Refuge sharing network predicts ectoparasite load in a lizard

Living in social groups facilitates cross-infection by parasites. However, empirical studies on indirect transmission within wildlife populations are scarce. We investigated whether asynchronous overnight refuge sharing among neighboring sleepy lizards, Tiliqua rugosa, facilitates indirect transmission of its ectoparasitic tick, Amblyomma limbatum. We fitted 18 neighboring lizards with GPS recorders, observed their overnight refuge use each night over 3 months, and counted their ticks every fortnight. We constructed a transmission network to estimate the cross-infection risk based on asynchronous refuge sharing frequencies among all lizards and the life history traits of the tick. Although self-infection was possible, the network provided a powerful predictor of measured tick loads. Highly connected lizards that frequently used their neighbors’ refuges were characterized by higher tick loads. Thus, indirect contact had a major influence on transmission pathways and parasite loads. Furthermore, lizards that used many different refuges had lower cross- and self-infection risks and lower tick loads than individuals that used relatively fewer refuges. Increasing the number of refuges used by a lizard may be an important defense mechanism against ectoparasite transmission in this species. Our study provides important empirical data to further understand how indirectly transmitted parasites move through host populations and influence individual parasite loads

Aggregation dynamics explain vegetation patch-size distributions

Vegetation patch-size distributions have been an intense area of study for theoreticians and applied ecologists alike in recent years. Of particular interest is the seemingly ubiquitous nature of power-law patch-size distributions emerging in a number of diverse ecosystems. The leading explanation of the emergence of these power-laws is due to local facilitative mechanisms. There is also a common transition from power law to exponential distribution when a system is under global pressure, such as grazing or lack of rainfall. These phenomena require a simple mechanistic explanation. Here, we study vegetation patches from a spatially implicit, patch dynamic viewpoint. We show that under minimal assumptions a power-law patch-size distribution appears as a natural consequence of aggregation. A linear death term also leads to an exponential term in the distribution for any non-zero death rate. This work shows the origin of the breakdown of the power-law under increasing pressure and shows that in general, we expect to observe a power law with an exponential cutoff (rather than pure power laws). The estimated parameters of this distribution also provide insight into the underlying ecological mechanisms of aggregation and death

Surviving drought: a framework for understanding animal responses to small rain events in the arid zone

Large rain events drive dramatic resource pulses and the complex pulse‐reserve dynamics of arid ecosystems change between high‐rain years and drought. However, arid‐zone animal responses to short‐term changes in climate are unknown, particularly smaller rain events that briefly interrupt longer‐term drought. Using arthropods as model animals, we determined the effects of a small rain event on arthropod abundance in western New South Wales, Australia during a longer‐term shift toward drought. Arthropod abundance decreased over 2 yr, but captures of 10 out of 15 ordinal taxa increased dramatically after the small rain event (\u3c40 \u3emm). The magnitude of increases ranged from 10.4 million% (collembolans) to 81% (spiders). After 3 months, most taxa returned to prerain abundance. However, small soil‐dwelling beetles, mites, spiders, and collembolans retained high abundances despite the onset of winter temperatures and lack of subsequent rain. As predicted by pulse‐reserve models, most arid‐zone arthropod populations declined during drought. However, small rain events may play a role in buffering some taxa from declines during longer‐term drought or other xenobiotic influences. We outline the framework for a new model of animal responses to environmental conditions in the arid zone, as some species clearly benefit from rain inputs that do not dramatically influence primary productivity

Searching for sustainability within public health policy: insights from an injury prevention perspective

Background: Sustaining public health programmes in the long-term is key to ensuring full manifestation of their intended benefits. Although an increasing interest in sustainability is apparent within the global literature, empirical studies from within the European setting are few. The factors that influence sustainability are generally conceptualized at three levels: programme level, the immediate context and the wider environment. To-date attention has focused primarily on the former two. Using a community-based child injury prevention programme in England as an exemplar, this paper explores the concept of sustainability within the wider policy environment, and considers the impact of this on local programmes. Methods: A content review of global and UK national public health policies (1981–2014) relevant to child safety was undertaken. Interviews were held with senior representatives of global and UK agencies involved in developing child safety policy. Results Forty-nine policies were reviewed. The term ‘sustain’, or its derivatives, featured in 36 (73%) of these. Its’ use however, related primarily to conservation of resources rather than continued programme operation. Potential mechanisms for supporting programme sustainability featured within some documents; however, the approach to sustainability was inconsistent between policies and over time. Policy stakeholders identified programme sustainability as relevant to their core business, but its’ conceptualization varied according to individual interpretation. Conclusions: Programme sustainability is poorly addressed within global and UK-based public health policy. Strengthening a national and international policy focus on sustainability and incorporating sustainability into public health planning frameworks may create a more supportive environment for local programmes

Expression of Lipogenic Factors Galectin-12, Resistin, SREBP-1, and SCD in Human Sebaceous Glands and Cultured Sebocytes

