Maternal Effects

Abstract

A maternal effect can be considered a causal effect of the parent phenotype on the phenotype of its offspring. Maternal effects contribute fundamentally to organismal life cycles. Maternal effects also contribute to phenotypic variation, to fitness differences between individuals, and to heredity. They are therefore important to many fields of evolutionary biology, which has generated a large and heterogeneous body of literature. One of the earliest (and still most important) motivations to study maternal effects in ecology and evolution is that they influence how populations respond to environmental change. Traits that are affected by maternal effects can exhibit different evolutionary dynamics compared to traits that are not influenced by parents. Maternal effects can also make population size fluctuate over time and contribute to range expansion. Many studies of reproductive investment and parental care are effectively studies of maternal effects, even if the term was not widely used in this context before the 1990s. While traits of parents and offspring can be expected to be co-adapted, the evolution of maternal effects is complicated by the fact that parents and offspring can have different fitness optima: a phenomenon known as “parent-offspring conflict.” Maternal effects are also widely studied in the context of phenotypic plasticity. The parent can act as a cue that enables offspring to adjust their phenotype to match local conditions, a phenomenon often referred to as “adaptive transgenerational plasticity.” Transfer of information between generations is one way to think of inheritance, and the evolution of non-genetic inheritance is one of the more recent additions to the growing literature on maternal effects and evolution. To handle this diversity of perspectives, the sections below are divided into main research themes.