On cognitive epidemic models: spatial segregation versus nonpharmaceutical interventions

Fick's law and the Fokker-Planck law of diffusion are applied to manifest the cognitive dispersal of individuals in two reaction-diffusion SEIR epidemic models, where the disease transmission is illustrated by nonlocal infection mechanisms in heterogeneous environments. Building upon the well-posedness of solutions, threshold dynamics are discussed in terms of the basic reproduction numbers for the two cognitive epidemic models. The numerical investigation reveals that the Fokker-Planck law can better describe the diffusion of individuals by taking different dispersal strategies of exposed individuals in our cognitive epidemic models, and provides some insights on spatial segregation and nonpharmaceutical interventions: (i) spatial segregation occurs in the random diffusion model when the nonlocal infection radius is small, while it appears in the symmetric diffusion model when the radius is large; (ii) nonpharmaceutical interventions on restricting the dispersal of exposed and infected individuals do not contribute to reducing the infection proportion, but rather eliminate the disease in a region, which expands as the nonlocal infection radius increases. We additionally find that the final infection size in the random diffusion model is significantly smaller than that in the symmetric diffusion model and decreases as the nonlocal infection radius increases.

Marked differences in foraging area use and susceptibility to predation between two closely-related tropical seabirds

Ecological theory predicts that closely-related species must occupy different niches to coexist. How marine top predators achieve this during breeding, when they often gather in large multi-species colonies and are constrained to central-place foraging, has been mostly studied in productive temperate and polar oceans with abundant resources, but less so in poorer, tropical waters. Here, we track the foraging movements of two closely-related sympatric seabirds-the white-tailed and red-tailed tropicbirds Phaethon lepturus and P. rubricauda-breeding on Aldabra Atoll, Seychelles, to investigate potential mechanisms of niche segregation and shed light on their contrasting population trends. Combining data from GPS, immersion, depth and accelerometry loggers, we show that the two species have similar behaviour at sea, but are completely segregated spatially, with red-tailed tropicbirds flying further to feed and using different feeding areas than white-tailed tropicbirds. Using nest-based camera traps, we show that low breeding success of both species-which likely drives observed population declines-is caused by high nest predation. However, the two species are targeted by different predators, with native avian predators mainly targeting red-tailed tropicbird nests, and invasive rats raiding white-tailed tropicbird nests when they leave their eggs unattended. Our findings provide new insight into the foraging ecology of tropicbirds and have important conservation implications. The extensive range and spatial segregation highlight the importance of considering large-scale protection of waters around tropical seabird colonies, while the high level of nest predation provides evidence in support of rat eradication and investigating potential nest protection from native avian predators.

Residential Age Segregation: Evidence from a Rapidly Ageing Asian City

The problem of residential age segregation has been relatively under-studied, since spatial separation of older and younger people tends to be normalized. Prior literature demonstrates that age segregated environments may be socially isolating, especially for older adults, which may have detrimental impacts on their physical and mental health. While there are some studies on residential age segregation in Western contexts, there is scarce literature on age segregation in Asian cities. This mixed methods study examines changing patterns of residential age segregation in Hong Kong, through analyzing a combination of secondary census data and qualitative, in-depth interview data. The findings reveal that the extent of age segregation has remained consistently low from 2006 to 2016, although age segregation appears to be more pronounced between young adults in their early 20s and older adults above 65. Furthermore, in-depth interviews with 26 older people reveal that older people perceive themselves as being socially separated from younger people, especially older people who remain in ageing housing estates in urban districts. The findings add to the growing international literature on generational divides in spatial inequalities, while highlighting the influence of local housing policies on age segregation. The paper concludes by considering the policy implications of the findings, and the practical interventions that might contribute to reducing social isolation experienced by older people.

First evidence for anaerobic oxidation of methane process in landfill cover soils: Activity and responsible microorganisms

Landfill cover soils (LCS) play important roles in mitigating methane emissions from landfills. Anaerobic oxidation of methane (AOM) has been demonstrated as a potential methane removal process in aquatic ecosystems. However, whether AOM could occur in LCS is largely unknown. Here, microcosm incubations with ¹³CH₄ were applied to track the potential activities of AOM and quantitative PCR was used to identify the responsible microorganisms. AOM was found to be active in the bottom and middle layers of LCS. In the bottom layer, sulfate-AOM was the most active process, mainly dominated by ANME archaea (without ANME-2d). Meanwhile, in the middle layer, nitrate and nitrite were the major electron acceptors involved in AOM with high abundances of ANME-2d archaea and NC10 bacteria. Our results implied a spatial segregation of methane oxidizing microbes in LCS and might be helpful for future control of methane emissions by the enhancement of AOM.

