Animal dispersal modelling: handling landscape features and related animal choices

Animal dispersal in a fragmented landscape depends on the complex interaction between landscape structure and animal behavior. To better understand how individuals disperse, it is important to explicitly represent the properties of organisms and the landscape in which they move. A common approach to modelling dispersal includes representing the landscape as a grid of equal sized cells and then simulating individual movement as a correlated random walk. This approach uses a priori scale of resolution, which limits the representation of all landscape features and how different dispersal abilities are modelled. We develop a vector-based landscape model coupled with an object-oriented model for animal dispersal. In this spatially explicit dispersal model, landscape features are defined based on their geographic and thematic properties and dispersal is modelled through consideration of an organism's behavior, movement rules and searching strategies (such as visual cues). We present the model's underlying concepts, its ability to adequately represent landscape features and provide simulation of dispersal according to different dispersal abilities. We demonstrate the potential of the model by simulating two virtual species in a real Swiss landscape. This illustrates the model's ability to simulate complex dispersal processes and provides information about dispersal such as colonization probability and spatial distribution of the organism's path.

Tests for sex-biased dispersal using bi-parentally inherited genetic markers.

Understanding why dispersal is sex-biased in many taxa is still a major concern in evolutionary ecology. Dispersal tends to be male-biased in mammals and female-biased in birds, but counter-examples exist and little is known about sex bias in other taxa. Obtaining accurate measures of dispersal in the field remains a problem. Here we describe and compare several methods for detecting sex-biased dispersal using bi-parentally inherited, codominant genetic markers. If gene flow is restricted among populations, then the genotype of an individual tells something about its origin. Provided that dispersal occurs at the juvenile stage and that sampling is carried out on adults, genotypes sampled from the dispersing sex should on average be less likely (compared to genotypes from the philopatric sex) in the population in which they were sampled. The dispersing sex should be less genetically structured and should present a larger heterozygote deficit. In this study we use computer simulations and a permutation test on four statistics to investigate the conditions under which sex-biased dispersal can be detected. Two tests emerge as fairly powerful. We present results concerning the optimal sampling strategy (varying number of samples, individuals, loci per individual and level of polymorphism) under different amounts of dispersal for each sex. These tests for biases in dispersal are also appropriate for any attribute (e.g. size, colour, status) suspected to influence the probability of dispersal. A windows program carrying out these tests can be freely downloaded from http://www.unil.ch/izea/softwares/fstat.html

Is a Virtual Library cost effective?

The Andalusian Public Health System Virtual Library (Biblioteca Virtual del Sistema Sanitario Público de Andalucía, BV-SSPA), was created in June 2006. In this paper an evaluation is made to see whether the investment made by the Andalusian Government has been worthwhile. The cost-effectiveness and efficiency of the project together with the management criteria are explored.

Dispersal of Triatoma infestans and other Triatominae species in the arid Chaco of Argentina: Flying, walking or passive carriage? The importance of walking females

The aim of this paper was to analyse the active dispersal of Triatoma infestans and the role of chickens as passive carriers of this insect in peridomestic areas of La Rioja, Argentina. To measure active dispersal, monthly catches were made on six consecutive nights for five months (in the warm season) using light traps (for flying insects) and sticky dispersal barriers (for walking insects). The nutritional and reproductive states of adults were evaluated. Over the course of the sampling period, a total of eight flying adults, six walking nymphs and 10 walking adults of the species T. infestans were captured, as well as specimens of Triatoma guasayana, Triatoma eratyrusiformis and Triatoma platensis. Our data demonstrate for the first time that females of T. infestans can disperse by walking. This may be an adaptive strategy because it allows them to move with eggs and/or with good blood reserves, which are not possible when flying. All flying and walking individuals of both genders were of an appropriate physiological state that would allow for colonisation of the target habitat. However, manual inspection of 122 chickens suggests that it is unlikely that these animals passively transport T. infestans. Finally, the dispersal activity of T. infestans was compared with other triatomines using a dispersion index.

Toward Protein Biomarkers for Allergy: CD4+ T Cell Proteomics in Allergic and Nonallergic Subjects Sampled in and out of Pollen Season.

