing order, on: life history, what part of the demography the noise was acting on, and noise colour. The non-structured growth approximation had smaller errors with red noise while the three age-structured approximations had their largest errors with red noise. Since it is generally understood that the most common noise in nature is red noise, we conclude that the non-structured approximation will be the best predictor of population growth in most cases. We also conclude that evenness in distribution over age classes is a possible predictor for the sensitivity of long-run growth rate to type of approximation and therefore a promising object for further studies. Finally, our results indicate that in general, more focus ought to be on reducing the error in the data collection on population densities, especially for studies over longer time periods, than of collecting age-specific data