How is the equilibrium of continuous strategy game different from that of discrete strategy game?

Cooperation in the prisoner's dilemma (PD) played on various networks has been explained by so-called network reciprocity. Most of the previous studies presumed that players can offer either cooperation (C) or defection (D). This discrete strategy seems unrealistic in the real world, since actual provisions might not be discrete, but rather continuous. This paper studies the differences between continuous and discrete strategies in two aspects under the condition that the payoff function of the former is a linear interpolation of the payoff matrix of the latter. The first part of this paper proves theoretically that for two-player games, continuous and discrete strategies have different equilibria and game dynamics in a well-mixed but finite population. The second part, conducting a series of numerical experiments, reveals that such differences become considerably large in the case of PD games on networks. Furthermore, it shows, using the Wilcoxon sign-rank test, that continuous and discrete strategy games are statistically significantly different in terms of equilibria. Intensive discussion by comparing these two kinds of games elucidates that describing a strategy as a real number blunts D strategy invasion to C clusters on a network in the early stage of evolution. Thus, network reciprocity is enhanced by the continuous strategy.     

The manipulation mechanism of “push–pull” habitat management strategy and advances in its application

The “push–pull” habitat management strategy, as a new powerful and effective tool in integrated pest management (IPM), uses a combination of behavior-modifying stimuli to manipulate the distribution and abundance of pests and/or their natural enemies for pest control. In the “push–pull” strategy, pests are repelled or deterred away from the protected resource (push) by stimuli that disturb the host location and modulate the host become unattractive or unsuitable for the feeding and oviposition of pests. By using highly attractive stimuli, the target pests are simultaneously attracted (pull) to the specific source in which they are subsequently concentrated, facilitating their elimination and leaving the protected resource. Since stimuli usually are nontoxic, either “push” or “pull” components, the strategy is usually companied by population-reduced methods, such as using insecticides, exploiting nature enemies, and placing traps. Among them, methods of biological control are the most preferred. The “push–pull” strategies maximize efficacy of behavior-modifying stimuli through the additive and synergistic effects of integrating the use of methods for population reduction. In this review, the principles of the “push–pull” strategy were firstly described, then the potential behavior-modifying stimuli for “push” and “pull” components were introduced. The stimuli for use in “push–pull” strategies primarily include visual cues and chemical cues (synthetic or plant- or insect-derived semiochemicals). Visual stimuli, repellent and trap plants, host and non-host volatiles, insect pheromones, and antifeedants and oviposition deterrents are usually applied as the potential stimuli in the “push–pull” strategy for pest control. The stimuli are grouped as long-range stimuli and short-range stimuli. In addition, we also summarize models of “push–pull” habitat management strategy, such as agriculture, horticulture and forestry, of pest control and some successful case studies in applying of “push–pull” strategy and its potential ecological benefits. The “push–pull” technology (PPT), so far the most effective “push–pull” strategy in practice by farmers, developed for management of both stemborers and Striga hermonthica in maize-based farming system in eastern Africa were reviewed. The PPT uses an intercrop of repellent plants and border crops of attractive trap plants. Stemborer moths are effectively repelled away from the maize crop (push) by Desmodium and molasses grass, and are subsequently attracted (or trapped) to (pull) by the Napier grass and Sudan grass which emit the green leaf volatiles (GLVs) showing attractant properties. Finally, the problems in current research and future perspectives of the “push–pull” habitat management strategy are discussed in the present paper.     

The developmental strategy of an idiobiont ectoparasitoid, Dendrocerus carpenteri : influence of variations in host quality on offspring growth and fitness

Dendrocerus carpenteri (Curtis) (Hymenoptera: Megaspilidae) is a solitary hyperparasitoid, which attacks prepupal and pupal stages of hymenopteran parasitoids inside mummified aphids. The larva feeds externally on the host, which is envenomed by the female at oviposition. To evaluate the influence of variations in host quality on the growth, development and fitness of D. carpenteri, we varied the size and developmental stage of the primary parasitoid host (Aphidius ervi Haliday), which was reared on different instars of pea aphid [Acyrthosiphon pisum (Harris)] and English grain aphid [Sitobion avenae (F.)]. Within each kind of host, females eclosed from the relatively larger mummies, while males eclosed from the smaller mummies. Host size and hyperparasitoid size were correlated, and females were larger than males. In hyperparasitoids developing on prepupal and pupal hosts, development time from oviposition to adult eclosion was proportional to size; females required more time for development than males. The mean relative growth rate was the same in males and females and increased with host quality, as predicted by the growth model of Mackauer and Sequeira (1993) for idiobiont parasitoids. Larvae developing on late-pupal stages and pharate adults of A. ervi were unable to consume sclerotized host tissues; they were smaller and needed more time for development. The average number of mature eggs at eclosion was six, except in females developing on suboptimal hosts, which contained only one egg or none. Egg volume was correlated with female size, possibly reflecting differences in larval ontogeny. We provide equations describing the relationship between host quality as indexed by hind-tibia length of the mummified aphid and adult body size in terms of dry mass, development time and mean relative growth rate of D. carpenteri. We discuss the usefulness of host size as a proxy of host quality for idiobiont parasitoids, and provide examples of exceptions. Received: 14 December 1997 / Accepted: 23 July 1998     

