In this paper, we present a three-step methodological framework, including location identification, bias modification, and out-of-sample validation, so as to promote human mobility analysis with social media data. More specifically, we propose ways of identifying personal activity-specific places and commuting patterns in Beijing, China, based on Weibo (China’s Twitter) check-in records, as well as modifying sample bias of check-in data with population synthesis technique. An independent citywide travel logistic survey is used as the benchmark for validating the results. Obvious differences are discerned from Weibo users’ and survey respondents’ activity-mobility patterns, while there is a large variation of population representativeness between data from the two sources. After bias modification, the similarity coefficient between commuting distance distributions of Weibo data and survey observations increases substantially from 23% to 63%. Synthetic data proves to be a satisfactory cost-effective alternative source of mobility information. The proposed framework can inform many applications related to human mobility, ranging from transportation, through urban planning to transport emission modeling.
We analyze the exploitation of an antibiotic in a market subject to open access on the part of antibiotic producers to the common pool of antibiotic efficacy. While the market equilibrium depends only on current levels of antibiotic efficacy and infection of the epidemiological system, the social optimum accounts for the dynamic externalities which relate those levels to the intertemporal use being made of the antibiotic. We show that depending on the parameters of the model, in particular the cost of production and the improvement in the recovery rate that results from antibiotic treatment, the positive steady-state level of antibiotic efficacy to which the system tends under open access can be lower or higher than the level which should prevail in the socially optimal steady state. In fact there are parameter configurations for which the steady states can be exactly the same. However, the paths leading to the steady state always differ. 相似文献
Communication signals used in animal social interactions are frequently performed repetitively, but the function of this repetition
is often not well understood. We examined the effects of signal repetition by investigating the behavior of worker honey bees
that received differing numbers of vibration signals in established and newly founded colonies, which could use signal repetition
differently to help adjust task allocations to the labor demands associated with the different stages of colony development.
In both colony types, more than half of all monitored workers received more than one vibration signal, and approximately 12%
received ≥5 signals during a given 20-min observation period. Vibrated recipients exhibited greater activity and task performance
than same-age non-vibrated controls at all levels of signal activity. However, vibrated workers showed similar levels of task
performance, movement rates, cell inspection rates, and trophallactic exchanges regardless of the number of signals received.
Thus, the repeated performance of vibration signals on individual bees did not cause cumulative increases in the activity
of certain workers, but rather may have functioned to maintain relatively constant levels of activity and task performance
among groups of recipients. The established and newly founded colonies did not differ in the extent to which individual workers
received the different numbers of vibration signals or in the levels of activity stimulated by repeated signals. Previous
work has suggested that compared to established colonies, newly founded colonies have a greater number of vibrators that perform
signals on a greater proportion of the workers they contact. Taken in concert, these results suggest that vibration signal
repetition may help to adjust task allocations to the different stages of colony development by helping to maintain similar
levels of activity among a greater total number of recipients, rather than by eliciting cumulative effects that cause certain
recipients to work harder than others. 相似文献
Social interactions are critical to the organization of worker activities in insect colonies and their consequent ecological
success. The structure of this interaction network is therefore crucial to our understanding of colony organization and functioning.
In this paper, I study the properties of the interaction network in the colonies of the social wasp Ropalidia marginata. I find that the network is characterized by a uniform connectivity among individuals with increasing heterogeneity as colonies
become larger. Important network parameters are found to be correlated with colony size and I investigate how this is reflected
in the organization of work in colonies of different sizes. Finally, I test the resilience of these interaction networks by
experimental removal of individuals from the colony and discuss the structural properties of the network that are related
to resilience in a social network.
This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau,
and R. James). 相似文献
Several environmental factors have been shown to shape the pattern of investment of carotenoids into the expression of sexual
signals. Surprisingly, the impact of the social environment has been neglected. If a carotenoid-based sexual trait is used
by females to choose a mate or by males to assess the quality of potential competitors for mates, males, in the presence of
females, should upregulate expression of the trait. We tested this hypothesis in male zebra finches that were housed either
with females or in a male-only social environment. Additionally, to investigate whether the social modulation of the expression
of a sexual trait depends on the physiological need of carotenoids, we challenged half of the males with Escherichia coli lipopolysaccharide (LPS). We found that the social environment modulated the expression of bill color, with males kept in
the presence of females harboring a redder bill at the end of the 3 weeks that the experiment lasted. Males injected with
LPS showed duller bill color regardless of the presence of females, and social interactions with females result in upregulated
bill color similarly for phosphate-buffered saline (PBS) and LPS males. Thus, social environment and immune activation had
an additive effect on the expression of bill color. The effect of social environment on plasma carotenoids was less clear.