Allergy is an immunological disorder of the upper airways, lung, skin, and the gut with a growing prevalence over the last decades in Western countries. Atopy, the genetic predisposition for allergy, is strongly dependent on familial inheritance and environmental factors. These observations call for predictive markers of progression from atopy to allergy, a prerequisite to any active intervention in neonates and children (prophylactic interventions/primary prevention) or in adults (immunomodulatory interventions/secondary prevention). In an attempt to identify early biomarkers of the "atopic march" using minimally invasive sampling, CD4+ T cells from 20 adult volunteers (10 healthy and 10 with respiratory allergies) were isolated and quantitatively analyzed and their proteomes were compared in and out of pollen season (± antigen exposure). The proteome study based on high-resolution 2D gel electrophoresis revealed three candidate protein markers that distinguish the CD4+ T cell proteomes of normal from allergic individuals when sampled out of pollen season, namely Talin 1, Nipsnap homologue 3A, and Glutamate-cysteine ligase regulatory protein. Three proteins were found differentially expressed between the CD4+ T cell proteomes of normal and allergic subjects when sampled during pollen season: carbonyl reductase, glutathione S-transferase ω 1, and 2,4-dienoyl-CoA reductase. The results were partly validated by Western blotting.

Genetic clusters and sex-biased gene flow in a unicolonial Formica ant.

BACKGROUND: Animal societies are diverse, ranging from small family-based groups to extraordinarily large social networks in which many unrelated individuals interact. At the extreme of this continuum, some ant species form unicolonial populations in which workers and queens can move among multiple interconnected nests without eliciting aggression. Although unicoloniality has been mostly studied in invasive ants, it also occurs in some native non-invasive species. Unicoloniality is commonly associated with very high queen number, which may result in levels of relatedness among nestmates being so low as to raise the question of the maintenance of altruism by kin selection in such systems. However, the actual relatedness among cooperating individuals critically depends on effective dispersal and the ensuing pattern of genetic structuring. In order to better understand the evolution of unicoloniality in native non-invasive ants, we investigated the fine-scale population genetic structure and gene flow in three unicolonial populations of the wood ant F. paralugubris. RESULTS: The analysis of geo-referenced microsatellite genotypes and mitochondrial haplotypes revealed the presence of cryptic clusters of genetically-differentiated nests in the three populations of F. paralugubris. Because of this spatial genetic heterogeneity, members of the same clusters were moderately but significantly related. The comparison of nuclear (microsatellite) and mitochondrial differentiation indicated that effective gene flow was male-biased in all populations. CONCLUSION: The three unicolonial populations exhibited male-biased and mostly local gene flow. The high number of queens per nest, exchanges among neighbouring nests and restricted long-distance gene flow resulted in large clusters of genetically similar nests. The positive relatedness among clustermates suggests that kin selection may still contribute to the maintenance of altruism in unicolonial populations if competition occurs among clusters.

Enhanced diagnosis of pollen allergy using specific immunoglobulin E determination to detect major allergens and panallergens.

BACKGROUND Pollen is one of the main causes of allergic sensitization. It is not easy to make an etiological diagnosis of pollen-allergic patients because of the wide variety of sensitizing pollens, association with food allergy, and increasing incidence of polysensitization, which may result from the presence of allergens that are common to different species, as is the case of panallergens. OBJECTIVE To compare the results of skin prick tests (SPT) using whole pollen extract with specific immunoglobulin (Ig) E determination for several allergens (purified panallergens included) in the diagnosis of polysensitized pollen-allergic patients. METHODS The study sample comprised 179 pollen-sensitized patients who underwent SPT with pollen extract and allergen-specific IgE determination against different allergens. RESULTS The level of concordance between the traditional diagnostic test (SPT) and IgE determination was low, especially in patients sensitized to the panallergens profilin and polcalcin. In the case of SPT, the results demonstrated that patients who are sensitized to either of these panallergens present a significantly higher number of positive results than patients who are not. However, IgE determination revealed that while patients sensitized to polcalcins are sensitized to allergens from a higher number of pollens than the rest of the sample, this is not the case in patients sensitized to profilins. On the other hand, sensitization to profilin or lipid transfer proteins was clearly associated with food allergy. CONCLUSIONS Sensitization to panallergens could be a confounding factor in the diagnosis of polysensitized pollen-allergic patients as well as a marker for food allergy. However, more studies are required to further investigate the role of these molecules.

Effective diagnosis of Alzheimer's disease by means of large margin-based methodology.

