Biology Reference
In-Depth Information
CHAPTER 8
Parental Care
and Family
Conflicts
Photo © Bruce Lyon
In the last chapter, we showed that there is sexual conflict over mating as rival males
compete for copulations and females choose between males, and that this conflict
continues after mating, as rival sperm compete for fertilizations and females choose
sperm. In this chapter, we shall see that conflicts continue further when there is parental
care of the eggs or young. We shall explore three interrelated conflicts (Fig. 8.1):
conflicts between male and female parents over how much care each should provide;
conflicts between siblings over how much care each should demand; and conflicts
between parents and offspring over the supply and demand of care. We shall discuss the
theory and evidence for each of these conflicts in turn, but before we do so we need to
consider the circumstances that favour the evolution of parental care.
Three inter-
related conflicts:
between male
and female
parents, between
siblings and
between parents
and offspring
Evolution of parental care
There are remarkable differences in patterns of parental care across the animal kingdom
(Table 8.1). In many species there is no parental care (most invertebrates), either
because parents are unable to protect their young effectively, or because selection
favours the production of a large number of eggs, whose fate is then left to chance.
Parental care in invertebrates tends to occur where fewer young are produced and they
can be protected from the physical or biotic environment (predators, parasites). Parental
care includes the preparation of nests and burrows, the provisioning of eggs with yolk
food reserves and the feeding and protection of eggs and young before and after birth
(Clutton-Brock, 1991). In some species only the female cares (most mammals), in
others only the male (many fish), and in some both sexes care (most birds). To explain
these patterns, we need to examine two factors. Firstly, different groups of animals have
Variation in
parental care
across the animal
kingdom
