Time-Ordered Networks Reveal Limitations to Information Flow in Ant Colonies

BACKGROUND: An important function of many complex networks is to inhibit or promote the transmission of disease, resources, or information between individuals. However, little is known about how the temporal dynamics of individual-level interactions affect these networks and constrain their function. Ant colonies are a model comparative system for understanding general principles linking individual-level interactions to network-level functions because interactions among individuals enable integration of multiple sources of information to collectively make decisions, and allocate tasks and resources. METHODOLOGY/FINDINGS: Here we show how the temporal and spatial dynamics of such individual interactions provide upper bounds to rates of colony-level information flow in the ant Temnothorax rugatulus. We develop a general framework for analyzing dynamic networks and a mathematical model that predicts how information flow scales with individual mobility and group size. CONCLUSIONS/SIGNIFICANCE: Using thousands of time-stamped interactions between uniquely marked ants in four colonies of a range of sizes, we demonstrate that observed maximum rates of information flow are always slower than predicted, and are constrained by regulation of individual mobility and contact rate. By accounting for the ordering and timing of interactions, we can resolve important difficulties with network sampling frequency and duration, enabling a broader understanding of interaction network functioning across systems and scales

Disease Dynamics in a Specialized Parasite of Ant Societies

Coevolution between ant colonies and their rare specialized parasites are intriguing, because lethal infections of workers may correspond to tolerable chronic diseases of colonies, but the parasite adaptations that allow stable coexistence with ants are virtually unknown. We explore the trade-offs experienced by Ophiocordyceps parasites manipulating ants into dying in nearby graveyards. We used field data from Brazil and Thailand to parameterize and fit a model for the growth rate of graveyards. We show that parasite pressure is much lower than the abundance of ant cadavers suggests and that hyperparasites often castrate Ophiocordyceps. However, once fruiting bodies become sexually mature they appear robust. Such parasite life-history traits are consistent with iteroparity– a reproductive strategy rarely considered in fungi. We discuss how tropical habitats with high biodiversity of hyperparasites and high spore mortality has likely been crucial for the evolution and maintenance of iteroparity in parasites with low dispersal potential

Social Transfer of Pathogenic Fungus Promotes Active Immunisation in Ant Colonies

Social contact with fungus-exposed ants leads to pathogen transfer to healthy nest-mates, causing low-level infections. These micro-infections promote pathogen-specific immune gene expression and protective immunization of nest-mates

Interleukin-10 Promotes Pathological Angiogenesis by Regulating Macrophage Response to Hypoxia during Development

Aberrant angiogenesis in the eye is the most common cause of blindness. The current study examined the role of interleukin-10 (IL-10) in ischemia-induced pathological angiogenesis called neovascularization during postnatal development. IL-10 deficiency resulted in significantly reduced pathological retinal angiogenesis. In contrast to the choroicapillaris where IL-10 interferes with macrophage influx, IL-10 did not prevent anti-angiogenic macrophages from migrating to the retina in response to hypoxia. Instead, IL-10 promoted retinal angiogenesis by altering macrophage angiogenic function, as macrophages from wild-type mice demonstrated increased vascular endothelial growth factor (VEGF) and nitric oxide (NO) compared to IL-10 deficient macrophages. IL-10 appears to directly affect macrophage responsiveness to hypoxia, as macrophages responded to hypoxia with increased levels of IL-10 and STAT3 phosphorylation as opposed to IL-10 deficient macrophages. Also, IL-10 deficient macrophages inhibited the proliferation of vascular endothelial cells in response to hypoxia while wild-type macrophages failed to do so. These findings suggest that hypoxia guides macrophage behavior to a pro-angiogenic phenotype via IL-10 activated pathways

Dynamic social networks in guppies (Poecilia reticulata)

One of the main challenges in the study of social networks in vertebrates is to close the gap between group patterns and dynamics. Usually scan samples or transect data are recorded to provide information about social patterns of animals, but these techniques themselves do not shed much light on the underlying dynamics of such groups. Here we show an approach which captures the fission-fusion dynamics of a fish population in the wild and demonstrates how the gap between pattern and dynamics may be closed. Our analysis revealed that guppies have complex association patterns that are characterised by close strong connections between individuals of similar behavioural type. Intriguingly, the preference for particular social partners is not expressed in the length of associations but in their frequency. Finally, we show that the observed association preferences could have important consequences for transmission processes in animal social networks, thus moving the emphasis of network research from descriptive mechanistic studies to functional and predictive ones. © 2014 Springer-Verlag Berlin Heidelberg

