Backward Unraveling over Time: The Evolution of Strategic Behavior in the Entry-Level British Medical Labor Markets

This paper studies an adaptive artificial agent model using a genetic algorithm to analyze how a population of decision-makers learns to coordinate on the selection of an equilibrium or a social convention in a two-sided matching game. In the contexts of centralized and decentralized entry-level labor markets, evolution and adjustment paths of unraveling are explored using this model in an environment inspired by the Kagel and Roth (Quarterly Journal of Economics, 2000) experimental study. As an interesting result, it is demonstrated that stability need not be required for the success of a matching mechanism under incomplete information in the long run.Genetic algorithms, linear programming matching, stability, two-sided matching, unraveling

Cophylogeny reconstruction via an approximate bayesian computation

Despite an increasingly vast literature on cophylogenetic reconstructions for studying host-parasite associations, understanding the common evolutionary history of such systems remains a problem that is far from being solved. Most algorithms for host-parasite reconciliation use an event-based model, where the events include in general (a subset of) cospeciation, duplication, loss, and host switch. All known parsimonious event-based methods then assign a cost to each type of event in order to find a reconstruction of minimum cost. The main problem with this approach is that the cost of the events strongly influences the reconciliation obtained. Some earlier approaches attempt to avoid this problem by finding a Pareto set of solutions and hence by considering event costs under some minimization constraints. To deal with this problem, we developed an algorithm, called Coala, for estimating the frequency of the events based on an approximate Bayesian computation approach. The benefits of this method are 2-fold: (i) it provides more confidence in the set of costs to be used in a reconciliation, and (ii) it allows estimation of the frequency of the events in cases where the data set consists of trees with a large number of taxa. We evaluate our method on simulated and on biological data sets. We show that in both cases, for the same pair of host and parasite trees, different sets of frequencies for the events lead to equally probable solutions. Moreover, often these solutions differ greatly in terms of the number of inferred events. It appears crucial to take this into account before attempting any further biological interpretation of such reconciliations. More generally, we also show that the set of frequencies can vary widely depending on the input host and parasite trees. Indiscriminately applying a standard vector of costs may thus not be a good strategy

