We are taught early in our education as evolutionists that Charles Darwin got the mechanism of heredity wrong. He supposed that there are an arbitrary number of ductile transmissible gemmules that migrate from the organs to the gonads, allowing the possibility of a kind of blending inheritance along with the inheritance of acquired characters. Of course, Gregor Mendel’s discrete “hard” model for inheritance, which we now call genetics, turned out to be the correct mechanism for inheritance in eukaryotes. Furthermore, Darwin’s mistake about inheritance probably cost the field of evolutionary biology some decades of delay. Genetics wasn’t properly incorporated into...

Experimental studies complement the several other major approaches to analyzing evolutionary processes. Each approach has both advantages and limitations. We first describe the advantages of experimental evolution, and then we contrast it with other approaches.

The essence of experimental evolution is conceptually quite simple. For many generations, a series of replicated populations is exposed to a novel environment, while a parallel series of populations is maintained within the ancestral environment, thereby serving as experimental controls. The environmental novelty may involve alteration of any aspects of the abiotic, biotic, or demographic condition of the ancestral population. Usually only a single environmental...

Experimental evolutionas used in this volume encompasses both artificial selection and “laboratory” evolution in which populations are introduced into a novel environment and allowed to breed without any overt selection by the experimenter. Any selection that occurs in laboratory evolution experiments is assumed to be imposed by aspects of the novel environment. The major advantage of this latter approach over artificial selection is that the organisms are allowed to evolve relatively naturally in response to diverse selection acting on the whole phenotype, and hence the observed evolutionary processes may more closely mimic those that occur in nature (see also...

One of the most important uses of experimental evolution is the study of natural selection, its causes and its consequences. This involves mapping genotype onto phenotype (genetic architecture; Hanson 2006) and mapping phenotype onto fitness. Implicitly or explicitly, these mappings also include any impact the environment has on each.

Natural selection is studied using two very different approaches in experimental evolution, which we call “top down” and “bottom up.” In the top-down approach, an experimenter sets up the environmental conditions, such as media, temperature, and growth regime, and allows the culture to evolve over thousands of generations (e.g., see Forde...

Many millennia before we understood the basic laws governing biological evolution, we bred our commensal species to our liking, whether for economic or leisure purposes. A range of species from plants to animals were thereby domesticated. In a sense, the longest-running experimental evolution projects are those of domestication, and they have produced an astonishing variety of animal breeds and plant varieties. Naturally enough, Darwin used cases of pigeon and dog domestication to illustrate the capacity of selection to produce evolutionary change inThe Origin of Species(1859), and then he later expanded greatly on this theme in the volumes devoted...

Long-term evolution studies are selection experiments that explore evolutionary consequences. Rather than focusing on the potential for selection to act, which is typical of short-term selection studies, long-term studies emphasize the process and eventual outcome of evolution.

The major benefit of this type of study is that evolutionary outcomes can be directly studied in terms of the processes that gave rise to them, such as mutation and adaptation, leading to a better understanding of the mechanisms underlying evolutionary change. The focus on consequences, rather than potential, typically involves multiple sequential genetic differences, rather than only one or a few, an...

Darwin was the first to suggest that selection of small differences among individuals for characters related to survival and reproduction was sufficient to promote directional evolutionary change in those characters. Evolution, understood as common descent of organisms with modification over time, was quickly accepted by the scientific community. However, the role of natural selection in the evolution of biodiversity was controversial since the inheritance of phenotypic information both during development and transmission across generations was unexplained.

The major problem confronted by evolutionary theory derived from the observation that when individuals were selected, character values in their offspring showed partialregression...

The field of evolutionary biology has primarily adopted a descriptive approach throughout its history, in large part due to the difficulty of replicating evolutionary processes under controlled conditions. However, experimental approaches provide a powerful tool kit for researchers to disentangle cause and effect (Hurlbert 1984; Futuyma and Bennett this volume; Huey and Rosenzweig this volume). In the context of evolution, experimental approaches are especially attractive because of the potential for replicating rarely observed evolutionary forces, such as natural selection, drift, or the occurrence of movement into a novel environment (Garland and Kelly 2006). Laboratory experimental approaches to evolution have long...

