15 research outputs found

    Telling ecological networks apart by their structure: A computational challenge.

    No full text
    Ecologists have been compiling ecological networks for over a century, detailing the interactions between species in a variety of ecosystems. To this end, they have built networks for mutualistic (e.g., pollination, seed dispersal) as well as antagonistic (e.g., herbivory, parasitism) interactions. The type of interaction being represented is believed to be reflected in the structure of the network, which would differ substantially between mutualistic and antagonistic networks. Here, we put this notion to the test by attempting to determine the type of interaction represented in a network based solely on its structure. We find that, although it is easy to separate different kinds of nonecological networks, ecological networks display much structural variation, making it difficult to distinguish between mutualistic and antagonistic interactions. We therefore frame the problem as a challenge for the community of scientists interested in computational biology and machine learning. We discuss the features a good solution to this problem should possess and the obstacles that need to be overcome to achieve this goal

    El Diario de Pontevedra : periódico liberal: Ano XXXV Número 10412 - 1918 decembro 30

    No full text
    Scientists often perceive a trade-off between quantity and quality in scientific publishing: finite amounts of time and effort can be spent to produce few high-quality papers or subdivided to produce many papers of lower quality. Despite this perception, previous studies have indicated the opposite relationship, in which productivity (publishing more papers) is associated with increased paper quality (usually measured by citation accumulation). We examine this question in a novel way, comparing members of the National Academy of Sciences with themselves across years, and using a much larger dataset than previously analyzed. We find that a member's most highly cited paper in a given year has more citations in more productive years than in in less productive years. Their lowest cited paper each year, on the other hand, has fewer citations in more productive years. To disentangle the effect of the underlying distributions of citations and productivities, we repeat the analysis for hypothetical publication records generated by scrambling each author's citation counts among their publications. Surprisingly, these artificial histories re-create the above trends almost exactly. Put another way, the observed positive relationship between quantity and quality can be interpreted as a consequence of randomly drawing citation counts for each publication: more productive years yield higher-cited papers because they have more chances to draw a large value. This suggests that citation counts, and the rewards that have come to be associated with them, may be more stochastic than previously appreciated

    Self-regulation and the stability of large ecological networks

    No full text
    The stability of complex ecological networks depends both on the interactions between species and the direct effects of the species on themselves. These self-effects are known as self-regulation when an increase in a species abundance decreases its per-capita growth rate. Sources of self-regulation include intraspecific interference, cannibalism, time-scale separation between consumers and their resources, spatial heterogeneity and nonlinear functional responses coupling predators with their prey. The influence of self-regulation on network stability is understudied and in addition, the empirical estimation of self-effects poses a formidable challenge. Here, we show that empirical food web structures cannot be stabilized unless the majority of species exhibit substantially strong self-regulation. We also derive an analytical formula predicting the effect of self-regulation on network stability with high accuracy and show that even for random networks, as well as networks with a cascade structure, stability requires negative self-effects for a large proportion of species. These results suggest that the aforementioned potential mechanisms of self-regulation are probably more important in contributing to the stability of observed ecological networks than was previously thought.Funding Agencies|National Science Foundation [1148867]; United States Department of Education grant [P200A150101]</p

    Violin plots of the strength of pairwise correlation between quantity and quality for members of the National Academy of Sciences.

    No full text
    <p>The panels are divided based on which summary statistic is being compared across years (<i>e</i>.<i>g</i>. maximally-cited paper published in that year). A value of 1 (-1) indicates that, for every pair of adjacent years, the more productive one had a higher (lower) statistic. A value of 0 (horizontal black line) indicates that the larger statistic is equally likely to be from the more or less productive year. In blue (left in each plot) are the empirically observed correlation values for each author. In red (right in each plot) are the correlation values observed when citation counts were randomized within each author’s corpus.</p

    The relationship between sample size and the maximum/minimum citation count drawn in that sample.

    No full text
    <p>Right: histogram of citation counts for a given member of the National Academy of Sciences across their more than 1000 publications. Left: boxplots for the maximum (red, top) and minimum (orange, bottom) citation count drawn in samples of the size indicated by the horizontal axis. Each sample of a given size was repeated 1000 times to generate the distributions indicated by the boxplots.</p

    The illusion of personal health decisions for infectious disease management: disease spread in social contact networks

    No full text
    Close contacts between individuals provide opportunities for the transmission of diseases, including COVID-19. While individuals take part in many different types of interactions, including those with classmates, co-workers and household members, it is the conglomeration of all of these interactions that produces the complex social contact network interconnecting individuals across the population. Thus, while an individual might decide their own risk tolerance in response to a threat of infection, the consequences of such decisions are rarely so confined, propagating far beyond any one person. We assess the effect of different population-level risk-tolerance regimes, population structure in the form of age and household-size distributions, and different interaction types on epidemic spread in plausible human contact networks to gain insight into how contact network structure affects pathogen spread through a population. In particular, we find that behavioural changes by vulnerable individuals in isolation are insufficient to reduce those individuals’ infection risk and that population structure can have varied and counteracting effects on epidemic outcomes. The relative impact of each interaction type was contingent on assumptions underlying contact network construction, stressing the importance of empirical validation. Taken together, these results promote a nuanced understanding of disease spread on contact networks, with implications for public health strategies
    corecore