The role of health care workers and antiviral drugs in the control of pandemic influenza

Until a vaccine against the new strain becomes available, the response to newly emerged pandemic influenza will consist of the use of antiviral drugs and measures that limit exposure to infectious individuals. These first-line defence measures include isolating cases upon diagnosis, reducing close contacts, the use of personal protective equipment and hygiene, and using antiviral drugs for treatment and prophylaxis. There are significant 'costs' associated with control measures, so to justify such interventions it is important to assess their potential to reduce transmission. In this paper, we determine the effect that a number of different antiviral interventions have on the reproduction number of infectives and the probability that an imported infection fades out, and determine parameter scenarios for which these interventions are able to eliminate an emerging pandemic of influenza. We also assess the role that health care workers play in transmission and the extent to which providing them with antiviral prophylaxis and personal protective equipment modifies this role. Our results indicate that this class requires protection to avoid a greatly disproportionate contribution to early infective numbers, and for the maintenance of a stable health care system. Further, we show that the role children play in increasing transmission is moderate, in spite of closer mixing with other children.     

Evolutionary ecology of resistance to herbivory: an investigation of potential genetic constraints in the multiple-herbivore community of Solanum carolinense

As part of a study of the ecological and evolutionary dynamics of herbivore resistance in Solanum carolinense (horsenettle), potential genetic constraints to the evolution of resistance to 11 of its most common herbivores were investigated. Leaf, flower, fruit, and stem herbivory were measured in a field experiment involving 24 ramets of each of 40 horsenettle genets. The experimental plant population contained significant genetic variation for resistance to all 11 species of herbivore. For only one species was there an indication of a genotype-by-environment interaction in the expression of resistance that might constrain its evolution. Genetic correlations in resistance to different species were common but not universal, with seven negative and 12 positive correlations out of the 55 pairwise species comparisons. Correlations were independent of plant part fed upon. The evolution of the resistance of horsenettle to most of its diverse community of herbivores does not appear to be prevented by a lack of genetic variation or by genotype-by-environment interactions in resistance. Negative genetic correlations in resistance to different herbivores may play a small role in slowing the evolution of resistance, but positive correlations may play at least as large a role in facilitating its evolution.     

Butterfly seed predation: effects of landscape characteristics,plant ploidy level and population structure

Polyploidization has been suggested as one of the most common mechanisms for plant diversification. It is often associated with changes in several morphological, phenological and ecological plant traits, and therefore has the potential to alter insect–plant interactions. Nevertheless, studies evaluating the effect of plant polyploidy on interspecific interactions are still few. We investigated pre-dispersal seed predation by the butterfly Anthocharis cardamines in 195 populations of two ploidy levels of the herb Cardamine pratensis (tetraploid ssp. pratensis, 2n = 30 vs. octoploid ssp. paludosa, 2n = 56–64). We asked if differences in incidence and intensity of predation among populations were related to landscape characteristics, plant ploidy level and population structure. The incidence of the seed predator increased with increasing plant population size and decreasing distance to nearest population occupied by A. cardamines. The intensity of predation decreased with increasing plant population size and was not affected by isolation. Probability of attack decreased with increasing shading, and intensity of predation was higher in grazed than in non-grazed habitats. The attack intensity increased with increasing mean flower number of plant population, but was not affected by flowering phenology. Individuals in tetraploid populations suffered on average from higher levels of seed predation, had higher mean flower number, were less shaded and occurred more often in grazed habitats than octoploid populations. When accounting for differences in habitat preferences between ploidy levels there was no longer a difference in intensity of predation, suggesting that the observed differences in attack rates among populations of the two ploidy levels are mediated by the habitat. Overall, our results suggest that polyploidization is associated with differentiation in habitat preferences and phenotypic traits leading to differences in interspecific interaction among plant populations. This, in turn, may facilitate further divergence of ploidy levels.     

Intraspecific variation in group size in the blackbuck antelope: the roles of habitat structure and forage at different spatial scales

The main ecological factors that are hypothesized to explain the striking variation in the size of social groups among large herbivores are habitat structure, predation, and forage abundance and distribution; however, their relative roles in wild populations are not well understood. I combined analyses of ecological correlates of spatial variation in group size with analyses of individual behaviour in groups of different sizes to investigate factors maintaining variation in group size in an Indian antelope, the blackbuck Antilope cervicapra. I measured group size, habitat structure, forage, and the occurrence of predators in ten blackbuck populations, and, at a smaller spatial scale, within an intensively studied population. To examine the processes by which these ecological factors influence group size, I used behavioural observations and an experiment to estimate the shape of the relationship between group size and potential costs and benefits to individuals. Group size varied extensively both among and within populations. Analyses of spatial variation in group size suggested that both forage and habitat structure influence group size: large-scale, among-population variation in group size was primarily related to habitat structure, while small-scale, within-population variation was most closely related to forage abundance. Analyses of individual behaviour suggested that larger groups incur greater travel costs while foraging. However, individuals in larger groups appeared to experience greater benefits, namely the earlier detection of a “predator”, a reduction in vigilance, and an increase in the time spent feeding. Overall, these findings suggest that individuals in groups experience a trade-off between predation-related benefits and costs arising from feeding competition. Habitat structure and forage likely influence the nature of this trade-off; thus, variation in these ecological factors may maintain variation in group size. The role of predation pressure and other factors in explaining the remaining variation needs further exploration. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of resource level and habitat type on behavioral and morphological plasticity in Eurasian perch