Cognitive Models of Defense Behaviors in Hosts of Brood Parasites

Social parasites exploit the behavioral repertoire of their hosts for their own benefit, thereby reducing host reproductive success. Whether and how hosts respond to prevent, reduce, or eliminate the costs of parasitism requires the characterization of host cognitive algorithms in response to parasites. In this dissertation, I review the suite of the defense behaviors and decision rules of hosts targeted by avian and insect brood parasites, and present new experimental data on the detection of parasitism through the visual system of focal host species. In Chapter 1, I review extensive data already accumulated to isolate the cognitive mechanisms used by avian hosts to assess, identify, and reject foreign eggs in the nest. The two most commonly evoked candidate heuristics are the discordancy mechanism, wherein the host rejects the egg most dissimilar in appearance to the other eggs in the clutch, and the template-based mechanism, wherein the host compares an egg to an internal template of its own eggs’ appearance. When experimenters directly pitted these competing mechanisms against one another, they found dominant support of the template-based process for egg discrimination. More recent and detailed analyses, however, to tease these mechanisms apart suggested that these alternatives are not mutually exclusive, and may be simultaneously activated to work in tandem to effect egg rejection decisions. Furthermore, Chapter 1 overviews a growing body of work demonstrating, at the individual level, the extent of plasticity that exists in setting the phenotypic threshold for own-foreign discrimination by hosts. To examine egg rejection behaviors experimentally, the potential host species investigated must meet certain requirements. These include that they be rejecters of foreign eggs to some level of predictability and consistency in the first place. The globally ubiquitous house sparrow Passer domesticus is known to engage in conspecific brood parasitism, and its invasive proliferation across many continents and biomes represents a potentially attractive system to study anti brood parasite behaviors across ecological contexts and scales. Chapter 2, therefore, assesses the generalizability of previous studies demonstrating egg rejection patterns in house sparrows in Spain and South Africa, especially following the publication of more recent data from China suggesting that this species is not an egg rejecter. Here we robustly examined house sparrow responses to experimental parasitism in the distinct regions of North America, Israel, and New Zealand, and found negligible rejection rates in all three, suggesting that the house sparrow is not a suitable global model for antiparasitic egg rejection behaviors. In Chapter 3, the cognitive mechanisms of rejection responses characterized in chapter 1 were experimentally tested by analyzing diverse published and unpublished datasets from the great reed warbler Acrocephalus arundinaceus, a well-studied host species of a mimetic race of the obligate brood parasitic common cuckoo Cuculus canorus. Specifically, the simultaneous activation of the discordancy and template-based decision rules suggested in chapter 1 was considered to test whether multiple methods were employed at the same time in a way that they may have interfered with one another to reduce rejection accuracy. Host individuals were experimentally parasitized with painted eggs of varying colors, quantities, and uniformities. Hosts were found to be more permissive of foreign eggs, and thus more error prone, when both the proportion of foreign eggs the nest increased and the eggs in the nest became more perceptually distinct from one another. This indicates that host defenses could be compromised by causing recognition mechanisms to yield differing rejection targets, and that multiple parasitism (or repeated targeting: more than one parasitic egg laid in the host nest) can mediate this beneficial outcome for the parasite itself. No matter which cognitive egg rejection mechanism(s) is(are) employed, most studies agreed that the primary visual cue used by hosts to distinguish foreign eggs is the overall degree of distance in color between the egg being assessed and the host’s own egg(s). Until recently, rejection decisions were attributed to the absolute (regardless of direction) perceptual distance between own vs. foreign eggs. Chapter 4 is a new original but also parallel study to Hanley et al. 2017 and 2019’s discoveries that directional difference on a continuous color gradient of avian eggshell colors may be the relevant salient recognition cue. In particular, Hanley et al. found that their hosts preferentially rejected eggs browner than their own, but not eggs more blue/green than their own, suggesting a single threshold of rejection only on one side of the natural avian color gradient, rather than multiple symmetrical thresholds of absolute distance. We examined this phenomenon focusing on the European redstart Phoenicurus phoenicurus, which in contrast to the house sparrow observed in Chapter 2, consistently demonstrated rejection of non-mimetic eggs and acceptance of mimetic eggs in prior studies, thereby providing an attractive subject for variable egg rejection rates to investigate the limits of color-based rejection threshold(s). In addition, this study assessed Hanley et al.’s hypothesis in the context of a host species parasitized by a mimetic parasite race, which none of their prior studies included. Specifically, we experimented with redstarts in Finland, where they were simultaneously under parasitic pressure from the common cuckoo, and in the Czech Republic, where no parasitic pressure was present. Using 3D printed eggs painted along a continuous color gradient of natural brown to blue/green avian eggshell background colors, we experimentally parasitized redstart nests and recorded their rejection behaviors. In support of the single threshold model, we found the redstarts, regardless of locality, preferentially rejected noticeably browner eggs but not noticeably more blue/green eggs. Finally, in Chapter 5, I shift the lens to the insect kingdom to examine highly analogous host vs. brood parasite systems to what we have seen in birds. Though the exact antiparasitic sensory modalities and recognition mechanisms differ, the evolutionary arms race of mimicry and recognition as parasites attempt to exploit unrelated individuals for offspring care is remarkably similar, and the relative advantages of examining host-parasite interactions from this new perspective are carefully enumerated. Relative to avian brood parasitism, the study of social parasitism in insects is still patchy, even when there are strong analogies (such as parasitic larvae manipulating caretakers to receive disproportionate attention, just as many avian brood parasite chicks manipulate foster parents to receive biasedly greater share of the provisioning), yet the sensory mechanisms of the larval manipulation remain largely unknown. Making use of these multiple perspectives on host-parasite dynamics across taxa can inspire more cohesive research across taxonomic boundaries. Such work then also inspires both conceptual advancement and applied analyses, for example, in the context of an impending conservation crisis as the collapse of honeybee colonies in Africa accelerates due to the recent surge of virulence of its brood parasitic congener. All but Chapter 4 of this dissertation represent peer-reviewed and published articles that have already appeared in print and online as Manna et al. Chapter 4 in turn, will be the basis of a new manuscript with the same first author and institutional affiliation, yet again

Home Country Effects on Internationalization: Chinese Agrifood Investment in Advanced Economies

