Evolution of dispersal under spatio-temporal heterogeneity.

Theoretical studies over the past decades have revealed various factors that favor or disfavor the evolution of dispersal. Among these, environmental heterogeneity is one driving force that can impact dispersal traits, because dispersing individuals can obtain a fitness benefit through finding better environments. Despite this potential benefit, some previous works have shown that the existence of spatial heterogeneity hinders evolution of dispersal.

Evolutionary stability of cooperation in indirect reciprocity under noisy and private assessment.

Indirect reciprocity is a mechanism that explains large-scale cooperation in humans. In indirect reciprocity, individuals use reputations to choose whether or not to cooperate with a partner and update others' reputations. A major question is how the rules to choose their actions and the rules to update reputations evolve.

Reputation structure in indirect reciprocity under noisy and private assessment.

Evaluation relationships are pivotal for maintaining a cooperative society. A formation of the evaluation relationships has been discussed in terms of indirect reciprocity, by modeling dynamics of good or bad reputations among individuals. Recently, a situation that individuals independently evaluate others with errors (i.

Non-zero-sum neutrality test for the tropical rain forest community using long-term between-census data.

For community ecologists, "neutral or not?" is a fundamental question, and thus, rejecting neutrality is an important first step before investigating the deterministic processes underlying community dynamics. Hubbell's neutral model is an important contribution to the exploration of community dynamics, both technically and philosophically. However, the neutrality tests for this model are limited by a lack of statistical power, partly because the zero-sum assumption of the model is unrealistic.

Impact of social dominance on the evolution of individual learning.

A major question in cultural-evolution studies is the phenotype of individual learners. Evidence suggests that social dominance is one influential factor, where socially subordinate individuals are more apt to learning of trial-and-error type than the dominants. Despite the accumulating evidence, the evolutionary dynamics leading to such outcomes remains largely elusive, partly because of the cost of individual learning.

Fecundability and Sterility by Age: Estimates Using Time to Pregnancy Data of Japanese Couples Trying to Conceive Their First Child with and without Fertility Treatment.

Fecundability, the probability of conception in a month or in a menstrual cycle, varies across and within age groups for both women and men. Fertility treatment has become common in a number of countries including Japan, but its impact on the age pattern of fecundability is unknown. By utilizing the previously collected data on time to pregnancy (TTP) of Japanese couples trying to conceive their first child, the present study aimed to estimate fecundability and sterility by women's age and to assess how the estimates may differ by including or excluding assisted conceptions.

Coevolutionary dynamics of genetic traits and their long-term extended effects under non-random interactions.

Organisms continuously modify their living conditions via extended genetic effects on their environment, microbiome, and in some species culture. These effects can impact the fitness of current but also future conspecifics due to non-genetic transmission via ecological or cultural inheritance. In this case, selection on a gene with extended effects depends on the degree to which current and future genetic relatives are exposed to modified conditions.

The components of directional and disruptive selection in heterogeneous group-structured populations.

We derive how directional and disruptive selection operate on scalar traits in a heterogeneous group-structured population for a general class of models. In particular, we assume that each group in the population can be in one of a finite number of states, where states can affect group size and/or other environmental variables, at a given time. Using up to second-order perturbation expansions of the invasion fitness of a mutant allele, we derive expressions for the directional and disruptive selection coefficients, which are sufficient to classify the singular strategies of adaptive dynamics.

Familiarity with humans affect dogs' tendencies to follow human majority groups.

Recently, copying others' behaviour has attracted attention among researchers. It aids individuals in reducing uncertainty about the knowledge of the environment and helps them in acquiring an adaptive behaviour at a lower cost than by learning it by themselves. Among the copying strategies, conformity, which is the copying of behavioural decisions presented by the majority, has been well studied and reported in many animals, including humans.

Evolution of dispersal in a spatially heterogeneous population with finite patch sizes.

Dispersal is one of the fundamental life-history strategies of organisms, so understanding the selective forces shaping the dispersal traits is important. In the Wright's island model, dispersal evolves due to kin competition even when dispersal is costly, and it has traditionally been assumed that the living conditions are the same everywhere. To study the effect of spatial heterogeneity, we extend the model so that patches may receive different amounts of immigrants, foster different numbers of individuals, and give different reproduction efficiency to individuals therein.

Evolution of cumulative culture for niche construction.

A mathematical model of the joint evolution of learning and niche construction in a spatially subdivided population is described, in which culture is used to practice niche construction and can evolve by accumulating small improvements over generations. Individuals allocate their lifetimes to social learning, individual learning, niche construction to improve the environment, and exploitation of resources according to their genetically determined strategies. The coordinated optimal strategy (COS) is defined as the allocation strategy which maximizes the equilibrium fecundity of the population, as opposed to the convergence stable strategy (CSS), which is the strategy favored by natural selection.

Evolution of self-limited cell division of symbionts.

