The role of maternal and paternal effects in the evolution of parental quality by sexual selection

Parents can provide considerably more than genes to their offspring, and parents often vary in the quality of their extra-genetic contributions. This variation in parental quality can signi®cantly affect offspring ®tness and thus has been widely investigated by behavioural ecologists, particularly in the context of sexual selection and mate choice (Weatherhead & Robertson, 1979; Clutton-Brock, 1991; Andersson, 1994; Westneat & Sargent, 1996; Choe & Crespi, 1997). The focus on the relationship between sexual selection, parental quality and parental investment in offspring is not surprising given taxonomically widespread parental care. For example, nutritional provisioning of offspring by parents occurs in taxa as diverse as mammals, birds, ®shes, frogs, insects and arachnids (Clutton-Brock, 1991; Choe & Crespi, 1997). However, parents affect the ®tness of their offspring in ways other than care, and variation in parental quality can re ̄ect any variable contribution or characteristic of parents that in ̄uences growth, survival or development of their offspring. This includes, but is not limited to, characteristics such as provisioning