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Social selection

Graham Bell

in Selection: The Mechanism of Evolution

Selection is often generated by interaction with other organisms: neighbours, partners, or antagonists. The force and direction of selection in these social contexts is very generally influenced by ... More

Selection is often generated by interaction with other organisms: neighbours, partners, or antagonists. The force and direction of selection in these social contexts is very generally influenced by the density and composition of the population. It may result in some degree of cooperation or helpfulness, rather than unrestricted competition among individuals. The first section here is called Selection within a single uniform population: density-dependent selection and details density regulation; density-dependent fitness; the principle of frugality; resource competition in continuous culture; r-K selection; r-K selection experiments; and selection in seasonal environments. The second section is called Selection within a single diverse population: frequency-dependent selection and describes GxG; frequency-dependent fitness; and also frequency-dependence in complex environments. The third section is about social behaviour and describes the phenotypic theory of aggression and exploitation; cross-feeding; selfish cooperation; the prisoners' dilemmas; intransitive social interactions; and time-lagged social interactions. The final section is called Kin selection and group selection and describes kin selection; kin proximity and kin choice; spite; group selection in structured populations; productivity and diversity; artificial group selection; and cultural evolution.Less

Introduction

Michael Doebeli

in Adaptive Diversification (MPB-48)

This introductory chapter provides an overview of frequency-dependent selection—the phenomenon that the evolving population is part of the changing environment determining the evolutionary ... More

This introductory chapter provides an overview of frequency-dependent selection—the phenomenon that the evolving population is part of the changing environment determining the evolutionary trajectory. Selection is frequency-dependent if the sign and magnitude of the correlations between heritable variation and reproductive variation change as a consequence of changes in the trait distribution that are themselves generated by such correlations. From the perspective of mathematical modeling, the realm of frequency dependence in evolution is larger than the realm of situations in which selection is not frequency dependent, because the absence of frequency dependence in a mathematical model of evolution essentially means that some parameters describing certain types of biological interactions are set to zero. Thus, in a suitable parameter space, frequency independence corresponds to the region around zero, while everything else corresponds to frequency dependence. In this way, frequency-dependent selection should therefore be considered the norm, not the exception, for evolutionary processes.Less

The theory of natural selection

Glenn-Peter Sætre and Mark Ravinet

in Evolutionary Genetics: Concepts, Analysis, and Practice

Natural selection is the scientific explanation for the evolution of adaptations. Wonders of the living world, such as the anatomy and physiology that grants the cheetah its unchallenged running ... More

Natural selection is the scientific explanation for the evolution of adaptations. Wonders of the living world, such as the anatomy and physiology that grants the cheetah its unchallenged running speed; the seductive colors and scents of a flower that are irresistible to its pollinators; and the accuracy and sophistication of sense organs such as the human eye are the ultimate results of this one creative force in evolution. This chapter investigates simple models of natural selection to explore its power in causing evolutionary change. Mathematical techniques including invasion fitness analysis and adaptive landscapes are powerful tools for analyzing such models and for identifying evolutionarily stable and unstable equilibria. The chapter further investigates frequency-dependent selection and evolutionary game theory. An important goal here is to show that selection can take many different forms and yield very different evolutionary outcomes.Less

Evolutionary genetics

Robert L. Perlman

in Evolution and Medicine

Evolution is often thought of in genetic terms, as a change in allele frequencies and in the phenotypes associated with these alleles in populations over time. Several evolutionary processes in ... More

