布氏田鼠合作贮食行为及其影响因素

合作贮食是社会性动物应对食物匮乏的重要对策,但其内在的生态学机制尚未阐明。本文以布氏田鼠为研究对象,根据亲缘关系划分为亲缘组和非亲缘组。在人工实验箱中录像统计不同组别合作贮食行为占用时间的差异,探究亲缘关系对合作贮食行为的影响,并利用相关性分析探究亲缘组个体对贮食的贡献—收益关系以及与贮食行为相关的个体特征因素。结果表明,在组间水平上,与非亲缘组相比,亲缘组的布氏田鼠表现更多的合作贮食。在亲缘组个体水平上,不同个体对贮食的参与度和贡献度存在很大差异。个体对合作贮食的付出与其取食的收益呈显著负相关关系,并且个体合作贮食贡献越大,其睾丸指数和睾酮含量降低越显著。研究结果说明,亲缘关系的存在有利于布氏田鼠的合作贮食,但合作贮食贡献大的个体,其繁殖受到了抑制。     

Evolution of coordinated alternating reciprocity in repeated dyadic games

A genetic algorithm incorporating mutation and crossing-over was used to investigate the evolution of social behaviour in repeated Prisoner's Dilemma, Chicken (Hawk-Dove), Battle of the Sexes, and Leader games. The results show that the strategic structure of an interaction has a crucial determining effect on the type of social behaviour that evolves. In particular, simulations using repeated Prisoner's Dilemma and Chicken (Hawk-Dove) games lead to the emergence of genes coding for symmetric reciprocity and the evolution of mutual cooperation, whereas simulations using repeated Battle of the Sexes and Leader games lead to near-fixation of genes coding for asymmetric strategic choices and the evolution of coordinated alternating reciprocity. A mechanism is suggested whereby, in games with asymmetric equilibrium points, coordinated alternating reciprocity might evolve without insight or communication between players.     

Cooperation and Competition as a Function of Zygosity in 7- to 9-Year-Old Twins

A study of 31 monozygotic (MZ) and 24 dizygotic (DZ) Singapore twin pairs (aged 7.6 to 9.7 years) is reported. MZ and DZ twins differed in cooperative and competitive behaviors measured by within-pair reactions to payoff structures designed to elicit simultaneous cooperation (SCO) or reciprocal altruism (RA) on a marble-pull task. Reciprocation entailed turn-taking in rewards. DZ twins showed greater competition than MZ twins when competing for marbles in the RA condition, as predicted. Unexpectedly, however, MZ twins were markedly more competitive than DZ twins under the SCO condition, when success on the task always rewarded both twins. The competition arose over which end of the apparatus was to be used on a given trial. This interaction between condition and zygosity could not be related to differences in parents’ reported treatment of their children or zygosity beliefs, nor did it appear to be related to differences in factors such as time spent together and shared activities. An explanation in terms of uncertain or unstable dominance in MZ twinships is suggested.     

新型复合生物乳化剂的性质及其在多环芳烃降解中的作用

对一株能利用多种石油烃的Em1菌株产生的生物乳化剂 ,采用柱层析方法进行分离纯化 ,其表面活性组分存在于氯仿、甲醇、浓盐酸混合物 (V V V =5∶1∶0 0 1 )的洗脱液中 ,挥发洗脱溶剂即为纯化的生物乳化剂。该生物乳化剂可使蒸馏水的表面张力由 72mN m降至 30mN m ,其临界胶团浓度 (CMC)为 75mg L。它不含糖类、蛋白、中性脂、磷酸基团和α 氨基酸 ,采用红外光谱 (IR)、气质联用 (GC MS)和核磁共振 (NMR)测定其化学组成和结构 ,表明其主要由十六烷酸、脂肪醇类、酯类和脂肪酰胺类等组成 ,这些物质的协同作用是该生物乳化剂高表面活性的关键。该生物乳化剂可明显促进菌株对多环芳烃的降解作用 ,可将降解率提高 2 0 % ,其促进降解的机制主要是提高多环芳烃在水中的溶解度 ,平均可提高约 1 0倍的溶解度     

Reproductive behavior,egg trading,and correlates of male mating success in the simultaneous hermaphrodite,Serranus tabacarius

Synopsis Serranus tabacarius (Serranidae), the tobaccofish, is a simultaneous hermaphrodite which belongs to a group of seabasses that exhibit a wide variety of social and mating systems. The reproductive behavior of tobaccofish is similar to other hermaphroditic seabasses, with individuals assuming sex-specific spawning behaviors that allow for the assignment of male and female roles in a mating sequence. Virtually all matings involved pairs of individuals, although streaking, an alternative male mating tactic, was observed once. Pairs engage in egg trading, where individuals divide their daily clutch into a series of sequentially released parcels and take turns releasing eggs for their partner to fertilize. Individuals mate over a late afternoon spawning period with a number of partners sequentially. Larger individuals have both more total matings and more spawning partners. Egg trading is not symmetrical, the number of male and female matings for an individual in a spawning sequence is often unequal. Overall, the ratio of male to female matings increases with individual size. Large individuals are socially dominant, chase conspecifics during the reproductive period, and are more likely to end a spawning bout with a partner immediately after mating in the male role. In addition, larger individuals are less likely to reciprocate female matings by a partner, either by only mating once (as a male) in a spawning bout or by mating consecutively as a male within a series of matings. Although larger individuals show this relative specialization in the male role, they maintain their simultaneous hermaphroditism and obtain a substantial percentage of their mating success through female function. Egg trading appears to reduce the opportunity for large individuals to specialize as pure males, and thus interacts with the environmental potential for polygamy in shaping the mating system and sex allocation pattern in this species.     