Determinants of habitat occupancy and spatial segregation of primates in the central Western Ghats, India

Primates are among the globally imperiled fauna requiring urgent conservation interventions to protect their habitat. Information on species distribution and factors influencing it are vital to species management and habitat protection. In this study, we assessed habitat occupancy of the lion-tailed macaque (Macaca silenus), bonnet macaque (M. radiata), and black-footed gray langur (Semnopithecus hypoleucos) that occur in the Kudremukh Wildlife Division, a large protected area network in the central Western Ghats. We examined the influence of habitat variables on the occupancy probability of these primates. We carried out four temporally replicated detection/non-detection surveys to assess detection probability and site occupancy of the primate species. We surveyed 244 sites of 5 Km², with each site surveyed for 4 days, to assess detection probability and site occupancy. Among the three species, the langur had the highest habitat occupancy estimate (0.66 ± 0.05_SE) and the lion-tailed macaque had the lowest estimate (0.28 ± 0.08_SE). The habitat occupancy estimate for the bonnet macaque was (0.56 ± 0.05_SE)_. Wet and semi-evergreen forest cover and mean elevation positively influenced the lion-tailed macaque's occurrence. Covariates influencing bonnet macaque's occurrence were plantations, semi-evergreen and moist deciduous forests, and non-forest areas. Mean elevation negatively affected its occurrence. Wet evergreen forests and plantations positively influenced the occurrence of the langur. We examined spatial segregation between the species based on their site occupancy. Pairwise comparisons revealed a significant negative association between the bonnet macaque and the other two primates. However, we found a significant positive association between the lion-tailed macaque and the langur. We discuss these results and their implications for conservation of primates in the region. Given the cost-effectiveness of carrying out surveys at large spatial scales, we recommend occupancy surveys for future surveys of forest primates.

Social inequalities in the metropolitan area of Rome. A multidisciplinary analysis of the urban segregation of the "formerly-Bastogi" compound

BACKGROUND

This study tries to evaluate, through a multidisciplinary approach, the relationship between urban structure, isolation and distribution of social determinants of health, in the so-called "formerly-Bastogi, a compound, with more than 1,500 inhabitants, located in north-western Rome, Italy.

METHODS

The architectural-urban analysis, conducted through site visits and evaluations of urban situation, showed how strongly the compound is isolated from the neighbourhoods, and structurally degraded. The socio-demographic analysis, based on the National Census data, showed significant differences in the distribution of the social determinants of health between "formerly-Bastogi" and the surrounding areas.

RESULTS

The area under study appears to be isolated from the surrounding urban space, both because of social and architectural factors. This situation could have some association with inhabitants' health.

CONCLUSIONS

If our preliminary investigation was useful for a diagnosis of the situation, a more complete - qualitative and quantitative - investigation of the context will be needed to plan appropriate multidisciplinary health-promoting interventions.

Looking for the right mate in diploid species: How does genetic dominance affect the spatial differentiation of a sexual trait?

Divergence between populations for a given trait can be driven by sexual selection, interacting with migration behaviour. Mating preference for different phenotypes may lead to specific migration behaviour, with departures from populations where the preferred trait is rare. Such preferences can then trigger the emergence and persistence of differentiated populations, even without any local adaptation. However the genetic architecture underlying the trait targeted by mating preference may have a profound impact on population divergence. In particular, dominance between alleles encoding for divergent phenotypes can interfere with the differentiation process. Using a diploid model of a trait determining both mating success and migration rate, we explored differentiation between two connected populations, assuming either co-dominance or strict dominance between alleles. The model assumes that individuals prefer mating with partners displaying the same phenotype and therefore tend to move to the other population when their own phenotype is rare. We show that the emergence of differentiated populations in this diploid moded is limited as compared to results obtained with the same model assuming haploidy. When assuming co-dominance, differentiation arises only when migration is limited compared to the strength of the preference. Such differentiation is less dependent on migration when assuming strict dominance between haplotypes. Dominant alleles frequently invade populations because their phenotype is more frequently expressed, resulting in higher local mating success and a rapid decrease in migration. However, depending on the initial distribution of alleles, this advantage associated with dominance (i.e. Haldane's sieve) may lead to fixation of the dominant allele throughout both populations. Depending on the initial distribution of heterozygotes in the two populations, persistence of polymorphisms within populations can also occur because heterozygotes displaying the predominant phenotype benefit from high mating success. Altogether, our results highlight that heterozygotes' behaviour has a strong impact on population differentiation and highlight the need for diploid models of differentiation and speciation driven by sexual selection.