The reproductive strategy of Leporinus friderici (Characiformes, Anostomidae) in the Paraná River basin: the effect of reservoirs

The reproductive strategy of a species depends upon the interaction between intrinsic and extrinsic factors. Examining the population of Leporinus friderici in two reservoirs of the Upper Paraná River basin in reference to first gonadal maturation and breeding season and sites, the present investigation tested whether the environment formed by damming promoted spatial and temporal changes in the reproductive strategy of this species. Analyses of sex ratios showed that females significantly predominated in Itaipu, while in Corumbá the sexes were about equal with a slight predominance of males. Size-associated sexual dimorphism was observed, that is females dominated the longer length categories, and males the shorter. The minimum size at which L. friderici initiated reproduction varied from year to year, and was larger in the periods soon after formation of both reservoirs. In Itaipu, stabilization between the maximum and minimum lengths at first maturation was also noted after year 6 following closure and continuing until year 15. In general, the breeding season lasted from October through April, although cyclic changes in the duration and intensity of this season were evident. Young individuals predominated during the entire study period in Corumbá. The formation of Itaipu Reservoir had a greater effect on the reproduction of L. friderici, where a gradual adaptation of the reproductive strategy of this species may possibly have been occurring. It is also possible that some of the characteristics of the Itaipu population will in the future be shown by the Corumbá population. It was concluded that reproductive strategies constitute ecological adaptations that are temporally and spatially altered and are fitted to resource availability and environmental pressure.     

Optimal radio-tracking strategy — The best results with the least effort?

We tested the need to radio-track nocturnal mammals, such as raccoon dogsNyctereutes procyonoides (Gray, 1834) and badgersMeles meles (Linnaeus, 1758), throughout the night for reliable estimates of home range size and habitat selection. We also tested the possibility to reduce the tracking effort by decreasing the number of tracking-nights. The results indicated that the locations collected before midnight gave good estimates of home range sizes but those collected after midnight or by reducing the number of tracking-nights resulted in smaller home ranges than those estimated using the total data. Thus, if one aims to estimate only the home range size, locations before midnight would be adequate. Locations of raccoon dogs taken only before or after midnight did not reveal all habitats, which were favoured on the basis of the total data. Although locations of badgers before midnight seemed to give correct results of habitat selection, we recommend radio-tracking also badgers at least few times through the night, because their core areas shifted during the night. In the case of badgers, but not of raccoon dogs, we obtained correct results of habitat selection by reducing the tracking effort by decreasing the number of tracking-nights.     

The Badge of Jiuzhai

1. The background is a maple leaf, whose vein is the transformation of the first letter of "Jiu", that is J. In the front, there is a waterfall, which is the transformati on of Z, the first letter of Zhai. This makes "Jiuzhai" obvious. The first letter of China, "C", is transformed into a globe, symbol-     

The influence of environmental instability on the reproductive strategy of the critically endangered Acıgöl killifish (Aphanius transgrediens)

To investigate the variability in the reproductive tactics of Acıgöl killifish (Aphanius transgrediens), one of the most seriously threatened freshwater teleost species, this study compared its reproductive ecology in two contrasting habitats that differ substantially in terms of stability of environmental parameters, particularly salinity regime (stable vs. unstable). Fish were sampled monthly from October 2013 to September 2014 with the aim of testing whether the reproductive life-history response of fish to stable and unstable conditions differed. The reproductive effort (gonad weight) of both sexes did not differ significantly between the two habitats, but females in the unstable habitat had significantly lower fecundity and larger eggs. The relationship between fecundity and fish size was stronger in the stable habitat, whereas the relationship was quite variable and uncertain in the unstable habitat. Fish born in the unstable habitat reached their first maturity at a smaller size than those in the stable habitat. The gonado-somatic index and the duration of hydrated eggs showed that reproduction continued from February to May in both habitats; nonetheless, a second spawning event occurred during July and August in the unstable habitat, which included the reproductive contributions of YOY individuals and older generations. This study’s results suggest that A. transgrediens employs varying reproductive strategies against environmental instability in its restricted unique range. This may have further implications for the ways in which habitat-specific conservation methods are used.     

The Nature of Materials

This first essay is about a pending marriage between biology and some of the technologies of engineering. It is a story of a long-standing flirtation that has been consummated a number of times, but never properly solemnised, despite repeated attempts, and no one is quite sure how many of the offspring, if any, have been viable. Whether the union will be blessed in the near future is anyone‘ s guess. In the hope of helping the marriage on its way, I start with four lucky things the bride has to wear at the wedding for the marriage to succeed, at least in one of the more recent Western traditions.     

