Phylogenetics And Molecular Evolution Of Highly Eusocial Wasps

Societies where workers sacrifice their own reproduction and cooperatively nurture the offspring of a reproductive queen caste have originated repeatedly across the Tree of Life. The attainment of such reproductive division of labor enabled the evolution of remarkable diversity in development, behavior, and social organization in the Hymenoptera (ants, bees, and wasps). Wasps of the family Vespidae exhibit a gamut of social levels, ranging from solitary to highly social behavior. The highly social yellowjackets and hornets (Vespinae) have well developed differences in form and function between queens and workers, large colony sizes, and intricate nest architecture. Moreover, certain socially parasitic species in the Vespinae have secondarily lost the worker caste and rely entirely on the workers of a host species to ensure the survival of parasitic offspring. Understanding the evolution of behavioral traits in the Vespinae over long periods of time would be greatly enhanced by a robust hypothesis of historical relationships. In this study, I analyze targeted genes and transcriptomes to address three goals. First, infer phylogenetic relationships within yellowjackets (Vespula and Dolichovespula) and hornets (Vespa and Provespa). Second, test the hypothesis that social parasites are more closely related to their hosts than to any other species (Emery\u27s rule). Third, test the protein evolution hypothesis, which states that accelerated evolution of protein coding genes and positive selection operated in the transition to highly eusocial behavior. The findings of this study challenge the predominant understanding of evolutionary relationships in the Vespinae. I show that yellowjacket genera are not sister lineages, instead recovering Dolichovespula as more closely related to the hornets, and placing Vespula as sister to all other vespine genera. This implies that traits such as large colony size and high paternity are mostly restricted to a particular evolutionary trajectory (Vespula) from an early split in the Vespinae. I demonstrate that obligate and facultative social parasites do not share immediate common ancestry with their hosts, indicating that socially parasitic behavior likely evolved independently of host species. Moreover, obligate social parasites share a unique evolutionary history, suggesting that their parasitic behavior might have a genetic component. Lastly, I analyze transcriptomic data to infer a phylogeny of vespid wasps and use this phylogeny to discover lineage-specific signatures of positive selection. I identify more than two hundred genes showing signatures of positive selection on the branch leading to the highly eusocial yellowjackets and hornets. These positively selected genes involve functions related mainly to carbohydrate metabolism and mitochondrial activity, in agreement with insights from studies of bees and ants. Parallels of functional categories for genes under positive selection suggests that at the molecular level the evolution of highly eusocial behavior across the Hymenoptera might have followed similar and narrow paths

Three essays on female labor supply and assortative mating

This thesis focuses on female labor supply, human capital and assortative mating. The first chapter examines the link between the gap in spousal education and the labor supply behavior of married women over the life-cycle. Based on data from the 1965-2011 March Current Population Surveys and the National Longitudinal Study of Youth 1979, it documents that, all else equal, if the wife's education exceeds her husband's then she is substantially more likely to be employed than if she is less educated than her husband (up to 14.5 percentage points). A dynamic life-cycle model of endogenous marriage and labor supply decisions in a collective framework is formulated and structurally estimated. It establishes that the link between a husband's educational attainment and a wife's labor supply decision, at the time of marriage, produces dynamic effects due to human capital accumulation and implied wage growth. Returns to experience account for 57 percent of the employment gap observed between women who had married "down" and those who married "up". Counterfactuals also indicate that, alone, the changes in assortative mating patterns across cohorts, which are implied by the changes in the marginal distributions of education, are able to explain a sizable proportion (roughly 25 percent) of the observed rise in married women's labor force participation. The second chapter analyzes the evolution of educational assortative mating along racial lines. Previous studies suggest that preferences have changed across cohorts in the US to produce an increase in assortative mating. The analysis in the second chapter challenges the metric of measurement for assortative mating and shows that educational assortative mating has been stable over time for blacks and whites despite social and economic changes that might have impacted individual's incentives to form a marriage. The third chapter proposes a novel instrument for catholic school attendance that exploits the abrupt shock to catholic schools' human capital in the aftermath of the second Vatican council. It shows that the positive correlation between Catholic schooling and student outcomes is explained by selection bias

