Optimal Culling and Biocontrol in a Predator–Prey Model

Invasive species cause enormous problems in ecosystems around the world. Motivated by introduced feral cats that prey on bird populations and threaten to drive them extinct on remote oceanic islands, we formulate and analyze optimal control problems. Their novelty is that they involve both scalar and time-dependent controls. They represent different forms of control, namely the initial release of infected predators on the one hand and culling as well as trapping, infecting, and returning predators on the other hand. Combinations of different control methods have been proposed to complement their respective strengths in reducing predator numbers and thus protecting endangered prey. Here, we formulate and analyze an eco-epidemiological model, provide analytical results on the optimal control problem, and use a forward–backward sweep method for numerical simulations. By taking into account different ecological scenarios, initial conditions, and control durations, our model allows to gain insight how the different methods interact and in which cases they could be effective.     

Dynamics of a Prey–Predator System with Herd Behaviour in Both and Strong Allee Effect in Prey

Biophysics - This paper mainly deals with the prey?predator dynamics where both the prey and predator exhibit herd behavior. Positivity, boundedness, some extinction criteria, stability of...     

A Sensory-Driven Trade-Off between Coordinated Motion in Social Prey and a Predator’s Visual Confusion

Social animals are capable of enhancing their awareness by paying attention to their neighbors, and prey found in groups can also confuse their predators. Both sides of these sensory benefits have long been appreciated, yet less is known of how the perception of events from the perspectives of both prey and predator can interact to influence their encounters. Here we examined how a visual sensory mechanism impacts the collective motion of prey and, subsequently, how their resulting movements influenced predator confusion and capture ability. We presented virtual prey to human players in a targeting game and measured the speed and accuracy with which participants caught designated prey. As prey paid more attention to neighbor movements their collective coordination increased, yet increases in prey coordination were positively associated with increases in the speed and accuracy of attacks. However, while attack speed was unaffected by the initial state of the prey, accuracy dropped significantly if the prey were already organized at the start of the attack, rather than in the process of self-organizing. By repeating attack scenarios and masking the targeted prey’s neighbors we were able to visually isolate them and conclusively demonstrate how visual confusion impacted capture ability. Delays in capture caused by decreased coordination amongst the prey depended upon the collection motion of neighboring prey, while it was primarily the motion of the targets themselves that determined capture accuracy. Interestingly, while a complete loss of coordination in the prey (e.g., a flash expansion) caused the greatest delay in capture, such behavior had little effect on capture accuracy. Lastly, while increases in collective coordination in prey enhanced personal risk, traveling in coordinated groups was still better than appearing alone. These findings demonstrate a trade-off between the sensory mechanisms that can enhance the collective properties that emerge in social animals and the individual group member’s predation risk during an attack.     

Predator–prey interactions and metabolic rates are altered in stable and unstable groups in a social fish

Understanding the determinants and consequences of predation effort, success and prey responses is important since these factors affect the fitness of predators and prey. When predators are also invasive species, the impacts on prey can be particularly far-reaching with ultimate ecosystem-level consequences. However, predators are typically viewed as behaviourally fixed within this interaction and it is unclear how variation in predator social dynamics affects predator–prey interactions. Using the invasive eastern mosquitofish Gambusia holbrooki and a native glass shrimp Paratya australiensis in Australia, we investigated how varying levels of social conflict within predator groups influences predator–prey interactions. By experimentally manipulating group stability of G. holbrooki, we show that rates of social conflict were lower in groups with large size differences, but that routine metabolic rates were higher in groups with large size differences. Predation effort and success did not vary depending on group stability, but in stable groups predation effort by aggressive dominants was greater than subordinates. The anti-predator responses of prey to the stability of predator groups were mixed. While more prey utilized shelters when exposed to stable compared to unstable groups of predators, a greater proportion were sedentary when predator groups were unstable. Overall, this study demonstrates predator group stability is modulated by differences in body size and can influence prey responses. Further, it reveals a hidden metabolic cost of living in stable groups despite reduced overt social conflict. For invasive species management, it is therefore important to consider the behavioural and physiological plasticity of the invasive predators, whose complex social interactions and metabolic demands can modulate patterns of predator–prey interactions.     

