Threshold games and cooperation on multiplayer graphs

Objective: The study investigates the effect on cooperation in multiplayer games, when the population from which all individuals are drawn is structured - i.e. when a given individual is only competing with a small subset of the entire population. Method: To optimize the focus on multiplayer effects, a class of games were chosen for which the payoff depends nonlinearly on the number of cooperators - this ensures that the game cannot be represented as a sum of pair-wise interactions, and increases the likelihood of observing behaviour different from that seen in two-player games. The chosen class of games are named "threshold games", and are defined by a threshold, $M > 0$, which describes the minimal number of cooperators in a given match required for all the participants to receive a benefit. The model was studied primarily through numerical simulations of large populations of individuals, each with interaction neighbourhoods described by various classes of networks. Results: When comparing the level of cooperation in a structured population to the mean-field model, we find that most types of structure lead to a decrease in cooperation. This is both interesting and novel, simply due to the generality and breadth of relevance of the model - it is likely that any model with similar payoff structure exhibits related behaviour. More importantly, we find that the details of the behaviour depends to a large extent on the size of the immediate neighbourhoods of the individuals, as dictated by the network structure. In effect, the players behave as if they are part of a much smaller, fully mixed, population, which we suggest an expression for.Comment: in PLOS ONE, 4th Feb 201

On the brink between extinction and persistence

The nature of size fluctuations is crucial in forecasting future population persistence, independently of whether the variability stems from external forces or from the dynamics of the population renewal process. The risk of intercepting zero is highly dependent on the way the variance of the population size relates to its mean. The minimum population size required for a population not to go extinct can be determined by a scaling equation relating the variance to the arithmetic mean. By the use of a derived expression for the harmonic mean defined by the parameters of the scaling equation we show how it is possible to separate the domains of persistence from those of extinction and to facilitate the identification of populations on the brink of extinction

Orangulas: effect of scheduled visual enrichment on behavioral and endocrine aspects of a captive orangutan (Pongo pygmaeus)

Captivity may have adverse effects on captive great apes, as they spend much more of their time engaged in foraging and other activities in the wild. Enrichment interventions have the potential to alleviate the adverse effects of captivity by introducing novel stimuli. In orangutans (Pongo pygmaeus), interactive digital enrichment has proven effective at engaging users out of their own free will, in exchange for nothing but the experience. This article reports the results of scheduled visual enrichment in the form of “orangulas”—one-hour long videos of footage consisting mainly of open spaces in different environments, with which the pongid participant could engage at free will. The efficacy of the orangulas were measured with both behavioural and endocrine measurements, concluding that scheduled visual enrichment has the potential to improve the welfare of captive orangutans by providing novel stimuli in the context of largely stable environments

Quantitative trait evolution and environmental change

Peer reviewe

Challenging claims in the study of migratory birds and climate change

Recent shifts in phenology in response to climate change are well established but often poorly understood. Many animals integrate climate change across a spatially and temporally dispersed annual life cycle, and effects are modulated by ecological interactions, evolutionary change and endogenous control mechanisms. Here we assess and discuss key statements emerging from the rapidly developing study of changing spring phenology in migratory birds. These well-studied organisms have been instrumental for understanding climate-change effects, but research is developing rapidly and there is a need to attack the big issues rather than risking affirmative science. Although we agree poorly on the support for most claims, agreement regarding the knowledge basis enables consensus regarding broad patterns and likely causes. Empirical data needed for disentangling mechanisms are still scarce, and consequences at a population level and on community composition remain unclear. With increasing knowledge, the overall support (‘consensus view’) for a claim increased and between-researcher variability in support (‘expert opinions') decreased, indicating the importance of assessing and communicating the knowledge basis. A proper integration across biological disciplines seems essential for the field's transition from affirming patterns to understanding mechanisms and making robust predictions regarding future consequences of shifting phenologies

Association of lithium use with rate of out-of-hospital cardiac arrest in patients with bipolar disorder

Background: Lithium has been linked with induction of proarrythmic electrocardiographical changes. However, it is unclear whether lithium use is associated with an increased rate of cardiac arrest. We investigated the rate of out-of-hospital cardiac arrest associated with lithium exposure in a nationwide cohort of patients with bipolar disorder. Methods: Data from Danish registries was used to conduct a nationwide nested case-control study assessing the rate of out-of-hospital cardiac arrest associated with lithium exposure among 47,745 bipolar disorder patients from 2001 through 2015. 284 cases with out-of-hospital cardiac arrest were matched on age, sex, and age at first diagnosis of bipolar disorder with 1,386 controls. Rate analyses were performed using Cox regression. Results: Fewer cases than controls were exposed to lithium (24.3% vs. 34.9%, p&lt;.001). In adjusted analyses, lithium monotherapy was not significantly associated with increased rate of out-of-hospital cardiac arrest compared with no mood stabilizing treatment (Hazard ratio [HR] = 0.71 [95% CI, 0.46–1.10]), atypical antipsychotic monotherapy (HR = 0.69 [95% CI, 0.41–1.15]), and anticonvulsant monotherapy (HR = 1.37 [95% confidence interval [CI], 0.65–2.88]). Combination therapy with lithium plus one or more other mood stabilizers was not associated with increased rate of out-of-hospital cardiac arrest compared with combination therapy with two or more non-lithium mood stabilizers (HR = 0.58, [95% CI, 0.31–1.08]). Limitations: Possible residual confounding due to unmeasured variables. Lack of statistical power to detect weak associations. Conclusions: Lithium was not associated with increased rate of out-of-hospital cardiac arrest in bipolar disorder patients compared with other guideline-recommended mood stabilizing pharmacotherapy, nor compared with no mood stabilizer treatment.</p

Genetic Inactivation of Trpml3 Does Not Lead to Hearing and Vestibular Impairment in Mice

TRPML3, a member of the transient receptor potential (TRP) family, is an inwardly rectifying, non-selective Ca2+-permeable cation channel that is regulated by extracytosolic Na+ and H+ and can be activated by a variety of small molecules. The severe auditory and vestibular phenotype of the TRPML3(A419P) varitint-waddler mutation made this protein particularly interesting for inner ear biology. To elucidate the physiological role of murine TRPML3, we conditionally inactivated Trpml3 in mice. Surprisingly, lack of functional TRPML3 did not lead to circling behavior, balance impairment or hearing loss