Demography and the tragedy of the commons

Individual success in group-structured populations has two components. First, an individual gains by outcompeting its neighbors for local resources. Second, an individual's share of group success must be weighted by the total productivity of the group. The essence of sociality arises from the tension between selfish gains against neighbors and the associated loss that selfishness imposes by degrading the efficiency of the group. Without some force to modulate selfishness, the natural tendencies of self interest typically degrade group performance to the detriment of all. This is the tragedy of the commons. Kin selection provides the most widely discussed way in which the tragedy is overcome in biology. Kin selection arises from behavioral associations within groups caused either by genetical kinship or by other processes that correlate the behaviors of group members. Here, I emphasize demography as a second factor that may also modulate the tragedy of the commons and favor cooperative integration of groups. Each act of selfishness or cooperation in a group often influences group survival and fecundity over many subsequent generations. For example, a cooperative act early in the growth cycle of a colony may enhance the future size and survival of the colony. This time-dependent benefit can greatly increase the degree of cooperation favored by natural selection, providing another way in which to overcome the tragedy of the commons and enhance the integration of group behavior. I conclude that analyses of sociality must account for both the behavioral associations of kin selection theory and the demographic consequences of life history theory

Does game theory work? The bargaining challenge

Book description: This volume brings together all of Ken Binmore's influential experimental papers on bargaining along with newly written commentary in which Binmore discusses the underlying game theory and addresses the criticism leveled at it by behavioral economists. When Binmore began his experimental work in the 1980s, conventional wisdom held that game theory would not work in the laboratory, but Binmore and other pioneers established that game theory can often predict the behavior of experienced players very well in favorable laboratory settings. The case of human bargaining behavior is particularly challenging for game theory. Everyone agrees that human behavior in real-life bargaining situations is governed at least partly by considerations of fairness, but what happens in a laboratory when such fairness considerations supposedly conflict with game-theoretic predictions? Behavioral economists, who emphasize the importance of other-regarding or social preferences, sometimes argue that their findings threaten traditional game theory. Binmore disputes both their interpretations of their findings and their claims about what game theorists think it reasonable to predict. Binmore's findings from two decades of game theory experiments have made a lasting contribution to economics. These papers—some coauthored with other leading economists, including Larry Samuelson, Avner Shaked, and John Sutton—show that game theory does indeed work in favorable laboratory environments, even in the challenging case of bargaining

Robot life: simulation and participation in the study of evolution and social behavior.

This paper explores the case of using robots to simulate evolution, in particular the case of Hamilton's Law. The uses of robots raises several questions that this paper seeks to address. The first concerns the role of the robots in biological research: do they simulate something (life, evolution, sociality) or do they participate in something? The second question concerns the physicality of the robots: what difference does embodiment make to the role of the robot in these experiments. Thirdly, how do life, embodiment and social behavior relate in contemporary biology and why is it possible for robots to illuminate this relation? These questions are provoked by a strange similarity that has not been noted before: between the problem of simulation in philosophy of science, and Deleuze's reading of Plato on the relationship of ideas, copies and simulacra

“Economic man” in cross-cultural perspective: Behavioral experiments in 15 small-scale societies

Researchers from across the social sciences have found consistent deviations from the predictions of the canonical model of self-interest in hundreds of experiments from around the world. This research, however, cannot determine whether the uniformity results from universal patterns of human behavior or from the limited cultural variation available among the university students used in virtually all prior experimental work. To address this, we undertook a cross-cultural study of behavior in ultimatum, public goods, and dictator games in a range of small-scale societies exhibiting a wide variety of economic and cultural conditions. We found, first, that the canonical model – based on self-interest – fails in all of the societies studied. Second, our data reveal substantially more behavioral variability across social groups than has been found in previous research. Third, group-level differences in economic organization and the structure of social interactions explain a substantial portion of the behavioral variation across societies: the higher the degree of market integration and the higher the payoffs to cooperation in everyday life, the greater the level of prosociality expressed in experimental games. Fourth, the available individual-level economic and demographic variables do not consistently explain game behavior, either within or across groups. Fifth, in many cases experimental play appears to reflect the common interactional patterns of everyday life