Does Intraspecific Size Variation in a Predator Affect Its Diet Diversity and Top-Down Control of Prey?

It has long been known that intraspecific variation impacts evolutionary processes, but only recently have its potential ecological effects received much attention. Theoretical models predict that genetic or phenotypic variance within species can alter interspecific interactions, and experiments have shown that genotypic diversity in clonal species can impact a wide range of ecological processes. To extend these studies to quantitative trait variation within populations, we experimentally manipulated the variance in body size of threespine stickleback in enclosures in a natural lake environment. We found that body size of stickleback in the lake is correlated with prey size and (to a lesser extent) composition, and that stickleback can exert top-down control on their benthic prey in enclosures. However, a six-fold contrast in body size variance had no effect on the degree of diet variation among individuals, or on the abundance or composition of benthic or pelagic prey. Interestingly, post-hoc analyses revealed suggestive correlations between the degree of diet variation and the strength of top-down control by stickleback. Our negative results indicate that, unless the correlation between morphology and diet is very strong, ecological variation among individuals may be largely decoupled from morphological variance. Consequently we should be cautious in our interpretation both of theoretical models that assume perfect correlations between morphology and diet, and of empirical studies that use morphological variation as a proxy for resource use diversity.     

Pattern Formation,Long-Term Transients,and the Turing–Hopf Bifurcation in a Space- and Time-Discrete Predator–Prey System

Understanding of population dynamics in a fragmented habitat is an issue of considerable importance. A natural modelling framework for these systems is spatially discrete. In this paper, we consider a predator–prey system that is discrete both in space and time, and is described by a Coupled Map Lattice (CML). The prey growth is assumed to be affected by a weak Allee effect and the predator dynamics includes intra-specific competition. We first reveal the bifurcation structure of the corresponding non-spatial system. We then obtain the conditions of diffusive instability on the lattice. In order to reveal the properties of the emerging patterns, we perform extensive numerical simulations. We pay a special attention to the system properties in a vicinity of the Turing–Hopf bifurcation, which is widely regarded as a mechanism of pattern formation and spatiotemporal chaos in space-continuous systems. Counter-intuitively, we obtain that the spatial patterns arising in the CML are more typically stationary, even when the local dynamics is oscillatory. We also obtain that, for some parameter values, the system’s dynamics is dominated by long-term transients, so that the asymptotical stationary pattern arises as a sudden transition between two different patterns. Finally, we argue that our findings may have important ecological implications.     

Orientation and excitonic interactions of the Fenna—Matthews—Olson bacteriochlorophyll a protein in membranes of the green sulfur bacterium Chlorobium tepidum

Linear and circular dichroism spectra of isolated bacteriochlorophyll a proteins (FMO proteins) and membrane vesicles containing FMO protein from the green sulfur bacterium Chlorobium tepidum were measured at room temperature and 77 K. The orientation of membranes and isolated FMO protein was obtained by gel squeezing. Linear dichroism (LD) data indicate that isolated FMO protein and membrane vesicles associated with the FMO protein are oriented in a similar way in a squeezed polyacrylamide gel. Both samples show a characteristic negative LD band around 814 nm with flanking positive bands at 802 and 824 nm ascribed to the Q_y excitonic transitions of BChl a of the FMO protein. This confirms that the C3 symmetry axis of the trimer is perpendicular to the membrane plane, which is supported by the model of the disc-like structure of FMO protein trimers of Cb. tepidum [Li Yi-Fen, Zhou W, Blankenship RE, and Allen JP (1997) J Mol Biol 272: 456–471]. The LD data are consistent with either BChl 3 or 6, but not 7 as the principal contributor to the low temperature band at 825 nm. The low temperature linear and circular dichroism spectra of FMO protein trimers from Chlorobium tepidum show significant differences from the low temperature LD and CD spectra of FMO protein trimers from Prosthecochloris aestuarii. The data are interpreted in terms of somewhat different pigment-protein and pigment-pigment interactions in the two complexes.     

