Donors to charity gain in both indirect reciprocity and political reputation.

Darwinian evolution can explain human cooperative behaviour among non-kin by either direct or indirect reciprocity. In the latter case one does not expect a return for an altruistic act from the recipient as with direct reciprocity, but from another member of the social group. However, the widespread human behaviour of donating to poor people outside the social group, for example, to charity organizations, that are unlikely to reciprocate indirectly and thus are equivalent to defectors in the game is still an evolutionary puzzle. Here we show experimentally that donations made in public to a well-known relief organization resulted both in increased income (that the donors received from the members of their group) and in enhanced political reputation (they were elected to represent the interests of their group). Donations may thus function as an honest signal for one's social reliability

Reputation helps solve the ''tragedy of the commons''

The problem of sustaining a public resource that everybody is free to overuse-the ''tragedy of the commons''(1-7)-emerges in many social dilemmas, such as our inability to sustain the global climate. Public goods experiments(4), which are used to study this type of problem, usually confirm that the collective benefit will not be produced. Because individuals and countries often participate in several social games simultaneously, the interaction of these games may provide a sophisticated way by which to maintain the public resource. Indirect reciprocity(8), ''give and you shall receive'', is built on reputation and can sustain a high level of cooperation, as shown by game theorists(9-11). Here we show, through alternating rounds of public goods and indirect reciprocity games, that the need to maintain reputation for indirect reciprocity maintains contributions to the public good at an unexpectedly high level. But if rounds of indirect reciprocation are not expected, then contributions to the public good drop quickly to zero. Alternating the games leads to higher profits for all players. As reputation may be a currency that is valid in many social games, our approach could be used to test social dilemmas for their solubility

Water quality variability in a deep (8 m) reservoir for simultaneous fish farming and field irrigation

The paper presents water quality studies carried out in a deep (8 m) dual purpose reservoir in the Jordan Valley during the 1991 fish culture season. In Israeli dual purpose reservoirs for fish culture and field crop irrigation, two processes overlap: (1) an increase of loading through the culture season due to fish growth and the corresponding increase of feed inputs, and (2) a decrease of the water level during the dry summer due to irrigation. These two trends strongly affect the water quality in which fish grow, and hence the success or failure of the fish culture. The water quality changes in time (through months and daily) and space (vertically and horizontally) are analyzed in relation to biological transformations, hydrological processes and reservoir management. Results are compared to shallow (4 m) dual purpose reservoirs located in the Coastal area of the country, where the seasonal stratification observed in deep reservoirs does not develop. It is concluded that fish culture management in deep reservoirs where seasonal stratification develops requires special care and a follow up of stratification breaking, and that seasonal stratification should be avoided when designing new reservoirs which include fish farming among their purposes

Biased Distributions and Decay of Long Interspersed Nuclear Elements in the Chicken Genome

The genomes of birds are much smaller than mammalian genomes, and transposable elements (TEs) make up only 10% of the chicken genome, compared with the 45% of the human genome. To study the mechanisms that constrain the copy numbers of TEs, and as a consequence the genome size of birds, we analyzed the distributions of LINEs (CR1's) and SINEs (MIRs) on the chicken autosomes and Z chromosome. We show that (1) CR1 repeats are longest on the Z chromosome and their length is negatively correlated with the local GC content; (2) the decay of CR1 elements is highly biased, and the 5′-ends of the insertions are lost much faster than their 3′-ends; (3) the GC distribution of CR1 repeats shows a bimodal pattern with repeats enriched in both AT-rich and GC-rich regions of the genome, but the CR1 families show large differences in their GC distribution; and (4) the few MIRs in the chicken are most abundant in regions with intermediate GC content. Our results indicate that the primary mechanism that removes repeats from the chicken genome is ectopic exchange and that the low abundance of repeats in avian genomes is likely to be the consequence of their high recombination rates

Impact of weather on a lake ecosystem, assessed by cyclo-stationary MCCA of long-term observations.

Temperate lake ecosystems are generally characterized by a strong annual cycle, and the relationships between observations of such ecosystems and external forcing variables can exhibit a complex structure. Furthermore, the observational data record is often short. This makes it difficult to assess the relationships between external forcing factors and their impact on the biological succession. Cycle-stationary maximum cross-covariance analysis (MCCA) allows the effects of seasonality to be modeled in a flexible way, and we describe this statistical technique in detail. MCCA offers an objective method to approximate the high-dimensional total cross-covariance structure by defining "weighting" patterns. With a predictor set of reduced dimension, a suitable regression between forcing variables and ecological response variables can be set up. Cyclo-stationary MCCA is used here to analyze the influence of meteorological variables (air temperature, wind speed, global radiation, humidity, and precipitation) on 13 biological and biogeochemical indicator variables of Plussee, a small lake in northern Germany. The main weather influence on the indicator variables was found to be connected to winter temperature. From the covariance structure the following major signals were detected to be related to higher winter temperature: a more intense spring algal maximum, a higher zooplankton biomass during the algal maximum, a less intense loss of nutrients to the hypolimnion, a higher summer bloom together with changes in the nutrient concentrations, and stronger oxygen consumption in autum

I Dare You to Punish Me—Vendettas in Games of Cooperation

<div><p>Everybody has heard of neighbours, who have been fighting over some minor topic for years. The fight goes back and forth, giving the neighbours a hard time. These kind of reciprocal punishments are known as vendettas and they are a cross-cultural phenomenon. In evolutionary biology, punishment is seen as a mechanism for maintaining cooperative behaviour. However, this notion of punishment excludes vendettas. Vendettas pose a special kind of evolutionary problem: they incur high costs on individuals, i.e. costs of punishing and costs of being punished, without any benefits. Theoretically speaking, punishment should be rare in dyadic relationships and vendettas would not evolve under natural selection. In contrast, punishment is assumed to be more efficient in group environments which then can pave the way for vendettas. Accordingly, we found that under the experimental conditions of a prisoner’s dilemma game, human participants punished only rarely and vendettas are scarce. In contrast, we found that participants retaliated frequently in the group environment of a public goods game. They even engaged in cost-intense vendettas (i.e. continuous retaliation), especially when the first punishment was unjustified or ambiguous. Here, punishment was mainly targeted at defectors in the beginning, but provocations led to mushrooming of counter-punishments. Despite the counter-punishing behaviour, participants were able to enhance cooperation levels in the public goods game. Few participants even seemed to anticipate the outbreak of costly vendettas and delayed their punishment to the last possible moment. Overall, our results highlight the importance of different social environments while studying punishment as a cooperation-enhancing mechanism.</p> </div

Frequencies where a participant in the public goods game punished a subgroup member in punishment round 1 and either a vendetta or no vendetta occurred (pooled over all periods).

<p>Punishment was classified as justified if a contributing participant punished a non-contributor (n = 106, individual level); it was termed unjustified if a non-contributing participant punished a contributor (n = 26); all other cases were rather ambiguous and not further classified (n = 42).</p