The role of echolocation in the hunting of terrestrial prey – new evidence for an underestimated strategy in the gleaning bat, Megaderma lyra

The observation that gleaning bats detect prey by its noises, together with difficulties in recording their faint sonar calls, have led some authors to conclude that gleaning bats may not use echolocation in certain hunting situations. In particular, it is conjectured that echolocation plays no role in the classification and tracking of prey. In the present study, we show that the gleaning bat, Megaderma lyra, is able to find silent and motionless prey on the ground. The significance of sonar for catching a variety of terrestrial prey is established in a standardized situation. Sonar calls were found to be emitted during all stages, i.e. approach, hovering above the prey, and return to the roost, of every hunting flight. The harmonic pattern of the calls differed significantly between these stages, calls with three or more prominent components prevailing during hovering. Bats identified prey and rejected dummies while hovering above them. During this stage, increased call rates and reduced call durations were found. Echolocation activity during, and the duration of, the hovering phase depended on prey type, in particular on prey movement. The prey-dependent shifts in sonar activity, the broadband call structure with an emphasis on higher harmonics, and a systematic shift of the calls' peak frequencies during hovering, are discussed as adaptations to identifying prey by sonar.     

Partial maturation: an immune-evasion strategy of dengue virus?

Cleavage of the precursor membrane (prM) protein is required for the activation of flavivirus infectivity. However, many studies have shown that, for dengue virus in particular, prM cleavage and maturation is inefficient. Heterogeneity of wild-type dengue virus preparations with regard to the presence of uncleaved prM in the virion is mirrored in the substantial levels of prM-specific antibodies that are produced following dengue infection. What might be the evolutionary advantage for the virus to produce so many prM-containing particles? In this review we summarize the latest achievements of dengue research that contribute to a better understanding of the role of prM-containing virions in the pathogenesis of dengue.     

The strategy concept and John Maynard Smith’s influence on theoretical biology

Here we argue that the concept of strategies, as it was introduced into biology by John Maynard Smith, is a prime illustration of the four dimensions of theoretical biology in the post-genomic era. These four dimensions are: data analysis and management, mathematical and computational model building and simulation, concept formation and analysis, and theory integration. We argue that all four dimensions of theoretical biology are crucial to future interactions between theoretical and empirical biologists as well as with philosophers of biology.     

The animal origin of SARS-CoV

The first case of severe acute respiratory syndrome(SARS)in Guangdong province was reported on2Jan2003,whileretrospective survey has datedthe first index case on16Nov2002.In months that followed,pandemic of SARS widelyspread over the world until July2003,infecting8454people and claiming908deathsin39countries andregions global-ly.On16Dec2003,a32years old photographerlivinginsuburban Guangzhou presented withsymptoms of SARSinfec-tion.There were3other ensuing cases betweenthe end of2003and…     

The first humans travelling on ice: an energy‐saving strategy?

Economy of locomotion is a constant challenge for animals, particularly when related to migrations and travelling. The present study focuses on human locomotion and particularly on the development of ice skating. The aim of our research was to understand whether an environmental feature such as a strong presence of lakes (frozen in winter) could force humans to develop ice skates in order to limit the energy cost of travelling. We hypothesized that the energy-saving principle was a determinant factor in the development of human locomotion on ice. Five healthy adult participants took part in the experiments, during which we recorded the speed (1.2 ± 0.3 m s⁻¹) and metabolic energy cost (4.6 ± 0.9 J kg⁻¹ m⁻¹) associated with travelling on bone skates. Simulations were also performed to demonstrate whether the benefit given by the use of skates was different in the areas where ice skating appears to have evolved originally. The gain reachable by using bone skates could lead to an extremely high energy saving (equal to 10% of the energy needed to survive during the cold season) and differs significantly between the regions considered in the present study. An analysis of the geometrical shape of lakes associated with fractal analysis of their distribution suggests that, in order to better adapt to the severe conditions imposed by the long lasting winters, Finnish populations could benefit more than others from developing this ingenious locomotion tool. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 1–7.     

The Ascent of Man?

Anyone who cares about the moral and social implications of genomics, genetic engineering and biotechnology should read Michael J. Sandel's article, 'The Case Against Perfection', in the April 2004 issue of The Atlantic Monthly.     

The stereospecificity of α-chymotrypsin

1. The rates of deacylation of acyl-alpha-chymotrypsins in which the hydrogen-bonding capacity of the acylamino group of the substrate has been systematically removed were measured. 2. The ratio of deacylation rates of l- and d-acyl-enzymes is found to depend largely on the existence in the substrate of an amido -NH- group. 3. The data presented agree with the postulate that the stereospecificity of alpha-chymotrypsin is exercised in catalytic rather than binding steps, and that the active site of the enzyme presents three loci to the substrate: the site containing the catalytic functionalities (including serine-195), the hydrophobic area for amino acid side-chain binding, and a hydrogen-bond acceptor site for acylamino group binding. 4. It is noted that, though the hydrogen-bonding site is crucial for the stereospecificity, the free energy of binding of substrates and inhibitors is dominated by the hydrophobic interaction. 5. It is tentatively proposed that alpha-chymotrypsin selects a high-energy conformation of the substrate when the latter binds at the enzyme's active site.