Recent advances in microbial glutaminase production and applications—a concise review

Abstract

This article focuses on significant advances in the production and applications of microbial glutaminases and provides insight into the structures of different glutaminases. Glutaminases catalyze the deamidation of glutamine to glutamic acid, and this unique ability forms the basis of their applications in various industries such as pharmaceutical and food organizations. Microbial glutaminases from bacteria, actinomycetes, yeast, and fungi are of greater significance than animal glutaminases because of their stability, affordability, and ease of production. Owing to these notable benefits, they are considered to possess considerable potential in anticancer and antiviral therapy, flavor enhancers in oriental foods, biosensors and in the production of a nutraceutical theanine. This review also aims to fully explore the potential of microbial glutaminases and to set the pace for future prospects.     

It is a matter of timing: asynchrony during pollen development and its consequences on pollen performance in angiosperms—a review

Functional pollen is needed to successfully complete fertilization. Pollen is formed inside the anthers following a specific sequence of developmental stages, from microsporocyte meiosis to pollen release, that concerns microsporocytes/microspores and anther wall tissues. The processes involved may not be synchronous within a flower, an anther, and even a microsporangium. Asynchrony has been barely analyzed, and its biological consequences have not been yet assessed. In this review, different processes of pollen development and lifetime, stressing on the possible consequences of their differential timing on pollen performance, are summarized. Development is usually synchronized until microsporocyte meiosis I (occasionally until meiosis II). Afterwards, a period of mostly asynchronous events extends up to anther opening as regards: (1) meiosis II (sometimes); (2) microspore vacuolization and later reduction of vacuoles; (3) amylogenesis, amylolysis, and carbohydrate inter-conversion; (4) the first haploid mitosis; and (5) intine formation. Asynchrony would promote metabolic differences among developing microspores and therefore physiologically heterogeneous pollen grains within a single microsporangium. Asynchrony would increase the effect of competition for resources during development and pollen tube growth and also for water during (re)hydration on the stigma. The differences generated by developmental asynchronies may have an adaptive role since more efficient pollen grains would be selected with regard to homeostasis, desiccation tolerance, resilience, speed of (re)hydration, and germination. The performance of each pollen grain which landed onto the stigma will be the result of a series of selective steps determined by its development, physiological state at maturity, and successive environmental constrains.     

Ants and extrafloral nectaries: no evidence for plant protection in Helichrysum spp. — ant interactions

Summary Characterstics of Australian endemic Helichrysum bracteratum and H. viscosum suggest that foraging ants act as guards of developing flowerheads, protecting capitula from seed predators: (1) extrafloral nectar is secreted from leaves subtending the capitula and from bracts encircling the floral disc during pre- to post-flowering periods; (2) capitula are attended by ants; and, (3) encounters between ants and other capitula visitors, including predispersal seed predators such as Tephritis sp. (Diptera), can be frequent. In experiments to test the ant-guard hypothesis, exclusion of ants from plants increased abundance of other insects on the developing capitula. The difference between ant-access and ant-exclusion treatments was related to ant abundance on the access plants. These effects were statistically significant in spite of the large variation in insect activity between sites and through the season.The increased abundance of insects on capitula following ant-exclusion did not, however, result in significant increases in the number of adult seed predators observed on capitula, the number of immature seed predators in capitula, or capitula damage as estimated between ant-access and exclusion treatments of either H. bracteatum or H. viscosum. Further, the ant-exclusion treatment on H. bracteatum had no significant influence on pollination as measured by seed set or on the degree of parasitism of Tephritis sp. by Megastigmus sp. Site and season most strongly affected numbers of immature seed predators and damage to capitula.We discuss these findings in relation to the ant-guard hypothesis and suggest that generalization of the protection hypothesis to all plants with extrafloral nectaries is premature.     