Climate response of oak (Quercus spp.), an evidence of a bioclimatic boundary induced by the Carpathians

Tree-ring information and climate response data were applied to investigate the potential of the Carpathian Mountains to influence tree-growth patterns. Recent studies reveal the importance of constructing a dense spatial network of oak tree-ring chronologies in this area, which may be the key to linking the North Central European and East Mediterranean tree records. We establish sixteen oak (Quercus robur L.) and sessile oak (Quercus petraea (Matt.) Liebl.) site chronologies along a longitudinal gradient (from 22.47 to 26.58 E) in Northern Romania in an attempt to elucidate the impact of climate on oak growth. Even with differences generated by interspecific features, habitats and climatic regimes, a common macroclimatic marker for the NW and NE sites was established by comparing two groups of chronologies separated by the Carpathian chain. We found that precipitation in April (P4) and June (P6) were the primary climate factors that affected tree growth in the NW region. For the NE region, the temperature in January (T1) and March (T3) and precipitation in May (P5) were revealed to be the major limiting climatic factors. The spatial variability of the correlation coefficients indicates a decreasing trend in correlation intensity with precipitation from NW to NE, particularly during the current growing season (March-July). Oak trees from the NW and NE regions have adapted to different local climatic conditions and only respond uniformly to severe climate events (e.g., the 1904 drought). The higher occurrence of extreme years during the 20th century, particularly in the NE region, was in accordance with the rise of precipitation variability in the current growing season. The changes in the tree-growth pattern and climatic response of the chronologies of the studied sites in the NW and NE regions were linked to the local climates induced by the Carpathian Mountains.

A few long versus many short foraging trips: different foraging strategies of lesser kestrel sexes during breeding

BACKGROUND

In species with biparental care both members of the breeding pair cooperate to raise the offspring either by assisting each other in every reproductive task or by specializing in different ones. The latter case is known as reproductive role specialization. Raptors are considered one of the most role-specialized groups, but little is known about parental behavior away from the nest. Until the advent of biologgers, avian role specialization was traditionally studied with direct observations at the nest because of the difficulties of following and recording the behavior of free-ranging individuals. In this paper we analyze how the role specialization of the lesser kestrel (Falco naumanni) influences foraging movement patterns throughout the breeding season. We tracked 30 lesser kestrel breeders from two breeding colonies using high-frequency GPS-dataloggers during four consecutive breeding seasons.

RESULTS

We found no differences between sexes in lesser kestrel foraging movements early in the breeding season before the formation of the breeding pair. However, we observed sexually distinct foraging movement strategies later in the breeding season once breeding pairs were formed. Lesser kestrel males performed a large number of short foraging trips while females made a few long ones. This maximized the provisioning rate by males to feed their mates and offspring. Meanwhile, lesser kestrel females spent more time at the colony than males in order to defend the nest, incubate the eggs and brood the nestlings. Females also helped their mates to provision the nestling once these had grown and required more food and less protection. Furthermore, lesser kestrels showed a sexual spatial segregation in foraging areas, with males foraging closer to the colony than females.

CONCLUSIONS

The lesser kestrel responds to changes in energy demand throughout the breeding season with its foraging movement strategy, but in a different way depending on parental sex. The sexual spatial segregation observed is likely to be the result of an adaptive foraging strategy based on role specialization to reduce prey depletion close to the colony and intersexual competition in order to improve breeding success.

Reproductive constraints influence habitat accessibility, segregation, and preference of sympatric albatross species

BACKGROUND

The spatiotemporal distribution of animals is dependent on a suite of factors, including the distribution of resources, interactions within and between species, physiological limitations, and requirements for reproduction, dispersal, or migration. During breeding, reproductive constraints play a major role in the distribution and behavior of central place foragers, such as pelagic seabirds. We examined the foraging behavior and marine habitat selection of Laysan (Phoebastria immutabilis) and black-footed (P. nigripes) albatrosses throughout their eight month breeding cycle at Tern Island, Northwest Hawaiian Islands to evaluate how variable constraints of breeding influenced habitat availability and foraging decisions. We used satellite tracking and light-based geolocation to determine foraging locations of individuals, and applied a biologically realistic null usage model to generate control locations and model habitat preference under a case-control design. Remotely sensed oceanographic data were used to characterize albatross habitats in the North Pacific.

RESULTS

Individuals of both species ranged significantly farther and for longer durations during incubation and chick-rearing compared to the brooding period. Interspecific segregation of core foraging areas was observed during incubation and chick-rearing, but not during brooding. At-sea activity patterns were most similar between species during brooding; neither species altered foraging effort to compensate for presumed low prey availability and high energy demands during this stage. Habitat selection during long-ranging movements was most strongly associated with sea surface temperature for both species, with a preference for cooler ocean temperatures compared to overall availability. During brooding, lower explanatory power of habitat models was likely related to the narrow range of ocean temperatures available for selection.

