The coevolution of altruism and punishment: role of the selfish punisher

Punishment is an important mechanism promoting the evolution of altruism among non-relatives. We investigate the coevolution of altruism and punitive behavior, considering four possible strategies: the altruist punisher (AP, a cooperator who punishes defectors), the altruist non-punisher (AN, a pure cooperator), the selfish punisher (SP, a defector who punishes defectors), and the selfish non-punisher (SN, a pure defector). The SP uses a paradoxical strategy as it punishes other defectors. We analyse the effects of SP and AN on the coevolution of altruism and punishment. We study both the score-dependent viability model (whereby the game's score affects survivorship only) and the score-dependent fertility model (whereby the score affects fertility only). In the viability model of a completely mixed population, SP first drives out SN, and hence it helps cooperators (AP and AN) to evolve. In contrast, in the fertility model of a completely mixed population, neither SP nor AN helps the evolution of cooperation. In both the viability and fertility models of a lattice-structured population, SP promotes the spread of AP. In contrast, AN discourages the evolution of AP. These results can be understood that punishment is a form of spite behavior, paying a cost to reduce the fitness of the opponents, and that different models give different magnitude of advantage to spite behavior.     

Mitochondrial ribosomes in a trypanosome

The nature, and even the existence, of trypanosome mitochondrial ribosomes has been the subject of some debate. We investigated this further in the insect trypanosome, Crithidia fasciculata. In sucrose gradients of parasite lysates, mitochondrial ribosomal RNA co-sediments at approximately 35S with nascent peptides synthesized in the presence of the cytosolic translational inhibitor, cycloheximide. Co-sedimenting peptides in this peak are much reduced when the parasites are treated with the bacterial translational inhibitor, chloramphenicol. In CsCl gradients this peak resolves at a buoyant density of 1.42 g/cm(3), a value typical for mito-ribosomes. Electron microscopy of peak material shows particles smaller than cytosolic ribosomes, but with characteristic ribosomal shapes. We propose that these particles represent the parasite's mitochondrial ribosomes.     

Geometry for a selfish foraging group: a genetic algorithm approach

The advantages of group living are not shared equally among all group members and these advantages may depend on the spatial position occupied by a forager within the group. For instance, it is thought that socially dominant individuals prefer the predator-safe central position of groups forcing subordinates to the periphery. Uneven spread of benefits among group members can occur when some animals (the scroungers) parasitically exploit the food findings of other foragers (the producers). Here we focus on how playing producer or scrounger affects an individual''s spatial position within a group. We model the movement of foraging animals playing scrounger or producer using a spatially explicit simulation and use a genetic algorithm to establish movement rules. We find that groups containing producers and scroungers are more compact compared to an equivalent group of producers only. Furthermore, the position occupied by strategies varies: scroungers are mainly found in central positions, while producers in the periphery, suggesting that the best position for strategies differs. Dominants, therefore, should prefer movement rules which lead to central positions because of the positional benefits provided to the scrounger strategy they use. Moreover, position within a group will introduce an asymmetry among otherwise phenotypically symmetric individuals.     

The enigmatic nature of altruism in organ transplantation: a cross-cultural study of transplant physicians' views on altruism

Background

Although altruism is a key principle in our current organ donation and transplantation system, the meanings and implications of the term have been widely debated. Recently, a new type of living organ donation--anonymous and non-directed, also called living altruistic donation (LAD)--has brought the issue into sharper focus. Transplant physicians' views on altruism might influence their attitudes and actions toward living altruistic donors. This study aimed to explore such views among transplant physicians in France and Quebec.

Findings

A total of 27 French and 19 Quebec transplant physicians participated in individual, semi-structured interviews between October 2004 and December 2005. The majority of these participants associated altruism with gratuitousness and saw altruistic acts as multiple and varied, ranging from showing consideration to saving a person's life.

Conclusions

The transplant physicians' discourses on altruism were quite diverse, leading us to question the relevance of the concept in organ transplantation and the appropriateness of the term "living altruistic donation."

     

Mutualism among safe, selfish sentinels: a dynamic game

Sentinels are group members that watch from prominent positions. Sentinel interchanges often appear orderly, and groups with sentinels rarely have zero or many sentinels. A dynamic game was constructed to examine if these observations about sentinels could be based on selfish actions by individual group members. In this game, each group member chose to forage or be a sentinel based on its own energetic state and the actions of others. Sentinels received a selfish antipredator benefit if their ability to detect approaching predators more than compensated for their increased exposure to undetected predators. Provided sentinels were relatively safe and that detection information spread to other group members when sentinels detected predators, sentinels appeared highly coordinated for all combinations of parameters. This apparent coordination was based on mutualism because each individual gained by being a sentinel when other group members were not (and foraging when other group members were being sentinels). The model was very robust, but exact level of sentinel behavior varied somewhat with changes in foraging and predation parameters. This model could best be tested by testing its assumptions about sentinel safety, foraging-predation trade-offs, and information transfer in groups.     

Evolution,altruism and cognitive architecture: a critique of Sober and Wilson’s argument for psychological altruism

Sober and Wilson have propose a cluster of arguments for the conclusion that “natural selection is unlikely to have given us purely egoistic motives” and thus that psychological altruism is true. I maintain that none of these arguments is convincing. However, the most powerful of their arguments raises deep issues about what egoists and altruists are claiming and about the assumptions they make concerning the cognitive architecture underlying human motivation.     