Evolution is often thought of in genetic terms, as a change in allele frequencies and in the phenotypes associated with these alleles in populations over time. Several evolutionary processes in addition to selection — mutation, genetic drift, and gene flow — can change allele frequencies and increase the frequency of disease-associated alleles in populations. When they happen to be linked to beneficial alleles, deleterious or disease-associated alleles may also spread by genetic hitchhiking. Frequency dependent selection, heterozygote advantage, and environmental heterogeneity all contribute to the maintenance of genetic polymorphisms, the existence of multiple alleles of a gene. Most genes are pleiotropic; they have multiple phenotypic effects. The spread of alleles of pleiotropic genes depends upon the balance between their beneficial and deleterious effects. Epigenetic mechanisms, heritable changes in gene expression and therefore in phenotype that are not dependent on changes in DNA sequence, include DNA methylation, covalent modifications of histones, and expression of noncoding regulatory RNA molecules. The Hardy-Weinberg model is an idealized model that provides a starting point for thinking about the relationship between allele frequencies and genotype frequencies. The dramatic growth of the human population since the agricultural revolution has resulted in the production of many new, rare, alleles, some of which may be associated with disease. Contrary to what some people believe, the human population is subject to ongoing natural selection.Less

Experimental Evolution of Adaptive Diversification in Microbes

Michael Doebeli

in Adaptive Diversification (MPB-48)

This concluding chapter argues that experimental evolution with microbes has emerged as a very attractive alternative to overcome the problem of long time scales in empirical studies of evolution. ... More

This concluding chapter argues that experimental evolution with microbes has emerged as a very attractive alternative to overcome the problem of long time scales in empirical studies of evolution. This is exemplified by the long-term evolution experiments of Richard Lenski, whose experimental Escherichia coli lines have evolved for more than 40,000 generations to date. Lenski and his many collaborators convincingly argued that the diversified strains have coexisted over long time periods, and hence that this diversification represents a case of asexual speciation. The ecological mechanism for diversification in this case appears to be related to crossfeeding, a scenario in which one strain or species persists by scavenging on nutrients that accumulate in the environment as metabolic byproducts of the coexisting strain. With crossfeeding, polymorphisms can be maintained even in simple environments with a single limiting resource such as glucose. This is an excellent example of frequency-dependent selection, as the fitness of the crossfeeder depends on the presence or absence of the glucose specialist.Less

Host–pathogen coevolution

Robert L. Perlman

in Evolution and Medicine

Humans are home to a myriad of microorganisms that are known collectively as the human microbiome. Our bodies may also become infected by disease-causing organisms, or pathogens. Pathogens have ... More

Humans are home to a myriad of microorganisms that are known collectively as the human microbiome. Our bodies may also become infected by disease-causing organisms, or pathogens. Pathogens have complex life histories, which involve replication within an individual host and transmission among hosts. In general, pathogens evolve in ways that maximize their basic reproductive number, R0 , the number of secondary infections that would result from the introduction of one infectious host into a population of susceptible individuals. Pathogens do not necessarily evolve to be benign; instead, they evolve the level of virulence that optimizes their R0 . Because pathogens evolve to grow most efficiently in abundant host genotypes, they cause frequency-dependent selection of rare host genotypes. Hosts evolve in ways that minimize the fitness cost of pathogen infections. The manifestations of infectious diseases may be adaptations that benefit the hosts or manipulations of host physiology that enhance replication and transmission of the pathogens. The recent spread of methicillin-resistant Staphylococcus aureus (MRSA) is a reminder that evolution of antibiotic resistance remains a major challenge for medicine. Study of host-pathogen coevolution should help to guide medical and public health practices such as regimens of antibiotic therapy and immunization strategies.Less

The Evolution of Animal Personalities

Max Wolf, G. Sander Van Doorn, Olof Leimar, and Franz J. Weissing

in Animal Personalities: Behavior, Physiology, and Evolution

This chapter focuses on evolutionary causes of animal personalities. First, it discusses the causes of variation within populations, and, in particular, describes how state differences, ... More

This chapter focuses on evolutionary causes of animal personalities. First, it discusses the causes of variation within populations, and, in particular, describes how state differences, frequency-dependent selection, spatiotemporal variation in the environment, and non-equilibrium dynamics can cause variation in behavior. The chapter also examines the role of the architecture of behavior, stable state variables, and social conventions in causing adaptive behavioral correlations.Less