CONCLUSIONS

Laysan and black-footed albatrosses differ from other albatross species in that they breed in an oligotrophic marine environment. During incubation and chick-rearing, they travel to cooler, more productive waters, but are restricted to the low-productivity environment near the colony during brooding, when energy requirements are greatest. Compared to other albatross species, Laysan and black-footed albatrosses spend a greater proportion of time in flight when foraging, especially during the brooding period; this strategy may be adaptive for locating dispersed prey in an oligotrophic environment.

Seasonal variation in microhabitat of salamanders: environmental variation or shift of habitat selection?

Relationships between species and their habitats are not always constant. Different processes may determine changes in species-habitat association: individuals may prefer different habitat typologies in different periods, or they may be forced to occupy a different habitat in order to follow the changing environment. The aim of our study was to assess whether cave salamanders change their habitat association pattern through the year, and to test whether such changes are determined by environmental changes or by changes in preferences. We monitored multiple caves in Central Italy through one year, and monthly measured biotic and abiotic features of microhabitat and recorded Italian cave salamanders distribution. We used mixed models and niche similarity tests to assess whether species-habitat relationships remain constant through the year. Microhabitat showed strong seasonal variation, with the highest variability in the superficial sectors. Salamanders were associated to relatively cold and humid sectors in summer, but not during winter. Such apparent shift in habitat preferences mostly occurred because the environmental gradient changed through the year, while individuals generally selected similar conditions. Nevertheless, juveniles were more tolerant to dry sectors during late winter, when food demand was highest. This suggests that tolerance for suboptimal abiotic conditions may change through time, depending on the required resources. Differences in habitat use are jointly determined by environmental variation through time, and by changes in the preferred habitat. The trade-offs between tolerance and resources requirement are major determinant of such variation.

Modeling spatial segregation and travel cost influences on utilitarian walking: Towards policy intervention

We develop an agent-based model of utilitarian walking and use the model to explore spatial and socioeconomic factors affecting adult utilitarian walking and how travel costs as well as various educational interventions aimed at changing attitudes can alter the prevalence of walking and income differentials in walking. The model is validated against US national data. We contrast realistic and extreme parameter values in our model and test effects of changing these parameters across various segregation and pricing scenarios while allowing for interactions between travel choice and place and for behavioral feedbacks. Results suggest that in addition to income differences in the perceived cost of time, the concentration of mixed land use (differential density of residences and businesses) are important determinants of income differences in walking (high income walk less), whereas safety from crime and income segregation on their own do not have large influences on income differences in walking. We also show the difficulty in altering walking behaviors for higher income groups who are insensitive to price and how adding to the cost of driving could increase the income differential in walking particularly in the context of segregation by income and land use. We show that strategies to decrease positive attitudes towards driving can interact synergistically with shifting cost structures to favor walking in increasing the percent of walking trips. Agent-based models, with their ability to capture dynamic processes and incorporate empirical data, are powerful tools to explore the influence on health behavior from multiple factors and test policy interventions.

Sex ratio variation and spatial distribution of Siparuna grandiflora, a tropical dioecious shrub

Populations of dioecious plant species often exhibit biased sex ratios. Such biases may arise as a result of sex-based differences in life history traits, or as a result of spatial segregation of the sexes. Of these, sex-based differentiation in life history traits is likely to be the most common cause of bias. In dioecious species, selection can act upon the sexes in a somewhat independent way, leading to differentiation and evolution toward sex-specific ecological optima. I examined sex ratio variation and spatial distribution of the tropical dioecious shrub Siparuna grandiflora to determine whether populations exhibited a biased sex ratio, and if so, whether the bias could be explained in terms of non-random spatial distribution or sex-based differentiation in life history traits. Sex ratio bias was tested using contingency tables, a logistic regression approach was utilized to examine variation in life history traits, and spatial distributions were analyzed using Ripley's K, a second-order neighborhood analysis. I found that although populations of S. grandiflora have a male-biased sex ratio within and among years, there was no evidence of spatial segregation of the sexes. Rather, the sex ratio bias was shown to result primarily from sex-based differentiation in life history traits; males reproduce at a smaller size and more frequently than females. The sexes also differ in the relationship between plant size and reproductive frequency. Light availability was shown to affect reproductive activity in both sexes, though among infrequently flowering plants, females require higher light levels than males to flower. The results of this study demonstrate that ecologically significant sex-based differentiation has evolved in S. grandiflora.