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This chapter describes an effect which produces population cycles and may be thought of as the mechanism for inertia in population growth. This effect, the maternal effect, is the passing of quality from mothers to daughters. Although this effect has been well known for some time, it has only recently attracted attention. It is argued that this effect provides an important part of the inertial model of population growth.

An individual’s phenotype may frequently be affected by the phenotypes (and hence genotypes) of other individuals with whom it interacts. Phenotypic effects that are caused by the genotype of another individual are referred to as indirect genetic effects, and these can have large and sometimes counterintuitive effects on evolutionary dynamics. Despite their potential importance, studies of indirect genetic effects in the wild are still rare. One class of indirect effect that has been investigated more commonly in natural populations is the effects of mothers on the phenotypes of their offspring. Maternal effects are defined as the contribution that a mother makes to the phenotypes of her offspring beyond the direct inheritance of genes from mother to offspring. Maternal effects have been widely studied phenotypically, and genetic variation in many important maternal traits has been quantified in the wild but rarely in the context of the indirect effects of this genetic variation on offspring traits. As a result, the importance of maternal genetic effects for evolutionary dynamics remains largely unexplored. This chapter provides conceptual background to the importance of maternal effects for evolution, and an overview of the various methods that can be employed to quantify maternal effects in the wild. Finally, this chapter provides some examples of important emerging questions in the field that could most rapidly advance our understanding of the importance of indirect genetic effects for evolutionary dynamics in the wild.

This chapter examines the influence of maternal effects on genetics and evolution. It defines maternal effects as the effects of the environment provided by the mother on the development of her offspring and describes how variation in these maternal environments can be caused by maternal genes and ambient environments. This chapter analyzes genetic models that describe genotype-phenotype relationships and expected evolutionary response in the presence of maternal effects and argues that these models show that evolution can be expected to proceed in the opposite direction of natural selection when the genetic covariance between maternal and direct effects is strongly negative.

This chapter reviews recent theoretical advances in relation to maternal-effect genes and the theory of relaxed selective constraint (RSC). It explains how to test theoretical predictions using sequence data and discusses how genetic questions on the evolution of maternal effects can be approached using a combination of microarray expression data and DNA sequence data. This chapter also highlights the importance of genetic models of maternal effects and maternal zygotic interactions in improving our understanding of how maternal effects evolve.

This chapter examines the influence of maternal effects on the evolutionary dynamics of wild small mammals. It analyzes work on a natural population of North American red squirrels and discusses some of the implications of genetic maternal effects and maternal-effect evolution for internally driven population cycles in small mammals. The analysis reveals the importance of the model of maternal-effect evolution in explaining the changes in nestling growth rates across generations and the observed changes in red squirrel growth rates in response to episodes of strong directional selection.

This chapter reviews the evidence for maternal effects in wild ungulate populations, discussing their prevalence and the mechanisms by which they are mediated. The analysis reveals that maternal effects contribute not only to observed phenotypic diversity in wild ungulates but also in evolutionary dynamics. This chapter stresses the need to determine what specific behavioral, physiological, and genetic mechanisms mediate maternal effects and suggests that candidate gene approaches could offer a useful alternative for scrutinizing loci underlying genetic maternal effects.

This chapter explores the maternal effects on offspring personality development in both oviparous and placental vertebrates. In particular, it discusses how prenatal maternal stress and prenatal exposure to varying levels of androgens and estrogens can result in stable individual differences in offspring physiology and behavior later in life.

The term “inertia” was first used in population ecology in relation to the property of overshooting equilibria due to any one of a variety of causes. This chapter tries to flesh out the details of a general account of inertia in population growth that can accommodate a number of possible mechanisms. To motivate this discussion, the chapter considers a couple of difficulties for the maternal effect. Both difficulties concern the inadequacy of existing data and require a little technical detail.

This chapter examines the influence of maternal effects on the size and development of pinnipeds. The analysis reveals that pinniped offspring are affected by maternal decisions about the timing and location of birth, the foraging ability of mothers, and the ability of mothers to defend and maintain contact with dependent offspring. The results also indicate that the expression of maternal effects on offspring phenotype in pinnipeds is influenced by maternal and offspring environments. These include changes in colony density within and among breeding seasons and social structure.

This chapter sums up the key findings of this study of maternal effects in mammals. It suggests that maternal effects occur when a mother's phenotype influences her offspring's phenotype independent of the genes it inherits from its mother and that these effects can arise before or after birth and can be mediated by the mother's nutrition, physiology, behavior, social status, physical environment, or some combination of these variables. This chapter also proposes long-term studies of wild mammals to better understand variation in maternal effects within individuals across reproductive events as a function of climatic variables, anthropogenic effects, demographic shifts, or senescence.