Individual differences: The unique woman

in A mind of her own: The evolutionary psychology of women

The early aim of evolutionary psychology was to explain human universals. Recently attention has turned to explaining individual differences which present a theoretical challenge. Differences in ... More

The early aim of evolutionary psychology was to explain human universals. Recently attention has turned to explaining individual differences which present a theoretical challenge. Differences in personality and intelligence are partially heritable: if evolution acts to select the most adaptive traits, why do we see differences in intelligence and personality? Why do we not all show the same “optimal” level of intelligence or emotional stability? This chapter examines how and why genetic and non-genetic sources make each of us unique.Less

Robust coexistence and population regulation

Liz Pásztor, Zoltán Botta-Dukát, Gabriella Magyar, Tamás Czárán, and Géza Meszéna

in Theory-Based Ecology: A Darwinian approach

The larger the difference between competing varieties in their method of growth regulation the more robust their coexistence. Stable coexistence assumes frequency-dependent fitness with the advantage ... More

The larger the difference between competing varieties in their method of growth regulation the more robust their coexistence. Stable coexistence assumes frequency-dependent fitness with the advantage of the rare variant, which is empirically demonstrated for alleles, clones, and species. This principle is demonstrated in the implicit Lotka–Volterra model and in the explicit resource competition model of Tilman, and is generalized for arbitrary density-dependence. The generalized competitive exclusion principle states that a necessary condition for stable coexistence is that there be at least as many regulating factors as variants. Asymmetric competition for space through colonization-competition trade-offs, and for light via the trade-off between the vertical growth of trees and the reproductive potential also provides opportunities for coexistence. Trophic interactions may lead to complex population dynamics, as demonstrated by chemostat examples and the Rosenzweig–MacArthur model. Discussion of the conditions for coexistence in the food web context closes the chapter.Less

Generalized food deception

Steven D. Johnson and Florian P. Schiestl

in Floral Mimicry

The majority of rewardless plant species are not specific mimics of the flowers of other species; instead, they deploy a generalized set of floral signals to attract pollinators. These generalized ... More

The majority of rewardless plant species are not specific mimics of the flowers of other species; instead, they deploy a generalized set of floral signals to attract pollinators. These generalized food-deceptive (GFD) species have a number of unique evolutionary and ecological properties that are discussed in this chapter. The success of GFD plants needs to be understood in light of the fact that flower-visiting animals regularly encounter reward-depleted flowers during their foraging bouts. The evolutionary strategy of GFD species succeeds because the process whereby flower visitors learn to avoid deceptive species is sometimes slow and uncertain and depends on a number of factors. Most of the known GFD species are orchids, but the principles outlined in this chapter apply broadly to other deceptive plant–pollinator interactions and underline the relative ease by which plants can manipulate food-seeking insects.Less

Parasite-Host Interactions

Curtis M. Lively

in Evolutionary Ecology: Concepts and Case Studies

The diversity of known strategies for parasitic lifestyles is truly astonishing. Many species of parasitic worms, for example, utilize only one host ... More

The diversity of known strategies for parasitic lifestyles is truly astonishing. Many species of parasitic worms, for example, utilize only one host species, while others cycle between two or more (as many as four) different species of hosts. Some parasites are highly virulent, seriously debilitating or even killing their hosts, while others cause only minor damage. Some parasites (such as viruses) are very small relative to their hosts and have the capacity for explosive reproduction. Others are almost as large as their hosts, and have relatively slow generation times. Therefore, parasites are difficult to categorize. Here, I use parasite to refer to organisms that have an obligate association with, and a negative effect on, another organism (the host). Host strategies for dealing with parasites are equally complex. Vertebrates have highly specialized immune systems that can rapidly respond to infection and then store information that can be used to mount future responses to the same type of infection. Invertebrates lack the memory cells of true immune systems, but they do have complex self-nonself recognition systems for recognizing and killing foreign tissues. Plants also have highly specialized defenses against pathogens, and the genetic basis of these defenses is especially well known due to the work of plant pathologists on crop plants. The myriad of details involved in the interactions between hosts and their parasites is overwhelming, but there are some shared, general aspects of these interactions that are of particular interest to evolutionary ecologists. First, parasites may attack in a frequency-dependent way. In other words, the probability of infection for a particular host genotype is expected to be, at least in part, a function of the frequency of that host genotype. This expectation has implications for sexual selection and the evolutionary maintenance of cross-fertilization (Sakai, this volume; Savalli, this volume). Second, parasites may affect the population density of their hosts, and host density may feed back to affect the numerical dynamics of the parasite. Host density may also affect natural selection on the reproductive rates of parasites, which in turn is likely to affect host fitness and host dynamics. Less