Home country effects on internationalization has been conventionally conceived as a contrast to the pull of host countries determinants. While scholarship acknowledges that home country support matters more to internationalizing emerging market multinational enterprises, the focus of extant literature has been underpinned by assumptions of stable macro-level and unidirectional institutional support for the internationalization of firms. This thesis contrasts with previous studies by repositioning the conversation to incorporate the temporal dimension, and investigate the multi-level relationships across institutions, industries and markets in the home country and the varied effects on internationalization. Chinese agrifood investment to advanced economies from 2008 to 2017 against the backdrop of rebalancing and consumption-led growth economy is the phenomenon and research context. The overarching research question is “How do home country effects shape the internationalization of Chinese firms?”. This is addressed in four contextual and case study chapters. Drawing on interdisciplinary literature and applying an abductive research process, I developed a dynamic home country relational model to study the internationalization process of Chinese firms that enriches existing process and institutional frameworks. There are four central findings presented in this thesis. First, home country support engenders different meanings constructed by heterogeneous dispensers and recipients who adopt discretionary selection in a competitive environment. Second, experienced agrifood firms have learned to deliberately avoid controversial farmland purchases and targeted downstream businesses in advanced economies to access resources and gain management skills. Third, wealthy non-agricultural Chinese groups lacking in specialized industry knowledge, face compounded challenges diversifying into agrifood sector and internationalizing simultaneously. Fourth, risk perception and risk mitigation have accentuated as internationalization of Chinese firms evolved, shifting from self-checking to tightening of regulatory controls and reinforced by businesses’ confirmation of support. This study has enhanced the understanding of evolving institutions, and the nuances and irregularity of internationalization processes through the explanation of complex interactions and responses from the perspective of home country actors

Identifying Factor Productivity from Micro-data: The case of EU agriculture. Factor Markets Working Paper No. 34, January 2013

The classical problem of agricultural productivity measurement has regained interest owing to recent price hikes in world food markets. At the same time, there is a new methodological debate on the appropriate identification strategies for addressing endogeneity and collinearity problems in production function estimation. We examine the plausibility of four established and innovative identification strategies for the case of agriculture and test a set of related estimators using farm-level panel datasets from seven EU countries. The newly suggested control function and dynamic panel approaches provide attractive conceptual improvements over the received ‘within’ and duality models. Even so, empirical implementation of the conceptual sophistications built into these estimators does not always live up to expectations. This is particularly true for the dynamic panel estimator, which mostly failed to identify reasonable elasticities for the (quasi-) fixed factors. Less demanding proxy approaches represent an interesting alternative for agricultural applications. In our EU sample, we find very low shadow prices for labour, land and fixed capital across countries. The production elasticity of materials is high, so improving the availability of working capital is the most promising way to increase agricultural productivity

Behavioural drivers of fertility in red junglefowl Gallus gallus and commercial chicken flocks

The fowl, Gallus gallus, has been used to study sexual behaviour and sexual selection for many years: its combination of reproductive biology that is fairly typical of birds and a polygynandrous mating system makes it an ideal model species for studying the effects of pre- and post- copulatory competition and of conflict between the sexes. There is a large body of research spanning many decades on these processes in domestic chickens and their wild ancestor, the red junglefowl. As well as being an ideal model system, the sexual behaviour and fertility of this species is of great significance to the poultry industry, where the reproductive efficiency of broiler breeders (birds whose commercial purpose is to produce hatching eggs) is a key concern. However, the behaviour of broiler breeders in a commercial setting, and how their behaviour links to fertility, is little understood. Females of this species are subject to intense sexual harassment, and some behavioural strategies exhibited by females in response to sexual harassment have been described. However, we lack a detailed and systematic understanding of the suite of female responses to sexual harassment, despite these having the potential to significantly affect reproductive success for males and females. In this thesis, I build on existing knowledge of sexual behaviour and its influence on fertility, with a focus on female responses to sexual coercion and on commercially relevant insights in broiler breeders. I use a mix of approaches, from a theoretical model, to an experiment on a captive population of junglefowl, to translational research in broiler breeders. The findings of this thesis add new detail to our understanding of female resistance against sexual coercion, both in this species and in general, and inform suggestions for husbandry optimisations that could be trialled in broiler breeders

Evolutionary games on graphs

Game theory is one of the key paradigms behind many scientific disciplines from biology to behavioral sciences to economics. In its evolutionary form and especially when the interacting agents are linked in a specific social network the underlying solution concepts and methods are very similar to those applied in non-equilibrium statistical physics. This review gives a tutorial-type overview of the field for physicists. The first three sections introduce the necessary background in classical and evolutionary game theory from the basic definitions to the most important results. The fourth section surveys the topological complications implied by non-mean-field-type social network structures in general. The last three sections discuss in detail the dynamic behavior of three prominent classes of models: the Prisoner's Dilemma, the Rock-Scissors-Paper game, and Competing Associations. The major theme of the review is in what sense and how the graph structure of interactions can modify and enrich the picture of long term behavioral patterns emerging in evolutionary games.Comment: Review, final version, 133 pages, 65 figure