6,609 research outputs found
The rise of the superorganism
Review of Domains and Major Transitions of Social Evolution by Jacobus J. Boomsma, Oxford University Press: 2022. 320 pp. ÂŁ83
Playing god with evolution
Darwin’s theory of natural selection describes how competition between individuals leads to organisms becoming adapted to their environments — giving the appearance of design, without a designer. Four recent board games have turned different aspects of natural selection into a game. But are they fun? And could they even be used to teach the science
Radiation-induced luminescence in terbium-doped silicate glasses
The purpose of this study is to characterize radiation-induced luminescence of terbium-doped silicate glasses. Experiments performed investigated the optical properties, isothermal time-evolution, and temperature dependence of the radiation-induced luminescence of two commercially available terbium-doped glasses. A problem common to this type of glass is the persistent luminescence, or afterglow, that occurs following the end of excitation from an external source of radiation. While the processes that govern characteristic luminescence of rare earth ions, including terbium, are well understood, the processes that give rise to afterglow in doped glasses are not. Identifying the source of long-term luminescence is essential for controlling problems that may arise from practical applications of luminescent glasses.;It was determined that the stimulation of terbium fluorescence is the result of direct excitation from the external radiation source, and indirect excitation from the delayed recombination of charge carriers releasing from traps in the host glass. The range of trap depths is found to be well represented by quasi-continuous distribution functions. The characteristic decay time during the initial response of both glasses studied is approximately 3.5 milliseconds. Decay of the afterglow was observed to persist for several hours, depending on the acquired dose of radiation. Comparison of the response to x-rays and ultraviolet radiation yielded the same results, indicating that the same processes are involved in producing afterglow for both cases. This result suggests a more efficient means of characterizing scintillating glasses by using ultraviolet lasers instead of x-rays
Interview with Rev. Keith Stuart
Keith Stuart talks about the First Congregational United Church of Christhttps://digital.kenyon.edu/ps_interviews/1046/thumbnail.jp
The cost and benefit of quorum sensing-controlled bacteriocin production in Lactobacillus plantarum
This study was funded by the AndalucĂa Talent Hub Program launched by the Andalusian Knowledge Agency and co-funded by the European Union's Seventh Framework Program, Marie SkĹ‚odowska-Curie actions (COFUND—grant agreement no. 291780) and the Ministry of Economy, Innovation, Science and Employment of the Junta de AndalucĂa.Bacteria eliminate competitors via 'chemical warfare' with bacteriocins. Some species appear to adjust bacteriocin production conditionally in response to the social environment. We tested whether variation in the cost and benefit of producing bacteriocins could explain such conditional behaviour, in the bacteria Lactobacillus plantarum. We found that: (a) bacterial bacteriocin production could be upregulated by either the addition of a synthetic autoinducer peptide (PLNC8IF; signalling molecule), or by a plasmid which constitutively encodes for the production of this peptide; (b) bacteriocin production is costly, leading to reduced growth when grown in poor and, to a lesser extent, in rich media; (c) bacteriocin production provides a fitness advantage, when grown in competition with sensitive strains; and (d) the fitness benefits provided by bacteriocin production are greater at higher cell densities. These results show how the costs and benefits of upregulating bacteriocin production can depend upon abiotic and biotic conditions.PostprintPeer reviewe
Split sex ratios in the social Hymenoptera: a meta-analysis
The study of sex allocation in social Hymenoptera (ants, bees, and wasps) provides an excellent opportunity for testing kin-selection theory and studying conflict resolution. A queen-worker conflict over sex allocation is expected because workers are more related to sisters than to brothers, whereas queens are equally related to daughters and sons. If workers fully control sex allocation, split sex ratio theory predicts that colonies with relatively high or low relatedness asymmetry (the relatedness of workers to females divided by the relatedness of workers to males) should specialize in females or males, respectively. We performed a meta-analysis to assess the magnitude of adaptive sex allocation biasing by workers and degree of support for split sex ratio theory in the social Hymenoptera. Overall, variation in relatedness asymmetry (due to mate number or queen replacement) and variation in queen number (which also affects relatedness asymmetry in some conditions) explained 20.9% and 5% of the variance in sex allocation among colonies, respectively. These results show that workers often bias colony sex allocation in their favor as predicted by split sex ratio theory, even if their control is incomplete and a large part of the variation among colonies has other causes. The explanatory power of split sex ratio theory was close to that of local mate competition and local resource competition in the few species of social Hymenoptera where these factors apply. Hence, three of the most successful theories explaining quantitative variation in sex allocation are based on kin selectio
Equilibria and oscillations in cheat–cooperator dynamics
Cooperative societies can be threatened by cheats, who invest less in cooperation and exploit the contributions of others. The impact of cheats depends on the extent to which they are maintained in the population. However, different empirical studies, across organisms ranging from RNA replicators to bacteria, have shown diverse cheat–cooperator dynamics. These vary from approaching a stable equilibrium to dynamic cyclical oscillations. The reason for this variation remains unclear. Here, we develop a theoretical model to identify the factors that determine whether dynamics should tend toward stable equilibria or cyclical oscillations. Our analyses show that (1) a combination of both periodic population bottlenecks and density-dependent selection on cheating is required to produce cyclical oscillations and (2) the extent of frequency-dependent selection for cheating can influence the amplitude of these oscillations but does not lead to oscillations alone. Furthermore, we show that stochastic group formation (demographic stochasticity) can generate different forms of oscillation, over a longer time scale, across growth cycles. Our results provide experimentally testable hypotheses for the processes underlying cheat–cooperator dynamics
Restricting mutualistic partners to enforce trade reliance
Mutualisms are cooperative interactions between members of different species, often involving the trade of resources. Here, we suggest that otherwise- cooperative mutualists might be able to gain a benefit from actively restricting their partners’ ability to obtain resources directly, hampering the ability of the restricted partner to survive and/or reproduce without the help of the restricting mutualist. We show that: (i) restriction can be favoured when restricting individuals increase their comparative advantage and thus receive more favourable terms of trade; (ii) restriction maintains cooperation in conditions where cooperative behaviour would otherwise collapse; and (iii) restriction can lead to either an increase or decrease in a restricted individual’s fitness. We discuss the applicability of this scenario to mutualisms such as those between plants and mycorrhizal fungi. These results identify a novel conflict in mutualisms as well as several public goods dilemmas, but also demonstrate how conflict can help maintain cooperation.Publisher PDFPeer reviewe
Kin discrimination, negative relatedness, and how to distinguish between selfishness and spite
Spiteful behaviors occur when an actor harms its own fitness to inflict harm on the fitness of others. Several papers have predicted that spite can be favored in sufficiently small populations, even when the harming behavior is directed indiscriminately at others. However, it is not clear that truly spiteful behavior could be favored without the harm being directed at a subset of social partners with relatively low genetic similarity to the actor (kin discrimination, causing a negative relatedness between actor and harmed recipient). Using mathematical models, we show that (1) the evolution of spite requires kin discrimination; (2) previous models suggesting indiscriminate spite involve scenarios where the actor gains a direct feedback benefit from harming others, and so the harming is selfish rather than spiteful; (3) extreme selfishness can be favored in small populations (or, more generally, under local competition) because this is where the direct feedback benefit of harming is greatest
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