Production of 6-[18F]fluoro-l-DOPA and its metabolism in vivo—a critical review

This report critically appraises methods for the synthesis of 6-[¹⁸F]fluoro-l-3,4-dihydroxyphenylalanine (6-FDOPA) that are based on labelling by non-regioselective electrophilic fluorination, regioselective fluorodemetalation or nucleophilic substitution. Recommendations for the standardization of labelling procedures, the optimization of radiochemical yield and the assurance of product quality and safety are given. Studies of the metabolism of 6-FDOPA in vivo are also reviewed to emphasize the importance of the biochemical component of the development of this tracer for positron emission tomography (PET).     

Can an Invasive Prey Species Induce Morphological and Behavioral Changes in an Endemic Predator？ Evidence from a South Korean Snake （Oocatochus rufodorsatus）

Introduction of an invasive prey species into an ecosystem may affect an endemic predator＇s fitness by altering the prey-predator system. Successful adaptation may allow the endemic predator to eat and control the invasive species, while unsuccessful adaptation may result in extinction of the predator. We examine the possible effects of the invasive North American bullfrog （Rana [Lithobates] catesbeiana） on the endemic Red-backed rat snake （Oocatochus rufodorsatus） in South Korea. We do so by comparing the morphology and behavior of adult and hatchling snakes from bullfrog-exposed （Taean） and bullfrog-unexposed （Hongcheon） populations. Among the seven morphological characteristics investigated, relative tail length （tail length/snout-vent length） of both adults and hatchlings from Taean was significantly greater than that of adults and hatchlings from Hongcheon. Also, adult snakes from Taean had a signiifcantly shorter latency of ifrst tongue lfick in response to prey compared to adults from Hongcheon. This difference was not observed in hatchlings. In other snake species, a longer relative tail length and shorter latency of ifrst tongue lfick are known to improve foraging efifciency, and these characters may be adaptations ofO. rufodorsatus to prey on bullfrogs. This study provides preliminary evidence that the presence of an invasive prey species may cause morphological and behavioral changes in an endemic predator.     

Role of Quantity of Additional Food to Predators as a Control in Predator–Prey Systems with Relevance to Pest Management and Biological Conservation

Necessity to understand the role of additional food as a tool in biological control programs is being increasingly felt, particularly due to its eco-friendly nature. A thorough mathematical analysis in this direction revealed the vital role of quality and quantity of the additional food in the controllability of the predator–prey systems. In this article controllability of the additional food—provided predator–prey system is studied from perspectives of pest eradication and biological conservation. Time optimal paths have been constructed to drive the state of the system to a desired terminal state by choosing quantity of the additional food as control variable. The theory developed in this article has been illustrated by solving problems related to pest eradication and biological conservation.     

Production of phycocyanin—a pigment with applications in biology, biotechnology, foods and medicine

C-phycocyanin (C-PC) is a blue pigment in cyanobacteria, rhodophytes and cryptophytes with fluorescent and antioxidative properties. C-PC is presently extracted from open pond cultures of the cyanobacterium Arthrospira platensis although these cultures are not very productive and open for contaminating organisms. C-PC is considered a healthy ingredient in cyanobacterial-based foods and health foods while its colouring, fluorescent or antioxidant properties are utilised only to a minor extent. However, recent research and developments in C-PC synthesis and functionality have expanded the potential applications of C-PC in biotechnology, diagnostics, foods and medicine: The productivity of C-PC has been increased in heterotrophic, high cell density cultures of the rhodophyte Galdieria sulphuraria that are grown under well-controlled and axenic conditions. C-PC purification protocols based on various chromatographic principles or novel two-phase aqueous extraction methods have expanded in numbers and improved in performance. The functionality of C-PC as a fluorescent dye has been improved by chemical stabilisation of C-PC complexes, while protein engineering has also introduced increased stability and novel biospecific binding sites into C-PC fusion proteins. Finally, our understanding of the physiological functions of C-PC in humans has been improved by a mechanistic hypothesis that links the chemical properties of the phycocyanobilin chromophores of C-PC to the natural antioxidant, bilirubin, and may explain the observed health benefits of C-PC intake. This review outlines how C-PC is produced and utilised and discusses the novel C-PC synthesis procedures and applications.     