BACKGROUND Functional brain images such as Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) have been widely used to guide the clinicians in the Alzheimer's Disease (AD) diagnosis. However, the subjectivity involved in their evaluation has favoured the development of Computer Aided Diagnosis (CAD) Systems. METHODS It is proposed a novel combination of feature extraction techniques to improve the diagnosis of AD. Firstly, Regions of Interest (ROIs) are selected by means of a t-test carried out on 3D Normalised Mean Square Error (NMSE) features restricted to be located within a predefined brain activation mask. In order to address the small sample-size problem, the dimension of the feature space was further reduced by: Large Margin Nearest Neighbours using a rectangular matrix (LMNN-RECT), Principal Component Analysis (PCA) or Partial Least Squares (PLS) (the two latter also analysed with a LMNN transformation). Regarding the classifiers, kernel Support Vector Machines (SVMs) and LMNN using Euclidean, Mahalanobis and Energy-based metrics were compared. RESULTS Several experiments were conducted in order to evaluate the proposed LMNN-based feature extraction algorithms and its benefits as: i) linear transformation of the PLS or PCA reduced data, ii) feature reduction technique, and iii) classifier (with Euclidean, Mahalanobis or Energy-based methodology). The system was evaluated by means of k-fold cross-validation yielding accuracy, sensitivity and specificity values of 92.78%, 91.07% and 95.12% (for SPECT) and 90.67%, 88% and 93.33% (for PET), respectively, when a NMSE-PLS-LMNN feature extraction method was used in combination with a SVM classifier, thus outperforming recently reported baseline methods. CONCLUSIONS All the proposed methods turned out to be a valid solution for the presented problem. One of the advances is the robustness of the LMNN algorithm that not only provides higher separation rate between the classes but it also makes (in combination with NMSE and PLS) this rate variation more stable. In addition, their generalization ability is another advance since several experiments were performed on two image modalities (SPECT and PET).

Multiple causes of the evolution of dispersal in metapopulations

Abstract This work investigates the outcome of the interaction of the multiple causes of selection acting on dispersal in metapopulations. Dispersal, defined here as the ability of individuals to move out of their natal population to reproduce in an other one, has three main causes. First, population variability, as caused by random population extinctions, induces high incentives to disperse through the probability to recolonize an empty population and thus to escape competition for space. This adds to the second cause, kin competition avoidance where individuals in a crowded patch will benefit from the release of competition with relatives caused by dispersal. Dispersal may thus be viewed as an altruistic act. Third, dispersal might evolve as a strategy of avoiding inbred matings which are expected to bear fitness costs due to the presence of a mutation load. The interaction of inbreeding avoidance and kin competition is explored in chapter 2. Conditions conducive to the establishment of a high relatedness within population are expected to induce high dispersal through both kin competition avoidance and inbreeding avoidance. However, the dynamics of inbreeding depression is bound to depend on the level of gene flow as well as on the deleterious mutation parameters. Mutations more prone to settle a high level of inbreeding depression will select for increased dispersal. Chapter 3 investigates the effect of the mating system on the joint dynamics of dispersal and inbreeding depression. Higher inbreeding rates as those found in various mating systems lead to a more efficient purge of the deleterious mutations. However, this decrease in the costs of inbreeding are usually accompanied by a higher within deme relatedness which balances the decreased effect of inbreeding avoidance on the evolution of dispersal. Finally, population turnover, as found in most natural populations has a dual effect on dispersal. Indeed, it increases dispersal by the increased probability of winning a breeding slot in extinct demes it creates but, on the other hand, it counter-selects for dispersal through the slow establishment of unsaturated demic conditions which contribute to lower the local competition for space. Résumé Ce travail se propose d'étudier les effets conjoints des multiples causes de l'évolution de la dispersion en métapopulation. La dispersion, définie ici comme étant la capacité de quitter sa population d'origine pour se reproduire dans une antre population, possède trois principales causes. Premièrement, l'extinction aléatoire de populations sélectionne pour plus de dispersion car elle augmente la Probabilité de recoloniser un patch éteint et donc d'échapper à la compétition locale. La seconde cause, l'évitement de la compétition de parentèle, sélectionne pour plus de dispersion par les bénéfices qu'elle apporte par diminution de la compétition entre individus apparentés. Troisièmement, la dispersion évolue "comme stratégie d'évitement de la dépression de consanguinité présente dans des petites populations isolées. L'interaction entre l'évitement de la consanguinité et de la compétition de parentèle est étudiée dans le chapitre 2. Les conditions conduisant à l'établissement d'un fort apparentement à l'intérieur des populations sont celles qui génèrent le plus de sélection pour la dispersion. Cependant, la dynamique de la dépression de consanguinité est dépendante de la dispersion entre populations ainsi que des paramètres des mutations délétères. Les mutations créant le plus de dépression de consanguinité sont celles qui sélectionneront le plus pour de la dispersion. Le chapitre 3 s'intéresse aux effets du système de reproduction sur la dynamique conjointe du fardeau de mutation et de la dispersion. La purge des mutations délétère étant plus sévère dans des conditions de forte consanguinité, elle diminue les coûts de la consanguinité mais est habituellement accompagné par une augmentation de l'apparentement et donc l'effet peut être neutre sur la dispersion. Finalement, le turnover de populations a un effet dual sur la dispersion. La dispersion est sélectionnée par l'augmentation de la probabilité de gagner une place de reproduction dans des patchs éteints mais elle est également contre sélectionnée par la désaturation des patchs causée par l'extinction et la diminution de la compétition pour l'espace qui intervient dans ce cas.

