Prevalence in News Media of Two Competing Hypotheses about COVID-19 Origins

The COVID-19 pandemic has been one of the most disruptive and painful phenomena of the last few decades. As of July 2021, the origins of the SARS-CoV-2 virus that caused the outbreak remain a mystery. This work analyzes the prevalence in news media articles of two popular hypotheses about SARS-CoV-2 virus origins: the natural emergence and the lab-leak hypotheses. Our results show that for most of 2020, the natural emergence hypothesis was favored in news media content while the lab-leak hypothesis was largely absent. However, something changed around May 2021 that caused the prevalence of the lab-leak hypothesis to substantially increase in news media discourse. This shift has not been uniformed across media organizations but instead has manifested itself more acutely in some outlets than others. Our structural break analysis of daily news media usage of terms related to the laboratory escape hypothesis provides hints about potential sources for this sudden shift in the prevalence of the lab-leak hypothesis in prestigious news media.

Physiology and behavior under food limitation support an escape, not preparative, response in the nomadic Pine Siskin (Spinus pinus)

Migration allows animals to use resources that are variable in time and/or space, with different migratory strategies depending on the predictability of resource variation. When food varies seasonally, obligate migrants anticipate and prepare for migration. In contrast, facultative migrants, whose movements are unpredictable in timing and destination, may either prepare for migration or escape when resources are depleted. We propose and test two alternative hypotheses regarding the behavioral and physiological responses of facultative migrants to declining food availability. (1) The Prepare Hypothesis predicts that facultative migrants prepare for departure by increasing fuel stores in response to declining food availability, and elevations of baseline corticosterone (CORT) facilitate increased activity. (2) The Escape Hypothesis predicts that facultative migrants do not prepare for departure, body condition declines as food availability declines, and stress-induced levels of CORT induce escape behavior when both energetic condition and food resources are low. We conducted a 16-day experiment, measuring body composition (using Quantitative Magnetic Resonance), activity (using force perches), and baseline CORT in Pine Siskins (Spinus pinus) given ad libitum food or a slow decline, fast decline, or randomly changing amount of food. Our results support the Escape Hypothesis: body condition declined as food declined, decreases in body and fat mass were associated with increases in baseline CORT, and activity increased only when food availability was low. This work suggests that facultative migration in autumn allows birds to escape low resource areas and that the underlying physiological mechanisms differ from those driving both seasonal, obligate migrations and spring nomadic movements.

Changes in liana density over 30 years in a Bornean rain forest supports the escape hypothesis

In two permanent plots of lowland dipterocarp forest at Danum a liana census in 1988 was repeated in 2018 using the same method. Trees ≥ 30 cm gbh (girth at breast height) were recorded for number of lianas ≥ 2 cm gbh on their stems. The forest was evidently in a late stage of recovery from a large natural disturbance. Over the interval, mean number of lianas per tree decreased by 22 and 34 % in plots 1 and 2. By 2018 there were relatively more trees with few lianas and relatively fewer trees with many lianas than in 1988. The redistribution was strongest for overstorey trees of the Dipterocarpaceae (more with no lianas by 2018) and understorey trees of the Euphorbiaceae (many losing high loads in plot 2). Proportion of trees with lianas rose overall by 3.5%. Number of lianas per tree showed a quadratic relationship with tree size (ln[gbh]): maximal for large trees, fewer for smaller and very large trees. Tree survival and stem growth rate were significantly negatively related to number of lianas, after accounting for spatial autocorrelation. Monte Carlo random samples of half of trees in 1988 were compared with the other half of trees in 2018. Relative frequency distributions differed significantly over time, but dipterocarps and euphorbs varied noticeably in their liana dynamics between plots. Regressions achieved best significant fits when number of lianas was a function of date, ln(gbh) and ln(gbh)2, but differently in the plots reflecting complicated host-liana dynamics. Analysis of most abundant trees species, individually, highlighted a group of emergent dipterocarps with low liana counts decreasing with time. Building on an earlier hypothesis, these trees lose their lianas with branch shedding, as they move into, and emerge from, the main canopy. They escape from the parasite. The process may in part explain the uneven nature of the forest canopy at Danum. Change in liana density was contingent on forest history and site succession, and plot-level structure and dynamics. Liana promotion in intermittent dry periods was seemingly being offset by closing of the forest and continued dominance by the Dipterocarpaceae.