Hypera postica [Col.: Curculionidae] and its natural enemies in Maryland and West Germany — 1971

A comparative study of field populations ofHypera postica (Gyllenhal), the alfalfa weevil, and its natural enemies was conducted in Maryland and West Germany in 1971. Populations of alfalfa weevil larvae peaked at 231/.09 m² in Maryland versus 45/.09 m² in West Germany. The ichneumonid parasiteBathyplectes curculionis (Thomson), and the eulophid,Tetrastichus incertus (Ratzeburg), were recovered in both Maryland and West Germany.Bathyplectes anurus (Thomson) was recovered only in West Germany, and the braconid,Microctonus colesi Drea, was recovered only in Maryland. A review of the agricultural practices and climatological conditions indicated that these factors may contribute to the regulation of the alfalfa weevil in West Germany and the United States. This paper is the 2nd in a series of 3 studies on the biology, ecology and biological control of the alfalfa weevil from 1966–1979.     

The effect of ischaemia-reperfusion on [3H]inositol phosphates and Ins(1,4,5)P3 levels in cardiac atria and ventricles — a comparative study

In this study incorporation of [³H]inositol into inositol phosphates and phosphoinositides as well as tissue Ins(1,4,5)P₃ levels of the atria and ventricles of isolated, perfused rat hearts were compared. Although the incorporation of [³H]inositol into the phosphoinositides of atria and ventricles was similar, significantly higher (2–3 fold) incorporation rates into inositol phosphates were observed in atrial tissue. Using a D-myo-[³H]Ins(1,4,5)P₃ assay system, the Ins(1,4,5)P₃ levels observed in atria from perfused rat hearts were also significantly higher than those obtained under the same experimental circumstances in the ventricles.Since previous studies on whole hearts showed inhibition of the phosphatidylinositol (PI) pathway during ischaemia with an immediate significant stimulation upon reperfusion [12, 20], the effects of ischaemia and 1 min postischaemic reperfusion were also examined separately in atria and ventricles. The results showed that 20 min of global ischaemia significantly depressed Ins(1,4,5)P₃ levels as well as incorporation of [3H]inositol into ventricular InSP₂ and InSP₃. Reperfusion caused an immediate (within 1 min) increase in Ins(1,4,5)P₃ levels and also [³H]inositol incorporation into all three cytosolic inositol phosphates in the ventricles. However, the effect of ischaemia and reperfusion on Ins(1,4,5)P₃ levels as well as the incorporation of [³H]inositol into the inositol phosphates were less prominent in the atria. It therefore appears that the differential responses of the atria and the ventricles to an oxygen deficiency [41] are also reflected in the differences in PI metabolism during ischaemia-reperfusion.     

Holocene vegetation history and tree-line changes on a north–south transect crossing major climate gradients in southern Norway—evidence from pollen and plant macrofossils in lake sediments

Long-term tree-line fluctuations have been studied using pollen and plant macrofossils preserved in lake sediments from three sites on an oceanic to continental transect in southern Norway. After deglaciation the early Holocene vegetation developed from an open pioneer herb-dominated vegetation into dwarf-shrub heath with shrubs, which was soon colonised by Betula and later also by Pinus sylvestris at the two lower sites. Maximum tree-line altitudes occurred in the early-to mid-Holocene. P. sylvestris reached 100–150 m higher than at present in continental areas, and 35–100 m higher on the west coast during the Holocene. Betula pubescens grew at altitudes that today reach 1300 m a.s.l. in Jotunheimen and 800 m a.s.l. in western Norway. The Pinus forest was at the two southwestern sites mixed with Betula and Alnus was closer to the sites between 8500 and 7500 cal years BP. A shift from mixed pine-birch woodland to birch woodland is seen from ca. 4300 cal years BP with the development of a sub-alpine birch belt followed by further recession of the birch forest. On the west coast, birch dominated only during the last 500–1000 years. Further decrease of woodland and opening of the landscape in the last 2000 years occurred due to climatic change and human impact such as sheep and cattle grazing.     