Is imidacloprid an effective alternative for controlling pyrethroid-resistant populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco ecoregion?

The prevention of Chagas disease is based primarily on the chemical control of Triatoma infestans (Klug) using pyrethroid insecticides. However, high resistance levels, correlated with control failures, have been detected in Argentina and Bolivia. A previous study at our laboratory found that imidacloprid could serve as an alternative to pyrethroid insecticides. We studied the delayed toxicity of imidacloprid and the influence of the blood feeding condition of the insect on the toxicity of this insecticide; we also studied the effectiveness of various commercial imidacloprid formulations against a pyrethroid-resistant T. infestans population from the Gran Chaco ecoregion. Variations in the toxic effects of imidacloprid were not observed up to 72 h after exposure and were not found to depend on the blood feeding condition of susceptible and resistant individuals. Of the three different studied formulations of imidacloprid on glass and filter paper, only the spot-on formulation was effective. This formulation was applied to pigeons at doses of 1, 5, 20 and 40 mg/bird. The nymphs that fed on pigeons treated with 20 mg or 40 mg of the formulation showed a higher mortality rate than the control group one day and seven days post-treatment (p < 0.01). A spot-on formulation of imidacloprid was effective against pyrethroid-resistant T. infestans populations at the laboratory level.

Monotherapy with darunavir/ritonavir is effective and safe in clinical practice.

INTRODUCTION Monotherapy against HIV has undoubted theoretical advantages and has good scientific fundaments. However, it is still controversial and here we will analyze the efficacy and safety of MT with darunavir with ritonavir (DRV/r) on patients who have received this treatment in our hospitals. MATERIALS AND METHODS Observational retrospective study that includes patients from 10 Andalusian hospitals that have received DRV/r in MT and that have been followed over a minimum of 12 months. We carried out a statistical descriptive analysis based on the profile of patients who had been prescribed MT and the efficacy and safety that were observed, paying special attention to treatment failure and virological evolution. RESULTS DRV/r was prescribed to 604 patients, of which 41.1% had a CD4 nadir <200/mmc. 33.1% had chronic hepatitis caused by HCV, had received an average of five lines of previous treatment and had a history of treatment failure to analogues in 33%, to non-analogues 22 and protease inhibitors (PI) in 19.5%. 76.6% proceeded from a previous treatment with PI. The simplification was the main criteria for the instauration of MT in the 81.5% and the adverse effects in the 18.5%. We managed to maintain MT in 84% of cases, with only 4.8% of virological failure (VF) with viral load (VL) >200 c/mL and 3.6% additional losses due to VF with VL between 50 and 200 copies/mL. Thirty three genotypes were performed after failure without findings of resistance mutations to DRV/r or other IPs. Only 23.7% of patients presented some blips during the period of exposition to MT. Eighty seven percent of all determinations of VL had <50 copies/mL, and only 4.99% had >200 copies/mL. Although up to 14.9% registered at some point an AE, only 2.6% abandoned MT because of AE and 1.2% because of voluntary decision. Although the average of total and LDL cholesterol increases 10 mg/dL after 2 years of follow-up, so did HDL cholesterol in 3mg/dL and the values of triglycerides (-14 mg/dL) and GPT (-6 UI/mL) decreased. The average count of CD4 lymphocytes increased from 642 to 714/mm(3) at 24 weeks. CONCLUSIONS In a very broad series of patients obtained from clinical practice, data from clinical trials was confirmed: MT with DRV as a de-escalation strategy is very safe, it's associated to a negligible rate of adverse effects and maintains a good suppression of HIV replication. VF (with >50 or >200 copies/mL) is always under 10% and in any case without consequences.

Protection from HIV-1 infection of primary CD4 T cells by CCR5 silencing is effective for the full spectrum of CCR5 expression.

Stable gene silencing by RNA interference (RNAi) can be achieved by expression of small hairpin RNAs (shRNAs) from RNA polymerase III promoters. We have tested lentiviral vectors expressing shRNAs targetting CCR5 in primary CD4 T cells from donors representing various CCR5 and CCR2 genetic backgrounds covering the full spectrum of CCR5 expression levels and permissiveness for HIV-1 infection. A linear decrease in CCR5 expression resulted in a logarithmic decrease in cellular infection, giving up to three logs protection from HIV-1 infection in vitro. Protection was maintained at very high multiplicity of infection. This and other recent reports on RNAi should open a debate about the use of RNAi gene therapy for HIV infection.