Attentiveness to eyes predicts generosity in a reputation-relevant context

Eyes play a vital role in human social interactions. In fact, some prior work indicates that simply the presence of eyes or eye-like stimuli increases people's prosocial behavior, arguably because the eyes serve as cues of being watched and thus elicit reputational concerns. The current study was designed to address two questions in this regard. First, we examined how salient the eyes are among the human features. Second, we asked whether individual differences in attentiveness to eyes (but not other human features such as ears or hands) are predictive of reputation-enhancing behavior. Using an eye-tracking paradigm, we found that participants looked longest to eyes compared to other human features. Critically, greater attentiveness to eyes correlated with greater generosity on a donation task, but only in a reputation-relevant context (i.e., when donations were public but not when they were anonymous). Attentiveness to other human features did not predict donation behavior. Eyes are thus an especially salient human feature, and attentiveness to eyes may signal individuals' concerns about their reputations.     

Dyadic associations of red Colobus and diana monkey groups in the Taï National Park, Ivory Coast

Members of the genus Colobus have been observed to associate frequently with Cercopithecus monkeys in several African sites. In the Taï National Park, Ivory Coast, one group of western red colobus was found to be in association with one particular group of diana monkeys more than could be expected by chance (Holenweg et al., 1996). We show that dyadic association is not an idiosyncrasy of these two groups, but rather a pattern that is general for our study site. All five red colobus groups we studied were closely associated with diana monkeys during more than 60% of the time. Four groups had one particular diana partner group, the fifth two different partners. Apart from the red colobus, three more primate species, the olive colobus, Campbell's monkey, and the lesser spot-nosed monkey, were also strongly attracted to diana monkeys.     

Cooperation under predation risk: a data-based ESS analysis

Two fish that jointly approach a predator in order to inspect it share the deadly risk of capture depending on the distance between them. Models are developed that seek ESS inspection distances of both single prey and pairs, based on experimental data of the risk that prey (sticklebacks) incur when they approach a predator (pike) to varying distances. Our analysis suggests that an optimal inspection distance can exist for a single fish, and for two equal fish behaving entirely cooperatively so as to maximize the fitness of the pair. Two equal fish inspecting cooperatively should inspect at an equal distance from the predator. The optimal distance is much closer to the predator for cooperative pairs than for single inspectors. However, optimal inspection for two equal fish behaving cooperatively operates across a rather narrow band of conditions relating to the benefits of cooperation. Evolutionarily stable inspection can also exist for two equal fish behaving non-cooperatively such that each acts to make a best reply (in terms of its personal fitness) to its opponent''s strategy. Non-cooperative pairs should also inspect at equal distance from the pike. Unlike the ''single fish'' and ''cooperative'' optima, which are unique inspection distances, there exists a range of ESS inspection distances. If either fish chooses to move to any point in this zone, the best reply of its opponent is to match it (move exactly alongside). Unilateral forward movement in the ''match zone'' may not be possible without some cooperation, but if the pair can ''agree'' to move forward synchronously, maintaining equal distance, inspection will occur at the nearest point in this zone to the predator. This ''near threshold'' is an ESS and is closer to the predator than the single fish optimum: pairs behaving almost selfishly can thus attain greater benefits from inspection by the protection gained from Hamilton''s dilution effect. That pairs should inspect more closely than single fish conforms with empirical findings. Phenotypic asymmetries in costs and benefits between the fish are not yet included in the model.     

Self-deception as a mediator of cooperation and defection in varying social contexts described in the iterated prisoner''s dilemma

Deception and self-deception may be two related psychological capacities serving to enhance an individual's inclusive fitness. Self-deception has been defined as any psychological act in which one thought or belief is held at the expense of another. This study was designed to test the notion that we may deceive ourselves about our own intentions or the intentions of others in order to facilitate cooperation, if the cooperative behavior has the potential to improve fitness. We may also deceive ourselves in situations where we may need to compete with others, if not competing might represent a loss of fitness. The Self-Deceptio Questionnaire was administered to 80 women and 70 men to determine their levels of self-deception. A series of vignettes, conforming to the Prisoner's Dilemma game format, were administered in questionnaire material to measure participant's predispositions to cooperate or defect in three different contexts (family, mating, and neutral). Men predicted they would be less cooperative than women over all conditions, and participants anticipated cooperating more with kin than with non-kin. Moreover, participants who were high self-deceivers chose more cooperative responses in both family and mating contexts than those with low self-deception scores. Finally, the three-way interaction among sex, context, and level of self-deception suggested that the role of selfdeception in cooperation may vary according to the sex of the individual and the context.     

Sample path analysis of contribution and reward in cooperative groups

Explaining cooperative behavior is one of the major challenges in both biology and human society. The individual reward in cooperative group depends on how we share the rewards in the group. Thus, the group size dynamics in a cooperative group and reward-allocation rule seem essential to evaluate the emergence of cooperative groups. We apply a sample path-based analysis called an extension of Little's formula to general cooperative group. We show that the expected reward is insensitive to the specific reward-allocation rule and probabilistic structure of group dynamics, and the simple productivity condition guarantees the expected reward to be larger than the average contribution. As an example, we take social queues to see the insensitivity result in detail.