Hidden altruism in a real-world setting

Concerns for reputation can promote cooperative behaviour. Individuals that behave cooperatively stand to benefit if they gain in influence, status or are more likely to be chosen as interaction partners by others. Most theoretical and empirical models of cooperation predict that image score will increase with cooperative contributions. Individuals are therefore expected to make higher contributions when observed by others and should opt to make contributions publicly rather than privately, particularly when contributions are higher than average. Here, however, I find the opposite effect. Using data from an online fundraising website, I show that donors are more likely to opt for anonymity when making extremely low and extremely high donations. Mid-range donations, on the other hand, are typically publicized. Recent work has shown that extremely generous individuals may be ostracized or punished by group members. The data presented here suggest that individuals may hide high donations to avoid these repercussions.     

Host-parasite interactions and trypanosome morphogenesis: a flagellar pocketful of goodies

Trypanosomes are characterised by the possession of a single flagellum and a subpellicular microtubule cytoskeleton. The flagellum is more than an organelle for motility; its position and polarity along with the sub-pellicular cytoskeleton enables the morphogenesis of a distinct flagellar pocket and the flagellar basal body is responsible for positioning and segregating the kinetoplast--the mitochondrial genome. Recent work has highlighted the molecules and morphogenesis of these cytoskeletal/flagellum structures and how dynamic events, occurring in the flagellar pocket and kinetoplast, are critical for host-parasite interactions.     

Grooming and agonistic support: a meta-analysis of primate reciprocal altruism

Grooming and agonistic support are 2 common primate behaviorsthat have been hypothesized to constitute examples of reciprocalaltruism. In particular, because primates often direct theirgrooming up the dominance hierarchy, it has been suggested thatthey may exchange grooming for agonistic support. Empiricaltests of this hypothesis have resulted in highly inconsistentfindings. I synthesized the published literature on the relationbetween grooming and agonistic support in primates using modernmeta-analytical techniques. A meta-analysis of 36 studies carriedout on 14 different species showed that a significant positiverelation exists between grooming and agonistic support (weightedaverage r = 0.154, corrected for publication bias). These findingssuggest that grooming and agonistic support may have evolvedas part of a system of low-cost reciprocal altruism. They alsohighlight the potential of meta-analysis in tackling the studyof behavioral phenomena characterized by low overall frequencyand small effect sizes.     

Inside and outside of the trypanosome flagellum:a multifunctional organelle

Amongst the earliest eukaryotes, trypanosomes have developed conventional organelles but sometimes with extreme features rarely seen in other organisms. This is the case of the flagellum, containing conventional and unique structures whose role in infectivity is still enigmatic.     

Prosocial primates: selfish and unselfish motivations

Non-human primates are marked by well-developed prosocial and cooperative tendencies as reflected in the way they support each other in fights, hunt together, share food and console victims of aggression. The proximate motivation behind such behaviour is not to be confused with the ultimate reasons for its evolution. Even if a behaviour is ultimately self-serving, the motivation behind it may be genuinely unselfish. A sharp distinction needs to be drawn, therefore, between (i) altruistic and cooperative behaviour with knowable benefits to the actor, which may lead actors aware of these benefits to seek them by acting cooperatively or altruistically and (ii) altruistic behaviour that offers the actor no knowable rewards. The latter is the case if return benefits occur too unpredictably, too distantly in time or are of an indirect nature, such as increased inclusive fitness. The second category of behaviour can be explained only by assuming an altruistic impulse, which—as in humans—may be born from empathy with the recipient''s need, pain or distress. Empathy, a proximate mechanism for prosocial behaviour that makes one individual share another''s emotional state, is biased the way one would predict from evolutionary theories of cooperation (i.e. by kinship, social closeness and reciprocation). There is increasing evidence in non-human primates (and other mammals) for this proximate mechanism as well as for the unselfish, spontaneous nature of the resulting prosocial tendencies. This paper further reviews observational and experimental evidence for the reciprocity mechanisms that underlie cooperation among non-relatives, for inequity aversion as a constraint on cooperation and on the way defection is dealt with.     

Inbreeding depresses altruism in a cooperative society

In some animal species, individuals regularly breed with relatives, including siblings and parents. Given the high fitness costs of inbreeding, evolutionary biologists have found it challenging to understand the persistence of these inbred societies in nature. One appealing but untested explanation is that early life care may create a benign environment that offsets inbreeding depression, allowing inbred societies to evolve. We test this possibility using 21 years of data from a wild cooperatively breeding mammal, the banded mongoose, a species where almost one in ten young result from close inbreeding. We show that care provided by parents and alloparents mitigates inbreeding depression for early survival. However, as adults, inbred individuals provide less care, reducing the amount of help available to the next generation. Our results suggest that inbred cooperative societies are rare in nature partly because the protective care that enables elevated levels of inbreeding can be reduced by inbreeding depression.     

Androgenesis: a review through the study of the selfish shellfish Corbicula spp

Among the asexual reproductive modes, androgenesis is probably one of the most astonishing and least studied mechanisms. In this 'paternal monopolization', the maternal nuclear genome fails to participate in zygote development and offspring are paternal nuclear clones. Obligate androgenesis is known in only a few organisms, including multiple species of clam in the genus Corbicula. Corbicula is a good system to review the evolutionary consequences of this 'all-male asexuality' because the cytological mechanisms of androgenetic reproduction have been described. In Corbicula, sperm are unreduced and, after fertilization, the maternal nuclear chromosomes are extruded as two polar bodies. Hermaphroditic lineages of Corbicula have a worldwide distribution and seem to reproduce through androgenesis, whereas their sexual relatives have restricted ranges. The invasive success of these androgenetic Corbicula lineages may be linked to their asexual mode of reproduction. We review the phenomenon of androgenesis, focusing on evolutionary perspectives, using the genus Corbicula as an exemplar system.