In mutualism between unicellular hosts and their endosymbionts, symbiont's cell division is often synchronized with its host's, ensuring the permanent relationship between endosymbionts and their hosts. The evolution of synchronized cell division thus has been considered to be an essential step in the evolutionary transition from symbionts to organelles. However, if symbionts would accelerate their cell division without regard for the synchronization with the host, they would proliferate more efficiently.

Spatial heterogeneity and evolution of fecundity-affecting traits.

It is widely recognized that spatial structure in a population has some, and occasionally great, impacts on ecological and evolutionary dynamics. However, it has been observed that in the homogeneous Wright's island model with a certain standard demographic assumption, spatial structure does not affect the fitness gradient of a fecundity-affecting trait. The location and convergence stability of singular strategies thus remain unchanged.

Genealogies and ages of cultural traits: An application of the theory of duality to the research on cultural evolution.

A finite-population, discrete-generation model of cultural evolution is described, in which multiple discrete traits are transmitted independently. In this model, each newborn may inherit a trait from multiple cultural parents. Transmission fails with a positive probability unlike in population genetics.

Emergence of opinion leaders in reference networks.

Individuals often refer to opinions of others when they make decisions in the real world. Our question is how the people's reference structure self-organizes when people try to provide correct answers by referring to more accurate agents. We constructed an adaptive network model, in which each node represents an agent and each directed link represents a reference.

Evolution of emotional contagion in group-living animals.

Emotional contagion refers to an instantaneous matching of an emotional state between a subject and an object. It is believed to form one of the bases of empathy and it causes consistent group behavior in many animals. However, how this emotional process relates to group size remains unclear.

Forward and backward evolutionary processes and allele frequency spectrum in a cancer cell population.

A cancer grows from a single cell, thereby constituting a large cell population. In this work, we are interested in how mutations accumulate in a cancer cell population. We provide a theoretical framework of the stochastic process in a cancer cell population and obtain near exact expressions of allele frequency spectrum or AFS (only continuous approximation is involved) from both forward and backward treatments under a simple setting; all cells undergo cell divisions and die at constant rates, b and d, respectively, such that the entire population grows exponentially.

Inclusive fitness analysis of cumulative cultural evolution in an island-structured population.

The success of humans on the globe is largely supported by our cultural excellence. Our culture is cumulative, meaning that it is improved from generation to generation. Previous works have revealed that two modes of learning, individual learning and social learning, play pivotal roles in the accumulation of culture.

The effect of fecundity derivatives on the condition of evolutionary branching in spatial models.

By investigating metapopulation fitness, we present analytical expressions for the selection gradient and conditions for convergence stability and evolutionary stability in Wright's island model in terms of fecundity function. Coefficients of each derivative of fecundity function appearing in these conditions have fixed signs. This illustrates which kind of interaction promotes or inhibits evolutionary branching in spatial models.

Stable polymorphism of cooperators and punishers in a public goods game.

The role of punishment in the maintenance of cooperation has been emphasized recently. However, the maintenance of punishment is not an obvious consequence because punishment itself is also a public good; it is costly to perform and hence vulnerable to exploitation. For example, cooperative punishers, who help others and punish free riders, are disadvantageous in competition against pure cooperators, who cooperate but do not punish free riders.

Robustness of linkage strategy that leads to large-scale cooperation.

One of the most well-known models to characterize cooperation among unrelated individuals is Social dilemma (SD). However there is no consensus about how to solve the SD by itself. Since SDs are often embedded in other social interactions, including indirect reciprocity games (IR), human can coordinate their behaviors across multiple games.

The price of being seen to be just: an intention signalling strategy for indirect reciprocity.

Cooperation among strangers is a marked characteristic of human sociality. One prominent evolutionary explanation for this form of human cooperation is indirect reciprocity, whereby each individual selectively helps people with a 'good' reputation, but not those with a 'bad' reputation. Some evolutionary analyses have underscored the importance of second-order reputation information (the reputation of a current partner's previous partner) for indirect reciprocity as it allows players to discriminate justified 'good' defectors, who selectively deny giving help to 'bad' partners, from unjustified 'bad' defectors.

Population size vs. social connectedness - A gene-culture coevolutionary approach to cumulative cultural evolution.

It has long been debated if population size is a crucial determinant of the level of culture. While empirical results are mixed, recent theoretical studies suggest that social connectedness between people may be a more important factor than the size of the entire population. These models, however, do not take into account evolutionary responses of learning strategies determining the mode of transmission and innovation and are hence not suitable for predicting the long-term implications of parameters of interest.

Does Sexual Conflict between Mother and Father Lead to Fertility Decline? : A Questionnaire Survey in a Modern Developed Society.

Fertility decline is a great challenge to evolutionary approaches to human behavior. In this study, we apply the perspective of sexual conflict between mother and father to the fertility decline. We predict that, under serial monogamy allowing for mate changes, the ideal number of children for women should be smaller than that for men, because the cost of reproduction for women should be higher than that for men.