This chapter describes a wide range of maternal effects on offspring development in fissiped carnivores. It discusses the influence of maternal social rank on offspring status, reproductive development, play behavior, dispersal patterns, and association patterns in spotted hyenas. This chapter also explains the mechanisms underlying these effects which include differential maternal care, nutritional variables, androgenic hormones, insulin-like growth factors, and stress hormones.

This chapter discusses the objective of this volume which is to provide a comprehensive representation of maternal effects research in different mammalian groups, with a balanced emphasis between theory and data, genetic and environmental effects, evolutionary approaches and studies of mechanisms, field and laboratory approaches, and analyses at the populational, organismal, and molecular level. It explains that maternal effects have been the focus of intense scrutiny in recent evolutionary biology research because knowledge of maternal effects is required to fully understand the evolution of traits by natural selection. In addition, maternal effects may also provide a mechanism by which maladaptive phenotypic traits are transmitted across generations.

This chapter presents an overview of potential maternal effects on behavioral development, including pre- and postnatal effects of social experiences, stress, and seasonality on the expression of developing phenotypes. It suggests that maternal effects will have a selective advantage when they increase the survival and reproductive success of offspring. This chapter also discusses effects of maternal physiology including gonadal hormones, glucocorticoids and melatonin on offspring phenotype.

For most mammals, motherhood is an important investment. This is especially true among humans. While the ultimate rewards can include increased reproductive fitness, motherhood is costly to females, in ways that conspecific males do not experience. At the same time, gestation and lactation provide a time during which maternal care translates into offspring survival, growth, and development. Offspring also benefit from maternal investments, by taking cues from their mother as a forecast of the environment into which they will be born. This allows offspring to adaptively, facultatively, respond to the environment by way of their mother. In this chapter, we use an evolutionary biological perspective to briefly review mammalian maternal effects on offspring development. Maternal effects on offspring start in utero during fetal development and continue through adulthood.

The conspicuous nature of birds and their high-energy lifestyles has made them an attractive research model for many behavioral and physiological studies. Previous chapters give a sense of the scope of physiological research undertaken to date, but also reveal a growing interest in avian physiological studies. This stems in part from their utility in addressing questions fundamental to evolutionary and ecological theories, but also from the growing concern of the consequences of rapidly deteriorating habitat and resource availability on the world's fauna. This presents an urgency to better understand how animals respond to rapidly changing environments from a conservation perspective, but also creates natural experiments for testing life-history and evolutionary theories. The book strongly advocates that physiological studies of birds are very important in addressing these questions and highlight a few research areas that they feel are particularly pertinent.

In a variety of settings—additive epistasis in a diploid, dominance in an autotetraploids, shared environmental effects (such as epigenetic contributions), maternal effects, and dominance under inbreeding—the response in the mean has both a permanent and a transient component. The latter arises because selection perturbs the population distribution of genotypes away from their Hardy-Weinberg values. Upon the cessation of selection, any change in allele frequencies remains, but any additional changes due to departures from Hardy-Weinberg decay away. The result is that, even in the presence of these transient components, the breeder's equation often accurately predicts the amount of permanent response.

Eggs have complex composition where nutrients (resources) and signals potentially also serve as ‘tools’ that mothers might use to influence embryonic and post-hatching development, adjusting offspring phenotype to current environmental conditions and maximising fitness. If females use maternally derived egg components adaptively is there some combination of macro- and micronutrients with which females provision eggs: an ‘optimum’ multivariate egg? If so, this would suggest maternal coupling/uncoupling of egg components which has important implications for several unresolved questions in this field: a) are different maternally derived egg components correlated (positively or negatively) within eggs and what implications does this have for maternal transfer mechanisms?; b) do embryonic mechanisms allow for uncoupling of effects of different egg components, especially where the mother’s ‘optimal’ egg composition does not match that of offspring?; c) are there certain ecological (or life-history) contexts where coupling or uncoupling of different egg components is advantageous, and how is this achieved?

This chapter examines maternal effects in human cognitive evolution. It discusses the changes in social intelligence and argues that the confluence of increased brain size, delayed maturation, and social complexity contributes to the changing nature of mental representation, and that this was most critical in the social realm. This chapter also discusses the possible influence that mothers had in affecting social-cognitive changes over the course of human evolution and argues that mothers are a central component to the developmental systems.