The transcription factors CCAAT enhancer-binding protein α, β, and δ, and peroxisome proliferator-activated receptor γ are known to be crucial to the differentiation of adipocytes and are expressed in sebaceous gland cells. As lipogenesis is key to both adipocyte and sebocyte differentiation we hypothesize that sebocytes follow a similar program of differentiation to adipocytes. We have investigated the expression of known adipogenic factors resistin, galectin-12, sterol response –element-binding protein–1 (SREBP-1) and stearoyl-CoA desaturase in the immortalized sebaceous gland cell line SZ95 and whole skin. Reverse transcriptase-PCR analysis showed the expression of galectin-12, resistin, SREBP-1, and stearoyl-CoA desaturase mRNAs in SZ95 sebocytes. Immunoreactivity was observed for galectin-12 and SREBP-1 in the nuclei and resistin in the cytoplasm of basal sebocytes, and stearoyl CoA desaturase in the cytoplasm of basal and luminal sebocytes of human scalp skin. Expression of galectin-12, resistin, and SREBP-1 in SZ95 sebocytes was confirmed by Western blot analysis. These data provide further evidence that pathways of differentiation in adipocytes and sebocytes could be similar and therefore further understanding of sebaceous gland differentiation and lipogenesis and potential therapies for sebaceous gland disorders may be obtained from our knowledge of adipocyte differentiation

Disease transmission promotes evolution of host spatial patterns

Ecological dynamics can produce a variety of striking patterns. On ecological time scales, pattern formation has been hypothesized to be due to the interaction between a species and its local environment. On longer time scales, evolutionary factors must be taken into account. To examine the evolutionary robustness of spatial pattern formation, we construct a spatially explicit model of vegetation in the presence of a pathogen. Initially, we compare the dynamics for vegetation parameters that lead to competition induced spatial patterns and those that do not. Over ecological time scales, banded spatial patterns dramatically reduced the ability of the pathogen to spread, lowered its endemic density and hence increased the persistence of the vegetation. To gain an evolutionary understanding, each plant was given a heritable trait defining its resilience to competition; greater competition leads to lower vegetation density but stronger spatial patterns. When a disease is introduced, the selective pressure on the plant's resilience to the competition parameter is determined by the transmission of the disease. For high transmission, vegetation that has low resilience to competition and hence strong spatial patterning is an evolutionarily stable strategy. This demonstrates a novel mechanism by which striking spatial patterns can be maintained by disease-driven selection

Predators reduce extinction risk in noisy metapopulations

Background Spatial structure across fragmented landscapes can enhance regional population persistence by promoting local “rescue effects.” In small, vulnerable populations, where chance or random events between individuals may have disproportionately large effects on species interactions, such local processes are particularly important. However, existing theory often only describes the dynamics of metapopulations at regional scales, neglecting the role of multispecies population dynamics within habitat patches. Findings By coupling analysis across spatial scales we quantified the interaction between local scale population regulation, regional dispersal and noise processes in the dynamics of experimental host-parasitoid metapopulations. We find that increasing community complexity increases negative correlation between local population dynamics. A potential mechanism underpinning this finding was explored using a simple population dynamic model. Conclusions Our results suggest a paradox: parasitism, whilst clearly damaging to hosts at the individual level, reduces extinction risk at the population level

Plasmodium falciparum Variant Surface Antigen Expression Patterns during Malaria

The variant surface antigens expressed on Plasmodium falciparum–infected erythrocytes are potentially important targets of immunity to malaria and are encoded, at least in part, by a family of var genes, about 60 of which are present within every parasite genome. Here we use semi-conserved regions within short var gene sequence “tags” to make direct comparisons of var gene expression in 12 clinical parasite isolates from Kenyan children. A total of 1,746 var clones were sequenced from genomic and cDNA and assigned to one of six sequence groups using specific sequence features. The results show the following. (1) The relative numbers of genomic clones falling in each of the sequence groups was similar between parasite isolates and corresponded well with the numbers of genes found in the genome of a single, fully sequenced parasite isolate. In contrast, the relative numbers of cDNA clones falling in each group varied considerably between isolates. (2) Expression of sequences belonging to a relatively conserved group was negatively associated with the repertoire of variant surface antigen antibodies carried by the infected child at the time of disease, whereas expression of sequences belonging to another group was associated with the parasite “rosetting” phenotype, a well established virulence determinant. Our results suggest that information on the state of the host–parasite relationship in vivo can be provided by measurements of the differential expression of different var groups, and need only be defined by short stretches of sequence data

Promiscuity in the part-phosphorylative Entner–Doudoroff pathway of the archaeon Sulfolobus solfataricus

AbstractThe hyperthermophilic archaeon Sulfolobus solfataricus metabolises glucose and galactose by a ‘promiscuous’ non-phosphorylative variant of the Entner–Doudoroff pathway, in which a series of enzymes have sufficient substrate promiscuity to permit the metabolism of both sugars. Recently, it has been proposed that the part-phosphorylative Entner–Doudoroff pathway occurs in parallel in S. solfataricus as an alternative route for glucose metabolism. In this report we demonstrate, by in vitro kinetic studies of d-2-keto-3-deoxygluconate (KDG) kinase and KDG aldolase, that the part-phosphorylative pathway in S. solfataricus is also promiscuous for the metabolism of both glucose and galactose

Response to "Toward Unified Satellite Climatology of Aerosol Properties. 3. MODIS Versus MISR Versus AERONET"

A recent paper by Mishchenko et al. compares near-coincident MISR, MODIS, and AERONET aerosol optical depth (AOD) products, and reports much poorer agreement than that obtained by the instrument teams and others. We trace the reasons for the discrepancies primarily to differences in (1) the treatment of outliers, (2) the application of absolute vs. relative criteria for testing agreement, and (3) the ways in which seasonally varying spatial distributions of coincident retrievals are taken into account