Genetic and ontogenetic variation in behaviour: its possible role in the maintenance of genetic variation in the wing dimorphism of Gryllus firmus

Abstract

Genetic variation may be preserved in populations by several different modes of behaviour. In this paper we examine the consequences of behaviour on genetic variation in traits that are determined by genetic factors and by environmental conditions experienced during ontogeny. The particular trait considered is wing dimorphism in the sand cricket Gryllus firmus. In this species, as is typical of wing dimorphic insects, the adult wing morph (macropterous or micropterous) is determined by both genetic constitution and the temperature experienced during a specific period of nymphal development. Wing morph may thus be controlled, in part, by the thermal preference of nymphs. The effective heritability of wing morphology will be increased if nymphs with a genetic disposition to a particular wing morph select the temperature that causes that morph to be expressed. By contrast, effective heritability will be decreased if nymphs show no preference, or nymphs select temperatures that reduce phenotypic variation among individuals. During the period of ontogeny when future wing morph is sensitive to temperature, nymphal crickets that are genetically disposed to become macropterous select lower temperatures than crickets that have the opposite genetic disposition. Likewise, nymphs that are being raised under conditions promoting macroptery select lower temperatures than nymphs being raised under conditions favouring microptery. The consequence of this behaviour is that genetic variation for wing morph may be masked, and hence preserved.