Nitrogen uptake by crops,soil distribution and recovery of urea-N in a sorghum—wheat rotation in different soils under Mediterranean conditions

The N uptake by crops, soil distribution and recovery of 15N labelled urea-N (100 kg N ha-1) were investigated in a sorghum-wheat rotation in two silty clay soils (Foggia and Rieti Casabianca) and one silt loam soil (Rieti Piedifiume) under different mediterranean conditions. Non-exchangeable labelled NH4-N represented an important pool at both Rieti sites with higher values (p<0.05) under sorghum (14.0 and 24.6% of the urea N in the 0-20 cm layer at the end of the cropping season) than wheat whereas it was much less important in the Foggia soil (10.0% in the surface soil under sorghum). This is probably related to the clay minerals composition of the three soils; because vermiculite was present in both Rieti sites but not in the Foggia soil. At harvest from 4.4 to 5.3% of the urea N initially applied was present as microbial biomass N in the surface soil layer with no generally significant differences due to location and type of crops. Both sorghum and wheat N yields were higher in the driest site (Foggia) probably due to better light conditions, higher temperatures and irrigation during summer of the sorghum cropping period. The recovery of plant fertilizer N (about 21% for sorghum and 27% for wheat) and the percentage of N in the plant derived from the fertilizer (NDFF) were the lowest at Rieti-Casabianca probably as the result of the protection of immobilized fertilizer N against microbial mineralization by the swelling clays. The fertilizer N unaccounted for was nil or very low (10.8% at Rieti-Casabianca under wheat and 11.8 and 4.9% at Rieti-Piedifiume under sorghum and wheat, respectively). Urea-N losses occurred when Rieti Piedifiume and Rieti Casabianca soils were kept bare. In this case the urea N unaccounted for ranged from 12 to 56% of the urea N with higher losses in Rieti-Piedifiume than in Rieti-Casabianca. The higher recoveries in the latter soil were probably confirmed by the stabilizing effect of clays on the immobilized urea N. This revised version was published online in July 2006 with corrections to the Cover Date.     

Crises and Resilience at the Frontline—Public Health Facility Managers under Devolution in a Sub-County on the Kenyan Coast

Background

Public primary health care (PHC) facilities are for many individuals the first point of contact with the formal health care system. These facilities are managed by professional nurses or clinical officers who are recognised to play a key role in implementing health sector reforms and facilitating initiatives aimed at strengthening community involvement. Little in-depth research exists about the dimensions and challenges of these managers’ jobs, or on the impact of decentralisation on their roles and responsibilities. In this paper, we describe the roles and responsibilities of PHC managers–or ‘in-charges’ in Kenya, and their challenges and coping strategies, under accelerated devolution.

Methods

The data presented in this paper is part of a wider set of activities aimed at understanding governance changes under devolution in Kenya, under the umbrella of a ‘learning site’. A learning site is a long term process of collaboration between health managers and researchers deciding together on key health system questions and interventions. Data were collected through seven formal in depth interviews and observations at four PHC facilities as well as eight in depth interviews and informal interactions with sub-county managers from June 2013 to July 2014. Drawing on the Aragon framework of organisation capacity we discuss the multiple accountabilities, daily routines, challenges and coping strategies among PHC facility managers.

Results

PHC in-charges perform complex and diverse roles in a difficult environment with relatively little formal preparation. Their key concerns are lack of job clarity and preparedness, the difficulty of balancing multidirectional accountability responsibilities amidst significant resource shortages, and remuneration anxieties. We show that day-to-day management in an environment of resource constraints and uncertainty requires PHC in-charges who are resilient, reflective, and continuously able to learn and adapt. We highlight the importance of leadership development including the building of critical soft skills such as relationship building.