"Thus, r can be thought of as the fraction of the total weighting of selection that happens at the group level, and 1 − r can be thought of as the fraction of the total weighting of selection that happens within groups. Here, r may often be interpreted as a form of the regression coefficient of relatedness from kin selection theory (Hamilton, 1970). Thus, we may think of this balance between levels of selection in terms of either kin or group selection (Hamilton, 1975; Frank, 1986). "
[Show abstract][Hide abstract] ABSTRACT: The theory of natural selection has two forms. Deductive theory describes how
populations change over time. One starts with an initial population and some
rules for change. From those assumptions, one calculates the future state of
the population. Deductive theory predicts how populations adapt to
environmental challenge. Inductive theory describes the causes of change in
populations. One starts with a given amount of change. One then assigns
different parts of the total change to particular causes. Inductive theory
analyzes alternative causal models for how populations have adapted to
environmental challenge. This chapter emphasizes the inductive analysis of
"Consequently, relatedness can be understood as the chance of gene sharing among kin, above and beyond average probability . Inclusive fitness partitions natural selection into direct and indirect effects; direct effects describe the impact of an individual's own genes on reproductive success, and indirect effects describe the impact of the focal individual's genes on the fitness of its social partners, weighted by genetic relatedness [24,26,48]. Cooperation may be mutually beneficial if it directly benefits the actor as well as the recipients, for example, by increasing the success of an individual's own group (table 1). "
[Show abstract][Hide abstract] ABSTRACT: One of the most striking facts about parasites and microbial pathogens that has emerged in the fields of social evolution and disease ecology in the past few decades is that these simple organisms have complex social lives, indulging in a variety of cooperative, communicative and coordinated behaviours. These organisms have provided elegant experimental tests of the importance of relatedness, kin discrimination, cooperation and competition, in driving the evolution of social strategies. Here, we briefly review the social behaviours of parasites and microbial pathogens, including their contributions to virulence, and outline how inclusive fitness theory has helped to explain their evolution. We then take a mechanistically inspired 'bottom-up' approach, discussing how key aspects of the ways in which parasites and pathogens exploit hosts, namely public goods, mobile elements, phenotypic plasticity, spatial structure and multi-species interactions, contribute to the emergent properties of virulence and transmission. We argue that unravelling the complexities of within-host ecology is interesting in its own right, and also needs to be better incorporated into theoretical evolution studies if social behaviours are to be understood and used to control the spread and severity of infectious diseases.
Philosophical Transactions of The Royal Society B Biological Sciences 05/2014; 369(1642):20130365. DOI:10.1098/rstb.2013.0365 · 7.06 Impact Factor
"The proper way of doing the calculation was the major theoretical advance. Hamilton  emphasized this causal perspective: Considerations of genetical kinship can give a statistical reassociation of the [fitness] effects with the individuals that cause them. "
[Show abstract][Hide abstract] ABSTRACT: Kin selection theory is a kind of causal analysis. The initial form of kin selection ascribed cause to costs, benefits and genetic relatedness. The theory then slowly developed a deeper and more sophisticated approach to partitioning the causes of social evolution. Controversy followed because causal analysis inevitably attracts opposing views. It is always possible to separate total effects into different component causes. Alternative causal schemes emphasize different aspects of a problem, reflecting the distinct goals, interests and biases of different perspectives. For example, group selection is a particular causal scheme with certain advantages and significant limitations. Ultimately, to use kin selection theory to analyse natural patterns and to understand the history of debates over different approaches, one must follow the underlying history of causal analysis. This article describes the history of kin selection theory, with emphasis on how the causal perspective improved through the study of key patterns of natural history, such as dispersal and sex ratio, and through a unified approach to demographic and social processes. Independent historical developments in the multivariate analysis of quantitative traits merged with the causal analysis of social evolution by kin selection.
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