Indeed, a first replicate of the entire experiment showed that both immune challenge and social context affected bill color,
with a negative effect of immune challenge and a positive effect of the presence of females on circulating carotenoids. However,
a second replicate of the experiment showed only a negative effect of the immune challenge. These results, therefore, suggest
that the social environment can affect the expression of carotenoid-based sexual traits under both benign and carotenoid-demanding
conditions. Whatever the signaling function of bill color (female mate choice or male–male competition for mates), the observed
flexibility may be adaptive because the expression of the signal can be modulated depending on the expected rewards or costs
associated with the presence or absence of females. Nevertheless, the mechanisms underlying such an effect are still unknown. 相似文献
In animal species, prey processing and the provisioning of nutrients are subject to several constraints related with finding,
ingesting and processing food. In most bird species, these constraints are obvious as a consequence of food morphology. In
the case of the bearded vulture (Gypaetus barbatus), in comparison with other species, its behavioural and physiological adaptations apparently allow this vulture to ingest
bone remains irrespective of their morphology. Here, by comparing bones delivered to the nest to be consumed (selected) and
remains found at an experimental feeding station and at bone-breaking sites or ossuaries (rejected), I tested whether bearded
vultures are capable of choosing from among the various anatomical parts of an animal carcass in relation to their fatty acid
content (nutrient concentration hypothesis), their size (width-reduction hypothesis) or both. The results suggest that bearded
vultures prefer the fatty anatomical parts (with a high percentage of oleic acid) of an animal carcass regardless of bone
length, although bone morphology as a consequence of handling efficiency or the ingestion process may also play a secondary
role in food selection. The close association between the bones selected and their high fat value implies an optimisation
of foraging time and of the increased energy gained from the food. This is in line with selective foraging to redress specific
nutritional imbalances (nutrient concentration hypothesis) and, secondarily, the width-reduction hypothesis. 相似文献
The number of nests containing egg masses a female makes over her lifetime and the pattern of scattering nests vary among
species in a genus of nest-weaving spider mites (Stigmaeopsis). We hypothesized that the scattered nests of small nest builders have a previously overlooked indirect effect in that the
void nests created after predation take on a new role as hindering devices that effectively decrease predator searching efficiency.
First, we demonstrated that the experimental design used in this study is a good reflection of the nest distribution pattern
of Stigmaeopsis takahashii (an intermediate-sized nest builder) in the field. Using this species as a model, we tested how different nest-scattering
patterns affect the predator to examine how scattering may indirectly provide an anti-predation strategy by increasing a predators
searching time. Next, we observed how artificially arranged void nests disturb predatory behavior in both starved and fully
fed predator females and showed that void nests have a strong hindering effect on predators. Thus, we concluded that the nesting
behavior of this mite species not only has anti-predator effects but must also have a stabilizing effect on predator–prey
interaction systems at the population level. 相似文献
Ecological factors differently affect male and female animals and thereby importantly influence their life history and reproductive
strategies. Caviomorph rodents are found in a wide range of habitats in South America and different social and mating systems
have evolved in closely related species. This permits to study the impact of ecological factors on social evolution. In this
study, we investigated the social organization and the mating system of the wild cavy (Cavia aperea), the ancestor of the domestic guinea pig, in its natural habitat in Uruguay. Based on our laboratory investigations, we
expected a polygynous system with large males controlling access to females. Results from radiotelemetry and direct observations
showed that females occupied small stable home ranges which were largely overlapped by that of one large male, resulting in
a social organization of small harems. In some cases, small satellite males were associated with harems and intermediate-sized
roaming males were occasionally observed on the study site. However, microsatellite analyses revealed that offspring were
exclusively sired by large males of the same or neighboring harems, with a moderate degree of multiple paternity (13–27%).
Thus, the mating system of C. aperea can be described as polygynous and contrasts with the promiscuous organization described for other species of cavies (Cavia magna, Galea musteloides and Microcavia australis) living under different ecological conditions. Our findings stress the strong impact of environmental factors on social evolution
in Caviomorphs as resource distribution determines female space use and, thereby, the ability of males to monopolize females.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Foraging activity in social insects should be regulated by colony nutritional status and food availability, such that both
the emission of, and response to, recruitment signals depend on current conditions. Using fully automatic radio-frequency
identification (RFID) technology to follow the foraging activity of tagged bumblebees (Bombus terrestris) during 16,000 foraging bouts, we tested whether the cue provided by stored food (the number of full honeypots) could modulate
the response of workers to the recruitment pheromone signal. Artificial foraging pheromones were applied to colonies with
varied levels of food reserves. The response to recruitment pheromones was stronger in colonies with low food, resulting in
more workers becoming active and more foraging bouts being performed. In addition to previous reports showing that in colonies
with low food successful foragers perform more excited runs during which they release recruitment pheromone and inactive workers
are more prone to leave the nest following nectar influx, our results indicate that evolution has shaped a third pathway that
modulates bumblebee foraging activity, thus preventing needless energy expenditure and exposure to risk when food stores are
already high. This new feedback loop is intriguing since it involves context-dependent response to a signal. It highlights
the integration of information from both forager-released pheromones (signal) and nutritional status (cue) that occurs within
individual workers before making the decision to start foraging. Our results support the emerging view that responses to pheromones
may be less hardwired than commonly acknowledged.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
China’s government is now promoting the Nomad Sedentarization Project (NSP) in large areas of grassland as a solution for ecological restoration and poverty alleviation. To examine the effects of this policy, we conducted in-depth interviews at two of the project’s sites and examined the social and ecological systems at village, county, and catchment scales in Jinghe County of Xinjiang. We found that (1) the NSP in one village greatly improved the household standard of living and changed their resource utilization modes; (2) the success in this village can be attributed to resources imported from the social and ecological systems at larger scales, and could not be repeated in a second nearby village with different constraints; and (3) the NSP is poorly adapted to local ecosystem characteristics, and may therefore have negative impacts at larger scales. To avoid these problems, holistic assessments are necessary to judge the NSP’s impacts on social and ecological systems at multiple scales, and the program must be implemented cautiously to account for the potential risks in ecologically vulnerable areas. 相似文献