At the Intersection of Motivational Relevance and Website Visual Complexity

This study investigated how resource allocation to and encoding of irrelevant peripheral information (advertisements) varied as a function of the emotional tone of a central event (movie clip) and website complexity (number of advertisements). Secondary task reaction times (STRTs) and ad recognition accuracy were used to test the predictions. Two competing hypotheses – a memory narrowing hypothesis and an escape hypothesis – were posed to explain encoding of advertisements paired with negative arousing movie clips at the highest level of website complexity. The results were more supportive of the memory narrowing hypothesis; participants had more resources while viewing positive rather than negative movies and advertisements were encoded better when they were presented with positive rather than negative movie clips. However, for calm movie clips this difference showed at the lowest level of website complexity, but gradually diminished as the level of complexity increased.

A new hypothesis for the importance of seed dispersal in time

Most studies on seed dispersal in time have focused on seed dormancy and the physiological triggers for germination. However, seed dispersed by animals with low metabolic and moving rates, and long gutpassage times such as terrestrial turtles, could be considered another type of dispersal in time. This study tests the hypothesis that seeds dispersed in time may lower predation rates. We predicted that seeds deposited below parent trees after fruiting fall has finished is advantageous to minimize seed predators and should show higher survival rates. Four Amazonian plant species, Dicranostyles ampla, Oenocarpus bataua, Guatteria atabapensis and Ocotea floribunda, were tested for seed survival probabilities in two periods: during fruiting and 10-21 days after fruiting. Experiments were carried out in two biological stations located in the Colombian Amazon (Caparú and Zafire Biological Stations). Seed predation was high and mainly caused by non-vertebrates. Out of the four plant species tested, only Guatteria atabapensis supported the time escape hypothesis. For this species, seed predation by vertebrates after the fruiting period increased (from 4.1% to 9.2%) while seed predation by nonvertebrates decreased (from 54.0% to 40.2%). in contrast, seed predation by vertebrates and by non-vertebrates after the fruiting period in D. ampla increased (from 7.9% to 22.8% and from 40.4% to 50.6%, respectively), suggesting predator satiation. Results suggest that for some species dispersal in time could be advantageous to avoid some type of seed predators. Escape in time could be an additional dimension in which seeds may reach adequate sites for recruitment. Thus, future studies should be address to better understand the survival advantages given by an endozoochory time-dispersal process.

The ‘male escape hypothesis’: sex-biased metamorphosis in response to climatic drivers in a facultatively paedomorphic amphibian

Paedomorphosis is a major evolutionary process that bypasses metamorphosis and allows reproduction in larvae. In newts and salamanders, it can be facultative with paedomorphs retaining gills and metamorphs dispersing. The evolution of these developmental processes is thought to have been driven by the costs and benefits of inhabiting aquatic versus terrestrial habitats. In this context, we aimed at testing the hypothesis that climatic drivers affect phenotypic transition and the difference across sexes because sex-ratio is biased in natural populations. Through a replicated laboratory experiment, we showed that paedomorphic palmate newts ( Lissotriton helveticus ) metamorphosed at a higher frequency when water availability decreased and metamorphosed earlier when temperature increased in these conditions. All responses were sex-biased, and males were more prone to change phenotype than females. Our work shows how climatic variables can affect facultative paedomorphosis and support theoretical models predicting life on land instead of in water. Moreover, because males metamorphose and leave water more often and earlier than females, these results, for the first time, give an experimental explanation for the rarity of male paedomorphosis (the ‘male escape hypothesis’) and suggest the importance of sex in the evolution of paedomorphosis versus metamorphosis.

Escaping Satiation Dynamics: Some Evidence from British Household Data

SummaryThe tendency of sectoral demand to satiate has long been argued to be a key driver of the structural change in an economy (Pasinetti 1981; Saviotti 2001). This literature raises the question as to what extent cross-sectional patterns of household expenditure can be used to make inferences about how the demand for goods and services will grow over time. Moreover, if indeed satiation does take place, then firms and entrepreneurs could react to this situation by innovating goods and services in order to overcome stagnation in demand growth (Witt 2001). We empirically investigate this ‘satiation-escape’ hypothesis by examining the inter-temporal dynamics of Engel curves and their derivatives, which reflect how household spending on a good changes with income. Taking into account changes in the price level, we investigate whether Engel curves that exhibit cross-section satiation tend to exhibit over time an upwards shift in the satiation level jointly with a shift in position and shape. Evidence suggests that this is actually the case.