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This chapter considers the problem of correctly defining fitness costs and benefits in inclusive fitness theory, when competition occurs between offspring who are relatives. It reviews the definition of evolutionary fitness and shows how its misinterpretation explains many previous misunderstandings as to whether inclusive fitness theory always makes accurate predictions. The chapter begins with a discussion of Haldane's dilemma, which can be formalized with fitness equations that show that the risk of death can make fitness effects all-or-nothing. It then examines how inclusive fitness models can be constructed to deal with reproductive value and class-structured populations. It also shows how costs and benefits can be expressed as payoffs that are proportional to reproductive success, as changes in production of offspring, or as changes in evolutionary fitness. Finally, it presents examples that illustrate when fitness, payoffs, and fecundity are different, and how inclusive fitness analyses can be performed properly in such situations.

This chapter examines which of the equivalent alternative partitions of fitness, including inclusive fitness and group fitness, can be interpreted as being subject to natural selection in a meaningful way. Inclusive fitness theory can deal with subtleties such as nonadditive fitness effects and conditionally expressed phenotypes. However, selection based on inclusive fitness gives equivalent predictions to other models of apparently different evolutionary processes, such as multilevel selection. The chapter considers how we can determine whether inclusive fitness really captures the essence of social evolution and whether inclusive fitness is really maximized by the action of selection, as suggested by William D. Hamilton. It also explains what heritability measures, and whether this makes sense biologically. Finally, it discusses the problem of classifying observed social behaviors in terms of their underlying evolutionary explanations.

This chapter studies the logic of evolution by natural selection and the origin of the levels of selection question. The abstract nature of the core Darwinian principles, and thus their potential applicability at multiple levels of the biological hierarchy, is emphasized. Price's equation — a key foundational result in evolutionary theory — is introduced and discussed, which teaches us that character-fitness covariance is the essence of natural selection. The relation between Price's equation and Lewontin's tripartite analysis of the conditions required for Darwinian evolution is briefly examined.

This chapter analyzes the causal dimension to multi-level selection theory. Particular attention is paid to the idea that direct selection at one hierarchical level may generate, as a side effect, a character-fitness covariance at a different level, and thus the appearance of direct selection at that level. Such ‘cross-level’ byproducts lie at the heart of the levels of selection problem and show that Price's equation cannot be an infallible guide to determining the level(s) at which selection is acting. The nature of cross-level byproducts in MLS1 and MLS2 is examined, and the statistical technique known as contextual analysis, which can be used to detect cross-level byproducts, is explored.

This chapter examines the notorious issue of group selection in behavioural ecology, one of the mainstays of the traditional levels of selection debate. The history of the group selection controversy is briefly traced. The relationship between group selection, kin selection, and evolutionary game theory is discussed. An important debate between Sober and Wilson and Maynard Smith concerning the correct way to conceptualize group selection is explored. Lastly, some arguments of L. Nunney concerning the distinction between weak and strong altruism, and how individual and group selection should be defined, are examined.

This chapter examines socialization and the process by which social norms become internalized, how this capacity for internalization could have evolved, and why the norms internalized tend to be group-beneficial. It begins with a discussion of cultural transmission and how it overrides fitness by taking account of two facts. First, the phenotypic expression of an individual's genetic inheritance depends on a developmental process that is plastic and open-ended. Second, this developmental process is deliberately structured—by elders, teachers, political leaders, and religious figures—to foster certain kinds of development and to thwart others. The chapter then introduces a purely phenotypic model in which, as a result of the effectiveness of socialization, a fitness-reducing norm may be maintained in a population. It also describes the gene-culture coevolution of a fitness-reducing norm before concluding with an analysis of the link between internalization of norms and altruism.

This chapter describes the Darwin-Wallace theory of evolution by natural selection. In particular, it explains the notion of fitness, which underlies the concepts of descent with modification and the appearance of species categorized into clades. It shows that descent with modification is a much better evolutionary theory than the “Great chain of being” model, which implies that evolution is driven toward the production of more perfect and complex life-forms. Finally, it explains how the science of genetics strongly supports evolution through the notions of mutation, gene frequencies in populations, and drift.

This chapter examines the geographical distribution of resistant forms of Mycobacterium tuberculosis and their time trends. Apart from drug resistance, there are plenty of other main questions about M. tuberculosis population genetics. To combat epidemics of drug-resistant TB, it is vital to understand why some resistant strains have greater reproductive fitness than drug-susceptible strains. The chapter first provides an overview of genetic variation in M. tuberculosis before discussing resistance (new and acquired) to first-and second-line drugs. It then considers the link between drug resistance and HIV coinfection, global distribution of drug-resistant TB, relative reproductive fitness, and absolute reproductive fitness. It shows that drug resistance is preventable and reversible, but this must be corroborated and expanded with longer series of data from a wider range of countries, countries with high rates of HIV infection (for example, Botswana and South Africa), and those reporting cases of extensively drug-resistant TB (XDR-TB).