An important theme in this review will be the importance of a close balance between theory and experiments. Theory has as a goal the creation of simple and general principles. Understandably, therefore, theoreticians are often loath to spend too much time and energy worrying about the details of any specific organism’s biology. However, experimental population biologists must determine if the assumptions of the specific theories that they wish to test are biologically unrealistic for the particular experimental organism that they wish to study. It is perilous for the experimental biologist to rely on the theoretician to determine if a particular...

The physiological basis of life-history traits and trade-offs has been a long-standing issue in the study of life-history evolution (Fisher 1930; Tinkle and Hadley 1975; Townsend and Calow 1981; Zera and Harshman 2001; Harshman and Zera 2007). Research on this topic has attempted to identify components of physiology (function at various levels of biological organization: Swallow et al. this volume) that contribute significantly to variation in individual life-history traits, such as early-age fecundity, and trade-offs between traits, such as the commonly observed negative correlation between early-age fecundity and longevity. The main goal of this research has been to illuminate the...

The tree of life is decorated with an extraordinary diversity of animal behavior (figure 11.1). Such behaviors as foraging, reproducing, moving through the environment, and avoiding predators are all clearly major determinants of survival and reproductive success and hence are thought to be under relatively strong natural and sexual selection. Although some behaviors are culturally transmitted, the vast majority evolve by genetic mechanisms. One of the earliest pieces of direct evidence that behavior can be shaped by evolutionary processes was domestication of wolves into dogs, which is thought to have occurred as far back as fifteen thousand years ago (Savolainen...

Since a seminal paper by Arnold (1983), direct measurement of whole-organism performance has become central to functional evolutionary biology (e.g., Arnold 2003; Ghalambor et al. 2003; Kingsolver and Huey 2003). In this context, “performance” can be most easily defined by example. Assuming that individuals can be fully motivated (e.g., see Swallow et al. 1998a; Harris and Steudel 2002; Losos et al. 2002; Tobalske et al. 2004), it is relatively easy to measure maximal sprint running speed of small mammals and lizards on photocell-timed racetracks or high-speed treadmills (e.g., Calsbeek and Irschick 2007; Chappell et al. 2007). Moving down one level...

Genome architecture is defined as the structure, content, and organization of a genome, and it is described in terms of genes, theircis-acting regulatory elements, and various noncoding entities that populate intergenic regions. This useful phrase has an unfortunate tendency to promote the view that genomes are static, perhaps because of the intuitive associations conjured up by the termarchitecture. This view has been reinforced by the recent proliferation of whole-genome maps. Such maps, however clever and colorful, are spatially limited to two dimensions and do not represent epigenetic processes that can alter genomes physical structure. (Jaenisch and Bird 2003)....

The primary goal of experimental evolution is to directly test theories of evolution using controlled experiments. Experiments in the laboratory offer particular control over both environmental conditions and the starting populations for evolutionary experimentation. Experiments in the laboratory also allow for a high degree of replication, and thus an increased probability of capturing the distribution of potential mutations, which is particularly important when testing evolutionary theory. Developments in molecular biology now make it possible to pinpoint the mutations responsible for adaptation and to determine how these mutations function. A comprehensive picture of adaptation, one that integrates genetic information with the...

Morphology most often evolves not through the appearance of new or “novel” traits, but through changes in the shape of existing structures (figure 15.1). Thompson presented shape variation as deformations in the dimensions and relative size of body parts (Thompson 1917); his approach captures differences in organismal shape across groups by compressing, stretching, or bending a reference image, such as a common ancestral form or the mean shape calculated from lineages exhibiting shape variation (figure 15.2). This approach illustrates intuitively how disproportionate changes in dimensions across a generic, reference shape can produce both subtle variations on morphological themes and dramatically...