Paleopsychopathology

Frederick L. Coolidge

in Evolutionary Neuropsychology: An Introduction to the Evolution of the Structures and Functions of the Human Brain

Paleopsychopathology is the study of mental problems and mental diseases that may have increased relative fitness in the ancestral environment but do not enhance fitness in the present environment. ... More

Paleopsychopathology is the study of mental problems and mental diseases that may have increased relative fitness in the ancestral environment but do not enhance fitness in the present environment. Some present pathologies (like Huntington’s chorea) may not have had any adaptive value in the ancestral environment, as some genetic disorders’ onset occurred well after what would have been prime reproductive years in the ancestral environment. Some psychopathologies may not have been advantageous in and of themselves, but either their polygenic basis or proximity to important genes may have given rise to successful adaptive phenotypes. For example, the location for the genes for schizophrenia are associated with the coding for immunity genes and creativity. Some personality disorders may have been adaptive in the ancestral environment because of their benefits in navigating social hierarchies. The evolution of an array of emotions may have also benefitted successful navigation in social groups.Less

Mating Systems

Ann K. Sakai and David F. Westneat

in Evolutionary Ecology: Concepts and Case Studies

The study of mating is one of the most active areas in evolutionary ecology. What fuels this research is curiosity about a stunning diversity of ways in ... More

The study of mating is one of the most active areas in evolutionary ecology. What fuels this research is curiosity about a stunning diversity of ways in which zygotes are formed. Many plants and some animals can reproduce without combining gametes. Many other plants combine gametes but do so within the same individual (selfing). Still other plants and animals require a gamete from another individual to stimulate reproduction but do not incorporate the genetic material contained in that gamete in the offspring. Finally, many organisms combine gametes produced from different individuals in sexual reproduction, but the ways in which these individuals get together to reproduce are also amazingly diverse and have major implications for how selection acts in these populations. Why are there so many different ways to reproduce? Answering this question is a major challenge for evolutionary ecologists. Our approach begins with how a variety of ecological factors affect selection on reproductive traits. Because many reproductive traits show genetic variation, diversity in selective pressures can lead to a diversity of evolutionary changes. Thus, understanding the evolutionary ecology of mating systems can help to interpret the significance of this variation and can provide new insight into related phenomena. For example, costs of female reproduction associated with development of offspring greatly impact other aspects of the life history, and males are often limited by mates (Savalli, this volume). Factors such as levels of selfing, inbreeding depression, and allocation of resources play a part in mating systems of both plants and animals (Waser and Williams, this volume), and sex allocation theory has been used in both plants and animals to explore the evolution of hermaphroditism and unisexuality (Campbell 2000; Orzack, this volume). This chapter explores some of the major forces affecting mating systems. Our treatments of plants and animals differ in emphasis, but our goal is to use the perspective of evolutionary ecology to define more fully the similarities, differences, and diversity in plant and animal mating systems, and to highlight potentially interesting yet currently unanswered questions. Diversity in patterns of zygote production arises in part from ecological factors influencing two issues: selection on the evolution of sexual reproduction itself and differentiation of the sexes. Less