This chapter examines how the logic of inclusive fitness theory can be mathematically formalized using the Price equation, and how that formalization can be used to derive Hamilton's rule in its simplest form, as applied to unconditional behaviors having additive effects on fitness. Various biological phenomena, such as sex allocation and working policing within eusocial insect colonies, have been analyzed by considering what strategies maximize individuals' inclusive fitness, and how observed social behaviors should correlate with quantities such as relatedness. The chapter derives Hamilton's rule by introducing some notation for the effects of behaviors on fitnesses of individuals that interact socially, to make explicit precisely how genes (and later phenotypes) affect fitness, and to give a general form of Hamilton's rule that will apply to any (unconditional, additive) behavior regardless of its details. It shows that inclusive fitness is a genuinely novel extension of the classical fitness studied by Charles Darwin, R. A. Fisher, and others.

The underlying assumption of much of the work on flower development and morphology is that these features serve to increase the attractiveness of the flower to pollinating animals, thus maximizing pollinator attention, and consequently seed set and fitness. It has long been believed that these elaborations are the consequence of adapting to attract particular pollinating animals, resulting in pollination syndromes. Before the existence of pollination syndromes and how frequently they are needed are examined, this chapter considers whether there is evidence that the underlying assumptions are met. This chapter addresses one fundamental issue: do plants actually benefit from increased pollinator attention and should floral attractiveness therefore be expected to increase across generations?

This chapter summarizes studies of lifetime reproductive success (LRS) conducted on odonates. Such studies have focused on many characters, but have typically concluded that survivorship — the main component of natural selection, is more important than mating efficiency — a primary component of sexual selection, in determining LRS. They have also frequently found that environmental factors are important and that selection and the opportunity for selection vary considerably depending on density, sex ratio, and community composition. LRS studies have been most successful when focused on specific traits and when complemented by experimental manipulations. Progress in understanding the current actions of natural and sexual selection is thus most likely to involve long-term LRS work combined with experimental or comparative approaches. Particularly desirable are studies that incorporate the larval stage in fitness calculations, perform parentage analyses to determine realized fitness, and consider the role of non-breeding behaviours such as foraging efficiency.

Parasites are thought to select for host traits, such as elaborate ornaments and intricate immune systems. Dragonflies have proven useful hosts for studying parasite-mediated selection. This chapter summarizes whether parasites exert fitness costs on their dragonfly hosts and affect signals and the mating success of males. It also reviews determinants of resistance against ectoparasitic mites, which is present in many dragonfly species and introduces recent work suggesting that host gender and age influence immunological responses to bacterial and artificial challenges. The chapter highlights that the likelihood of demonstrating parasite-mediated selection might depend on whether or not the species being considered is a generalist parasite. New ideas on elucidating how dragonfly prey species should deal with threats from multiple enemies, such as predators and parasites, are considered.

This chapter gives some quantitative information about the rates of genetic and environmental deterioration. The first section in this chapter is about history, chance, and necessity, and includes subsections on Lamarckian evolution; the selection of undirected variation; descent; and delection. The second section is about drift and includes subsections concerning the rate of genetic deterioration; two scaled mutation rates; the rate of deleterious mutation; decay of isolate lines in the absence of selection; mutation rate in other replicators; mutation rate in stressful environments; the genomic mutation rate; the effect of mutations; beneficial mutations; the effect of gene deletion on growth; the rate of accumulation of genetic variance in fitness; the replication limit; the size spectrum; the distribution of species abundance; and finally genetic variation and species abundance. The final section is on the rate of environmental deterioration. Subsections in this section concern aggregation; the ecological population concept; dispersal; and the genetic population concept. Five theories of the environment are offered and environmental variation in space; environmental variation over time; and the biotic environment are also detailed.

The development of multicellular organisms involves a balance between somatic and reproductive tissues. This chapter outlines how the action of selection is influenced by the age at which structures and behaviours are expressed. This chapter's first section is called Reproductive allocation and it explains all about the correlated response to selection; antagonism of fitness components; the evolution of genetic correlation; and the optimal allocation. The second section, entitled Life histories, details selection in age-structured populations; depreciation of later reproduction; artificial selection for early reproduction; senescence; soma and germ; the nature of senescence; the evolution of senescence; selection for delayed senescence in Drosophila; endogenous evolution; and the disposable soma.

Natural selection can be observed and measured in natural populations. This chapter argues that it is commonplace, strong, fluctuating, and oligogenic. The first section here is called Fitness in natural populations and describes the variance of fitness; immigration pressure; local selection coefficients; and the field gradient. The next section, the Phenotypic selection, details the environmental variance of fitness; the cost of selection; the lack of response: genostasis; field studies of selection in Cepaea; selection coefficients; heritability; the Secondary Theorem of Natural Selection; selection gradients; stabilizing selection; fluctuating selection; historical change; multiscale temporal variation; and genetic revolutions. The third section is called Selection experiments in the field and details habitat modification and the Rothamsted Park Grass Experiment. It then gives an introduction to guppies in Trinidad. The fourth section is called Adaptation to the humanized landscape and details the unexpected consequences of harvesting; the unintended consequences of pollution in terms of mining; the unintended consequences of pollution from smoke; the unintended consequences of pollution from carbon dioxide; the unwelcome effects of eradication concerning herbicides and pesticide; the unwelcome consequences of eradication from antibiotics; and human evolution in the humanized environment. Finally, the section called The ghost of selection past details an analysis of allele frequencies and an analysis of divergence.

This introductory chapter discusses what viruses are and how they fit into the living world. Topics covered include the three large families in the living world: bacteria, archaea, and eukarya; viruses never really die; all life forms can be divided into species, but viruses cannot; and viruses can be distinguished from each other genetically.