Cooperation in Mutualisms: Contracts, Markets, Space, and Dispersal (BIOCONTRACT)

解释物种之间的合作或互惠合作，对进化论提出了挑战。许多促进物种内合作的机制并不适用于物种间的合作。因此，尽管互惠互利在自然界中普遍存在并具有重要的经济意义(例如授粉)，但目前还没有一个通用的理论框架来解释互惠互利的进化。本研究试图通过采用经济学中的契约理论来构建这样一个框架，来模拟互惠互利物种之间的“自然契约”是如何演变的。互惠互利的研究计划围绕着将特定的互惠互利分配给现有的四类解决方案之一：副产品、合作伙伴忠诚度、合作伙伴选择和空间博弈的特殊情况。相比之下，经济契约理论是围绕经济主体面临的三类问题组织起来的：道德风险、逆向选择和信号传递。将四种生物解决方案映射到三个契约问题上表明，互惠理论关注道德风险，几乎不承认逆向选择和信号的存在是形式问题。事实上，在许多互惠关系中，逆向选择是一个问题，因为潜在的伴侣会经历配对或分类阶段，在这个阶段，作弊者可能会入侵。经济学理论提出了针对逆向选择问题的市场分割解决方案；这种方法被应用于互惠互利。这个项目首先利用契约理论的一个子集--委托代理理论，来研究自然契约的演变如何在合作伙伴之间分配互惠互利的利益。自然合同和人类合同的一个主要区别是，没有法律制度来执行自然界物种之间签订的合同。这项工作借鉴并扩展了自我执行契约的经济学理论，以调查面对潜在的欺诈者剥削时，互惠是如何坚持的。契约理论被修改以考虑在自然选择下个体具有有限理性和对动态过程的最优反应的情景。复制者动力学，灵感来自于种群遗传学，以调查哪些合同可以进化。这项研究的更广泛影响如下。第一，研究与教育的结合：该项目将在哈佛大学组织学、进化生物学和经济学系的共同参与下，培训一名契约理论和合作演变方面的博士后研究人员。第二，向广泛的跨学科受众传播：研究人员将通过与TRIP计划中的其他联盟进行互动，在经济和生物学的国际期刊上发表文章，以及创建和维护一个自编的经济学术语及其生物翻译词典的网页，使研究结果广泛可用。第三，加强研究和教育的基础设施：该项目是不同学科和国家的研究人员之间合作努力的一部分，目的是了解合作的基本性质。通过欧洲科学基金会(European Science Foundation)的一项研究合作与贸易演变的资助计划，美国、英国、奥地利、葡萄牙、匈牙利和法国的研究人员建立了合作伙伴关系。第四，社会效益：在经济学和生物学中，合作的研究往往排在冲突和竞争的研究之后。这个项目汇集了经济学家和生物学家，他们在各自的领域拥有研究合作现象的丰富经验。通过这种合作，经济学和生物学之间的思想交流将得到发展，从而丰富对人类和非人类有机体中合作行为进化的理解。

Explaining cooperation between species, or mutualism, poses a challenge to evolutionary theory. Many of the mechanisms that promote cooperation within species are not applicable to cooperation between species. Thus, although mutualisms are ubiquitous in nature and economically important (e.g. pollination), there is currently no general theoretical framework that explains the evolution of mutualisms. This study attempts to develop such a framework by adapting contract theory from economics to model how "natural contracts" evolve between mutualistic species. The research program in mutualism is organized around the assignment of specific mutualisms to one of four existing classes of solution: by-products, partner fidelity, partner choice, and a special case of spatial games. In contrast, economic contract theory, which was devised to model transactions in which information is asymmetrically distributed, is organized around three classes of problems faced by economic agents: moral hazard, adverse selection, and signaling. Mapping the four biological solutions onto the three contract problems reveals that mutualism theory concentrates on moral hazard and hardly recognizes the existence of adverse selection and signaling as formal problems. In fact, adverse selection is a problem in many mutualisms, as potential partners go through a pairing-off or assortment stage, during which cheaters can invade. Economic theory proposes market segmentation solutions to the problem of adverse selection; this approach is applied to mutualism. This project begins with the utilization of a subset of contract theory, Principal-Agent theory, to investigate how the evolution of natural contracts distributes the benefits of mutualism among partners. A major difference between natural and human contracts is that there is no legal system to enforce contracts made between species in the natural world. This work draws and expands on economic theory of self-enforcing contracts to investigate how mutualisms persist in the face of potential exploitation by cheaters. Contract theory is modified to contemplate scenarios in which individuals have bounded rationality and optimization responses to a dynamic process under natural selection. Replicator dynamics, inspired from population genetics, to investigate which contracts can evolve. The broader implications of this study are as follows. First, integration of research and education: this project will train a postdoctoral researcher in contract theory and the evolution of cooperation with the joint involvement of the Departments of Organismic and Evolutionary Biology and Economics at Harvard University. Second, dissemination to a wide, interdisciplinary audience: the researchers will make the results widely available by interacting with the other consortia in the TECT program, publishing in international journals, both economic and biological, and by creating and maintaining a webpage with a self-edited dictionary of economic terms and their biological translation. Third, enhancement of infrastructure for research and education: this project is part of a collaborative effort between researchers in different disciplines and countries to understand the fundamental nature of cooperation. Through a funding initiative from the European Science Foundation to study the evolution of cooperation and trading (TECT), a partnership is created between researchers in the U.S., U.K., Austria, Portugal, Hungary, and France. Fourth, benefits to society: in economics and biology, the study of cooperation has often taken second stage to the study of conflict and competition. This project brings together economists and biologists with considerable experience studying cooperative phenomena in their respective fields. Through this collaboration, an interchange of ideas between economics and biology will be developed that enriches the understanding of the evolution of cooperative behavior in both human and non-human organisms.