Synergy and Group Size in Microbial Cooperation

Microbes produce many molecules that are important for their growth and development, and the consumption of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Though the production of these public goods molecules has been studied intensely, little is known of how the benefits accrued and costs incurred depend on the quantity of public good molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density with a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether or not and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an “evolutionary trap” which can stymie the establishment and maintenance of cooperation. By allowing density dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results for experimental design

Pathways to social evolution: reciprocity, relatedness, and synergy

Many organisms live in populations structured by space and by class, exhibit plastic responses to their social partners, and are subject to non-additive ecological and fitness effects. Social evolution theory has long recognized that all of these factors can lead to different selection pressures but has only recently attempted to synthesize how these factors interact. Using models for both discrete and continuous phenotypes, we show that analyzing these factors in a consistent framework reveals that they interact with one another in ways previously overlooked. Specifically, behavioral responses (reciprocity), genetic relatedness, and synergy interact in non-trivial ways that cannot be easily captured by simple summary indices of assortment. We demonstrate the importance of these interactions by showing how they have been neglected in previous synthetic models of social behavior both within and between species. These interactions also affect the level of behavioral responses that can evolve in the long run; proximate biological mechanisms are evolutionarily stable when they generate enough responsiveness relative to the level of responsiveness that exactly balances the ecological costs and benefits. Given the richness of social behavior across taxa, these interactions should be a boon for empirical research as they are likely crucial for describing the complex relationship linking ecology, demography, and social behavior.Comment: 4 figure

Joint evolution of multiple social traits: a kin selection analysis

General models of the evolution of cooperation, altruism and other social behaviours have focused almost entirely on single traits, whereas it is clear that social traits commonly interact. We develop a general kin-selection framework for the evolution of social behaviours in multiple dimensions. We show that whenever there are interactions among social traits new behaviours can emerge that are not predicted by one-dimensional analyses. For example, a prohibitively costly cooperative trait can ultimately be favoured owing to initial evolution in other (cheaper) social traits that in turn change the cost-benefit ratio of the original trait. To understand these behaviours, we use a two-dimensional stability criterion that can be viewed as an extension of Hamilton's rule. Our principal example is the social dilemma posed by, first, the construction and, second, the exploitation of a shared public good. We find that, contrary to the separate one-dimensional analyses, evolutionary feedback between the two traits can cause an increase in the equilibrium level of selfish exploitation with increasing relatedness, while both social (production plus exploitation) and asocial (neither) strategies can be locally stable. Our results demonstrate the importance of emergent stability properties of multidimensional social dilemmas, as one-dimensional stability in all component dimensions can conceal multidimensional instability

Punishment in Public Goods games leads to meta-stable phase transitions and hysteresis

The evolution of cooperation has been a perennial problem in evolutionary biology because cooperation can be undermined by selfish cheaters who gain an advantage in the short run, while compromising the long-term viability of the population. Evolutionary game theory has shown that under certain conditions, cooperation nonetheless evolves stably, for example if players have the opportunity to punish cheaters that benefit from a public good yet refuse to pay into the common pool. However, punishment has remained enigmatic because it is costly, and difficult to maintain. On the other hand, cooperation emerges naturally in the Public Goods game if the synergy of the public good (the factor multiplying the public good investment) is sufficiently high. In terms of this synergy parameter, the transition from defection to cooperation can be viewed as a phase transition with the synergy as the critical parameter. We show here that punishment reduces the critical value at which cooperation occurs, but also creates the possibility of meta-stable phase transitions, where populations can "tunnel" into the cooperating phase below the critical value. At the same time, cooperating populations are unstable even above the critical value, because a group of defectors that are large enough can "nucleate" such a transition. We study the mean-field theoretical predictions via agent-based simulations of finite populations using an evolutionary approach where the decisions to cooperate or to punish are encoded genetically in terms of evolvable probabilities. We recover the theoretical predictions and demonstrate that the population shows hysteresis, as expected in systems that exhibit super-heating and super-cooling. We conclude that punishment can stabilize populations of cooperators below the critical point, but it is a two-edged sword: it can also stabilize defectors above the critical point.Comment: 22 pages, 9 figures. Slight title change, version that appears in Physical Biolog

BANKS CONSOLIDATION IN NIGERIA: A SYNERGISTIC HARVEST

In order to strengthen the competitive and operational capabilities of banks in Nigeria with a view towards returning global and public confidence to the Nigerian banking sector and the economy in general, the Central Bank of Nigeria instituted a banking reform which saw most of the then existing 89 banks merging with each other. It was earlier speculated in some financial analysis quarters that the exercise might turn out to be one of those overblown hypes of an ailing economy. This, however, has turned out to be the opposite as most post-merger results tend to highlight that financial synergies exist. This paper tries to evaluate the authenticity of this assertion. To do this, pre-merger and post merger financial statements of 4 consolidated banks were obtained, adjusted, carefully analyzed and compared. The result revealed that all the four merger groups produced in addition to operational and relational synergy, financial gains far more than the 2+2=5 synergistic effects. The validating two-way ANOVA test also revealed that variations in shareholders funds can significantly affect the value of total assets of a bank

Joint venture instability: a life cycle approach

Joint ventures represent one of the most fascinating developments in international business. In the last few decades, the rate of joint venture formation has accelerated dramatically. Nowadays joint ventures are much more widespread and occur in industries like telecommunications, biotechnology etc. At the same time, however, it must be noted that joint ventures are very unstable. In this paper we survey the phenomenon of joint venture instability. We draw on the relative recent theoretical literature on joint venture instability to provide a unified explanation of joint venture life-cycles, formation, as well as breakdown. Further, we do this for both research oriented, as well as production joint ventures.Joint ventures; formation; breakdown; synergy; moral hazard; learning

Small dams and social capital in Yemen: how assistance strategies affect local investment and institutions

Dams / Investment / Development aid / Irrigated farming / Villages / Water delivery / Yemen

Optical illusion? The growth and development of the Optics Valley of China

The ‘cultivated’ nature of the Chinese science parks, against the background of a transitional economy, differentiates them from spontaneous and cooperative Western models, and is a phenomenon deserving close examination. We study the dynamics and features of the so-called Optics Valley of China (OVC) in Hubei, aiming to explore the characteristics of an embryonic local innovation system constructed in a less-favoured region. The results show that institutional factors are the leading forces in a cultivated science park like the OVC. However, along with the shifting focus of the local government, the OVC’s industrial scale has remained small and its industrial chain has remained incomplete. Moreover, the lack of trust and interactions between various components in this innovation system has been highly noticeable. All these features may be seen as warnings to the OVC that a revision of this innovation system is needed in order to avoid the fate of becoming an ‘optical illusion’