Humans tend to be fascinated with sex. This is not surprising, as we are members of an obligate sexual species, composed of males and females that must experience sexual reproduction to make offspring. Thus, many of us are sometimes understandably fixated with actions relating to finding a mate, keeping a mate, and mating itself. Without such interests, we would not persist as a species, and there would be no one around to purchase this book.

Evolutionary biologists have also had a historical fascination with sex. This interest began when macroorganism researchers realized that sexual reproduction is a trait and that...

Almost any study in experimental evolution requires an altered environment in which selection is expected to occur. Sometimes the environmental variable can be biological (e.g., predators, potential mates). Often, however, it is the abiotic environment that is changed. In nature, thermodynamic variables such as temperature, pressure, and chemical activity (i.e., the concentration of salts, hydrogen ions, etc.) differ across habitats. Life itself requires input of raw materials from the environment (nutrients, water, ions, etc.) that can then be used to drive physiological processes and make more organisms.

We consider here two categories of environmental variables that have been used as...

Aging, like all biological characters, evolves. However, unlike many other biological characters, the evolution of aging is not primarily shaped by powerful natural selection balanced against such mitigating factors as clonal interference, linked deleterious alleles, directional mutation, and the like. Instead, aging is evolutionarily distinctive because it arises from the progressive fall in Hamilton’s forces of natural selection acting on the survival and reproduction of the somata of ovigerous species (Hamilton 1966; Rose et al. 2007). Therefore, the evolutionary mechanisms underlying aging are different from those underlying most other phenotypes. That is, aging does not have a function or purpose,...

One of the central themes in Donne’s meditation is the interconnectivity between human beings. Our lives are not stand-alone chapters from an edited volume (like the one you are reading), but more like chapters from an elaborate novel, each setting the stage for chapters to come while simultaneously depending on chapters already read. Biological systems, from subcellular biochemical networks to multispecies food webs, display striking forms of interconnectivity in their parts. How does the theory of biological evolution by natural selection handle this interconnectivity? The simplest description of natural selection starts byignoringinterdependence. For simplicity, individuals in a population...

After neglecting the subject for nearly a century after the publication ofThe Origin of Species, evolutionary biologists have been intensively investigating mechanisms of speciation in the last few decades (reviewed in Barton 2001; Coyne and Orr 2004; Rundle and Nosil 2005; Noor and Feder 2006; Rieseberg and Willis 2007). Experimental evolution approaches have made an important contribution to this resurgence of interest in speciation, complementing theoretical, genetic, and comparative approaches (see also Futuyma and Bennett this volume). This chapter will review the literature on speciation experiments, identify neglected questions that could be addressed by new experiments, and suggest general...

Already as an undergraduate, I had an inordinate fondness for phylogenetic trees, and few papers sparked my imagination more than one announcing the birth of experimental phylogenetics (Hillis et al. 1992). In that paper, Hillis and colleagues generated experimentally a phylogeny of viruses and used it to compare various phylogenetic methods. For the first time, researchers had at their disposal a phylogeny of “living” organisms generated in the lab for the express purpose of studying phylogenetic methods. This known phylogeny came at a time when the enterprise of testing phylogenetic methods was in its heyday. Even popular culture was enamored...

This book lays out a clear and compelling message: selection experiments are remarkably powerful tools in the armamentarium of evolutionary biologists. We ourselves have often used selection experiments during our careers and certainly expect to use them in the future. In fact, the power and elegance of selection experiments applied to life-history evolution by Rose and colleagues (Rose and Charlesworth 1980; Service 1987) motivated one of us (R.B.H.) to switch from conducting descriptive evolutionary studies on lizards in the field to performing evolution experiments onDrosophilain the laboratory.

In this chapter, we look critically at a particular type of...