Facies-trace fossil relationships in a plio-pleistocene fluvial sequence-the upper Siwalik subgroup, punjab sub-Himalaya, India

Documentation of the ichnofauna of a Plio-Pleistocene fluvial sedimentary sequence has been made from the "molasse" belt of the Himalayan Orogenic System. Ten types of ichnogenera have been recognised in addition to rhizoliths and tracks. Similarities to materials described previously from fluvial sequences are indicated. The relationships of the ichnofauna with the various lithofacies of the fluvial depositional system are established. This has resulted in the recognition of five ichnofacies and six bioturbate textures. Facies specificity of the ichnofossils is demonstrated in the case of overbank, levee and palaeosol deposits. A synthesis of the information on fluvial trace fossils has been attempted by summarizing the data on their toponomy, orientation and fill. A high incidence of vertical endichnial forms with meniscate fill is recognised in the channel facies, and a similar situation exists in the levee facies but for the structureless character of the fill. Hypichnial and epichnial horizontal traces are seen to dominate in the overbank facies

A 'pricing-to-market' model with unobserved variables: explaining New Zealand's import prices

A model of 'pricing-to-market' (PTM) behaviour in import prices is developed for a small open economy to allow for two measurement problems: (i) that neither the marginal production cost of imported goods nor their corresponding (foreign-currency) export price are observable by the econometrician; (ii) that PTM behaviour, if it exists, alters the relationship between foreign countries' export price indices for total exports and the true, unobservable price index. The analysis shows that variations in the measured markup on import prices depends on the degree to which domestic demand is synchronized with world demand, whether bilateral exchange rate movements are due to domestic or foreign factors, and on the degree to which PTM behaviour differs from such behaviour in other countries. Equations estimated for the price of New Zealand (NZ) imports from the US strongly supports the model, and finds that the degree of PTM by US exporters in response to price and exchange rate movements is substantially greater in NZ than the average for other countries. However, the degree of PTM in NZ in response to excess demand is similar to that of other countries.

Predicting the vulnerability of great apes to disease : the role of superspreaders and their potential vaccination

Charlotte Carne was funded by a scholarship from the University of Roehampton (http://www.roehampton.ac.uk/home/). The Royal Zoological Society of Scotland (http://www.rzss.org.uk/) provided core funding for the Budongo Conservation Field Station. The orang-utan field research was funded by the Wildlife Conservation Society (WCS: http://www.wcs.org/), the US Fish and Wildlife Service Great Ape Conservation Fund (http://www.fws.gov/international/wildlif​e-without-borders/great-ape-conservation​-fund.html), Orang-utan Tropical Peatland Project (OuTrop: http://www.outrop.com/), Primate Conservation Inc. (http://www.primate.org/), and the L.S.B. Leakey Foundation (http://leakeyfoundation.org/).Disease is a major concern for the conservation of great apes, and one that is likely to become increasingly relevant as deforestation and the rise of ecotourism bring humans and apes into ever closer proximity. Consequently, it is imperative that preventative measures are explored to ensure that future epidemics do not wipe out the remaining populations of these animals. In this paper, social network analysis was used to investigate vulnerability to disease in a population of wild orang-utans and a community of wild chimpanzees. Potential 'superspreaders' of disease - individuals with disproportionately central positions in the community or population - were identified, and the efficacy of vaccinating these individuals assessed using simulations. Three resident female orang-utans were identified as potential superspreaders, and females and unflanged males were predicted to be more influential in disease spread than flanged males. By contrast, no superspreaders were identified in the chimpanzee network, although males were significantly more central than females. In both species, simulating the vaccination of the most central individuals in the network caused a greater reduction in potential disease pathways than removing random individuals, but this effect was considerably more pronounced for orang-utans. This suggests that targeted vaccinations would have a greater impact on reducing disease spread among orang-utans than chimpanzees. Overall, these results have important implications for orang-utan and chimpanzee conservation and highlight the role that certain individuals may play in the spread of disease and its prevention by vaccination.Publisher PDFPeer reviewe