Spatial and temporal heterogeneity in the environment is a common feature affecting many natural populations. For example, both the resource levels and optimal habitat choices of individuals likely change over time. One way for organisms to cope with environmental variation is to display adaptive plasticity in traits such as behavior and morphology. Since trait plasticity is hypothesized to be a prerequisite for character divergence, studies of mechanisms behind such plasticity are warranted. In this study, we looked at the interaction of two potentially important environmental variables on behavioral and morphological plasticity in Eurasian perch (Perca fluviatilis L.). More specifically, the plastic responses in activity and morphology of perch exposed to different resource levels and simulated habitat types were studied in an aquarium experiment. The resource level experienced had a large influence on plasticity in both activity and morphology. Behavioral adaptations have been thought to mediate morphological transitions, and we suggest that the morphological response to the resource level was mediated by differences in activity and growth rates. The habitat type also affected morphological plasticity but to a lesser extent, and there was no effect on activity from habitat type. Based on these results, we suggest that it is essential to include several environmental factors acting in concert when studying mechanisms behind trait plasticity. We also propose that variation in resource levels might play a key role in fostering trait plasticity in at least fish populations, while other environmental variables such as divergent habitat complexities and prey types might be less influential. Dynamics in resource levels and optimal habitat choices might thus be important factors influencing character divergence in natural populations.     

On the Nature and Significance of Variability in Lions (Panthera leo)

Although the lion is one of nature’s best-known species, much remains to be learned about its variability. Recently documented variation in genetics, morphology, ecology and behavior help to explain its adaptability and illustrate the inter-dependencies of biological responses at different organizational scales.     

An SEIS epidemic model with transport-related infection

In this paper, an SEIS epidemic model is proposed to study the effect of transport-related infection on the spread and control of infectious disease. New result implies that traveling of the exposed (means exposed but not yet infectious) individuals can bring disease from one region to other regions even if the infectious individuals are inhibited from traveling among regions. It is shown that transportation among regions will change the disease dynamics and break infection out even if infectious diseases will go to extinction in each isolated region without transport-related infection. In addition, our analysis shows that transport-related infection intensifies the disease spread if infectious diseases break out to cause an endemic situation in each region, in the sense of that both the absolute and relative size of patients increase. This suggests that it is very essential to strengthen restrictions of passengers once we know infectious diseases appeared.     

Orientational control is an efficient control mechanism for phase switching in the E. coli fim system

The fim system in E. coli controls the expression of type-1 fimbriae. These are hair-like structures that can be used to attach to host cells. Fimbriation is controlled by a mechanism called "orientational control." We present two families of models for orientational control to understand the details of how it works. We find that the main benefits of orientational control are that (i) it allows rapid adjustment of fimbriation levels in response to a change of environmental conditions while (ii) keeping the overall frequencies with which a cell switches between the fimbriate state and the afimbriate state low. The main reason for the efficiency of orientational control in regulation of fimbriation levels is that it keeps the system far from its steady state.     

Individual relationship between aneuploidy of gill cells and growth rate in the cupped oysters Crassostrea angulata, C. gigas and their reciprocal hybrids

The Portuguese oyster, Crassostrea angulata, is taxonomically close to the Pacific oyster, C. gigas, but there are clear genetic and phenotypic differences between these taxa. Among those differences, the faster growth of C. gigas compared with C. angulata has often been observed in the field. Crosses between C. angulata and C. gigas were performed to investigate the relationship between growth variation and somatic aneuploidy at the individual level in the two taxa and their reciprocal hybrids. The different progenies were reared in Ria Formosa (Portugal) under standard farming conditions. Growth rate and survival were significantly higher in C. gigas than in C. angulata, and the hybrids showed intermediate performances. Significant differences were also observed in the proportion of aneuploid cells (PAC) and of missing chromosomes (PMC) between the two taxa, C. angulata showing the highest values. Intermediate values of PAC and PMC were observed in the hybrids, supporting additive genetic bases of these parameters. Our results also confirm the negative correlation between somatic aneuploidy and growth rate at the individual level, as previously reported in C. gigas.     

弄岗黑叶猴的日活动类型和活动时间分配

2005年10月-2006年9月,用瞬时扫描法对广西弄岗自然保护区内的一群黑叶猴(Trachypithecusfran oisi)的日活动节律和活动时间分配进行研究。结果表明:黑叶猴日活动中出现2个觅食高峰和1个休息高峰。觅食高峰分别出现在7:00-9:00和16:00-18:00;休息高峰出现在10:00-14:00。黑叶猴日活动节律表现出明显的季节性变化,表现为旱季上午的觅食高峰被推迟了1h,且觅食时间长于雨季;旱季下午的觅食活动提前1h结束。猴群在雨季较早进入休息高峰,而且中午休息时很少有移动或零星觅食。研究期间,猴群用于休息的时间平均占日活动时间分配的51.99%,移动占20.25%,觅食占18.61%,理毛占7.61%,玩耍占1.20%,其它行为(包括打斗、交配等)仅占0.14%。活动时间分配有明显的季节性差异,主要表现为:与雨季相比,黑叶猴在旱季花费更多的时间用于觅食和移动,而相应地减少用于休息的时间。活动时间分配在不同年龄和性别的个体之间也存在显著差异,表现为成年个体花费更多的时间用于休息和觅食,未成年个体则花费更多的时间用于移动和玩耍;雌性个体比雄性个体花费更多的时间用于理毛。